# Battery checking - Hydrometer - Voltage - best way?



## Road_Runner_644 (May 9, 2005)

Hi All 

Looking for a bit of hands on advice really - got all the web links i need  

Got myself into a state this week. We were away for just a couple of nights without hookup We have 2 x 110ah leisure setup. I have solar which tops up a little during the day, We do use the microwave, through the invertor, but by saturday night (2nd night) my batteries were dead on their feet and I was in mortal danger of missing the end of Donnie Darko on the TV. 

I added up the amps i reckoned on using, and it didn't tally, so been doing a battery check. 

The batteries rest 24 hours after charging at 12.9 volts, they will sit at 12.9 for at least a day or so. But the specific gravity at 12.9 volts is around 1.200 with one cell from each battery running at 1.150 to 1.175. I'm pretty much clear that i got well into the electrolyte, and didn't just pick up the weak stuff at the top as explained in some site i read. 

I'm happy that the hydrometer is ok, i've had it for years, its got the green, white and red bits on, as well as the sg reading, and it reads as it should on the vehicle battery - in the green, just under 1.275. 

any thoughts - I'm going to do a pull test on the batteries, with a lamp or something, I'm just giving them the ctek charge first, but anyone had experience with good standing voltage but poor sg. 

Dave


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## 88724 (May 9, 2005)

Hi Dave

I take it these are bog standard UK bought and suplied batteries?

If the standing voltage sits at 12.9v after a day, thats the actual settled voltage and its good spot on for UK spec battery, any surface charge will have dissapated by then Guaranteed.

I avoid using a spec gravity measure for charging and only use to check that cells pretty much match, the reason is that you need to know the manufacturers temperature compensated readings for that specific battery topology and for the right country too.....

the starter battery is as I would expect for a UK starter topology, the Leisures seem low (but could be right) and I dont like a single cell from each being lower.

for the drop test select a load thats 10% of capacity run for three hours, then allow to settle for at least 12 hours if you started at 12.9v settled, I would expect to see 12.6 after a 3 hour 10% drop and a good rest.

Mix up some 1.300 solution and add to lower cell in each battery to bring back up in line with other cells.

On the paralell linked batteries, do you take positive supply from one battery and negative from the other battery ?


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## Road_Runner_644 (May 9, 2005)

Hi George 

Thanks for the reply. 

The batteries are common or garden wet leisures, £35 variety. They have the "magic eye" in them which registers as green (charged) from one cell in battery. 

And yes, the batteries are wired so the load is drawn from pos one one and neg one the other. 

The only possible factor that may have affected them is that they are charged when running with a "smart" regulator that pretty much keeps them at 14.4 for a couple of hours, before dropping back to 13.8. When parked up, the hymer charger takes over which is a 13.8 ish constant voltage charger. 

There is little or no electrolyte loss since new (sep 2004), and this is the first time i have ever noticed poor performance. 

I'm gonna kick myself if i find the kids filled the electric kettle full and boiled it to make pot noodles, but they deny it. 

Dave 


In fact


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## 88724 (May 9, 2005)

Hi Dave

3 kw for top kettle 3 mins to boil 

thats only about 14 amps total so unles they did a few pot noodles.....

With a smart reg they are getting some good charge then, I did wonder whethor a load had been missed. its rare for performance to die that suddenly especially when top notch charging is employed, they usually die slowly losing a little performance at a time. Except for new season syndrome when people leave an uncharged battery over the winter then find its fubar at start oif next season.


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## Road_Runner_644 (May 9, 2005)

Hi George 

Thanks again for the reply, I'm pretty sure i've looked after the setup, and can't quite fathom why it should fail so miserably. 

Maybe just getting a little paranoid here, facing a week away without hookup, so will test the batteries as you have advised. 

Will report back hopefully by Friday. 

Regards 

Dave


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## 88966 (May 11, 2005)

Hi Dave, 

I understand what George is saying about hydrometer readings and corrections, etc but given the readings you have I strongly suspect dead or near dead batteries or at least cells. 

Can you pop them into a battery supplier and ask him to test them? They will put a very heavy load on for a short time which shows up a weakness very quickly. 

I would also look into your charging facility as I have doubts as to whether they are being charged adequately - this can lead to premature failure. 

Finally, it is worth checking that you have no problems on the discharge side. All this talk of microwaves, inverters and TV to name but a few!!! 

BillD


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## johnsandywhite (May 9, 2005)

:roll: Just a point to ask. How old are the batteries?


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## 88724 (May 9, 2005)

Hi BillD

That battery torture device is for checking starting loads and should never be used on a leisure battery (if its a real leisure it could buckle the plates)

The Ctek is a very good multistage charger, unless this as failed, there should not be any problem on the charging front.

With only 2 X 110 Ah batteries a microwave is a large load, but they are well charged via the Ctek, so unless they are reallly hammered and eft disscharged for any length of time one would hopethey aint dead yet.


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## Road_Runner_644 (May 9, 2005)

Hi - Thanks for the replies.

BillD, the charging system is pretty well thought out, the solar panel uses a smart regulator to condition the batteries. There is a smart regulator on the alternator side that wacks a good bit of charge when driving. The normal Hymer charger is a constant voltage job, and i use the C-tek every now and then when the solar isn't finding enough sun in the driveway. The battery setup looks ok in terms of voltage, with the charging system doing what is expected. 
I will look for anything else that may have caused higher discharge than i expected as you and George suggest.

I'm well used to this setup, and have never had problems before. The microwave total usage would be 20 mins over a whole weekend, which i reckon is about 30-35 amps. Nothing else comes near that in terms of power consumption.

The batteries are not a year old yet JSW, so I didn't expect any problems.

At the moment the c-tek is doing its stuff, so later on i should be able to let the batteries sit, check the sg again, and load them to about 20 amps as George suggests.

I'm tempted to try this via 12v only directly from the battery, and then via the invertor just to see if it can possibly have gone wrong in some way. 

I've never heard of it before, but can invertors lose efficiency i wonder.

Dave


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## 88724 (May 9, 2005)

Hi Dave

20 Mins by my calculations would be under 24 Amps and I have checked this out with a Sterling battery monitor (fancy ah meter measuring out going ampage on 4 channels and two way ampage on one of those)

You say you "I'm tempted to try this via 12v only directly from the battery, and then via the invertor just to see if it can possibly have gone wrong in some way." 

what do you mean by this ?


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## Road_Runner_644 (May 9, 2005)

Hi George

Ok on the lower amps - not got a fancy readout myself  

In theory 20 amps for 3 hours via the invertor should take out the same as 20 amps for 3 hours by a seperate 12v load, less the efficiency of the invertor, which should be 98% i think or something near that.

I'm questioning whether the invertor can have lost efficiency.

Dave


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## johnsandywhite (May 9, 2005)

I thought this might help someone reading this thread:-

There are many ways to kill batteries ...even very expensive batteries. Below are a few ways of how NOT to treat batteries.

Overcharge the battery by applying a voltage above 13.8 Volts for extended period 
Undercharge the battery by never charging it beyond 13.8 Volts. 
Discharge the battery and leave it that way for a few days or weeks. 
Let the battery sit unattended without charging for 3 weeks or longer. 
Repeatedly discharge the battery beyond the optimum 50%. 
Slosh the battery around when it is deeply discharged. 
Boil enough electrolyte from the battery that the plates are exposed to air. 
Periodically add more acid, or unpure water. 
Use a ferroresonant charger in a liveaboard situation. 
Sock the battery with a high output alternator that produces more than 40% of the Ah capacity of the battery. 
Mount the battery where it regularly gets above 90F. 
Charge it hot until you can't even touch the case anymore. 
Use a big inverter on a small battery and run the inverter until it cuts out from low voltage. 
Freeze the battery in a discharged state. 
Use a starter battery in a deep cycle application.

 I just might add. I have done several of these in the past.


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## 88724 (May 9, 2005)

Hi Dave

I really doubt that the invertor as lost efficiency.

I see what you are getting at now, trying to take out the same amount of power.

To test efficiency you need a device to check the mains output wattage from the invertor and something like my battery monitor to check "whats" going through.

I have the technology, but you want to find out before we meet. 

To use that much power due to inefficiency it would have boiled the battery, consider even at around 100 amps for 5 mins uses less than 6 amps (ignore Peukerts for now its not important in this situ) even if it went really inefficient lets double the ampage thats only 12 amps, see what I mean?


Hi John

All the best chargers apply over 13.8 volts for a good period

50% is the maximum discharge, not the optimum discharge point

sloshing a discharged battery cannot as far as I can see effect the battery at all

hitting a battery with C40 from a large alternator for a few mins is not going to do anything charging voltage drops very rapidly, thats why any alternator no matter its size will not charge a battery to more than say 65-70% max without an smart alternator regulator. A large alternator is for supplying large loads it does little towards charging without an advanced regulator.

In practice running a large invertor from a small battery does no lasting harm, reason? large current drawn from small battery drags the voltage down so rapidly (due to Peukerts) that it cuts out very rapidly.

Using a starter as a deep cycle, if they really were deep cycle I would agree in practice a deep cycle battery as a different label, non venting caps and a vent tube added. My local camping shop are still running there van on a leisure battery after 3 + years, their battery failed one morning and they put a new leisure in to get them going thinking it would soon fail and need replacing, like I say 3+ years later....

I also used a starter as a leisure in my old merc van, never had a problem there either.


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## johnsandywhite (May 9, 2005)

8O I don't wish to question your knowledge base *George*. But are you suggesting that http://www.amplepower.com/ don't know what they are talking about. They have been supplying power supply systems to RV's, Boats and sites unable to have a normal power supply for years. :roll:


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## 91929 (May 1, 2005)

hydrometer are invariably used in good industrial battery rooms
There they charge them to as near 1.25 as possible
When one - or more cells start to give a lowwer eading and dont come up when being charged then the cell is going duff

you can try as George suggests and draw off an amount of electrolyte and replace it with stronger, but I dont think that it will give ant considerable extra life - At least in our experience of doing just that; it only gave a few weeks extra life


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## 88966 (May 11, 2005)

Hi All, 

I don't want to get too involved in controversy - I can only give my best and honest opinion based on an electrical engineering training (in the RN) and many years of being in charge of engineering in a large factory where we had about 20 battery driven fork trucks, etc. 

In my leisure life I have sailed cruising boats for about 40 years and did some of the early work with suppliers of solar panels for boats. 

Recently I have a number of old tractors, mostly with dodgy or non-existent charging systems. I was introduced a couple of years ago by my local man to a battery called a leisure/marine. This has heftier plates than a normal leisure battery but can also deep cycle, it is about 20% more expensive than a normal lead acid. They were designed particularly for use by ambulances and fire tenders where they now have some quite heavy electrical loads. 

I have an old JCB that had a huge original battery, I replaced it with one of these (100AH if I remember). The JCB does not charge at all but the battery seems to start it endlessly before I am kind to it and give it a charge. 

After all that I am convinced that batteries rarely die of overwork but more often of neglect. For motorhome use I would heartily recommend the leisure/ marine battery - I have probably bought about 6 of them for various jobs. 

BillD


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## 88724 (May 9, 2005)

Hi John

I am happy my information is correct, I have the scientific principles and tests to back it up, if there is any particular part you wish to discuss feel free to email me or start another thread, this thread was started to help Dave with his present problem, a discussion of general battery principles is off topic (the spirit of the topic anyway)

BTW* some of the links you have posted regarding batteries also disagree *with the info you posted above.

Hi Pete

Up to a point I agree with you, I have always found that

a, after a good charge the odd cell comes back in line or near enough to make b worthwhile

b, it doesnt come totally in line and a slight addition to correct the hydrometer reading cures it
c. after the above the it goes down quickly again, then the cell is duff and the battery needs replacing.

In a battery room they know the topology and the temperature is stable then a blanket 1.250 is ok, anywhere else and the temperature compensation must be used otherwise it will never be right.

1.250 is the top end reading for true deep cycle laed acid batteries at a temperature of 26.7 degrees C fully charged (by a proper charger) (yes it is that precise)

The easiest is to assume that it was made with the correct mixture, use the Hydrometer to see that they are all the same, the actual reading though is meaningless unless you temperature compensate.

if you want t see this in action check out a battery at normal room temperature, then place battery (one end only) in direct sunlight on sunny day, give it 10 mins or so then check readings at either end and then you will see why unless you are temp compensating the numbers are totally meaningless.

Try night and day to alter temp or even a blow dryer (do use common sense gently warm dont melt the case) and dont not do this while charging or discharging the battery.


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## Road_Runner_644 (May 9, 2005)

Hi All

Well the Ctek charged the whole lot up, and then went into maintainance mode. So it doesn't think there’s anything wrong.

I've loaded them to about 18 amps now, no invertor involved, so will have a look at midnight. The lights in the van lights do seem a bit dim though.

The voltage has dropped to 12.5 under 18 amp load.

Ok JSW, Have i killed it? - I have run the batteries down to invertor cut off point, which is 11.5 ish under load. The invertor turns off and the batteries rest at about 12.1v. So yes the batteries have been run down to a voltage that suggests harm, but my understanding of that one is that the voltage is relevant when measured with the batteries unloaded.

The others ways - not guilty - at least not on these batteries :wink: 

I've certainly done 50% of the other ways to kill a battery in my life so far.

The charge that they are subjected to is never greater than 14.4v, possibly 50 or 60 amps, but the lack of electrolyte usage suggests that no excessive boiling has been taking place. In fact the only time i can sense the smell of a bit of boiling is when the ctek charger has peaked. The batteries are vented to the outside by the way.

I hope the invertor thing is just a red herring George, thanks for the offer to check it. The quoted efficiency is actually 87% maximum. Makes me wonder now what the minimum efficiency is and at what loading minimum efficiency occurs.

And ok PamNPete - That was my understanding of the SG thing, just needed to get my head around why the voltage looks good.

Hi BillD - Well these are what we generally call leisure or marine leisure batteries, the same type as sold in marinas or MH parts shops. I don't know about the plate thickness or anything though. I must say in the past, cheap leisure batteries have lasted fine for me, usually i'd expect to replace after 3 years, as a good maintainance move rather than because they had died.


I'll know if they are shot in a couple of hours I hope.

Dave


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## 88966 (May 11, 2005)

Hi George, 

I am sure the figures you give are right but it is so long since I looked at my books that I wouldn't attempt to argue with them anyway. 

What I do know is that in all my career I have never done or seen done a temperature correction on a hydrometer reading. The normal instrument (?) is far too crude and is only used in a simple way - in the Green sector charged, etc. The other thing it is used for is to compare cells s.g. - a pretty good sign if failure is on the way. In normal environments the whole battery is at about the same temp. 

Let's not make life too complicated and possibly confusing.. 

BillD


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## 88966 (May 11, 2005)

Hi Dave,

It was demostrated to me by the comparison of weight on a size for size basis, the one's I referred to are definitely not leisure batteries.

BillD


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## 88724 (May 9, 2005)

Hi Dave

18 Amps and 12.5 suggests to me that the batteries are fine, if its still at that after (was at that after) 10 mins (you could) abort the test, pretty certain they are fine.

Lights will dim due to whatever load you are using is I am guessing pretty close to battery and pulling the greatest load and voltage drop in wiring to lights due to the usual inadequate wiring, its a path of least resistance thing.

Incedently thats why a water pump usage can effect the TV on a fully charged battery, its pecking order on inadequate wiring.

87% best efficiency !!! is it pure sine or old model? Peak eff is usually at 50% of the accurate continous rating (so if its a Sterling thats the rating on the box for any other company it needs finding out, by the way I am guessing its not a Sterling invertor you have then? I dont think they ever made one that poor eff wise.


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## Road_Runner_644 (May 9, 2005)

Hi All

George

I think if you mention sterling again, I'll actually go out and buy something by them so you don't have to mention it  

You may remember from a previous post about how this invertor (Waeco or Mobitronic) doesn't like my lads toshiba laptop. It has been fine with everything else, but a bit eccentric I’ll admit.

Well I just looked into the van and I’ve now turned on the invertor and put the fridge on mains (invertor) for the last hour of the test.

This will add to the load to make it 28 amps, and by my rough calculation will be 25% for 3 hours at midnight.

So the unloaded voltage should be 12.4 ish when finished

220 amps 20 hours rated supply
18 amps for 2 hours load
28 amps for 1 hour load (minus the efficiency of the invertor)

Should knock the batteries to around 75% charged or 25% discharged.

It looks good - the voltage after 2 hours was still 12.5 under load.

So - Just need to find the rogue power stealer.

One suspect pops up. Sky minibox which is always on when 12v is on, it's a pre-amp and also supplies power to the lnb. My setup brings the flying saucer antenna through the sky box. This is something fairly new, and I thought I’d researched its draw of power, and dismissed it as irrelevant.

Dave


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## 88724 (May 9, 2005)

What are you running through the invertor? with nil load it wont be taking anything other than quiescent current, what I am trying to say is that when the fridge cycles off then you have not got a constant draw. What the hell kind of fridge draw is that anway?? an electrolux uses about 10-12 amps at 12v if memory serves me right, my full domestic mains fridge only takes 2.9 ah from the battery when run via invertor.

Bugger just realised 10 amps for fridge, 28 amps total  but it still will not be constant once fridge as cooled.

BTW your batteries are fine.

Have you got a Multimeter ? usually they are good for 10 AMPs on current test put that between battery and Sky box, I would think thats going to be the culprit.

I was going to ask have you changed anything recently? and then thought no you would have already thought of that DOH!


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## Road_Runner_644 (May 9, 2005)

Hi all

George

Its doing my head in slowly - I see the point about the fridge, Will it will take an hour to cool to the point where it doesn't draw max current, i dunno. 

Anyway - the batteries should have been 25% ish hammered by now.

I'm sitting here waiting for midnight to arrive to see what the result is.

and it's

12.48v off load - a bit better than i expected.

Ah damm - I must have something stealing those amps :? 

Dave


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## 88724 (May 9, 2005)

12.48v straight off load thats fantastic that will settle upwards too.

Would guess about 1/2 to 3/4 hour to cool. shoulda left door open too late now, but my brain wants to get horizontal, laterally knackered tonight.

Sky box? or something as daft as forgotten light?

Your batteries and charing systen A OK


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## 91929 (May 1, 2005)

Hi George well yes the battery rooms are mostly at an even temperature
have worked in them in Chemical works, steel works, military + other places since starting work some 50+ years back

One trick they use is to keep the chargeing current up at max to desulphenate the plates = that works just as well as adding stronger acid

Buut of course with the chargers that are available to most vanners to do that would be impossible - as would putting the battery on a timed discharge at max rate ( every 10 chargeing cycles) - those that did not last for the stated time were disposed of


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## Road_Runner_644 (May 9, 2005)

Hi All

Quote from George 

"Sky box? or something as daft as forgotten light?"

George gets the biscuit

Ok - Got an apology to make after making you all rack your brains so much.

It was the bl***y bathroom light    

In a Hymer 644 there is a big looking thing which you'd think was a fluorescent, but it takes 4 x 11w auto bulbs.

At the weekend I never ventured into to the bathroom as the showers were a quick hop away from the van. The kids and Mrs Roadrunner however always have some lame excuse for using onboard. I think someone used the bathroom Friday evening, and left the light on. 

I always turn of the 12v when we go out, but if it was on from say 9 in the eve on Friday till when we went out at 10.30 the next day. And on again from 4 pm till when we got back to say 9.30 in the evening, when I distinctly remember telling my daughter to turn off the light in the bathroom after she had used it. She didn't say "it's already on anyway" they don't do they .

So there’s my possible stolen or leaked amps.

I reckon on about 70amps gone that way.

I realised 5 mins ago, because last night I put the batteries back on charge, turned all the lights off, but not the 12v system. And guess what, I left the bathroom light on which was part of the load I was using to test. The ctek is a 7 amps charger, and it hadn't replaced the 1/4 discharge that occurred last night. 

Talk about a smack in the face and feeling stupid.

It was a good experiment though - And I’m still bemused over the low SG readings.


I'm done with that bathroom light now, must get some led's or something a bit more economical. Who'd have thought a bathroom light would be 44w - madness, and I never really thought about it before, as it "should" be on for no more than 5 or 10 mins at a time, but you can't see that it's on when the door is closed.

Dave


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## 88724 (May 9, 2005)

Hi Pete

Well that high voltage charging rapidly reconverts the sulphate back into sulphuric acid typically done between 15 and 16v (its the high voltage rather than current that desulphates) 

Which is why most camping batteries charged via zig (types) die so rapidly the low voltage cannot break down the hardened sulphate (it hardens due to being left discharged)

Hi Dave

Glad you are sorted, by sg you mean the difference in one cell I presume? as the numbers do not mean a thing unless temp compensated.

Have you still got one odd cell per battery? 

Yes I really do take the biscuit I hear  

After yesterdays test I would have them down as good strong batteries to maintain 12.5 through that test is very good..


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## 89074 (May 13, 2005)

he he, this thread made me laugh
this is something I would have done


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## Road_Runner_644 (May 9, 2005)

Hi George

Well, not the odd cell thing but the 1.2 reading - but i take on board the temperature compensation. There was no bumf with these batteries, they are called Platinum Lifestyle model no 6110L - but nothing on google.

I've not took readings since, but i'll let the ctek run its course and check again, and will drop a bit of electrolyte into the lower reading cells, from the equal ones.

Hey tweenievan

It's just my way - If i don't understand it, logic goes out the window. Logic says I must have left a light on, I think, "No - it's a disaster waiting to happen sent to try me" - and I start reading battery faqs - trying to learn about specific gravity - and asking these kind people on MHF.

It works in the end though  

I can now say to any other MHF punter with the same question - "I bet you left your bathroom light on"

Dave


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## 91929 (May 1, 2005)

Hi George well it all depends on what your meter reads / How it isconnected

I =V/R or V = I x R

Where R is the internal resistance of the battery - I agree you cannot have increased Current without the increase in Voltage

fact is that ALL the battery rooms that I have had the pleasure???? to vist have taken the measurement in Amperes, not Volts

The voltage screw is just turned up to give the required current reading

After all the specs on batteries usually give thee Chargeing and Load Currents not the voltages
So it ismore correct to talk in terms of the current rather than voltage


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## 88724 (May 9, 2005)

Hi Pete

Amps are always *drawn* in the required amount for whatever appliance, they are not pushed by the voltage. Higher voltage is required to overcome the resistance and so enable the battery to draw a higher current.

Resistance lowers the current that can be drawn, thats is why a bulb can draw just enough current to light, whereas if you place a spanner between the terminals it will vapourise, a solid steel spanner atomised, yet a little tiny filament in a bulb survives.

We are just seeing the same thing from a different perspective.

Watching the ampage is far more informative of whats going on in the filling and emptying of a battery.

I have found the opposite when speccing batteries though, all the (manufacturer) info shows maximum voltages especially for the weaker types (sealed, AGM and gel type batteries) this is always in conjunction with the C rating for the ampage.


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## 88966 (May 11, 2005)

Hi George,

I quote, "Amps are always drawn in the required amount for whatever appliance, they are not pushed by the voltage".

I am afraid you are incorrect, the potential difference (volts) is what controls the current flow assuming the resistance remains constant.

In a simple battery charging situation the voltage remains constant (more or less) and the state of charge (internal resistance) of the battery is what causes the current to vary (reduce as the battery becomes charged).

BillD


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## 88724 (May 9, 2005)

Hi Bill

If that is the case why doesnt a light filament blow? 12v is the same potential that according to your version is Driving several hundred amps through a starter motor? 

A lower voltage will allow all the current to exit at once in a direct short, a higher voltage only allows the current to overcome a greater resistance.

Cannot think of a better way to try and explain it.

Connect a drained battery to a fully charged one and the Ampage flying across is Very high, this is the reason so many split charge system fuses blow and this is all at lower voltage than the alternator puts out, amazing to watch on a high rated ameter.


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## 88966 (May 11, 2005)

Hi George, 

It all happens according to that chap Ohm and his law, as Pete said earlier. 

12 v across a lamp filament (resistance say 2 ohms) produces a current of about 6 amps (enough to make the filament glow) and produces a power output of about 72 watts ( a 70 watt bulb!). The rating of the wire (filament) in the bulb and the material of which it is a made decide whether it acts like a fuse (and blows) or like a filament ( and glows). 

The same 12 volts across a spanner ( resistance not a lot) produces a big flash and a knackered spanner (or worse). 

If you continue this, if you apply 6 v across the same bulb only 3 amps will flow and the bulb will only glow (at best). 

However if you apply the spanner you will still get a big splash and knackered spanner but if you were to measure the current it would only be half of what it was at 12 v. 

Your example of the 2 batteries is correct, it is because the voltage of the higher charged one is higher than the other that the current flows. 

I hope this helps your understanding. 

BillD


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## johnsandywhite (May 9, 2005)

Ohm’s Law states
The amount of current flowing in a circuit made up of pure resistances is directly proportional to the electromotive forces impressed on the circuit and inversely proportional to the total resistance of the circuit. Provided the temperature remains constant.


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## 88724 (May 9, 2005)

Hi Bill

Amps are drawn not pushed.

Yes you are correct in that the charged battery as a slightly higher voltage, but look at that for a second a fully charged battery is say 12.9 and a discharged battery is 12.4, then look at the ampage flowing across 0.5 of a volt is not going to do much pushing is it?

The discharged battery is a load, it draws more or less amps due to its resistance only.
Look at the example below










If you solve this simple circuit you will see that lower resistance draws more current, the potential at all times is 12v

If you connect a Drained battery to a charged battery after a while both will be at the medion point 12.65 volts (actually ends up less on both batteries due to loses) this could not happen if voltage pushed the ampage through because in very short order the potentail for both is the same.

If you look into electric powered vehicles the are looking at dump charging for electric vehicle battery banks, this works on exacly the same principle.

BTW yes 2 amps on a 6 ohm resistor at 12Volts, then you get 6Amps on a 2 Ohm resistor, so if we had a 1 Ohm resistor we would get 12 Amps
At 0 Ohms the spanner can draw infinate ampage all at 12v

Battery resistance is very very low, connect them as above and you can see that massive ampage can be drawn even with little difference in potential


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## johnsandywhite (May 9, 2005)

I have to agree with Bill. :-

A steady increase in voltage, in a circuit with constant resistance, produces a constant linear rise in current. (Voltage pushes)
A steady increase in resistance, in a circuit with constant voltage, produces a progressively weaker current


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## 88724 (May 9, 2005)

Hi John

How come 12v Pushes Infinate amps at 0 Ohms then John?


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## johnsandywhite (May 9, 2005)

Think Short cicuit. Perhaps it may even blow up the battery. I wouldn't like to try it. The weakest element in the circuit would give way first.


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## 88724 (May 9, 2005)

Hi John

What I am saying is the same 12v are now *supposed to be pushing *infinate amps.

Tiny increase in Volts only begets a tiny increase in amps (given the same resistance) and yet a tiny adjustment in resistance as a bigger impact on current! 1 Ohm = 12 Amps, zero ohm and infinate ampage can be drawn.


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## johnsandywhite (May 9, 2005)

GeorgeTelford said:


> Hi John
> 
> What I am saying is the same 12v are now *supposed to be pushing *infinate amps.
> 
> Tiny increase in Volts only begets a tiny increase in amps (given the same resistance) and yet a tiny adjustment in resistance as a bigger impact on current! 1 Ohm = 12 Amps, zero ohm and infinate ampage can be drawn.


Yes George you are correct because the Current flowing in a circuit is directly proportional to the Voltage and indirectly proportional to the Resistance

In other words increase the Voltage (Resistance stable) and the Current goes up. Increase the Resistance (constant Voltage) and the current goes down.


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## 88724 (May 9, 2005)

Hi John

Decrease the Resistance (constant Voltage) and the current goes up dramatically.

Also look up anywhere and you will see it refered to as the Amparage drawn by (whatever) and never will you see the amparage pushed through the circuit.

Read any expert or professional text.


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## johnsandywhite (May 9, 2005)

George. I have been quoting the theory of Ohm's Law. What you are saying is against what that law states. I studied Ohm's Law, Kirchoff's law and Boyles law when I was a Radio Techinician Trainee. I agree that an appliance usually quotes the current drawn. That's because the Voltage is (normally) is constant. But that Current is still inversely proportional to the resistance in the circuit. 
I have read professional text and Scientific texts and they say the Voltage pushes against the Resistance. Therefore the result is the Current drawn.


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## 88724 (May 9, 2005)

*Therefore the result is the Current drawn.*
At last


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## johnsandywhite (May 9, 2005)

:roll: No. Iincorrect George. A Battery is a device to electrically convert something called Potential energy to Kinetic energy. I believe Kinetic energy is a force. Therefore the Voltage pushes against the Resistance tor provide the current which the cicuit requires to operate.


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## 88724 (May 9, 2005)

John you are amazing in your duplicity and ability to try and keep an argument going

*You quote the professionals as saying current is drawn and then go on to say they are wrong?*

I say it is drawn and all professional texts agree

Debate over, unless you can show any professional opinion stating that ampage is pushed.

Fin

Edit was to had highlight and to add Fin, everyone can see what he is upto now.


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## johnsandywhite (May 9, 2005)

There is no argument is in progress as far as I am concerned. I am stating Ohm's Law. A scientific fact. Proven over countless years of pracftical design and use of circuits. The Voltage is what provides the EMF to Power a circuit. The current used in that circuit to overcome the resistance is provided by the Electro Motive Force. Therfore. It must PUSH.


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## 88966 (May 11, 2005)

Hi George and John, 

I am out of this - it is developing into what I regard as intellectual masturbation. 

I am happy to try and help anyone with a problem with motorhomes I am not into trying to teach basic electrics to somebody who only appears to want an argument. 

BillD


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## johnsandywhite (May 9, 2005)

Yes you are right *Bill*. You cannot argue against someone who is convinced that Ohm was wrong. I will therefore not make any more posts on this subject. :wink:


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## 88724 (May 9, 2005)

Just to point out that I have never disagreed with Ohms law, just another Bait from the Master Goader


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## johnsandywhite (May 9, 2005)

GeorgeTelford said:


> Just to point out that I have never disagreed with Ohms law, just another Bait from the Master Baiter


 :roll: *GEORGE*. Please refrain from discussing what I do in my private life on this Forum. *Thank you.*


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## Road_Runner_644 (May 9, 2005)

Anyway

Going back to my batteries  

From the first post you can see that I was confused why I see a good standing voltage but a poor specific gravity reading.

Here were the readings I jotted down when I first checked the batteries, and then readings I get now after I have run the batteries down by 25% twice, and then recharged with the ctek, which does the all singing and dancing stuff, like taking them up to 14.4 and boiling them for a bit. The batteries were again left after charging for a good six hours, and the standing voltage was 12.8 - 12.9.

Cell no - going from Pos terminal on Bat 1 one to Neg Terminal on Bat 2

1 - 1175 - now 1250
2 - 1175 - now 1250
3 - 1200 - now 1275
4 - 1200 - now 1275
5 - 1200 - now 1275
6 - 1200 - now 1275

1 - 1200 - now 1275
2 - 1150 - now 1225
3 - 1200 - now 1275
4 - 1200 - now 1275
5 - 1200 - now 1275
6 - 1200 - now 1275

It's noticeable that the cells with the lowest SG are the ones where there was a higher electrolyte level (maybe too high). I have levelled off all the cells, and I haven't needed to top up after doing this. I'm assuming the fill level is to just above a bar across the cell which is about half an inch below the lower part of the screw in bung. There was slight electrolyte loss after charging, with some moisture showing on the inside of the vent pipe.

The plates seem to be a good inch and a half below this level.

So whatever caused my irritation has gone, and I'm a happy bunny  

Why I got such low reading before, doesn't seem to be explained by temp compensation, as it's seems to be too much of a shift.

It's cold and raining here today, outside temp 15C, it was probably a bit colder this morning. Last week it was warm in the evening, at a real push it may have been 30C in the battery box.

But I suppose its the only theory that’s been given that is in any way plausible, unless I make a new theory up (like if its gonna happen - it'll happen to me)

Thanks for all comments and help.

Very much appreciated as always.

Dave


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## johnsandywhite (May 9, 2005)

Hi *Dave*. It;s called Equalising. :wink:


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## 88966 (May 11, 2005)

Hi Dave, 

John's right and it is possible that given another discharge and recharge or two followed by a couple of days levelling off at the top it may even improve more. 

If that doesn't do the trick it could still be a sign that those particular cells are a bit poorly - just keep your eye on them. As they are leisure batteries it isn't the end of the world if they fail - you can buy batteries anywhere. 

BillD


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## 91929 (May 1, 2005)

No George Voltage is the POWER to drive (or push ) a current through the circuit

Lets make it simple (like we had to do when teaching basic electricity to young apprentices of all trades)
(have to do this without diagrams )

Consider a Central Heating circuit wit radiators & a water pump

Turn the pump on and water is forced into the pipes and radiators by the pressure of the pump (Voltage)
As you open up more radiators water is pushed into the system at a faster rate (more current is forced into the pipes) 

Put in a pump with a lower operating pressure and less current is forced into the pipes

Put in a larger pump (higher voltage) and a greater flow/current will flow

The size of the pipes (restrictions) represent the electrical resistance

I have only worked in electrical/elecronics including teaching at all levels from basic to HNC level for over 50 years -


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## Road_Runner_644 (May 9, 2005)

Hi Again

Well having read the faq at www.batteryfaq.org at least a zillion times in the last 2 years or so, the only other possible that comes out and zaps me is this.

"Some new batteries can take up to 30 charge/discharge "preconditioning" cycles before they reach their rated capacity"

So i think if i'd tested the SG a while ago, i would have found the same. Good voltage but what appears to be poor SG.

A pound to a penny that the poor looking cells now find themselves up with the others after a few more cycles on the ctek.

I hope :wink:

Dave


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## johnsandywhite (May 9, 2005)

That's a good idea *Dave*. :wink:

 Thanks for the POWER push *Pete*. :wink:


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## 91929 (May 1, 2005)

Hi road runner so in spite of the arguments that dont really matter 

You seem to have got your battery back in the land of the living

Which is the MAIN FUNCTION of this forun after alls said an dun

if somebody has the time to remove all the clap trap I think this could be a usefull post item on how to recover a duff battery


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## Road_Runner_644 (May 9, 2005)

Hi PamNPete

I got my result, learned a bit along the way, and found there are some areas that are not always as clear as the technical faqs might have you believe. 

I'm off next weekend, I was literally about to go out and buy new batteries because i thought they'd failed. 

So like you say, it does work, my family can go out and have a couple of decent meals out next week, on the money I saved. 

Sometimes you have to accept that theres some disagreement on technical matters in the thread, but the bottom line was that everyone helped me, in spite of some heartfelt opinions of their own on related matters. Thats why I felt it was important to post the results, as it may help someone else.

Cheers 

Dave


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## 88966 (May 11, 2005)

Well done, Dave and thanks for letting us know the results.

BillD


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## johnsandywhite (May 9, 2005)

Glad everything worked out OK for you *Dave*. What a lot of people don't realise. Is that evern NEW batteries require breaking in to work best. A few cycles now and again never does any harm. In fact we enjoy cycling. :roll:


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## james (May 15, 2005)

Hi All,
I have been watching this thread with interest, not because of the splendid disagreement about what, I am not sure, but which I think everyone is both wrong and right, (those standing on the positive terminal will think that the current is being pushed out while those standing on the negative will think that it is being drawn in and doubly confused because you are dealing with a negativity as far as electrons are concerned) but because I too have one or two cells that give much lower readings than the others. Looking at Dave's results he has certainly got higher readings but the differences remain exactly as before. I too have tried equalising them with a multi stage charger but the differences remain. They are fairly new 110 amp batteries that have been looked after. These batteries are under guarantee, should I complain?
James


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## johnsandywhite (May 9, 2005)

Hi *james*. When you say they are fairly new? How old are they? Maybe the batteries were old before you actually bought them. If you have a receipt? I would certainly suggest you take them back and exchange them. As I mentioned above. Not many people are aware that new batteries need breaking in properly to give of their best. :wink:


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## james (May 15, 2005)

Hi John,
They are about 9 months old. They don't give me any problems; it is just that I am worried that they may be about to fail prematurely. The previous batteries were replaced because one cell in one of the batteries started boiling and smelling strongly of sulphur, and as I used them in pairs I had to buy two. I don’t want to have to do that again so soon.
James


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## johnsandywhite (May 9, 2005)

8O Yes I know how it is when something goes wrong so quickly. To cut a long story short. I had 2 x 85ah which I replaced with 2 x 110ah. Six months later I added another 2 x 110ah. Around 10 months later I had to dash back to the UK for a Funeral. The Alternator had packed in. The generator had burnt out the starter motor. That left me with Solar Power to charge the motor and the 4 Leisure batteries. I got to France and it snowed. Weather down to -10C. To say the least. It killed all the batteries. The Solar power however did give us some power into the batteries and I used then for another 2 years. I would suggest to cycle them a few more times. If they Gas too much? Then they may well be on their way out. The problem when you buy batteries is you don't know how long they have been on the shelf before you buy them. Good luck. :wink:


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## johnsandywhite (May 9, 2005)

Just a point. This article might help you >> HERE << :wink:


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## Road_Runner_644 (May 9, 2005)

hi James 

Missed this earlier on - but had the same thoughts as you. 

My batteries perform fine, I did the load test, and the results came out ok. 

Because i have never really come across this problem before, i don't feel confident to stride into the supplier and say "hey - the sg is down in 4 cells on my battery bank, i demand new ones" - It may be that the cells will equalise in time, and past experience has told me that i should get at least 3 years out of these. I never worried too much about sg in the batteries or water levels, until i got a smart reg on the alternator, and worried about losing elecrolyte level. 

So i went over the top imho, and instead of just doing a load test, i wanted more  

But, I share your fear that, they may be dodgy, and i'll find out at xmas when the guarantee is 4 months done. 

My theory with my batteries is that the cells were not filled from new to the same level in every cell. I've done little camping with no hookup, and ran the batteries down perhaps 4 or 5 times. So the the statement on one of the battery sites had me thinking "Some new batteries can take up to 30 charge/discharge "preconditioning" cycles before they reach their rated capacity" 

I'm hoping thats me - And to be honest i never took much notice over the last 5 years, of sg, voltage or anything else to do with batteries, i just stuck em in, and got on with it. the only time i ever ran out of batteries before was when i got my first s/h coachbuilt, and it was supplied with a duff battery. They replaced it, and i ran that for 4 years, no prob. 

My fears came about due to a possible 5 day camp without hookup. 

Cheers 

Dave


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## 88966 (May 11, 2005)

Hi Guys 

I know that batteries are strange things that do not always perform exactly as per the book and their performance can be influenced by any number of external matters. 

What I mean is, apparently similar batteries can sometimes fail after a year or so and others go on for many years in what appears to be similar circumstances. I do not believe battery manufacture is a very exact science and certainly their maintenance and use can be extremely varied. Their usage can be from one extreme to another.

I am not advocating anyone else do what I do, mostly neglect my batteries and rarely even think about them until they start to perform poorly. I occasionally have a look at the electrolyte and if it looks low give it a drop of water (out of the tap!). 

I get very good life usually and cannot think of the last time I had a premature failure. The battery in my Discovery was, I felt, getting a little sluggish at starting in the morning so I thought I would have a look in the manual and found that the battery iis supposed to last 6 years - so I checked and it was about 8 years old. Anyway lethargy set in and I kept putting off buying a new one. Until recently when it really was grunting, so I bought a replacement - after 11 years. 

As I said before I am not suggesting anyone else do as I do - I know the risks I am taking. I know how batteries work and how they should be maintained my only point in writing this is so that people who don't take a little more relaxed view and not worry too much about them. What I would advocate is buying good quality (not fancy designs) lead acid batteries from a reputable supplier for most motorhome usages. 

Hope this helps someone. 

BillD


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## johnsandywhite (May 9, 2005)

Five days without hook-up *BillD*? That's when Solar Power comes in handy. :wink:


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## 88966 (May 11, 2005)

Hi JSW, 
I have solar panel and 5 days is no good - I've done 9 weeks without hook-up!!

BillD


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## johnsandywhite (May 9, 2005)

Yes it can be variable how long a battery bank will last. Up until December is Spain we manage OK. Then it's supplementation from the Genny until March.


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## Road_Runner_644 (May 9, 2005)

Hi

Love the post BillD

Tap water in the batteries, done it, but wouldn't do it to the motorhome.

Our MH is our saviour, we both work all the hours in a wholesale business, and love to get away. The car is a differant beast to our lovely MH. I'd happily fill the car battery with anything to hand, but not the treasured MH.

Thats why I get so paranoid if its looking like it's not going to work. Thankfully i get a lift when others pop in and say -"Try This" - And a great thanks to GT for pushing me to test the capacity of the batteries in a sensible way.

And don't wind me up cos i only do 5 days unhooked guys :wink: 

I'm getting there - 5 days is 2 days longer than i ever did before 

We dream of the day of we can just drive off and say to the family, "see you when we see you".

Cheers

Dave


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## johnsandywhite (May 9, 2005)

*Dave* we Wild-Camper's quite often go months without an Hook-up. In fact. Since I have had to spend the last 12 months in the UK? I haven't had an Hook-up or the generator running in all that time. Apart from that is for check-ups to make sure everthing is working. :wink: 8)


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## Road_Runner_644 (May 9, 2005)

Hi

2 weeks later and another thousand or so miles, I have checked the batteries again.

They now measure at the following - 12.8 volts sitting off charge for 24hrs

Cell no - going from Pos terminal on Bat 1 one to Neg Terminal on Bat 2

1 - 1175 - now 1250 - now 1265
2 - 1175 - now 1250 - now 1265
3 - 1200 - now 1275 - now 1275
4 - 1200 - now 1275 - now 1275
5 - 1200 - now 1275 - now 1275
6 - 1200 - now 1275 - now 1275

1 - 1200 - now 1275 - now 1265
2 - 1150 - now 1225 - now 1250
3 - 1200 - now 1275 - now 1275
4 - 1200 - now 1275 - now 1275
5 - 1200 - now 1275 - now 1275
6 - 1200 - now 1275 - now 1275

So there is some recovery in most of the cells that were down. But one does look a little forlorn.

I’m going to do another mix of electrolyte for it, just for an experiment, to see 
what happens after another month or so.

In use the batteries are fine and performing as expected.

Dave


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## 88966 (May 11, 2005)

Hi Dave,

If it ain't broke don't fix it !!
If the batteries are working OK, what more do you want.


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## Road_Runner_644 (May 9, 2005)

Hi Bill

I don't want anything more ?

Just interested in what has happened to the batteries, and posted just in case anyone else was interested  It might help some, you never know :wink:

If the sg recovers in the cells that are down, i'll put it down to the battery not being cycled enough since new.

For anyone reading the thread it should show that sg is not the be all and end all for checking battery condition. Voltage seems to be much more relevant.

Cheers

Dave


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