I bought this with known battery problem, under rack battery. Battery flashes 3 but will not charge. Tried 2 chargers, not the problem. Removal of battery pack shows minimum of 2.1 V on all packs, however testing different post readings on BMS shows 26 V (not 2.6, full 26) on one combination. Can I test the BMS ? Sound like bad cells in a pack? Worst case, any available battery 36V plug into trek harness, or schematic to splice one in ? Nice bike, gettin' too old to pedal.........
Trek Townie Go battery
- Thread starter sibernut
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docw009
10 MW
You probably know this, but here's a 36V battery made with 10 cell groups. The BMS will isolate the cell groups if any go below 3 volts. You'll measure nothing at the battery output, except maybe some stray voltage voltage leaking thru the BMS.
The BMS will not allow charge if any of the cell groups are below some designed minimum voltage, usually somewhere between 2.5 and 2,9 volts. If you're measuring 2.1 volts on a cell, this is what's happening. The BMS has shut off the battery and won't allow charging.
Seems to me though that the BMS is doing its job. Probably works fine, Your cells are low.
Now it's a matter of risk. Cell makers set a minimum voltage of 2.5V for a lithium cell. Going lower risks damage. Damage means a higher fire risk. Most people will say 1V is too low, The 2.1V is in a grey area. Personally, I don't like taking risks with lithium,
Written enough, Maybe you can get all ten group voltages, which will give more info.
BTW. If there are only two wires, pos/neg, coming out of the battery, another one can probably be used,
The BMS will not allow charge if any of the cell groups are below some designed minimum voltage, usually somewhere between 2.5 and 2,9 volts. If you're measuring 2.1 volts on a cell, this is what's happening. The BMS has shut off the battery and won't allow charging.
Seems to me though that the BMS is doing its job. Probably works fine, Your cells are low.Now it's a matter of risk. Cell makers set a minimum voltage of 2.5V for a lithium cell. Going lower risks damage. Damage means a higher fire risk. Most people will say 1V is too low, The 2.1V is in a grey area. Personally, I don't like taking risks with lithium,
Written enough, Maybe you can get all ten group voltages, which will give more info.
BTW. If there are only two wires, pos/neg, coming out of the battery, another one can probably be used,
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Low voltage cutoff point can be 2.0-3.0v, dependent on cell type.
If you can open the pack and tell us what cell is inside, someone can look up the cell datasheet and see what the minimum voltage for that cell is. If it's 2.5v, then some cells have been overdischarged and.. after a long time of sitting at that voltage, they're probably damaged.
BMSes prevent the user from charging a pack that has at least 1 cell below the minimum cutoff point in order to prevent the battery catching on fire when being charged.
If it turns out your cell type goes down to 2.0v then you may be in luck with the cells but probably not in luck with the BMS. On a proprietary bike, you won't be able to get parts like that. And it may be that the BMS/battery has some secret communication protocol with the bike that prevents you from replacing it with an aftermarket one.
If you can open the pack and tell us what cell is inside, someone can look up the cell datasheet and see what the minimum voltage for that cell is. If it's 2.5v, then some cells have been overdischarged and.. after a long time of sitting at that voltage, they're probably damaged.
BMSes prevent the user from charging a pack that has at least 1 cell below the minimum cutoff point in order to prevent the battery catching on fire when being charged.
If it turns out your cell type goes down to 2.0v then you may be in luck with the cells but probably not in luck with the BMS. On a proprietary bike, you won't be able to get parts like that. And it may be that the BMS/battery has some secret communication protocol with the bike that prevents you from replacing it with an aftermarket one.
lnanek
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Sometimes you can bring a pack back to life by disconnecting everything, opening it up, and connecting each p-group of cells to an old 1S cell phone charger in turn. RC hobby chargers can also charge several p-group at a time. I'd do it somewhere fire safe, though, like an old BBQ grill.
BMS won't start up if any p-group is below a certain voltage, but they also often require all the p-group's to be within a certain voltage difference between each other as well, like .1 V. So you might have to measure with a volt meter and tweak there too. I have an active balancer circuit I can plug in, but also my cell meter has a discharging balance function, and you can also just drain volts with a lightbulb.
Sometimes the BMS has to be fully disconnected and the terminals shorted before it will reset after a fault too, though.
BMS won't start up if any p-group is below a certain voltage, but they also often require all the p-group's to be within a certain voltage difference between each other as well, like .1 V. So you might have to measure with a volt meter and tweak there too. I have an active balancer circuit I can plug in, but also my cell meter has a discharging balance function, and you can also just drain volts with a lightbulb.
Sometimes the BMS has to be fully disconnected and the terminals shorted before it will reset after a fault too, though.
My batteries are 11865, recommend a seller ?
How many wires does the battery use to connect to the bike?
If two, great, just a matter of soldering on new connectors to a new battery. But this is extremely unlikely.
If more than two, the battery probably has a secret communication protocol, forcing you to use just that company's batteries. You would need an electrical engineer to sort that out.. or just reconvert the bike by replacing every EV part shy of the motor.
docw009
10 MW
Townie might put the electronics inside the battery cradle on the rear rack. Then what comes out of there will be a cable to the motor, another one to a pedal sensor, and a harness to the handlebars. That will make it harder to find a combo battery/cradle because it needs room for the controller too,
If it’s the version that uses the Bosch mid drive, you may be stuck purchasing a Bosch battery.
..or drilling into the bosch mid drive case and running and external controller into it, bypassing all the stock electronics... unlocking more power than stock, but losing torque sensing and other cool features.
OK, got pack out of the case. 5 packs, 8 cells per pack. NONE of the packs makes it above 2.0V. Now, I don't care how "factory" this looks, just want to ride bike on my own property. So how about I buy a 36V battery and cobble the BMS onto it ? Just want the OEM plug to work the controls & display. If I could just replace the packs Id be in business. any source ?
Cut apart all the cells. Did not charge 1st. The cells are in groups of 8 each, 5 groups l to r. Far left row of 4 marked are at 2.6 each. All others are below 1.0.
Trying to use my case , bms & wiring. Should i just buy 40 cells & put them in ? Mine say 11865, use 18650's ? Desperate in MD...........
Trying to use my case , bms & wiring. Should i just buy 40 cells & put them in ? Mine say 11865, use 18650's ? Desperate in MD...........
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