Chriull Posted September 23, 2019 Share Posted September 23, 2019 2 hours ago, yuweng said: i think that burnt mosfet is for charging, could it be that your fast charger is too powerful ? Theoretically, replacing it with a higher ampere mosfet should solve the problem but be careful, i think everyone of us, hands one guys here sure have experience it before, that accidental short circuit spark is really terrifying & dangerous @Eddie G. These should be the mosfets at the charge side, to cut off the charger in case of cell overvoltage, etc. They have a bit of a hard life (thermicly) beeing wrapped up, but normaly they withstand these burdens without any problems - with any other wheel and the ewheels fastcharger. Could be something badly manufactured/bad batch/some malfunction of the BMS? 35 minutes ago, Marty Backe said: There's no such thing as a too-powerful charger. A charger doesn't push amperes into the wheel. It simply makes available the amperes that the BMS consumes. You can plug a 2000-amp charger into a wheel but I assume the BMS will limit it's maximum ampere draw to some value much less than 2000-amps. Unfortionately the BMS will not limit the current draw. If one puts 84V at the charger plug and the battery is empty (66V) the only limiting thing are the internal resistances of the batteries and the wire/connector resistances. And these two mosfets. Just the Z10 BMS has some current limiting (?somewhere around 8A?). So theoreticly a malfunctioning charger (supporting too much constant current) in the first phase could heat up these two mosfets too much. 3 Quote Link to comment Share on other sites More sharing options...
FreeRide Posted September 23, 2019 Share Posted September 23, 2019 Certainly looks like the charger could be at fault. I would measure the voltage of the charger. Check that it was the correct charger, if you have more than one. Charger might be dead now as well. Quote Link to comment Share on other sites More sharing options...
Eddie G. Posted September 23, 2019 Author Share Posted September 23, 2019 so you guys think I should stop using that fast charger because I use it for my msx as well? Quote Link to comment Share on other sites More sharing options...
Chriull Posted September 23, 2019 Share Posted September 23, 2019 4 minutes ago, Eddie G. said: so you guys think I should stop using that fast charger because I use it for my msx as well? And it works normally with the MSX? You could open up the MSX and inspect the batteries/BMS if there are signs of overheating of the mosfets, too. As said it could be the charger or the BMS of both Tesla batteries. You have some way to measure the charging current/voltage? Do the GW wheels show this values maybe in the app - i'd assume there is no current measuring at the batteries charging inputs... 1 Quote Link to comment Share on other sites More sharing options...
Eddie G. Posted September 23, 2019 Author Share Posted September 23, 2019 yes it works on the msx but I'm going to discontinue using it as I dont want to loose my main wheel for work. That msx saves me 1200$ a year because the hotel I work at here in New Orleans wants to charge me 200 a month for parking. Quote Link to comment Share on other sites More sharing options...
meepmeepmayer Posted September 23, 2019 Share Posted September 23, 2019 Both battery packs are damaged in the same way. So it must have been some external cause creating a power surge or something. Charger or board, not sure what else it could even be. 50 minutes ago, Eddie G. said: That msx saves me 1200$ a year because the hotel I work at here in New Orleans wants to charge me 200 a month for parking. How is this even legal Quote Link to comment Share on other sites More sharing options...
ir_fuel Posted September 23, 2019 Share Posted September 23, 2019 4 hours ago, Marty Backe said: There's no such thing as a too-powerful charger. A charger doesn't push amperes into the wheel. It simply makes available the amperes that the BMS consumes. You can plug a 2000-amp charger into a wheel but I assume the BMS will limit it's maximum ampere draw to some value much less than 2000-amps. That's what a decently engineered product tends to do. Let's say that a device that allows you to get current out of the charging connector isn't one of those 1 Quote Link to comment Share on other sites More sharing options...
ir_fuel Posted September 23, 2019 Share Posted September 23, 2019 3 hours ago, FreeRide said: Certainly looks like the charger could be at fault. I would measure the voltage of the charger. Check that it was the correct charger, if you have more than one. Charger might be dead now as well. The best would be to measure how many amps the charger is pushing. That requires putting a multimeter in series however. Not something very straightforward. 2 Quote Link to comment Share on other sites More sharing options...
Mono Posted September 23, 2019 Share Posted September 23, 2019 6 hours ago, Marty Backe said: There's no such thing as a too-powerful charger. A charger doesn't push amperes into the wheel. It simply makes available the amperes that the BMS consumes. You can plug a 2000-amp charger into a wheel but I assume the BMS will limit it's maximum ampere draw to some value much less than 2000-amps. I am not sure that the battery side has always the means to limit the current to sane values. If it doesn't, a charger can well be too powerful current-wise. 2 Quote Link to comment Share on other sites More sharing options...
Eddie G. Posted September 23, 2019 Author Share Posted September 23, 2019 55 minutes ago, meepmeepmayer said: Both battery packs are damaged in the same way. So it must have been some external cause creating a power surge or something. Charger or board, not sure what else it could even be. How is this even legal lol well its legal and one thing I've noticed working here 13 yrs is everytime we get a raise the parking garage goes up a couple more dollars. That's why I was force to ride an EUC because it is the only thing that is compact. I use to ride a bike but the weather here is so humid I was always coming to work sweaty and the segway is too slow. 1 Quote Link to comment Share on other sites More sharing options...
Eddie G. Posted September 23, 2019 Author Share Posted September 23, 2019 37 minutes ago, ir_fuel said: The best would be to measure how many amps the charger is pushing. That requires putting a multimeter in series however. Not something very straightforward. when I get home today I will use a multimeter, I'll let you guys know the outcome 👍 Quote Link to comment Share on other sites More sharing options...
Marty Backe Posted September 23, 2019 Share Posted September 23, 2019 7 hours ago, Chriull said: @Eddie G. These should be the mosfets at the charge side, to cut off the charger in case of cell overvoltage, etc. They have a bit of a hard life (thermicly) beeing wrapped up, but normaly they withstand these burdens without any problems - with any other wheel and the ewheels fastcharger. Could be something badly manufactured/bad batch/some malfunction of the BMS? Unfortionately the BMS will not limit the current draw. If one puts 84V at the charger plug and the battery is empty (66V) the only limiting thing are the internal resistances of the batteries and the wire/connector resistances. And these two mosfets. Just the Z10 BMS has some current limiting (?somewhere around 8A?). So theoreticly a malfunctioning charger (supporting too much constant current) in the first phase could heat up these two mosfets too much. Good to know. How likely is it for a charger that is designed to supply a maximum of 5-amps to fail in such a way that it's now capable of generating 10, 20, or 30 amps and still function? Knowing a bit about electronics, that would seem to be a very odd failure mechanism. 1 Quote Link to comment Share on other sites More sharing options...
Mono Posted September 23, 2019 Share Posted September 23, 2019 (edited) 37 minutes ago, Marty Backe said: How likely is it for a charger that is designed to supply a maximum of 5-amps to fail in such a way that it's now capable of generating 10, 20, or 30 amps and still function? That doesn't sound to be likely at all. Edited September 23, 2019 by Mono 2 Quote Link to comment Share on other sites More sharing options...
Chriull Posted September 23, 2019 Share Posted September 23, 2019 33 minutes ago, Marty Backe said: Good to know. How likely is it for a charger that is designed to supply a maximum of 5-amps to fail in such a way that it's now capable of generating 10, 20, or 30 amps and still function? Knowing a bit about electronics, that would seem to be a very odd failure mechanism. Yes. Unprobable, and would "blow" up the charger, too (over time) And imho such a failure was never reported till now? But max current is regulated by a trim potentiometer - if this fails at the "maximum extreme" the charger provides as much current as he can while CC phase... 1 Quote Link to comment Share on other sites More sharing options...
Shad0z Posted September 25, 2019 Share Posted September 25, 2019 dont use that charger. can you tell us which charger it is and where you got it? could be a faulty charger tho. but if the same part fried on both batteries then it is most likely the charger, since a gotway battery failing like this is basically (1 / every battery), which means the probability of it being 2 bad BMS is very low. Quote Link to comment Share on other sites More sharing options...
Peter Le Lievre Posted September 25, 2019 Share Posted September 25, 2019 (edited) Guys, The charger is most likely just fine, however it's important to note that a 'quick charger' will pump more amps through the input mosfets of the BMS. No surprise is that they get hotter. And its not hard to imagine that when the input mosfet fries on one side that ALL the current will attempt to charge the other side and then fry that too. I bet the OP's input mosfets fried as he plugged the 'fast' charger straight after a long ride? When the battery and BMS were already hot? When battery volts were so low that the fast charger amped up to max? Below is a typical BMS (36V) which shows the single input mosfet which regulates the high voltage charge cutoff. Its the single INPUT mosfet on the bottom right. Not the same as ours but principle is similar. The input mosfet handles all the input power (charge). This BMS also has 3 OUTPUT mosfets which regulate the output low voltage cutoff. They handle all the output power. I haven't seen a Gotway BMS but most likely the output BMS mosfets are omitted as the wheel control board probably has a low voltage cutout of its own. However the input mosfets (x2 in our case) will be still there as pictured below. The input mosfets should easily be able to handle a fast charger current however until I can see the part number of them it's hard to know. Perhaps they are bad parts. Whatever the case it pays to be kind to your charge mosfets and use a 'fast charger' only when battery is cold, or even better use the normal charger routinely unless you have a special need to get back on the wheel more quickly. Remember, all the power that goes into your wheel first has to pass those input Mosfets and in this BMS design they are not actively cooled like the output ones are. We are so focussed on the insanely high amperage output mosfets that we forget the much lower rated input mosfets that must first accept all the power we put into our wheel. Edited September 25, 2019 by Peter Le Lievre Quote Link to comment Share on other sites More sharing options...
Chriull Posted September 25, 2019 Share Posted September 25, 2019 (edited) 1 hour ago, Peter Le Lievre said: Guys, The charger is most likely just fine, however it's important to note that a 'quick charger' will pump more amps through the input mosfets of the BMS. No surprise is that they get hotter. Every other wheel till now had no prob with the 5A from such a "fast" charger. 5A/4 ( 2 BMS with each 2 Mosfets in parallel) over some low two digit milli ohm rds on is no considerable power dissipation. 1.25A^2 * 50mOhm = 80mW. Quote I bet the OP's input mosfets fried as he plugged the 'fast' charger straight after a long ride? When the battery and BMS were already hot? The charge cut off mosfets have no load while riding and the li ion cells are (should) not be allowed to get any temp range that could get dangerous to the mosfets while charging. ... As long as the cells and BMS components are in good condition, the design is ok, ... Quote When battery volts were so low that the fast charger amped up to max? The first charging phase (up to reaching 4.2V per cell) is constant current and so always "amped up to max" as specified by the charger, no matter how low the battery voltage is. Quote ..The input mosfet handles all the input power (charge). The input current. It dissipates just fractions of the power that comes in. Quote ...I haven't seen a Gotway BMS but most likely the output BMS mosfets are omitted Yes. Afaik GW BMS have no output protection. Quote The input mosfets should easily be able to handle a fast charger current however until I can see the part number of them it's hard to know. Perhaps they are bad parts. Bad charges, bad quality control, "broken" components/pcbs happen... Edited September 25, 2019 by Chriull Typos 1 Quote Link to comment Share on other sites More sharing options...
Peter Le Lievre Posted September 25, 2019 Share Posted September 25, 2019 (edited) 1 hour ago, Chriull said: Every other wheel till now had no prob with the 5A from such a "fast" charger. 5A/4 ( 2 BMS with each 2 Mosfets in parallel) over some low two digit milli ohm rds on is no considerable power dissipation. 1.25A^2 * 50mOhm = 80mW. The charge cut off mosfets have no load while riding and the li ion cells are (should) not be allowed to get any temp range that could get dangerous to the mosfets while charging. ... As long as the cells and BMS components are in good condition, the design is ok, ... The first charging phase (up to reaching 4.2V per cell) is constant current and so always "amped up to max" as specified by the charger, no matter how low the battery voltage is. The input current. It dissipates just fractions of the power that comes in. Yes. Afaik GW BMS have no output protection. Bad charges, bad quality control, "broken" components/pcbs happen... My bad, LiOn is constant current charging like you say. Further, a 5amp 'fast' charger is not exactly high power loading for any mosfet. The only issue is that 84V is kind of up there so any internal unexpected Mosfet resistance is going to lead to a fritzed part way quicker than the good old days when 36V was 'high power'. I haven't seen the BMS design but if that is an 84V board and the gating voltage for the mosfet uses a resistor to drop the voltage, if that resistor fries and goes closed circuit and that gate gets even close to seeing 84V then its bye bye Mosfet. So if your fast charger has any DC ripple due to dead/dying caps or bad rectifier then that could kill the mosfet gate resistor/mosfet gate pretty quickly. So I take back what I said about the charger not being to blame. Looking more closely at this issue, I suspect the charger for sure. I see crappy capacitors all the time in Chinese electronics so I would replace the BMS mosfets then certainly buy another charger. Or if you decide to keep the charger, put it on a scope so any DC ripple can be checked. Edited September 25, 2019 by Peter Le Lievre Quote Link to comment Share on other sites More sharing options...
Chriull Posted September 25, 2019 Share Posted September 25, 2019 (edited) 54 minutes ago, Peter Le Lievre said: haven't seen the BMS design but if that is an 84V board and the gating voltage for the mosfet uses a resistor to drop the voltage, if that resistor fries and goes closed circuit and that gate gets even close to seeing 84V then its bye bye Mosfet. So if your fast charger has any DC ripple due to dead/dying caps or bad rectifier then that could kill the mosfet gate resistor/mosfet gate pretty quickly No matter if it's an n or p channel mosfet used, there are enough designs to keep then mosfets safely conducting and easily withstanding the power dissipation by the charging current. Unfortunately it can happen anytime inbetween that one gets a bad charge (bad components/bad design changes) in because of missing quality control So i am torn inbetween two bad BMS - which should normally never happen,.. or 54 minutes ago, Peter Le Lievre said: So I take back what I said about the charger not being to blame. Looking more closely at this issue, I suspect the charger for sure. I see crappy capacitors all the time in Chinese electronics so I would replace the BMS mosfets then certainly buy another charger. Or if you decide to keep the charger, put it on a scope so any DC ripple can be checked. a bad charger(1). Such a bad capacitor/ripple prob, the trim potentiometer causing with a contact loss/(short cut) causing an absolute maximum charging current or whatever in because of low quality component used causing a failure ... So best to let ewheels solve @Eddie G.G.'s problem. One never knows what died with/around the burned mosfets... Warranty is time limited - but design flaws have "unlimited" warranty. They "just" have to be custumer in case the reseller does not believe them/wants ti believe them. At least that's the situatuon in europe... Edit: (1) just remembered that the same charger worked with his other wheel (?msx?) without probs (at least until now)... Edited September 25, 2019 by Chriull Quote Link to comment Share on other sites More sharing options...
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