batteries

erehwon · Member

batteries

DeBe · Guru

Hi Erehwon. Mutch better to use one battery, with 2 batterys if one gets a faulty cell it will pull the other one down, if this happens then if you replace the faulty one you will have 2 unmatched batterys not a good situation. Cheers Daryl

jimricho · Guru

My experience has been that operating two "parallel" connected batteries will shorten their life. That includes identical types despite the claims of some battery suppliers. Take DeBe's advice and go for the 120 ah.

Peter_n_Margaret · Guru

DeBe wrote:

Hi Erehwon. Mutch better to use one battery, with 2 batterys if one gets a faulty cell it will pull the other one down, if this happens then if you replace the faulty one you will have 2 unmatched batterys not a good situation. Cheers Daryl

One big battery is identical electrically to 2 small ones in parallel.
All cells are 2V in both big batteries and small batteries.
If you lose a cell, you loose the battery.
If you have 2 batteries and identify a crook cell you can continue with the one battery left.
If you have one battery and loose a cell, you have zip left.
One big battery will usually be cheaper than 2 small ones.
One big battery needs less cables than 2 small ones.
2 small batteries may be easier to install than one big one.

Do what suits your circumstance best.....

Cheers,
Peter

-- Edited by Peter_n_Margaret on Tuesday 16th of March 2010 08:56:18 PM

PeterD · Guru

The biggest problem with parallel batteries is that people don't wire them properly. You may not think that the resistance in the cables connecting the batteries matters. It does, no matter how small the resistance is. The internal resistances of the batteries is also small so small external resistances are significant when you are paralleling batteries.

If you are going to parallel 2 batteries then interconnect them with identical cables. Then connect your system to the positive of one battery and the negative battery. If you connect in this way I think you can find equal arguments for both parallel and series connections

If you are going to parallel 3 or more batteries then make all the straps as close as identical as possible. Again connect your system to the outside batteries (one lead to each) and connect nothing to the middle batteries at all.

However I agree with an earlier reply. If you can fit one 110 to 120 AH battery in then you will be much better off.

jimricho · Guru

My comment on permanently connecting batteries in parallel is based on first hand experience. Having been caught out I replaced the batteries with two series wired 6 volt batteries. The batteries were on permanent float charge.

Peter_n_Margaret · Guru

PeterD wrote:
The biggest problem with parallel batteries is that people don't wire them properly.

I have had 5 @ 120Ahr AGMs in parallel for 5 years.
They are wired via a 'star' pattern (each battery +ve and -ve terminal is wired to the same common +ve and -ve point).

Every wire is identical in length and 35mm2 cable.

This method is quite successful.

Cheers,
Peter

erehwon · Member

Thanks to all of you who replied will go with the single AGM

PeterD · Guru

Peter_n_Margaret wrote:

PeterD wrote:
The biggest problem with parallel batteries is that people don't wire them properly.
I have had 5 @ 120Ahr AGMs in parallel for 5 years.
They are wired via a 'star' pattern (each battery +ve and -ve terminal is wired to the same common +ve and -ve point).

Every wire is identical in length and 35mm2 cable.

This method is quite successful.

Cheers,
Peter

Yes you have achieved equal paths. You just used a little more complicated way of achieving it.