Make sure that both batteries are the same, the same worn out and charged to the same extent.If it is not, by their serial or parallel connection of refuse.
To connect two batteries in series, connect the negative pole of the first of them with a positive second.The terminals remain free (the positive pole of the first and second negative), do not connect to each other in any case, otherwise there is a short circuit.Since they remove stress has doubled.
To connect two batteries in parallel, take two diodes capable of indefinitely withstand the load current.The negative pole of the battery connected together.The positive pole of one battery is connected to the anode of the first diode and the other - with the anode of the second diode.The cathodes of diodes connecte
d together.Connect the load to the negative pole of the battery connection point cons, positive - to the connection point of the cathodes of the diodes.This arrangement will give the same current in two times longer than a single battery.But its load twice as large current is impossible, because there is always open only one of the diodes.
Connect batteries in parallel without diodes are not recommended because they will be discharged through each other.Do this only with the full confidence that they are equally charged and worn.But with such a construction can remove twice as much current.
before to charge the battery, disassemble design.Charge them individually.This will significantly slow down the deterioration of the battery.If the batteries are connected in parallel with diodes to charge them without disassembling the structure, moreover, it is not impossible.
Once charging is complete, gather the design back and connect the load.Continue the use of batteries.