Parallel connecting nonidentical batteries.

[Neophyte]

Need some help.

I bought an eZee kit recently.

The included battery is a 48V10Ah LiMn as seen here…

http://ebikes.ca/store/photos/48V10_Upgrade.jpg

I also have a 48V20Ah Li-Ion NiCoMn battery as seen here…

http://www.bmsbattery.com/48v/249-48v-10ah-lithium-ion-electric-bicycle-battery-pack.html

The intent being to parallel connect the two using a wiring set as seen here…

http://ca.itselectric.ca/product_p/eparts-parallel-wire.htm

The wiring set being complete with two 40 Amp fuses as seen here…

http://www.consumabulbs.com/photo/40a%20Maxi.jpg

Am I inviting disaster?

Or will the parallel connection be a safe way of tripling, or so, my stock range?

Thanks for any/all assistance.

 

[Rassy]

Welcome to the forum. I have two 48V 10AH LiFePO4 batteries on my trike. Since one battery is sufficient for my style of riding, i.e. normally draw less than 1C, I decided not to parallel the two batteries. Instead, I just use one at a time, and when on a longer ride I can switch to the other battery for extended range.

Originally I had to unplug battery 1 and plug in battery 2, but now I have a battery selection switch wired in so I can just switch off the power to the controller, flip the selector switch to the alternate battery, and switch on the power to the controller.

I have read that if you protect the BMS of each battery with diodes you can protect them from damage when a battery shuts down under load, and perhaps some other bad things that can happen when the batteries (BMS) are hooked together in parallel. I have also read that the diodes can cause problems, such as overheating. Anyway, I haven't used any diodes for this purpose, so don't know.

Good luck with your battery usage.

 

[dogman dan]

Do they charge to the same voltage? If so, they can be paralell connected, using the diodes to protect the bms. Some bms will not like the volts entering it backwards, which happens when one battery shuts off while the other is till turned on.

If the voltage they charge to is too different, then one battery should be run for a bit, till the voltages match. Personally, I'd just run one, then the other. I never found stopping to unplug one battery and plug in another that big a deal. Takes like ten seconds to swap the plugs.

 

[dnmun]

i think manganese and cobalt always go together so they should be identical chemistry so they should charge to the same voltage. i don't think you need diodes.

does the charger voltage match and is the ezee pack 13S also?