I am 77 years old retired veteran and live on Vancouver island in British Columbia. I've cycled a fair bit years ago and ridden motorcycles for years. I spent my early working life as a mechanic so I'm pretty handy with tools. I am new to ebikes having purchased a second hand BPM trike with a samsung battery and bafang 750 amp motor about a month ago. I've had it out for a few rides and everything was going very well until today. I'm estimating that I traveled between 15 and 20 miles when my battery suddenly died. The display went blank. I checked the connector which was dry and tight. I checked the voltage when I got home and got less that one volt. Put in on the charger. After about 3 hours the charger went green. Checked the voltage and got 0. Checked the fuses and both were good. The display came on but showed an empty battery. I've always found that batteries die slowly. They give you a warning. Are ebike lithium ion batteries different? What could cause battery voltage to drop and stay at 0 volts? Any help would be appreciated and I thank you in advance. Cheers!
Battery died suddenly
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harryS
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Looked at a picture of a BPM trike. Do you have this style battery? Are you measuring at the bottom with the keyswitch on? The keyswitch on the one I owned is a robust unit that switches the power line directly. There is a BMS circuit card in the battery that monitors the internal cell voltages. These have to be in a certain range, 3.0-4.2V, for safety, If one cell is below this range, the BMS shuts off the battery and you read zero volts, unless the BMS switch has residual charge on it,
Meanwhile, if you have a handlebar display, it needs a minimum voltage to power up. It can't power up if the BMS has shut down the battery. It could power up if your're just above what the display needs to power up. Maybe 30V on a 36V battery and 40V on a 48V battery, Some displays can handle either voltage, so they will power up on a 48V battery that is too low to run the bike.
These batteries also have an LED display on the top? Does that show the battery is flat, partially charged or what>
Meanwhile, if you have a handlebar display, it needs a minimum voltage to power up. It can't power up if the BMS has shut down the battery. It could power up if your're just above what the display needs to power up. Maybe 30V on a 36V battery and 40V on a 48V battery, Some displays can handle either voltage, so they will power up on a 48V battery that is too low to run the bike.
These batteries also have an LED display on the top? Does that show the battery is flat, partially charged or what>
Thanks for the info HarryS. My battery is black but looks the same as your photo. The meter at the top shows a full charge. Could you decode this number from the battery? DWP 35 ET H200701 Y4821-500W 032. Looks like I have a 500 watt motor but I thought it was a 750. Is 750 a peak wattage? To sum up, the meter on top shows battery is fully charged but there is no voltage at the terminals on the bottom. Seems like the BMS has shut the battery down. Is the next step to take the battery apart?
I don't have a "lock" position, Only "unlock". I checked the voltage with the key in each position and there was no change. The meter at the top still shows battery fully charged. LCD is still powering up. I have the battery dismantled now. Is there a way to test the controller with a multi meter? At this point it looks like the controller is bad or one or more cells are bad. How do I find a bad cell? Thanks for your help. I appreciate it.
Gionnirocket
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Follow Harry's lead as something doesn't make sense so far.
To check the cells typically the easiest way is to check on the board where the multipin connector attaches.
Being VERY CAREFUL and following the diagram check B1+ to B1- then B2+ to B2- and so on. They all should be above 3v and equal within +/- 0.1V
This said... I wouldn't bother messing with an old battery to replace cells. If the internal resistance of all the cells aren't matched, it'll never work correctly not to mention it's no small task to change cells in the middle of a pack. You'll need the proper welder to begin.
If the cells check out and all the connectors are good, then it's the BMS. Replaceable if you understand what you are doing but again... No small task for an amateur.
Again... Be careful.
To check the cells typically the easiest way is to check on the board where the multipin connector attaches.
Being VERY CAREFUL and following the diagram check B1+ to B1- then B2+ to B2- and so on. They all should be above 3v and equal within +/- 0.1V
This said... I wouldn't bother messing with an old battery to replace cells. If the internal resistance of all the cells aren't matched, it'll never work correctly not to mention it's no small task to change cells in the middle of a pack. You'll need the proper welder to begin.
If the cells check out and all the connectors are good, then it's the BMS. Replaceable if you understand what you are doing but again... No small task for an amateur.
Again... Be careful.
I was doing something wrong because I now have 54.5 volts at the bottom terminals. I will put everything back together and update you when that's done. Thanks again.
I have 54.5 volts at the output terminals. When I install the battery, the display comes on. The battery icon on the first screen is empty. The voltage reading on the 3rd screen reads 54.5 volts. When I apply throttle, nothing happens. Everything else works. I hate to be a pita but where do I go now? Battery seems ok now. Could it be the controller still or am I looking at a motor problem? Thanks again for your help.
harryS
Well-Known Member
Next time, post a link to your trike on the net so people can look it up. It's important give the battery voltage, For imported bikes, knowing the display will help.
I noted this picture on the BPM site. They show the KT LCD3 display, Is this your display? You're seeing temperature in the lower right corner? If it is, see if Walk mode runs the motor. If it isn't see if it works anyway,
I noted this picture on the BPM site. They show the KT LCD3 display, Is this your display? You're seeing temperature in the lower right corner? If it is, see if Walk mode runs the motor. If it isn't see if it works anyway,
I will remember that in the future. Thank you. That is the same display that I have. The walk assist does nothing.
Slaphappygamer
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That display has an icon when pulling the brake lever. Pull the brake and look for the icon to come on. Does it come on? Or is it always on? A stuck brake sensor can halt the motor.
The brake icon is not on and does not come on when pulling the brake levers.
Gionnirocket
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Do you know if it did before? Not familiar with that display and if it has brake indicator.
I'm thinking you may have a faulty display. If you are sure all connections are good, that's the easiest, cheapest place to start.
harryS
Well-Known Member
A lot of us know the LCD3 pretty well. It only works with KT controllers, The controller looks like it is under the pedals. Access plate should be on the side, Open it up and put up a clear photo of the controller label so the amp rating is known.
Look for evidence of water too. These under the pedal compartments often get water coming in thru the cable openings, There is usually a drainhole for the water, but if the floor isn't level it will stay, I;'ve had water pool like that amd eventually get inside the controllers. A few sizzles and the controller is dead.
You're going see one of the above two types. The left model has r0ur separate cables from the handlebats going to the controller. A rat's nest. The one on the right has a single handle bar harness running down to the electronics.
Look for a round connector coming from the LCD3. Try reseating it. If you have the left side controller design. there may be a round connector, but the final connection is a flat 5 wire connector by the controller. Reseat that too.
Some things to look for.
-The temperature icon should change to a spinning rectangle when you rotate the throttle. If it doesn.'t , the display isn't getting a signal from the motor.
-Speed should show up on the display when you spin the drive wheel. If it doesn't, the display isn't receiving data packets from the controller.
-Does this bike use pedal assist?
-WIll the motor wheel rotate both forward and backward with wheel off the ground and power off. Will it still do so if power is on?
The LCD3 has about 20 internal parameters that are user accessible. Generally, I don't think these can be affected by a power glitch, but if they are, the throttle can be shut off and PAS may not work. If you pull a LCD3 manual (many available on wen), you can run thru them, but better to leave them alone for now.
A working KT controllers can be run without a display with a wire jumper on the right pins replacing the display. They default to throttle operation and a single PAS level. Before you go to this step, there are some other tests that can be run to see if it's a bad LCD, bad controller, or just bad connectors.
Look for evidence of water too. These under the pedal compartments often get water coming in thru the cable openings, There is usually a drainhole for the water, but if the floor isn't level it will stay, I;'ve had water pool like that amd eventually get inside the controllers. A few sizzles and the controller is dead.
Look for a round connector coming from the LCD3. Try reseating it. If you have the left side controller design. there may be a round connector, but the final connection is a flat 5 wire connector by the controller. Reseat that too.
Some things to look for.
-The temperature icon should change to a spinning rectangle when you rotate the throttle. If it doesn.'t , the display isn't getting a signal from the motor.
-Speed should show up on the display when you spin the drive wheel. If it doesn't, the display isn't receiving data packets from the controller.
-Does this bike use pedal assist?
-WIll the motor wheel rotate both forward and backward with wheel off the ground and power off. Will it still do so if power is on?
The LCD3 has about 20 internal parameters that are user accessible. Generally, I don't think these can be affected by a power glitch, but if they are, the throttle can be shut off and PAS may not work. If you pull a LCD3 manual (many available on wen), you can run thru them, but better to leave them alone for now.
A working KT controllers can be run without a display with a wire jumper on the right pins replacing the display. They default to throttle operation and a single PAS level. Before you go to this step, there are some other tests that can be run to see if it's a bad LCD, bad controller, or just bad connectors.
Thanks for the reply. It has a brake indicator that worked before.
Thanks for the info. I will check this out.
Gionnirocket
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We'll get you rolling again.
You're in good hands with Harry S.
You're in good hands with Harry S.
The one on the left is like mine. Reseated the round connector multiple times. Reseated the 5 wire connector. The temp icon does not change. Speed does not show when I spin the wheel. This bike uses pedal assist. The motor wheel rotated both ways with power on and off. I went through all the internal parameters and didn't see anything wrong. I've ordered a battery and a controller to help trouble shoot. I like redundancy so if the problem is not the controller, I have a spare. Thanks again for your help.
https://mail.google.com/mail/u/0?ui...=att&disp=safe&realattid=18efd04e1e2da5495121
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Does napa rebuild them or sell them or just recycle them?
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