An electric scooter rental company here in the United States 'Superpedestrian' went out of business (or shut down all US operations anyway), and ended up leaving a bunch of electric scooters abandoned in the streets of several US cities. One found its way into my hands, and I decided to hack the battery and make it run again, by removing all the electronics (dashboard & BMS) and adding a universal throttle (with power switch), new brake handles, and a universal battery management system (BMS). This particular battery is quite large - just shy of a kilowatt-hour (907.2Wh). Here's the specs:
Anyway, this is a nice big battery pack which can be used for a backup power supply, even if you don't care about ever using the scooter. Once I got the battery open, I saw that the battery consisted of 6 parallel sets of 14 cells in series (i.e. 14s6p). Here's a pic showing the battery (with original BMS) and the new BMS to be installed.
Actually, in order to test the scooter to verify it was functional, first I just bypassed the original BMS by soldering a wire from the BMS + terminal to the + output terminal, as seen here (I used 2 short red wires with spade connectors so the bypass could be 'cut' if desired - but never ended up using the option):
The above pic also shows the two thick wires (red and black, circled) coming from the original BMS and which go to the main battery power cable. The battery power cable has multiple pins, but only the two big pins (corresponding to the black & red cable here) are used after replacing the BMS.
Originally, the BMS and battery were wired with colored balance/voltage wires leading to each of the cell groups, as well as black 'temp' (temperature sensor) wires. The new universal BMS only needs the voltage/balance wires, so the black wires can all be cut away. The main work for this task is going to be splicing our new BMS balance wires onto the existing balance wire harness.
The above pic shows the original connector (colored wires, smaller size) next to the new BMS balance wires connector (red wires, bigger size). Looking closely, each of the two connectors has 15 wires, with a black wire on the far right. Thus the task is ALMOST a 1:1 wire 'swap' (cut/splice), from the old connector to the new one.
HOWEVER, for whatever reason (apparently just the way they ended up running the wires to this spot where the battery frame is bolted together in the very middle), this particular battery's connector has the order swapped, for the 2 wires near the middle of the connector - the gray and the purple. Here's a pic of the battery, showing the balance wires connected to the cells (from right-to-left) in the order Red/White/Purple/Gray:
Yet the order of the colors on the connector has the purple & gray wires in the opposite order (here from left-to-right), i.e. Red/White/Gray/Purple. Thus, the gray and purple wires should be spliced onto the NEW connector, swapped with eachother:
The way to check you've done it right is to use a multimeter to check the voltage between each of the wires, starting with the black wire and the one right next to it, then that wire and the one next to it, and so on. Each 2 adjacent wires should have a single Li-Ion cell's voltage between them, i.e. 3.5 or 4.0 volts or thereabouts. If the voltage between any 2 adjacent wires is DOUBLE, i.e. 7+ volts, then some wire has been connected in the wrong order.
BTW, here's how I recommend splicing the wires - get some appropriately sized heatshrink tubing (black here), and cut/strip each of the 2 wires to be connected, so that you have a couple cm of exposed wire. Then twist the 2 wires together, and then fold back the twisted wires to run alongside one of the wires, which may then be covered with heatshrink tubing and heated with a heat gun.
Here's a pic of my battery ALMOST totally connected to the new BMS's balance wires:
And finally with all the wires connected:
Here, the thick black wire from the battery gets spliced onto the blue "B-" wire of the BMS, the "P-" wire from the BMS will be our main - output, and the thick red wire from the battery will be our main + output. The main + and - output wires have 'male' spade terminals on them, to easily connect with the 'female' spade terminals which lead out to our battery power cable:
To fit the battery back into the deck, I had to cut off a small piece of the battery housing so that it could be screwed back together with the new larger BMS installed:
And once it's all buttoned back up:
Now put it back into the scooter deck:
Anyway, this is a nice big battery pack which can be used for a backup power supply, even if you don't care about ever using the scooter. Once I got the battery open, I saw that the battery consisted of 6 parallel sets of 14 cells in series (i.e. 14s6p). Here's a pic showing the battery (with original BMS) and the new BMS to be installed.
Actually, in order to test the scooter to verify it was functional, first I just bypassed the original BMS by soldering a wire from the BMS + terminal to the + output terminal, as seen here (I used 2 short red wires with spade connectors so the bypass could be 'cut' if desired - but never ended up using the option):
The above pic also shows the two thick wires (red and black, circled) coming from the original BMS and which go to the main battery power cable. The battery power cable has multiple pins, but only the two big pins (corresponding to the black & red cable here) are used after replacing the BMS.
Originally, the BMS and battery were wired with colored balance/voltage wires leading to each of the cell groups, as well as black 'temp' (temperature sensor) wires. The new universal BMS only needs the voltage/balance wires, so the black wires can all be cut away. The main work for this task is going to be splicing our new BMS balance wires onto the existing balance wire harness.
The above pic shows the original connector (colored wires, smaller size) next to the new BMS balance wires connector (red wires, bigger size). Looking closely, each of the two connectors has 15 wires, with a black wire on the far right. Thus the task is ALMOST a 1:1 wire 'swap' (cut/splice), from the old connector to the new one.
HOWEVER, for whatever reason (apparently just the way they ended up running the wires to this spot where the battery frame is bolted together in the very middle), this particular battery's connector has the order swapped, for the 2 wires near the middle of the connector - the gray and the purple. Here's a pic of the battery, showing the balance wires connected to the cells (from right-to-left) in the order Red/White/Purple/Gray:
Yet the order of the colors on the connector has the purple & gray wires in the opposite order (here from left-to-right), i.e. Red/White/Gray/Purple. Thus, the gray and purple wires should be spliced onto the NEW connector, swapped with eachother:
The way to check you've done it right is to use a multimeter to check the voltage between each of the wires, starting with the black wire and the one right next to it, then that wire and the one next to it, and so on. Each 2 adjacent wires should have a single Li-Ion cell's voltage between them, i.e. 3.5 or 4.0 volts or thereabouts. If the voltage between any 2 adjacent wires is DOUBLE, i.e. 7+ volts, then some wire has been connected in the wrong order.
BTW, here's how I recommend splicing the wires - get some appropriately sized heatshrink tubing (black here), and cut/strip each of the 2 wires to be connected, so that you have a couple cm of exposed wire. Then twist the 2 wires together, and then fold back the twisted wires to run alongside one of the wires, which may then be covered with heatshrink tubing and heated with a heat gun.
Here's a pic of my battery ALMOST totally connected to the new BMS's balance wires:
And finally with all the wires connected:
Here, the thick black wire from the battery gets spliced onto the blue "B-" wire of the BMS, the "P-" wire from the BMS will be our main - output, and the thick red wire from the battery will be our main + output. The main + and - output wires have 'male' spade terminals on them, to easily connect with the 'female' spade terminals which lead out to our battery power cable:
To fit the battery back into the deck, I had to cut off a small piece of the battery housing so that it could be screwed back together with the new larger BMS installed:
And once it's all buttoned back up:
Now put it back into the scooter deck:
