# additional battery?



## fjmike (May 10, 2005)

Having sorted out my Lidl sat. system and rf modulator (BIG thankyou to everyone who posted I don't know where I'd be without MHF). The challenge for me now is powering laptop(TV), rf modulator and sat. box, looking at the options I think that running an additional battery in parallel is fraught with complications:- 

1- leisure battery sited under passengers seat so not possible to replace with larger battery and to get another battery to run in parallel would get in the way 

2- the charging system is either gel or lead acid , the living area battery is a gel 

3- to match present gel battery 85 amp/hr. is rather expensive , cheapest quote so far is £100. 

A little lateral thinking poses the question - Why not have a separate battery that could be charged independently. The only downside that I can see to this is will the supply on campsites be enough to power the battery charger ?(Optimate). I would welcome anybodys thoughts on this (be gentle with me as electrics do tend to baffle me Thanks


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## 88724 (May 9, 2005)

Hi Mike

Easy to supply a battery charger from site, my 30 Amp charger only needs under 1 amp from mains, a little Ctek isnt going to use that much.

Optimate isnt that a winter trickle effort (have not got time to look up now)


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## 88742 (May 9, 2005)

Hi Mike,

We have an 85A/H Gel habitation battery, so a similar problem to yours.

Solution: I've put a 110A/H (Lead Acid) battery under the passenger seat which is left on charge whilst on the drive with an Optimate (And can also be charged if it we're on a site's hookup).

To this I have a cheap multimeter connected to monitor the state of the battery and a 600w (1400 peak) invertor, isolated via a double pole switch.

This solution gives me independent 240v without the risk of flattening the habitation battery and can easily be accessed if additional 12v is required.

Ian


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## 89425 (May 23, 2005)

The easiest way to charge three batteries is to fit a split charge diode block. You basically connect it to your alternator, then connect the batteries to it via individual terminals. This block prevents batteries drawing current from other batteries, thus keeping them isolated from each other. This system does away with the split charge relay.

To use the two leisure batteries for the Living accommodation, fit a two way switch so you only draw power from one battery at a time.


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## 88724 (May 9, 2005)

Hi Steve

That could prove disasterous with a gel battery (the Diode) could lead to a dead gel battery in very short order


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## spykal (May 9, 2005)

fjmike said:


> A little lateral thinking poses the question - Why not have a separate battery that could be charged independently. The only downside that I can see to this is will the supply on campsites be enough to power the battery charger ?(Optimate). I would welcome anybodys thoughts on this (be gentle with me as electrics do tend to baffle me Thanks


Hi Mike

This is exactly the approach I have taken in our van. We have an Autosleeper Executive which is great but when it comes to storage space we do need to be economic in what we carry. So I have a normal 85 amp/hr Leisure battery plus an extra 65 amp/hr battery which is used solely for our entertainment system.... Lcd TV and Dvd player. We do not watch an excessive amount of Tv or Dvds but when the battery is at 50% capacity the Lcd TV just shuts down ( very convenient as it does not harm the battery), this is about 3 days use, 8-12hrs or so, never actually timed it. When this happens if we are staying on without any hook up we limit our TV to just the news and weather running from the normal leisure battery.

I use a Ctek 3600 charger to charge on a hook up and at home to maintain, rotating it between the three batteries as necessary. I also have an accumate charger which is a stable mate of the Optimate you mention, both of theseare Ok for maintenance but the charge rate is very low and a full recharge to the TV battery is much quicker with the Ctek.

One other often neglected option for power that I use if necessary is the vehicle battery. I can run the TV, Dvd or laptop from the vehicle battery via a simple battery protector from Maplin , this cuts off the power to any appliance fed from the battery leaving enough power to start the engine. Note that my cigar socket is wired on, with ignition off!

http://tinyurl.com/8r5mq <<<link to maplin page for battery protector









We have just returned from a 5 day break over the Bank Holiday we stayed put for 5 days without a hook up, watched loads of TV computed a bit and ran all the normal things and had power to spare when we set off for home.

Another tip if you are using a charger (Ctek, or Optimate) that connects by the "tamiya type connectors" is get some of them from maplin and you can use them to connect/disconnect all your varous systems/batteries, including the charger.

http://tinyurl.com/88fru <<<link to maplin page for DIY tamiya connectors, buy the loose ones as the polarity of the wiring on the pre wired ones is reversed when compared to the Charger . ( :lol: sorry about that Jabber)









Mike


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## fjmike (May 10, 2005)

Thankyou all for the replies , what iI will do is buy a cheapish charger and probably a lead acid 110 amp/hr battery . then when we are up a mountain stage of the Tour de France with everything fully charged should give us a reasonable amount of viewing time. Mike , is it the LCD TV that gives you the 50% capacity shutdown or did i miss something?


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## spykal (May 9, 2005)

fjmike said:


> Mike , is it the LCD TV that gives you the 50% capacity shutdown or did i miss something?


Hi mike

What happens is that the LCD TV backlight starts to flicker when the battery gets to around 50% capacity and the voltage has dropped to around 11.9 - 12.0 at this stage we stop using that battery. It is just a fortunate coincidence that my LCD TV does this but it is very handy since using a battery to below 50% capacity does not do it a lot of good.

Mike


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## 88724 (May 9, 2005)

Hi Spykal

11.9 or 12v is very flat, the range is over about 1 volt ie if 12.8 is fully charged 11.8 is palookaville ,, 12.3 to 12.4 is about as low as you want to go, only thing thats preventing your battery dying at mo is the good charger you are using.

12.3 TO 12.4 is the rested voltage, that would equate to 12.1 to 12.2 under TV type load.

The cut outs on virtually everything that I have tested so far are way to low to save the battery.


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## 89425 (May 23, 2005)

GeorgeTelford said:


> Hi Steve
> 
> That could prove disasterous with a gel battery (the Diode) could lead to a dead gel battery in very short order


My mistake







I read it too quickly


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## 88790 (May 9, 2005)

I have fitted a second battery in the locker next to where the main is located. I did consider fitting it as an additional one to us just for entertainment but in the end fitted it with one of 'Spykal's' plugs and sockets.

On my last trip away turned the charger off, I can do that because I have fitted a separate fuse, and just ran on the batteries. At the end of four days voltage was 12.9v, I measured it from a 12v socket.

I expect I shall wire the extra battery in permanently. When I fitted it I also fitted a connector for the CTEK 3600, because I believe this so much better at preventing sulphation, and in fact rejuvenates the battery. (Must plug myself in some time) When I arrive back from trips now I always do a charge with the CTEK.

The other thing, copied from Spykal, is I have made a lead to go in the cab cigarette lighter socket to charge the cab battery from the CTEK.

It all works well and gives me a versatile system in this area.

John 8)


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## spykal (May 9, 2005)

Hi George

The voltages I quoted were at the stage that the TV Starts to complain and under the load of the TV and freeview box. After resting the battery does come back up to a rested voltage of 12.04/05 indicating that the battery is around 40-50%. The only thing I have not done is check the specific gravity of the electrolyte to get a better idea of the battery condition. The battery I use for the TV is an ordinary vehicle type Lead acid which pre this duty had been used for 18 monthsor so on a car so I can't be doing much wrong, it has lasted over a year now on TV duty (say 60 - 80 nights away). If I had to replace it it is still a relativly cheap way of powering the TV. I am sure I have heard you say that an ordinary Lead acid battery is hard to beat, I agree.

mike


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## fjmike (May 10, 2005)

This thread has thrown up some interesting points . The thing that now concerns me is how to easily / cheaply measure the battery voltage so that I'm not caning it too much


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## spykal (May 9, 2005)

Hi Mike
Get yourself a digital voltmeter:








http://www.maplin.co.uk/module.aspx?ModuleNo=37279&doy=
Maplins do them for £4.99 or often on a special at £2.99.

Then use a voltage chart to check your battery, the voltages only give an indication of the condition but over a period of time/use you will get an idea of how the battery is doing.










If you have the normal "two flat pin type"12 volt connectors in your van you can push the probes of the digital voltmeter directly into these to check the leisure battery.

*Please do not try to use a meter to test any mains electricity (240 volt AC) unless you feel qualified to do so.*

You can find lots of useful info on the web about how to use a meter...one place to start:
http://www.doctronics.co.uk/meter.htm#digital

Mike


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## 88724 (May 9, 2005)

Hi Mike

That chart is for foriegn climes, the electrolyte is altered to account for Higher ambient temperatures. and hence the top line figure is lower.

In the UK a standard Lead acid will be about 12.8 when fully charged, Knock off 10% of charge per 0.1v pretty much as per chart, but with higher starting point.

Only problem with this system is that the voltages should be measured after the battery as sat without charge or discharge for 12 Hours, BUT it will be fairly good if the load isnt high ie say your TV is drawing 3 amps or less, when switched off for 10 mins the reading will be near enough.

What I find with most "auto Cut off's" is that they are way to low to help save the battery


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## spykal (May 9, 2005)

GeorgeTelford said:


> "snipped" Hi Mike
> 
> That chart is for foriegn climes, the electrolyte is altered to account for Higher ambient temperatures. and hence the top line figure is lower.
> 
> What I find with most "auto Cut off's" is that they are way to low to help save the battery


Hi George

Re the figures on the chart ...you may well be right but I have posted this chart as a help to anyone wanting a rough guide to the state of the battery. It has helped me over the last couple of years to come to an understanding of my battery set up and my usage of them. What I suggest is, if anyone is interested in understanding the relationship between the capacity of the battery and its usage then get a meter and work with a voltage chart. Since my batteries are rarely "at rest" for long enough to test as you suggest ...we do use the van a lot so they are either on charge/maintenance or in use most of the time so a pinch of salt has to be taken with my voltage measurements...never the less the use of a digital voltage meter and my chart or your figures or in fact an old scrap pad just to record voltages will give anyone a better understanding of how the battery behaves.

Re the auto cut off: when I bought the Maplin battery Protector that I have I too was worried about what appeared to be a really low cut off voltage. So during a week back in the winter when we were at home I tested it under the conditions I would use it. I connected the TV via the cigar lighter socket to the vehicle battery. It worked just fine cutting off the power to the TV eventually after many hours use. Then without waiting for the battery to stabilise I was able to start the van. I started it several times just to make sure. After a little rest the battery....according to the battery voltage chart, was well within the safe area of the chart. If anyone else wants to use one of these devices I recommend testing it for themselves before using it when camping.

I think when talking about 12 volt power we have to remember that folks vans come in many different sizes, a small camper van with just the one battery to power the vehicle and the habitation should not be compared to a big A Class with a battery bank of several 120 amp/hr batteries. Sometimes batteries will get abused...maybe either through a lack of understanding or just necessity.

I do try to look after my batteries but even so, knowingly I do occasionally abuse them. As I see it they are a "consumable" item and although sensible usage and proper charging can prolong the battery life they still have a finite lifespan. I cant comment on any of the expensive "fancy" batteries but the humble "ordinary" lead acid battery is very good value for money and can and should be replaced cheaply before problems arise.

Mike


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## fjmike (May 10, 2005)

Thanks Gents have purchased my Maplins multimeter (though didn't manage to get it on special)


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## 88790 (May 9, 2005)

Hi Mike, (Spykal) the system and things you use more or less mirror mine as you know, it all seems very straight forward to me to use your chart and a multimeter if necessary. Like you I have one just for the caravan. Which I tend to use probably too much.

I think it is important for Mike and others to realise that what we have put in our posts on this thread is practical, as is, and not theory, which can at times be slightly different when talking about voltages etc.

John 8)


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## solentviews (May 9, 2005)

If you use the CTEK3600 charger do you need to undo the battery caps to vent the battery while charging or can you leave them in place?
thankyou
Ian


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## solentviews (May 9, 2005)

Another question. Can you use the charger whilst on hookup or does it affect the built in charging system?
thankyou again
Ian


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## 88724 (May 9, 2005)

Hi Ian

If its a proper leisure battery there should be vent pipe not caps. certain Models of Ctek are power supplies to but not all, be sure to buy the power supply version if you want to use while on hook up.

Jabber

People often use the word theory badly, what I was telling Spykal is Fact not a theory about whats happening, at a guess that chart is for middle America. IN UK and even northern parts of America the Specific Gravity will be Higher which works better in cooler climes.

Our Batteries would not work well in Hot climes they would overcharge to easily in hot weather. A Uk chart would start at around 12.8 and go down to 11.8 Use the American chart and you will lose on longivity, the Plus point being the good charger, use a good charger and also keep the settled voltage above 12.2 or 12.3 and the battery will last far longer.


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## johnsandywhite (May 9, 2005)

:roll: 8O Then again. Why not fit a B***** battery and charge it however you want with whatever you want and have done with it? Most people do so and are quiter happy with the results. Just my opinion. :roll: :wink:


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## 88790 (May 9, 2005)

No you should not need to remove any battery caps it is just a charger all be it a very sophisticated one. It starts at a higher charge rate and then comes down to a normal level.

I always use mine as a separate entity at home and switch off all things in the caravan whilst it is charging just in case the higher rate could damage any of the electronics, not really likely though. It is not the same as a normal caravan charger which is also a power pack, which I use when on site.

The only reason I use it is to keep my batteries up to scratch, I do not take it away with me.

Hope this helps,

John


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## spykal (May 9, 2005)

Hi George

I do know that in saying that you may not be correct is a bit like waving a red rag at a bull but here goes ...just for the sake of argument. The specific gravity is surely related to the ambient temperature and the state of charge of the battery. As far as I know...( but you may put me right and give me some references to look up) the electrolyte that is used to fill batteries is of the same concentration of sulphuric acid and water the world over...what may differ is the ambient temperature and this will affect the voltage reading at a given state of charge.

The voltage chart I posted came originally from a well known USA web site at:

http://www.ccis.com/home/mnemeth/12volt/12volt.htm
Some interesting info in there but again just another guy trying to be helpful and not necesarily 100% correct...who knows for sure? certainly not me.

The chart was drawn up for an average ambient temperature of around 70 degrees F. I agree maybe a little high for the UK but for my part I am only looking for a practical guide to sensible battery use I am not trying for a degree in Chemistry or Batteryology.

Mike


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## spykal (May 9, 2005)

johnsandywhite said:


> :roll: 8O Then again. Why not fit a B***** battery and charge it however you want with whatever you want and have done with it? Most people do so and are quiter happy with the results. Just my opinion. :roll: :wink:


Hi John

By B***** did you mean BIGGER cos' I can't think of another word that fits in there :lol: The reason that some of us cannot fit in a bigger battery is because..."we aint got that much room".........simple really. I suppose if I bought one of those little trailers I could carry the sort of battery bank that George has in his bus. Truly though I do not have a problem with available 12volt power....We have never run out of it yet :lol:

Mike


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## johnsandywhite (May 9, 2005)

Hi *skycal*. Yes I think I did mean a BIGGER battery ( :wink: ). However, one point I was trying to make was:- Yes It's nice to have a discussion on the merits of this and that way of using and charging batteries. But the majority want a fairly simple example that will work for them. :wink: I don't think there are many Rocket scientists and Physisists who are motorhomer's. They wouldn't need any assistance anyway because they probably wrote the book. Therefore, fit a battery, hook up some means of charging, then enjoy it until you have to replace it in 3 to 4 years time. :wink:


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## 88790 (May 9, 2005)

Hi John, I understand what you mean :wink: but there are some of us that make a hobby of making small changes to our Motor Homes 8O but in doing so do like to make sure it is safe and worthwhile.

Nobody would dispute the fact that Motor homes as they usually come from the manufacturers are well equipped, work well and require few if any extras.

I have added some 25 additions to our Motor Home, but before doing so like to make sure there is some logic for doing so and enjoy discussing with others on here the relative merits of various actions. I am pleased to say that by doing that I have in a number of cases adjusted my original thinking. I also like to think that my experiences have been helpful to others and enabled them to possibly make a decision about their modifications.

In making modifications it is essential to me to ensure that any thing looks as if it was there originally and not an amateurish add on.

Theorietical discussions about electrical topics and plumbing are interesting to some of us and can produce both good hearted banter and in some cases almost fierce comment - the latter is not helpful to anybody.

Oh well back to measuring the Motor Home and trying to decide the size of back box to fit the cycle carrier! :wink: 

John 8) 

Beware the third degree if in the third age!


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## spykal (May 9, 2005)

Hi johnsandywhite

You are just about spot on there John...but it is entertaining to "chew the fat" over things like batteries.....that's what MHF forums are all about isn't it?

Mike


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## johnsandywhite (May 9, 2005)

spykal said:


> Hi johnsandywhite
> 
> You are just about spot on there John...but it is entertaining to "chew the fat" over things like batteries.....that's what MHF forums are all about isn't it?
> 
> Mike


MHF is certainly about chewing the fat. But like the previous diatribes on the correct licensing of a motorhome and the legality of driving it (just as a for instance). There must come a point where all the arguments and opinions have been heard several times over and the discussion must come to an end. As I have mentioned several times in the past (apart from those who have a need to have an 100% accurate fitting and use of an item :? ), people want a fairly straight forward answer that will work for 99.999% of user's. :wink:


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## spykal (May 9, 2005)

Hi Johnsandywhite

Ok but if we all just buttoned our lip whenever a question on an old subject came up newer members would suffer. I try never to say in any of my posts answering questions...."that has been answered before so go away and look it up" this always seems such a negative way to behave in a forum. 

I do take your point about some subjects getting discussed to breaking point but with so many new members coming into the fold there is bound to be some repitition.

I enjoy reading and writing posts and you don't seem to do too bad yourself :wink: so lets just agree that it is a good thing that we all enjoy what is a great way to communicate the fun of owning a Motorhome even if at times it all becomes a bit too much of a good thing :lol: 

Mike


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## johnsandywhite (May 9, 2005)

:hello1: :hello1: :hello1:


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## 88724 (May 9, 2005)

Hi Mike

Quote

As far as I know...( but you may put me right and give me some references to look up) the electrolyte that is used to fill batteries is of the same concentration of sulphuric acid and water the world over...what may differ is the ambient temperature and this will affect the voltage reading at a given state of charge.

End quote

As you say its Temperature that alters the Specific Gravity, the concentration as far as I am aware is the same. Its the make up of the battery that needs to be altered. In Colder Climes its the CCA that is important, in Warmer countries its the RC Reserve capacity. This in turn effects the Top line volatge and spec grav.

Due to the differing plate make up being different the Top line voltage reading will be different.

Link to a far better explaination


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## fjmike (May 10, 2005)

I have installed a110amp/hour battery, have purchased a multimeter. Did a reading with multimeter -12.2 volts. Purchased cheap charger on Ebay, when it arrived put it on the battery using the three pin socket on board. The charger is one of those automatic jobbies with five led lights, trickle,1A, 2A, 4A and 6A.It also has a rocker switch 12v/2a and 12v/6a. So not wanting to cook the battery put it on the lower setting, when connected up 2A led was lit up. Next morning went to check the battery and its still on 2A, I was expecting it to have dropped to 1A or trickle by now. If in doubt RFM (politely translated = read the flaming manual). Oh dear second page says "DO NOT charge batteries smaller than 20ah or larger than 60ah. Now I'm not that good when it comes to electrics 8O but I thought a charger was a charger, so do I have to go and get a bigger charger or will this one be OK on the higher setting :?: .

tech spec of charger 
Input: 23/240V AC 50Hz
Output: 12V DC 402 (6A rms)
Would appreciate some knowledgeable input Thanks


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## 88790 (May 9, 2005)

Hi Mike,

a voltage of 12.2 probably means that you have used 40% or so of your 110 amp/hr battery, that is about 44 amp/hr. So if you are charging at 2amp/hr that would take 22 hrs which is a lot longer than you stated, I think.

Go back and put it on 6amp and let it charge and then you should see the charge rate lower over night. You need have no fear 6amp will not damage your battery.

I am sure the charger you have just got will do the job, just takes longer!

The CTEK 3600 would also be OK for you and do your Motor Bike battery. I know they are more expensive but should be the only one you ever need, they can be left on indefinitely.

John :wink:


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## fjmike (May 10, 2005)

Thanks for the input jabber. I went and put it on the 6A setting and left it overnight, looked at it this morning and it had the 2A led stil lit. Left it to rest after charging as George recommended , just gone out to take a reading and its 12.95 volts now. I suspect that the charger automatically drops the charge amps as the battery gets more charge so that the last bit takes for ever to get in(this is based on no knowledge what so ever just good guess work)


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## 88724 (May 9, 2005)

Hi Mike

If that reading is still there after 12 Hours then that your top line figure assume every .1 Volt drop (settled) is a 10% drop in Ah this would have a 50% discharge figure of 12.4 Volts, thats pretty much what I would expect in UK battery readings.

Re the 6 Amp thing, its always good to have 10% of batteries ah Capacity as a charger ie 110 ah battery 10 AMp Charger, I did some pretty serious checking when installing a 1100 Ah battery bank that the 30A charger would be ok, it is Obviously the bank would charge quicker with 110 A charger but my 30A will charge the batteries from 50 % back to full in under one day on hook up and it does that admirably and with no adverse effects. 

The problem with some cheaper and smaller chargers is that they could not cope with going balls out for the extra time required, Sterling or any Good make of switch mode charger should have no probs.


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## 88790 (May 9, 2005)

That is a good reading and indicates the battery is probably fully charged.

You are right in most chargers the charge rate decreases as the battery becomes fully charged.

Mike's (Spykal), table is worth printing out and having handy, it will give you a quick idea of the state of your battery, but I expect you have already got that.

All the best,

John 8)


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## 88724 (May 9, 2005)

Hi Jabber

As I mentioned earlier and as demonstrated by Mikes settled Voltage reading 12.95 Volts is way over the foriegn battery chart (probably american) and will throw out the ah left to a considerable degree

If I am right (and Mikes top line fgure supports what I said earlier) then that chart will be AT least 20% OUT 

IE 12.2 VOLTS could be down to 30% capacity left


A rough guide is get your top line figure 12.95 in Mikes case and for every .1 drop in voltage thats 10% of capacity used.


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## spykal (May 9, 2005)

Hi

I wonder whether Fjmike's battery will show a steady settled voltage of 12.95 after a longer settlement period, or a load applied for a few moments to remove any surface charge.......more like 12.7ish which still may give a 10% error on the chart so as George says if you measure the voltage from the settled voltage .1 of a volt drop equals about a 10% drop in charge. Using voltages to give an indication of charge is really only to be used as a guide and my experience seems to indicate that each and every battery will have its own pattern of discharge....I have long since given up trying to understand why, I just know it happens and take it into account.

mike


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## johnsandywhite (May 9, 2005)

8O If it works? Don't fix it. :roll:


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## spykal (May 9, 2005)

johnsandywhite said:


> 8O If it works? Don't fix it. :roll:


Very droll but very true.

mike


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## 88724 (May 9, 2005)

Hi Mike

FJMike said after settled as per "George" so if its still there after 12 hours its not surface charge, the other way to remove surface charge is to apply a small load for 30 secs than leave for a few mins and measure (its not as good as waiting, but waiting is long winded)

What I found is that my batteries stayed at 12.93 ish after 12 hours, if you are going down to a voltage while under load then you can go below the chart ie if you ran till say 12.2 V while under load it would rise again slowly when rested.

Its only ever a rough guide due to the fact that the 12 hour waiting period to resettle the battery for an accurate measurement is way to long for use when out and about, that is why I invested in a battery monitor which shows all ampage leaving the battery and allows for charger inefficiencies when recharging, ie it resets the zero point aftera good charge. without a lab calculating the discharge rates ambient temperature etc total accuracy is not really possible.


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## fjmike (May 10, 2005)

Just for the record I have just taken another reading , this is spot on 12 hours since taking it off charge(I work swing shifts) and the reading is 12..92. No load has been put on the battery since taking it off charge. Once again thankyou for all your input I have learned quite a bit from this thread


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