dmethvin Posted June 14, 2016 Share Posted June 14, 2016 I haven't ever needed to figure out the balance wires for my battery so I can't help there. Are you pretty sure that you connected the two cut wires correctly? If you have a voltmeter you could check the voltages at the point where the balance lines connect to see if any of the cell groups are out of balance right now, which they might be since two of the lines were cut. If the BMS is really defective the simplest thing to do may be to shunt it. Here is a picture of one of my battery packs with the BMS, showing the shunt with a red bladed 40A automotive fuse. Link to comment Share on other sites More sharing options...
Pingouin Posted June 14, 2016 Author Share Posted June 14, 2016 Do you know in which battery this BMS is located ? Link to comment Share on other sites More sharing options...
esaj Posted June 14, 2016 Share Posted June 14, 2016 15 minutes ago, Pingouin said: Do you know in which battery this BMS is located ? You should be able to feel it/see the bump through the shrink wrap. It's a thin, squarish piece of metal (it's heatsinked) pretty near the middle of the pack, on one side of single pack. Probably the one from where the wires go to the mainboard and charge port. Link to comment Share on other sites More sharing options...
Pingouin Posted June 14, 2016 Author Share Posted June 14, 2016 Oh I think I know which one, I don't have my unicycle though.. For the BMS shunt, what do I have to do ? Is it the same as on the topic of the BMS shunt ? When the BMS protects the batteries, does the firewheel stay on ? (I mean with the blue display and the red light on the power button) Link to comment Share on other sites More sharing options...
Chriull Posted June 14, 2016 Share Posted June 14, 2016 Imho you should first resolve the issue with the cut cables, be sure that all cells are ok and check the bms. Then you can consider shunting the bms. Link to comment Share on other sites More sharing options...
esaj Posted June 14, 2016 Share Posted June 14, 2016 31 minutes ago, Pingouin said: Oh I think I know which one, I don't have my unicycle though.. For the BMS shunt, what do I have to do ? Is it the same as on the topic of the BMS shunt ? If your BMS is similar as mine (don't know if they've changed to some other model in newer builds), you just need to solder a thick wire between two spots (P- and B-). There are pictures in the BMS shunting topic. BUT, like Chriull said, better make sure first that the cells are ok and there are no short circuits or such. Basically, you should get a multimeter to do some measurements (A basic one costs like 10-20 euros). 31 minutes ago, Pingouin said: When the BMS protects the batteries, does the firewheel stay on ? (I mean with the blue display and the red light on the power button) Yes, essentially the shunting bypasses the protection mosfets that cut the power. So they will still TRY to cut the power, but the wheel will stay powered because the current passes through the shunt-wire, bypassing the protections. Link to comment Share on other sites More sharing options...
Pingouin Posted June 14, 2016 Author Share Posted June 14, 2016 In my case the wheel shuts down completely...that's why I'm wondering if the BMS is in cause Link to comment Share on other sites More sharing options...
esaj Posted June 14, 2016 Share Posted June 14, 2016 10 hours ago, Pingouin said: I'm not sure, but when I plug/unplug the batteries to the mainboard, if I had just pluged the charger before, it sparks, then I wait until it shuts down, and if I try to plug it again, there are no sparks....maybe it's the BMS like you said. 40 minutes ago, Pingouin said: In my case the wheel shuts down completely...that's why I'm wondering if the BMS is in cause Yes, it sounds like the BMS is cutting the power, but the important thing is WHY the BMS is cutting the power. Usually the shunt is done because the BMS cuts the power when the voltage momentarily dips too low (especially when the battery is low on charge), and causes a faceplant. But if the BMS cuts the power with full battery, there's something else behind it. The BMS itself may be faulty, or something is causing the battery to go into a short circuit, in which case a shunted BMS wouldn't cut the power, either frying what ever is causing the short circuit, or overheating itself, which could even lead to the battery "venting with flame" (catching fire) or exploding. That's why I think it would be good to know what's going on, before trying to shunt it. These batteries hold a lot of energy (even when low on charge/"empty", a 16S -pack will have something like 40-50V voltage and can dish out a lot of current if short circuited) , and can be very dangerous. Likely reasons I can think of are dead cell or multiple cells (BMS cuts power detecting a too low voltage on one or more cells), in which case the faulty cells or the entire packs should be replaced, a broken BMS or over current protection triggering on short circuit... Link to comment Share on other sites More sharing options...
Pingouin Posted June 14, 2016 Author Share Posted June 14, 2016 About the dead cells, if there is likely to be some that are dead, can the display show 99% ? Link to comment Share on other sites More sharing options...
esaj Posted June 14, 2016 Share Posted June 14, 2016 1 hour ago, Pingouin said: About the dead cells, if there is likely to be some that are dead, can the display show 99% ? Maybe, it depends what voltage the board considers as "100%" (or 99%, as the display only has two digits). At least on mine, it can show 99% for several kilometers after full charge. The easiest way to check is to charge the battery to full, let it sit for a while so the voltage steadies, then measure the voltage from the connector going to the mainboard and if it's "low enough" (something like 65V or below?), measure the individual cells to see which one has (potentially) failed. All the cells should be above 4V after full charge (and around 4.2V "hot off the charger", ie. right after full charge). Link to comment Share on other sites More sharing options...
Pingouin Posted June 15, 2016 Author Share Posted June 15, 2016 Okay I'm going to try to get my hands on a multimeter to be sure, before shunting the BMS, however I'm wondering it it's the BMS or the maiboard that does all this Link to comment Share on other sites More sharing options...
Pingouin Posted June 17, 2016 Author Share Posted June 17, 2016 Ok, so I had a friend that tested the elements, he said they were fine, so I solded back the loose wires, and shunted the BMS. It seemed to work, but a few meters after going on the firewheel, it made a flash and smoke came out, I immediatly turned it off, haven't tried anything yet but definitely something has fried... Link to comment Share on other sites More sharing options...
dmethvin Posted June 17, 2016 Share Posted June 17, 2016 Oh no! Open it up and see if you can figure out where the problem was. It still may be possible to fix. Link to comment Share on other sites More sharing options...
Pingouin Posted June 17, 2016 Author Share Posted June 17, 2016 I handled the wheel to a specialist, he'll check and tell me if it's fixable, I'm a little bit deperate with this wheel.. Link to comment Share on other sites More sharing options...
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