Burstner Motorhome Leisure Batteries

[Merlin53]

Hi Folks,
We have just purchased a motorhome and hope to connect in parallel, the leisure battery from our PE caravan to the motorhome battery. (Both batteries are 12v). The motorhome has a solar panel which charges the leisure battery in the M/home. We are hoping that connecting an additional battery, that it will give us extra length in power when we are off grid.
Any comments would be really appreciated, many thanks,

 

[ProfJohnL]

There are a few things that need to checked.

Its not advisable to simply parallel connect two batteries of different models or condition such as age or usage. Differences in the condition of the cells can cause some problems with currents running between the batteries until the terminal voltages match.

Different batteries may have different charging characteristics which might cause problems.

Ideally both batteries should be exactly the same (make model, and amount of usage).

As the motor home already has a solar power system, it might already have a multi-battery charge controller that can be configured to separately mange two batteries. Its worth checking.

 

[Merlin53]

There are a few things that need to checked.

Its not advisable to simply parallel connect two batteries of different models or condition such as age or usage. Differences in the condition of the cells can cause some problems with currents running between the batteries until the terminal voltages match.

Different batteries may have different charging characteristics which might cause problems.

Ideally both batteries should be exactly the same (make model, and amount of usage).

As the motor home already has a solar power system, it might already have a multi-battery charge controller that can be configured to separately mange two batteries. Its worth checking.

Hi Prof,

Thanks for the response, I assumed that the batteries once connected, would 'settle down' with the same voltage, and the total connected system would even its self out very quickly. There is a space for another battery to be placed along side the existing leisure battery, so it therefore must be doable. The solar system is the only charging way the leisure battery is charged.
Interested to see if any other M/homers have connected up another leisure battery and have any comments. (Not sure about the solar controller having a another system to control another battery separately).

 

[ProfJohnL]

Hi Prof,

Thanks for the response, I assumed that the batteries once connected, would 'settle down' with the same voltage, and the total connected system would even its self out very quickly. There is a space for another battery to be placed along side the existing leisure battery, so it therefore must be doable. The solar system is the only charging way the leisure battery is charged.
Interested to see if any other M/homers have connected up another leisure battery and have any comments. (Not sure about the solar controller having a another system to control another battery separately).

Yes the batteries will assume the same voltage, but until they have equalised some quite heavy currents can flow between them. And then there is the problem that if you mix an old well used battery with a relatively new one or one of differnt design, there will be unequal charges on them and that will impede the total battery charge capacities. Its not advised.