ebike battery

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.


by bishy
August 27, 2018

2 Answers

Answer by mikerogerswsm

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

+1 vote
by mikerogerswsm
August 27, 2018

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

by mikerogerswsm
August 27, 2018

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.

by bishy
August 28, 2018

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.

by mikerogerswsm
August 28, 2018

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.

by mikerogerswsm
August 28, 2018

Answer by Olias

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.

+1 vote
by Olias
August 28, 2018

Your Answer

You must log in or create an account (free!) to answer a question.

Log in Create an account

Go Ad-Free. Activate your CircuitLab membership. No more ads. Save unlimited circuits. Run unlimited simulations.

Search Questions & Answers

Ask a Question

Anyone can ask a question.

Did you already search (see above) to see if a similar question has already been answered? If you can't find the answer, you may ask a question.

About This Site

CircuitLab's Q&A site is a FREE questions and answers forum for electronics and electrical engineering students, hobbyists, and professionals.

We encourage you to use our built-in schematic & simulation software to add more detail to your questions and answers.

Acceptable Questions:

  • Concept or theory questions
  • Practical engineering questions
  • “Homework” questions
  • Software/hardware intersection
  • Best practices
  • Design choices & component selection
  • Troubleshooting

Unacceptable Questions:

  • Non-English language content
  • Non-question discussion
  • Non-electronics questions
  • Vendor-specific topics
  • Pure software questions
  • CircuitLab software support

Please respect that there are both seasoned experts and total newbies here: please be nice, be constructive, and be specific!

About CircuitLab

CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.