# battery advice please



## whistlinggypsy (May 1, 2005)

I had a duff 110amp leisure battery ( i have 2, 18 month old ) had it checked whilst at B/hills and it was replaced under warranty. 

They wanted £120 to replace the second battery so as i had 2 brand new ones (as recommended on here) but i refused the offer as it seemed expensive and i can get one ( same make/model ) for £70 near home and fit it myself eventually. 

The question i need answering is how long will i have before i have to change the older battery before it drags the new one down to its condition, cannot do it for a while myself as i have my right hand in a cast. 

TIA 

Bob


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## Ginamo (Sep 5, 2006)

Bob,

I'm not sure that the time can be calculated but if they are wired in parallel as they should be I think performance wise it will be very quick.
There will be others along with more knowledge. Best advice is to get someone else to change it for you.
Hope the arm heals quickly.

Alec


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## whistlinggypsy (May 1, 2005)

Ta Alec, i think you may be right but i will wait a bit longer and see if any battery brains come along.

I have a 150w solar panel but i doubt it is putting anything in at the moment as it is in a barn with no outside light available.

Bob


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## peedee (May 10, 2005)

If I understand you correctly you are now running on one new one in parallel with and 18month old one. 

The way I see it you have two options, keep any eye on the specific gravities of both batteries, especially the older one. Make sure you are getting good readings from each cell. If you are not then disconnect the old battery until you can replace it. You could do this anyway and just run on the one battery but 18 months is not long in the life of a battery and providing you keep a regular eye on the SGs, you may not need a new second battery for sometime. 

That is what I would do and indeed have practised in the past.

peedee


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## whistlinggypsy (May 1, 2005)

Thanks peedee, i shall certainly look at the SGs on both batteries and disconnect if there looks like problem. 

If the SGs are indeed close in both batteries does that mean they will continue like that for some length of time or will indeed the older one bring down the newer one eventually. 


Bob


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## DABurleigh (May 9, 2005)

It means no more than "haven't knackered them yet" :-(

Of course, in time, all the cells in both batteries will be knackered by the mismatched batteries.

Dave


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## peedee (May 10, 2005)

If you have good SGs in all cells then I see no reason why they should not provided power until one of them packs up. Given that the older one has been used for 18 months it should be the first to degrade but I would not bank on it.

Even if you had installed two brand new batteries it is always wise to monitor the SGs in parallel configurations. It really is the only way you can detect one of them degrading. If you don't do this then it is quite possible the good battery will mask the failing battery and be dragged down so that you end up with a very much reduced capacity.

peedee


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## whistlinggypsy (May 1, 2005)

Thank you all, i now have the information i was looking for.

Bob


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## johng1974 (Jan 17, 2007)

I have a similar circumstance...

its not just that I am tight  

but i have a good 110 and a seemingly good 90 Ah

I want to connect them in parallel, and do a voltage test of them together or apart to keep an eye on them... I can do that no problems, but from the threads it seems SG may be a more useful check..
not sure checking seperate or together voltages will really tell me much , having this system would also mean I could isolate and use either battery if I needed to.. yet again, dont know if that is worth it or not....

John


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## spykal (May 9, 2005)

Hi Bob

From reading a quite a bit about this there does seem to be just one right way to do it and that is to use "matched" batteries .... but what if that is not possible, what then? Well as far as I can establish, again from reading about other folks experiences, so this is hearsay......the worst scenario is that the whole battery bank will last about as long as the oldest battery would have lasted. 

Ok this is not a very scientific answer but it is a practical one that will allow you to put a price on the job. I am not going to try to work out the exact costs, too difficult ...so i'll leave that to you :wink: but it goes something like this....... 1 new battery =£70 and may only last 12- 18 months wired in parallel to an older one ..... 2 new batteries = £140 should last 3 years + if you are lucky..... or something like that :lol: 

Luck will play a big part too... as one bad cell in either battery will drag down the whole battery bank if they are connected in parallel.


You also have the additional problem in that you have already bought one new battery.... to obtain another "matched" battery will now be difficult... best you can acheive is another simelar one. To match them you really need to buy them from the same supplier at the same time and from the same production batch.

I think you are left with no choice but to do as suggested by Peedee :wink: 

I dont think this helps really, does it  


Mike


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## Ginamo (Sep 5, 2006)

John,

I don't believe that mismatched ah ratings in parallel is a good thing to do. I guess 90ah will drag 110ah down but I think further input from others would help.

Alec


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## johng1974 (Jan 17, 2007)

thanks Alec..

in which case....

I can use both seperatly, keep the 90 as a reserve when the 110 runds down.. just need a relay switch between them ....


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## whistlinggypsy (May 1, 2005)

Mike, thanks for your input and i understand your reckoning, actually its the same as dab's but his response is short and to the point as usual ( i am a silly person not knowing that :roll: ) i have to now make my mind up which route to take as the new battery has been in 7 days now and had a 128 mile charge through them both returning home. 

I doubt very much i would get a matching one now so i have to either suck it and see, using peedee's solution, or figure out the expense and possible early failure of one or both batteries because they are not matching pair if i purchase another new 110ah, and i think after some time perusing it i will go the peedee route. 

Thanks for everyone's input. 

Bob


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## whistlinggypsy (May 1, 2005)

Today following some advice from peedee i have been to several places too try and obtain a turkey baster Specific Gravity monitor and had no success in 5 stores until i went into autopoint store were the assistant pointed out that they are no longer used because of health and safety reasons. 

Now i see his point, drawing acids from the battery could in effect cause mild irritation to the skin or damage painted surfaces if spilt, he phoned around his other depots and found one in salford that is a 2yr. old stock item and i have persuaded him too let me have it. 

So how would one find out the SG of a battery unless you took it to a battery supplier, and if you wanted to keep checking it every once in a while it would be a pain in the butt. 

Is there something else that will do the same thing? 

Bob


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## peedee (May 10, 2005)

If this is the case I am gob smacked 8O Its almost like saying, "We cannot sell you a screw driver because you might slip and do yourself and injury!" Halfords and the Motorists Centres used to have them. 

peedee


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## whistlinggypsy (May 1, 2005)

peedee, halfords was my first port of call, never stocked them for ages was their response. I went too 3 more motorist stores before i found one.

God knows why you cannot buy something so simple but yet i could buy a chainsaw anywhere.

Funnyold world isn't it :wink: 

bob


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## DABurleigh (May 9, 2005)

For anyone who would like to let their postie do the walking:

http://www.diytools.co.uk/diy/Main/sp-2-4561-29139-draper-battery-hydrometer.asp

http://www.abbeypowertools.co.uk/ba...sters-and-accessorie/showitem-8482-61792.aspx

http://www.prideofthefleet.org.uk/battery-hydrometer-p-696.html

http://www.tayna.co.uk/catalog/529/0/Durite-Products-Battery-Hydrometers-page1.html

Dave


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## whistlinggypsy (May 1, 2005)

Dave, you are a dream what would we numpties do without you, thanks for the info

Bob


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## whistlinggypsy (May 1, 2005)

OK i have been and got a SG battery tester, and went down the m/h storage to test the two batteries. 

Now for the numpties like me that no nowt about Specific Gravity what does the following mean in relation to my original post ( i am dreading the answers from someone:? ) 

The battery monitor read 12.5, 

the new 8 day old battery read 128 SG i assume this represents 1.280 SG, 

the second 18mth old battery read 1.250 SG 

and as 1.150 SG was the lowest reading on the gauge RED 

and the highest reading on the gauge is 1.300 SG full GREEN 

so please can someone tell if the difference between the 2 batteries is significant in anyway.


Bob


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## Ginamo (Sep 5, 2006)

Hi Bob,
Both of your batteries are registering charged. The important thing is that all six cells in a battery register the same sg, if one is significantly lower that the others this is an indication that the cell is faulty and dragging the whole battery down (weakest link and all that). As your hydrometer has green and red markings be guided by that. Any battery cell showing 1.250sg would be considered to be fully charged.
Are you coupling unequal a/h batteries in parallel or using them individually?
I believe that is more of a problem regarding performance.

Alec


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## whistlinggypsy (May 1, 2005)

Alec, yes all 6 cells in each battery register the same e.g. 

6 X 1.280 SG and 6 X 1.250 SG and they are coupled in parallel and both are 

110AH, the only difference is the age of the two of them. 

Want i don't know is what the difference between the two figures means, does it mean nothing or will the older battery drag the newer one down to the 1.250SG and if so does that really matter in the long term. 

Hopefully at the end of this post i will have learnt a little about testing the Specific Gravity of a battery  

Bob


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## johng1974 (Jan 17, 2007)

a little bit here Bob, sorry doesn't answer your question on 'dragging down'

Specific gravity

John


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## Ginamo (Sep 5, 2006)

Bob,
Scary stuff from Johng1974 link.
Both your batteries appear to be in good condition, I think run them and see what happens. Nothing to lose and experience to gain. Check them regularly and you should see a problem coming before it bites you.
Best I can come up with, good luck. Results could be interesting to a lot of others.
Alec


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## whistlinggypsy (May 1, 2005)

Alec, it frightened me as to how much i didn't know (and still don't) when i opened johng1974 post.

Your lastest advice was the way i was going to go, a suck it and see, i will check then often and keep a record it will help me understand SGs and maybe help someone else.

Thanks 

Bob


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## DABurleigh (May 9, 2005)

This MHF post may help:
http://www.motorhomefacts.com/ftopicp-82120.html#82120

What matters is the "effective internal resistance" of each battery as it is charged, and which changes during the charge cycle. This in turn is a complex mix of the battery design, production variations, age, and how it has been used or abused. Implicitly, but not necessarily explicitly, capacity, too. If the batteries have different "histories", including in production, then there is a good chance the internal resistances of two batteries charging in parallel will be different, so their charging currents will be different. Typically, this means one will be overcharged while the other is undercharged when under charge, and will have circulating currents to equalise the terminal voltages when off charge. In time, this is bad news for both batteries :-(

The SG check under such a scenario is merely that. Think of it as the equivalent of a man falling down a skyscraper, counting windows/floors, and yelling "OK so far!".

Dave


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## whistlinggypsy (May 1, 2005)

Dave, i'm just passing the 42nd floor and all is well so far, looking down i can see an uncertain future but that's life. 

Seriously though thanks for the link and i now understand a bit more about battery maintenance than i did at the first post, onwards and upwards i think is the way to go. 

Bob


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## tramp (May 25, 2005)

*batteries*

hi all, 
reference batteries all makes of cheap lead acid batts are for the lesiure industry only and have approx max 300 cycles- thats 300 full discharge and recharge before dead :roll: at 110amps thats only 50amps per batt max. Either keep reciept and exchange when 11 mnths old for new ones- dishonest but works 

or try "power batteries "on ebay they are a good company that sell new gel/agm batts basically deep discharge and fast recharge we paid £150 for one 250amp it does 900 discharge at 75% capasity so is better value than lad acid as it does not need a vent tube being as its sealed,but its a huge battery

tramp


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