Posts made by vulkito

Fixed the hot point. As i was expecting, that issue had no relation with the no-power issue. I measured V on the big mosfets next to the batt connectors. There is no V. However, i have V on the other smaller ones. I’m thinking that maybe they are not receiving anything on the gate terminal. I followed the gate track and looks like that are going to those sOT-23 thingies which i guess are transistors. Looks like those are OK but i do not know who is sending the triggering/gate signal. Do you guys have any guess/recommendation?

@lia yes, but it doesn’t turn on. I also cheched the button just in case and works. One thing i want to check though is if the switch signal reaches the bms.. but i jumped the wires and nothing happened ;,(

@lemur and did that issue make the OW to be dead or was just a diagnostics issue (voltage not showing ok)?

@lia yep, I found the MAX chip getting hot and I replaced it. Then the hot point went from there to Q4 (one of the m8t mosfets). replaced and shorted again. On this one i found the issue (short between the terminals of one of the sample capacitors to read V on cells). But besides this... I really don´t think that a short in the sampling reading of the cells can make the OW to be dead, right? I mean, the only thing i can think of is that the MAX is getting crazy and is sending bollocks to the PIC. the PIC is also getting bollocks with that info and I guess the controller interprets tht something is wrong. But i don´t think this design is that complex.

The summary of the current status is the same: if i plug it in it works (and voltage is at 100% -weird-) and I do not get any error, but if it is not plugged...dead. Should be something related to the power section of the BMS but I don´t know where to look besides the MOSFETS. everything looks good!

One cell was bad. Replaced it- i now have V output-. The OW still does not power on and still have a hot point. I’m trying to deal with the hot point to see which component is the culprit (this hot point is in one of the MOSFETs -Q4- on the cell balancing-sampling area of the BMS). I think though that this mosfet issue has nothing to do with the no power issue.

Ok guys, i really need your knowledge on this because i do not really have an explanation for the following:

I found out that the battery is giving me 0volt between terminals. I measured all the cells (15 cells) and every one of them is fine… except the last one. But here is the plot twist:
*Each cell (cells 1-14) voltage is 3,6-4 volts between cell - and cell +. Good so far
*The last cell (cell 15) is 0 volts between cell - and cell +
*If i measure between battery negative terminal and cell 14 positive terminal i get 52 volts. Taking into account that i think that this is not charging… i guess that this is fine; voltages are lower when discharged.
*If i measure between last cell positive terminal and battery negative i get 0 volts.

So the last cell is acting as an open circuit and that is why i’m not getting voltage on the battery terminals. I guess is not charging for the same reason.

Obviously the cell is bad, but i do not know enough about batteries to explain why the cell behaves as an open circuit. Anyone knows? I thought that if the cell is bad it behaves as a short.

@ando Hi there! I had to replace that same capacitor. it is a 1uF 2012 package and I used a 10V rating. You can buy them in Newark

https://www.newark.com/kemet/c0805c105k8ractu/ceramic-capacitor-1uf-10v-x7r/dp/64K2894?st=2012 1f capacitor 10v

@lemur any recommendations? I saw the mg chemicals but it is low temp. The chipquick looks good (with lead)

Guys… do you recommend solder paste for the big pad of the mosfet? I saw that the melting temp of the solder paste is 183C (361F), which i think is safe enough, but maybe those mosfet get really hot on normal conditions and i don’t want to screw it up

@loaffette LOL
I thought on the wire but then i remembered all the problems i had in the past with vibrations on things that move and i will try to repair the pad with epoxy and copper. If it doesn’t move i don’t have to worry. On motherboards that are usually static there is no problem, but i’ve seen broken cables just due to vibrations, which is a pain

@lemur yeah… one of the legs lifted up a little bit the pad, so this week i’ll have to fix it with some uv resin. I checked the components next to it because i was concerned i destroyed them with all that amount of heat. Looks like those are ok, but… let’s see when the part arrive. This is taking its time xD

I made it. Heat, flux, more heat, more flux… more heat… and more everything. That was a hell of a mosfet. The solder these guys used is hard to melt, even when cleaning the pads. Well… another month to receive the parts 🥲

Finally the mosfet is gone. I desoldered the terminals and it is actually out. The problem is now that i’m not able to desolder this mosfet out of the board… it is like is bonded! Terminals are ok but no matter how hot i hit it with the air station it doesn’t move

I do not want to damage the pcb even more. Any suggestions??

@lemur thanks! Actually error 16 is gone (hopefully for good!). Now the board only stays on when plugged.

Taking into account that what i´m experiencing now are power issues i decided to not to plug the board again for now (I don´t know if i can burn any other thing) and take a look into the main MOSFETs. SO:

On the left side we have the 240N10F7 and looks good. But on the left side I found what apparently is a 20N08N5 MOSFET that is gone. I took a look into the resistance and are pretty low:

D-G: 2.4k
D-S: 0.2
G-S: 2.4k
S-D: 0.2
G-D: 2.4k
S-G: 2.4k

With these low values I thought that maybe I turned on the MOSFET when measuring on the gate because I have the same resistance between D-S and between S-D, but I put the negative of the multimeter on it to try to turn it off (just in case) and the values are still the same as above. In any case the rest of the values are also pretty low I think; G-S and D-G should be on the MOhms and are 2.4kOhm. I´m not still confident because when I plugged the OW the other day i didn´t feel any of the MOSFETs getting hot and a short as I´m seeing now could turn that component into a frying pan. I should have the short elsewhere.

On the other hand this maybe could explain those power issues. I´ll keep checking things and once checked i will connect everything and short the blue-black wires on the connector and also will measure voltage values on the MOSFETs.

@lia thanks! I will try that tonight and see how it goes. Something also weird is that when i plugged the charger it showed 100% charged on the app; but i know that it wasn’t at 100% (it’s been disassembled for two months or so)

I actualli saw a post about M8t … hahahaha viva la search!!

And i’m actually stuck on the ics from the upper side of the balancing connector (i want to check them since there is a lot of heat in there). The only thing i can see on the silk screen is M8t, which if i search looks like it is a sOT-23 and these ones have 6 pins, so it is not the same thing. I saw one that has 6 pins but it is a 9V voltage regulator, which i think it is not the same one. Finally i found a 2N7002PS which has M8% marking (% for the manufacturer site code) and is a 60V,320mA Mosfet. This one could be an option but i’m kind of guessing here. Any ideas out there? If it is a mosfet the pins should be grouped (3-2-1 maybe?) i should take a look to that… but tomorrow; time to go to bed xD

@lia correct; once the charger is unplugged the ow does not turn on. Which i’m still thinking why could this be possible. The only thing i can think of is that the bms is not allowing the voltage to pass to the controller for some reason (which should be related with comms i think… but that’s a noob assumption xD)

Replaced max ic, installed missing capacitor. E16 is gone! Which means that max ic and pic are supposed to be ok.
However, the OW only stays on when plugged. As soon as i unplug the charger it turns off. I see that the area on the top of the balancing connector gets hot, but that’s a bunch of resistors mostly…

I reveived the parts! I’ll get to work tonight. Finger crossed!!!