Popular Post Mike Sacristan Posted May 22, 2022 Popular Post Share Posted May 22, 2022 I have had my early batch EXN HS since March 2021. In August 2021 after 4500km it died. The motor would not engage. The motor cables inside had rubbed against the inside of the motor cover. The hall sensor was damaged. After some fiddling the motherboard burned up. Who knows what backlashed into the batteries. New motherboard and new motor installed. Almost two weeks ago... I was leaning the wheel against a post. It tipped and fell on its side. After that it would not charge to full. A friend of mine also had his EXN on a stand. It tipped and fell on its side. After that it would not charge to full. We did a lot of things wrong when troubleshooting my wheel. We did not measure the groups.. only the packs. We charged all the packs together in the wheel instead of separately. Eventually the BMS got very toasty and it looks like overcharge / cell overvoltage protection failed. A couple of groups that I measured were at 4.47v and 4.48v. I am a noob at this and Sergei also has a lot to learn when it comes to batteries and BMS. No doubt this could have started a fire. No doubt either that if the BMS overcharge does fail and the cells get to such extremely high values... this can cause a fire. I don't know if the newer updated BMS from Begode have better failsafes. We installed three fresh LGM50T packs in my wheel so now it is back to it's original state. And let's see what happens. I will try not to knock it around... or maybe I will. There are still plenty of 1800Wh wheels out there with these old BMS and LGM50T packs. The updated LG M50T sheet shows that they are similar to the LGM50LT... in that they are rated at 14.4A continuous discharge but only at +10C to +25C. Otherwise 7.3A. Considering that at 5A they will climb +5C from ambient in just a matter of minutes.. and then if 5A continues they will eventually end up at +25C over ambient at around the 30 minute mark. This is the same for M50T, M50LT, Samsung 50E... which is expected as they are low discharge high capacity cells. My Nikola does have a SmartBMS with individual cell group monitoring as well as some very nice failsafes. The cell groups are always within 10mv of each other despite putting 14000km on my wheel. Perhaps if this was the "new" BMS from Begode it would have disconnected my pack to prevent output... redundancy be damned... and left me with a 24S4p EXN doing 60kmh+ in the middle of the road. Some quick sag and then an overlean would have been lovely. Still.. this is the "redundancy" we say we have. If this would have been a Master.... then the wheel tipped it would have just shut off and stayed off. The end. But maybe it would allow such insane values anyway... 4.47V 4.48V Some other potato value. 3.37V The rest at 4.2V... what does that spell? A 100.8V pack. It is a long clip... but I have summarised just about everything in this text. Time stamp embedded showing where I measure... incorrectly as I only measure every other group. But still... it is revealing. Shortly after the measurement there are some photos showing the naked cells and their condition. They did not look good. 9 1 2 4 Quote Link to comment Share on other sites More sharing options...
meepmeepmayer Posted May 22, 2022 Share Posted May 22, 2022 14 minutes ago, Mike Sacristan said: 4.47V 4.48V 1 Quote Link to comment Share on other sites More sharing options...
Popular Post supercurio Posted May 22, 2022 Popular Post Share Posted May 22, 2022 (edited) Awesome you posted it in full now @Mike Sacristan! I'm glad that it ended with gaining insight, especially since I was really concerned about what was likely to happen when we were chatting about it back then. Soldering the BMS back onto the live pack without checking cell group voltages, charging a pack in unknown state for days and all that, charging a whole wheel instead of the problematic pack alone and all that. A must watch probably for anyone working with these battery packs, including to learn what not to do. So it's great you posted the whole thing because it's likely not that uncommon unless professionally trained to work with battery packs. Then yes the protection which stops charging if any group reaches 4.25V or beyond can absolutely fail. I wonder if there is a time-out on it then it resumes, if it happened because of additional BMS damage or because of the total duration. The 2 balancing resistors that end up black were asked to do too much continuously. How many fires involving these packs were trigged by the BMS faults encountered here, a few I'm sure! Edited May 22, 2022 by supercurio 3 1 Quote Link to comment Share on other sites More sharing options...
Mike Sacristan Posted May 22, 2022 Author Share Posted May 22, 2022 29 minutes ago, supercurio said: Awesome you posted it in full now @Mike Sacristan! Thanks! It took a while and I needed all the follow-up data and measurements.. otherwise it would have been a very ugly video on "how to destroy an EUC". 29 minutes ago, supercurio said: I'm glad that it ended with gaining insight, especially since I was really concerned about what was likely to happen when we were chatting about it back then. Soldering the BMS back onto the live pack without checking cell group voltages, charging a pack in unknown state for days and all that, charging a whole wheel instead of the problematic pack alone and all that. A must watch probably for anyone working with these battery packs, including to learn what not to do. So it's great you posted the whole thing because it's likely not that uncommon unless professionally trained to work with battery packs. Oh geez... yes. Despite your warnings... Sergei and I did do some very dangerous things. Thank you for helping out and for all your advice and knowledge! 29 minutes ago, supercurio said: Then yes the protection which stops charging if any group reaches 4.25V or beyond can absolutely fail. I wonder if there is a time-out on it then it resumes, if it happened because of additional BMS damage or because of the total duration. The 2 balancing resistors that end up black were asked to do too much continuously. I would expect for there to be a recovery voltage value that once reached will allow the wheel to resume charging. It is possible that this value is very close to the overcharge value. I can imagine that it is due to physical damage. Let's really hope so! But also... we were asking a lot from the balancing. Still... it should be feasible although it would just take a looooot of time to resolve huge differences consisting of several volts. On my Nikola it is 4.22V for 2 seconds and then the charge port will stay off until the highest value of any cell group is 4.15V. But if the value would be 4.20V then it would resume charging again after very little time. 29 minutes ago, supercurio said: How many fires involving these packs were trigged by the BMS faults encountered here, a few I'm sure! I agree! And it is a pain for a normal user to open their packs and measure the cell group voltages. A SmartBMS would really make such monitoring easier! 2 1 Quote Link to comment Share on other sites More sharing options...
alcatraz Posted May 22, 2022 Share Posted May 22, 2022 10 hours ago, Mike Sacristan said: I have had my early batch EXN HS since March 2021. In August 2021 after 4500km it died. The motor would not engage. The motor cables inside had rubbed against the inside of the motor cover. The hall sensor was damaged. After some fiddling the motherboard burned up. Who knows what backlashed into the batteries. New motherboard and new motor installed. Almost two weeks ago... I was leaning the wheel against a post. It tipped and fell on its side. After that it would not charge to full. A friend of mine also had his EXN on a stand. It tipped and fell on its side. After that it would not charge to full. We did a lot of things wrong when troubleshooting my wheel. We did not measure the groups.. only the packs. We charged all the packs together in the wheel instead of separately. Eventually the BMS got very toasty and it looks like overcharge / cell overvoltage protection failed. A couple of groups that I measured were at 4.47v and 4.48v. I am a noob at this and Sergei also has a lot to learn when it comes to batteries and BMS. No doubt this could have started a fire. No doubt either that if the BMS overcharge does fail and the cells get to such extremely high values... this can cause a fire. I don't know if the newer updated BMS from Begode have better failsafes. We installed three fresh LGM50T packs in my wheel so now it is back to it's original state. And let's see what happens. I will try not to knock it around... or maybe I will. There are still plenty of 1800Wh wheels out there with these old BMS and LGM50T packs. The updated LG M50T sheet shows that they are similar to the LGM50LT... in that they are rated at 14.4A continuous discharge but only at +10C to +25C. Otherwise 7.3A. Considering that at 5A they will climb +5C from ambient in just a matter of minutes.. and then if 5A continues they will eventually end up at +25C over ambient at around the 30 minute mark. This is the same for M50T, M50LT, Samsung 50E... which is expected as they are low discharge high capacity cells. My Nikola does have a SmartBMS with individual cell group monitoring as well as some very nice failsafes. The cell groups are always within 10mv of each other despite putting 14000km on my wheel. Perhaps if this was the "new" BMS from Begode it would have disconnected my pack to prevent output... redundancy be damned... and left me with a 24S4p EXN doing 60kmh+ in the middle of the road. Some quick sag and then an overlean would have been lovely. Still.. this is the "redundancy" we say we have. If this would have been a Master.... then the wheel tipped it would have just shut off and stayed off. The end. But maybe it would allow such insane values anyway... 4.47V 4.48V Some other potato value. 3.37V The rest at 4.2V... what does that spell? A 100.8V pack. It is a long clip... but I have summarised just about everything in this text. Time stamp embedded showing where I measure... incorrectly as I only measure every other group. But still... it is revealing. Shortly after the measurement there are some photos showing the naked cells and their condition. They did not look good. My first thought was it got charged through the output. (The signaling to stop charging didn't make it to the other bms's.) 1 1 Quote Link to comment Share on other sites More sharing options...
alcatraz Posted May 22, 2022 Share Posted May 22, 2022 (edited) How do those communication wires look? Any damage? Were they connected? One gripe I've always had with measuring the groups is that I'd love to also test the charge cutoff functionality aswell, and I never do. I just assume it works and assumption is the mother... It would be cool to know more about it. Edited May 22, 2022 by alcatraz 1 Quote Link to comment Share on other sites More sharing options...
Funky Posted May 23, 2022 Share Posted May 23, 2022 It amazes me that those soldering "strips" are so tin/small.. Any small bump on road, or simple drop may damage them. Those strips, that connect batteries to bms should be 3x the size. Bigger - Stronger. Batteries/BMS need more padding around them, that's for sure.. Or i am the only one whos thinks that? Quote Link to comment Share on other sites More sharing options...
EMA Posted May 23, 2022 Share Posted May 23, 2022 managing BMS and batteries require some knowledge, glad everything is fine now thanks for posting it all Quote Link to comment Share on other sites More sharing options...
Greg X Posted May 23, 2022 Share Posted May 23, 2022 On 5/22/2022 at 1:57 PM, Mike Sacristan said: I have early batch EXN HS since March 2021. In 2021 - New motherboard and new motor installed. two weeks ago...- three fresh LGM50T packs so, finally You have almost new wheel now. I dont even ask how much it must have cost upgrading half of euc... First batches are prototypes, not final products. Risk of issues is very high. Quote Link to comment Share on other sites More sharing options...
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