Lead Acid Batteries - different types ?

[Wp100]

Hi,

Have a simple diy ups, battery, relay, inverter that works well, powered by a 80ah 12v Leisure battery.

Also now have 65ah 12v Car battery thats part used, so wondered if I can parallel the two to get a longer backup time or will connecting these two different types of battery cause a problem ? - charging is currently done manually.

 

[BusyBee]

I have no real experience with paralleling high capacity batteries, but it can be a problem if the two batteries are somewhat different in their terminal voltages (due to age etc). One way is to use suitable current capacity rectifier diodes in each hot lead such that any differential will be stopped from causing problems (eg one battery attempting to charge the other). This obviously results in a volt drop due to the diode drop. Whether this causes a problem depends upon your circuity. Charging would need more thinking of too.

Tracy

 

[rjenkinsgb]

Car starter batteries have rather different plate construction to deep-cycle / leisure batteries and cannot stand being fully discharged and recharged more than a very few times.

You are better keeping it for it's proper use or selling it and buying another similar rated deep cycle type as your present one; the car one will just be wrecked and lose capacity very quickly.