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Hi, I have an electric bike but the range is limited by the power in its battery. I can buy a second battery to use when the first runs flat, but they are very expensive. If I buy another battery (different, cheaper make) of similar power (24v, 10Ah) and plug it into the battery charge connector (when installed battery is low), would it charge the battery ok or could it 'fry' some electronics? Would it work and extend the range of my bike?

Thanks for your help.

Bishy

If it's the same voltage and the same Ah that should be okay.

Second thoughts, could you tell us a little more about what you propose to do, with a diagram if possible?

Thanks very much for the reply and the answer I had hoped for. Can’t really give a diagram as it’s just a simple solution- a bit like plugging a ‘power monkey‘ or battery pack into a mobile phone that is running low on power to give a boost.

I don't know enough about what you propose to do. The battery rating is okay, and if you remove the flat battery before adding the new one in the same place it will work okay. Do not connect two batteries in parallel if they differ in voltage. Do not connect the new battery in any other way.

I don't know what you mean by a power monkey. Your mobile phone battery needs careful charging from the approved charger to ensure that it is supplied with the correct current and voltage.

Firstly there is the question whether the batteries are of the same chemistry eg Lead Acid, Lithium Ferric Phosphate, LMO, etc. If they are of similar chemistry they will share charge in use. However they may be very poor/ slow still at transferring charge and at best half would be transferred.
Generally to charge a battery properly the voltage needs to be elevated above the float or operating voltage by an amount specific to the battery chemistry. Lastly there is a question whether there is anything between the charge port and the target battery (regulator, diode etc), I would expect not but could throw another spanner in the works. In short if your extra battery is the same chemistry and you can leave it connected, it should contribute fairly well. If you want it to quickly charge the original battery to any appreciable amount you are probably out of luck unless you add some electronics to boost it enough and in the right way to charge the chemistry in use.