Leisure battery question

B

bazzateer

0
The leisure battery that Peggy came with was flat as a pancake. I replaced it with a nearly new one I got last year for another, now abandoned, purpose. I've checked the twin-charging system etc and it's all as it should be.

I put the old battery on trickle charge and left it to see if it was still serviceable. After about 4 days it was fully charged. I have let it stand for about a week now and have checked the voltage regularly and it seems to be holding 12.5 volts quite happily. So I now have two good leisure batteries.

My question is this: Is there any benefit in connecting both batteries in parallel? If I'm right this should give more oomph to the battery set-up while still maintaining 12v (essentially like having a much bigger single battery) as opposed to in series which would give 24v. Will the charging system still work OK?
I'm not bothered about the logistics of locating a second battery or the connections thenselves as that is all within my abilities.

I'm just concerned that I might knacker the charging system or some other part of the electrics.

BAZROCKS.jpg
If I told you I was a pathological liar, would you believe me?
Peggy's got an MOT !!! (not a lie)
 
Our narrowboat used to have four batteries served from one alternator (with split charging), one for starting and three leisure batteries connected in parallel. With the engine running for about eight hours a day, this was adequate, but we ultimately changed it to a two alternater set-up.

I am sure that some of the more technically competant members will provide some advice, but I would have thought that if your alternator has sufficient capacity, you should be ok.

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'I intend to live forever - so far, so good'
 
Once both are fully charged there should be little draw on the alternator anyway. I'd only have them charging on a long run so hopefully should be fine. both batteries are relatively small for leisure types so both together is probably equivalent to one of the really big ones.

BAZROCKS.jpg
If I told you I was a pathological liar, would you believe me?
Peggy's got an MOT !!! (not a lie)
 
I run with 3 batteries. 1 for starting and I have a switcher set up so as I can run the other 2 batteries in parallel or series. IMHO Its also worth changing to an 80 amp alternator if you plan on running laptop chargers etc.

Cheers
Jules

RatSport www.ratsport.co.uk
 
the benefits of a parallel set up is that the drain will be shared and therefore voltage drop will be slower giving a more stable 12v for longer - the obvious drawback is that the batteries will take longer to charge - with Kirchoffs law, if the batteries have the same resistance then the charging current will be split equally between them which can double the charging time on a fixed amp charge - however the slower charge on a wet lead acid battery will reduce erosion of the battery plates due to less hydrogen bubbles being produced thus increasing the overall battery life. Also with the parallel system if one battery is slightly better than the other the charging can cope with this. Initially both batterys will charge at the same rate. As the better one reaches its full charge it draws less current and slows the charge rate as it approaches max. This means the good battery is drawing less of the total charging current donating the remainder to the slower battery - this increase of current will speed up the charge rate of the slower battery towards the end so they will both end up fully charged at roughly the same time

The Dog is on its way....
 
I used gel batteries as (unlike a caravan or modern camper) there isn't a separately vented compartment and I didnt like the idea of H2 leakage.

Cheers
Jules

RatSport www.ratsport.co.uk
 
All lead acid batteries will give off hydrogen if charged too agressively, the gel ones just stop the acid sloshing about and makes them easier to handle. I believe even sealed ones are not gas tight - under normal circumstances the hydrogen amount produced is small (hydrogen is only explosive over 6% in air)however keeping in a fairly gastight compartment may be an issue over a long period of time - bear in mind hydrogen will leak through tiny gaps so build up is negligible in 99.9999999999% of cases so dont worry about it. We use pure Hydrogen in our power station to cool the 11kv generators and they havent gone bang...........yet

The Dog is on its way....
 
Baz you want to get yourself a isuzu alternator on there. This is what i have on mine its 130amps you will only need one lesure battery on her think of the weight!!
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The standard alternator seems fine for the main and leisure batteries. You could be right about the weight though, especially when towing the Imp!

BAZROCKS.jpg
If I told you I was a pathological liar, would you believe me?
Peggy's got an MOT !!! (not a lie)
 
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