a question about 12V batteries in series

[tonycarguy]

I have two lead acid 12V batteries. One is significantly larger (has more capacity). If I hook up these two in series to make a battery pack, then what happens when...

1) ...the battery pack is used (discharged)? Would both batteries end up at (say) 60% charged state, or would the smaller battery be at 40% and the larger one at 80%?

2) ...the battery pack is charged with a 24V charger? Will each battery be adequately charged?

this is for an electric lawn mower, if it matters

 

[Captain_Klink]

smaller 40, larger 80. eventually smaller one would be depleted, larger one would still have a charge, but not be able to do anything

no, once the smaller is charged, this will prevent the larger one from charging

the batteries should be the same type, and be of the same condition.

 

[chevrofreak]

If you drain them far enough, the smaller battery will get reverse charged, and likely explode.

Never a good idea to mix two different size batteries.

 

[oilyriser]

Put them in parallel and get some EE experience building a switched capacitor voltage doubler.

 

[labman]

If you already have the batteries, it will be like having 2 small ones. Buying one larger one is more likely to cause problems as explained above than give you more capacity. Buying a smaller one will give you its capacity.

 

[ksJoe]

Originally Posted By: chevrofreak
If you drain them far enough, the smaller battery will get reverse charged, and likely explode.


That sounds like a project for the 4th of July.