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External e-bike battery information on reverse current handling

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kcsaba:
Hi dear community!

I have an electric scooter (xiaomi mi 365), and i would like to extend it's range. I thought of external e-bike batteries,
because they have a case and a charger, so i could just switch between the original and the external battery when needed.

The only problem i have is that i can't seem to find a pack that has a correct datasheet, from which i would be able to know if it can handle reverse current on the discharge port. Because my scooter does regenerative braking, and it would supply current backwards on the discharge port when i brake.

So can you please advise me what to do, how to solve this?

I would like to solve this the easiest way possible.

(I know of solutions that are common, e.g. firmware patching, or just putting the battery paralell, but i think they are nasty, and would like to avoid them.)

Thank you!

NiHaoMike:
Just connecting the batteries in parallel is fine as long as you let them equalize voltage first by leaving them connected through some resistance (e.g. an incandescent light bulb) until they're more or less the same voltage.

MosherIV:
Look at the charge specifications for regenerative braking. It is after all an instant change from discharge to charge.

The battery pack BMS should really handle this.

One tricky scenario is what happens when the battery is 100% SOC (full) and you go down a hill and you use regen braking ?
In a car (or lorry in my case) where does the charge current go? (Not into the battery, that would be very bad)

NiHaoMike:

--- Quote from: MosherIV on June 18, 2019, 06:55:32 am ---One tricky scenario is what happens when the battery is 100% SOC (full) and you go down a hill and you use regen braking ?
In a car (or lorry in my case) where does the charge current go? (Not into the battery, that would be very bad)

--- End quote ---
The actual charge level at "100%" should be more like 80% in order to extend lifetime. Also not that difficult to adjust charge level based on altitude.

In a car, one way to burn up excess energy is to run the heater and A/C at the same time. On a bike, I suppose you could turn on the headlight?

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