Badsley Scooter Build Battery and BMS Questions


1 µW
Mar 3, 2023
Seattle Wa
I’m not too bright with electrical stuff and I need some battery help.

I bought a Badsley emx scooter from one of my colleagues had modified like 15 years ago. He burnt out the original 750W motor and went a little overboard. He replaced the original drivetrain with a Brigs and Stratton eteck brushed dc motor (100A continuous 330A max 48V max), and an Alltrax AXE 300 amp controller along with the related wiring and other components. I destroyed the original controller and updated it to an Alltrax SR and rewired it to have modern comforts like a precharge resistor and diodes. Originally he was using 3 Odyssey PC925 AGM batteries in series. Currently, I just have some cheap SLA batteries installed so I can scoot to work and back when the weather is nice, about 3 miles. I’m ready to actually bring it back to its original ridiculous potential but with a modern battery system.

The issue with the battery setup is anything that is made for the drivetrain is too big for the form factor of the scooter(it's basically a golf cart drivetrain) and anything sized for a scooter isn't nearly enough juice for the drivetrain. It's a design disaster, but that makes it pretty fun.
I really like the idea of these prebuilt Samsung e-bike modules available on EVwest Samsung INR Lithium Ion Battery 20R Scooter and eBike Battery Modules, EV West - Electric Vehicle Parts, Components, EVSE Charging Stations, Electric Car Conversion Kits.

All the wiring is done and they are tidy little 48v 505WH modules that would fit well into the scooter. I would like to use 2 to 4 in parallel. I am pretty lost with the BMS though, as I understand it I would need one BMS for each module which would be pretty costly unless I were to only use it for charge balancing. The Alltrax has lots of settings for LVC and current limiting so I am not totally opposed to this. How would yall go about setting up a system with multiple modules in parallel for a high current draw without spending a fortune? Is there a better option that just does balancing and charging? I would love any alternative ideas for the battery setup as well. Preferably less than 1000 with the batteries BMS and charger. Pretty much any setup that would come close to being able to push the motor without melting would have more than enough range for my needs(10 or 15 miles).


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If there is a way to access each cell group connection in the battery modules, you can connect all of them in parallel and use a single BMS. You can use a big, expensive BMS that can handle the expected current (plus some headroom), or a small BMS that powers a large contactor relay which would open if any cell went too low. In that system you probably want a contactor somewhere to kill the power in the event the controller shorts out (which would give full power to the motor). In golf carts, there is a switch on the throttle that opens the contactor when at zero throttle. Just power this circuit from the BMS to add that layer of protection.