Battery pack question

I bought two 48volt 12ah packs of ebay it says that they have a pcb. Installed to protect them over charging or over discharging.
Voltage-48volt
Capacity-12ah
Cut-off voltage:34volts
Max discharging current 30amps
Max continuous Discharging amp.-15amps
Rated discharging amprage -15amps
Charging current- 5amps
Charging voltage- 57.6volts
I want to put the packs together and run 110volts at 12ah. To power my 24f 150volt controler which will power my cromotor is this pcb. That is built in to the batteries going to keep me from unlocking the full potential of my motor. I realy don't want to open the packs if I don't have to but I still want to be able to hit 50 or 60 mph. Also if I keep it this way what numbers do I set on my controler please any advice would be gratefully appreciated.

Those batteries are too weak for what you are doing. You are wasting your money and time. I assume your controller draws atleast 50amps and your cheap ebay batteries and bms will output 20a max. Your controller will try to draw 50a and one of the bms will trip almost instantly upon trying to go full throttle with a load on the bike. Even if you remove the pcb or bms boards..you will likely ruin the batteries from discharging them too fast. They will have voltage sag and only get you about 5 miles.

In my opinion i would sell the two batteries and get a stronger setup before its too late. Your motor and controller need either lipo with high C rating or a 18650 pack rated at 50-60a continuous

steven7601 said:

Max discharging current 30amps
Max continuous Discharging amp.-15amps
Rated discharging amprage -15amps

<snip>

I want to put the packs together and run 110volts at 12ah. To power my 24f 150volt controler which will power my cromotor is this pcb. That is built in to the batteries going to keep me from unlocking the full potential of my motor.

Click to expand...

My first thought is that you should send those back to wherever you got htem from for a refund, and get something designed and built for the power you want to pull from it.

Note that depending on exactly what you expect from the system, the packs you have may not be able to do what you want, regardless of connection choice, and you may either need to get or build completely different packs that can do what you want, or get or build packs to add to the existing ones to help them do what you want, depending on whatever size and weight restrictions your build will have.


However, you may not have that option for whatever reason, so:


They put protection in there for a reason; the limits of the protection might be due to cost of the BMS "PCB", or due to the limits of the cells themselves. (or of pack construction methods / materials).

Without knowing exactly what the cells are and their condition/quality, it's safest to assume that they are only capable of the same limits as given above.

So, since the packs are only designed for 15A, you'll need to set your controller to only draw 15A from the battery. Otherwise you'll either trip the protection (shutting off the packs), or damage the cells in the batteries.

I don't know how that will affect the performance of your system; you'll have to test it to find out.

Another potential issue is that if the output FETs of the BMS units can't handle the full voltage of the seriesed packs, possibly plus some margin depending on the rest of the system, then when either pack shuts down for whatever reason, there is a chance the FETs could fail on it from overvoltage. As they don't usually use parts with higher ratings than necessary, it's unlikely the FETs are designed to handle the voltage of two seriesed packs.


You would be better off running the two packs in parallel instead, so that even though the voltage and speed will be lower, the current capability will be doubled, and there will be (a lot) less voltage sag during higher current draws.

Yep, wrong batteries for anything but a 15 amps controller. And yours is 60?

You could parallel those batteries, and 15 amps plus 15 amps would allow you to run a 48v 30 amps controller.

But when you series, 15 amps and 15 amps still only equals 15 amps. They don't add up in series like they do in parallel.

To unlock the full potential of your bike, you just need to add a crapton of money for an 18650 pack so large it can do 60 amps continuous. Like 6 of the packs you have now. Or, go the hazardous RC lipo route.

With what you have now, you can do 96v 15 amps.