# your battery problems...



## spatz1 (May 19, 2011)

if this is a basic split charge circuit....

http://screencast.com/t/coI3Pa0R

When both leisure and engine battery are conected to charge by the relay in normal split charge mode....

Two differing Ah size batteries are in effect paralleled that are also of different age and condition...

This poses the question...

why do people go to so much trouble or considder it necessary to renew leisure batteries as a pair and insist they be of equal AH...?

Anyone able to supply a diffinative answer because i cant see any difference between conecting engine and hab in parallel to charge or just doing the same with two leisure batteries of differing sizes...


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## 747 (Oct 2, 2009)

You are not discharging them in parallel, just putting power in. :wink:


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## denisl (Mar 16, 2011)

In the circuit shown, if either the engine battery or the van battery are failing, you are going to know about it and would be able to replace that battery.

If you have 2 van batteries in parallel and one is older and failing, you may not know, and you would be losing some of the capacity of the good battery via the failing one. If they are both the same age, they should (hopefully) deteriorate together and be replaced together.

I doubt there is too much importance in having the batteries exactly the same size, although I guess any difference between the two batteries (type, make, size) may cause them to age at different rates.


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## DABurleigh (May 9, 2005)

And if you had superconducting wires linking the batteries you would be right. Or rather, the same problem would be experienced as with mismatched parallel leisure batteries - that the charge current and discharge current would be unequal between the batteries, according to the different batteries' effective internal resistances at each point in the cycle.

But insert resistance due to the cable run, and in practice this concern goes away, especially as the leisure battery at the end of the resistance run from the "charger" here will be separately charged by a mains charger periodically.

Dave


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## sallytrafic (Jan 17, 2006)

I'm glad to say I agree with Dave. 


and


Hopefully your two (or more) habitation batteries are closely coupled with short thick wires.


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## eddievanbitz (May 1, 2005)

And GEL batteries in parallel with Wet 8O !

:lol: 

Eddie


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## UncleNorm (May 1, 2005)

eddievanbitz said:


> And GEL batteries in parallel with Wet 8O !
> 
> :lol:
> 
> Eddie


Behave yourself, Eddie! This is a serious thread! :roll: :wink: :lol:

I have 2 GEL leisure batteries - one at 85 AH supplied with Our Coral; one at 104 AH bought a few months later. The second was installed by the late Peter, Humber-Traveller, who was very knowledgeable and a very thorough, immaculately neat worker.

Did Peter do anything wrong or is my system still OK after 4+ years?


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## eddievanbitz (May 1, 2005)

Certain rules have to be suspended in favour of "If it ain't broke don't fix it"

If it has been fine for four years, and is working fine, it's great!

Eddie


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