Battery connections + charging one battery with another

[Stu Summer]

I have a delivery-style ebike with the the drop-in, behind the seatpost, 36v battery like this: https://www.ebikes.ca/shop/electric-bicycle-parts/batteries/b3619lim-v-ez.html. It has a XLR charge port (female.)

To expand my range, can I take some extra parallel 36v hoverboard batteries (which I have) with xt60's and connect them directly to the drop-in battery charge port using a male xt60-male XLR adapter? I have made this adapter but am afraid to connect them and ruin the drop-in battery.

If I do this, is it better for the batteries to be connected throughout the trip or can the hoverboard batteries be used to charge the drop-in battery after it is depleted?

Thanks for your help!

 

[kdog]

NO! Don't do that. If you plug a charged 36v battery into the charging port of a depleted one (or even with more than about 0.5v diff) you will get massive currents that instantly fry whatever the weakest link is. Hopefully a charging fuse , but most likely your bms as well. If nothing fuses open then you have a fire on your hands.
Chargers have inbuilt current limiting circuitry to limit current...you will be relying on IR of the battery, which is very low leading to hundreds of amps.
Edit...spelling.

 

[Stu Summer]

kdog, THANK YOU SO MUCH!!!!! I guess we'll just have to travel with a charger and or break down and buy another battery.

Thank the lord for Endless Sphere, too.

Stu

 

[Hwy89]

If you can locate the battery wires between the battery and controller you could splice in a cable with a connector to match your hover board battery. Then AFTER REMOVING THE MAIN BATTERY you could safely plug in your hover board battery. Or if you verify that both batteries are at the same voltage you could use them in parallel.

 

[john61ct]

A. Best of all is to start with all your paralleled sub-packs at the same voltage and keep all them connected until the riding is done.

Higher usable total Ah capacity, no wastage flowing from on batt to another and less voltage drop when peak power needed.

Best by far.

B. Next best, stop and remove the pack once depleted and replace with a fresh full one.

Way distant second best.

C. Do **not** charge from one battery to another without an actual charge source active.

D. Do **not** join two packs together when their voltage is farther than 0.V per cell apart, e.g. 1.4V for 14S.

Unless you have a current-limiting device that you have tested in between the two and know it works.

Maybe test this out let us know how it goes

wattwagons "converter"
https://wattwagons.com/collections/accessories/products/dual-battery-converter
Just a set of resistors to slow current flow down? Or mcu to choose the higher voltage, then connect once they match?

But you will still lose a lot of stored energy, see C above.