WTF happend with my unity? (overvoltage error)

fallingdown · February 22, 2020, 8:33pm

Used my board yesterday but a belt snapped so did a long walk of shame home but motors was disconnected. Opened the enclosure and there was no water inside (always do this) so cleaned of the rest of the board.

Today I put it back together and charged the battery (12s4p 20700b full for the first time and now I suddenly get this error when turning on my unity

but my pack is at 50v not 61?!
BMS

Multimeter measurement

What the fu have happend? Any one got any advice to fix this? Have disconnected the pack a few min with no luck.

PixelatedPolyeurthan · February 22, 2020, 9:08pm

Jason took another shit i tell you. My theory needs still be prooved but i believe this is it

fallingdown · February 22, 2020, 9:31pm

that he would have implement this to activate at random in the code? Seems like a far fetch

fallingdown · February 22, 2020, 11:49pm

Might have found a workaround I will try tomorrow

I hope for the best and that the input will adjust when starting to drain the battery or ells I am screwed on low battery protection lol

fallingdown · February 23, 2020, 11:09am

Starting to piss me of real good now…
Anyone know a workaround?! Please!

BluPenguin · February 23, 2020, 8:18pm

@Deodand Help? What happened here?

fallingdown · February 23, 2020, 8:29pm

Just a FYI plugged in a 4cell lipo that was at 14.xx volts and it shows up as 21v.
Bumped the board on my way home so might be hardware related to if lets say a resistor came lose but impossible to say without some knowing of the circuits

Deodand · February 24, 2020, 1:43am

Yeah seems like one of the resistors on the voltage divider to measure voltage is somehow changed? Really strange I’d take off the silicone and wipe down the PCB make sure it’s all clean.

fallingdown · February 24, 2020, 8:15am

Will do. You don’t have any info on what resistors are used for voltage dividing and what values they should be? Could check them all to see if they are correct after cleaning
Good to hear that I’m not alone with this idea

fallingdown · February 24, 2020, 4:37pm

Was nice and clean but cleaned it with IPA but still no change Was considering that a solder is lost but then it should not show any voltage at all. Might need to check all resistors one by one and hope to find one out of spec.

Hate that I sold my focboxes now lol

Deodand · February 24, 2020, 9:35pm

R24 should measure 2.2 kOhm
R23 should measure 39kOhms

fallingdown · February 24, 2020, 10:10pm

thank you!!! Seems like R23 is at 4mohm
What resistors are these? Just messed with smd components a few times. Will se if my local supplier got in stock

Deodand · February 24, 2020, 10:40pm

They are 0603. Can buy them here:

https://www.digikey.com/product-detail/en/panasonic-electronic-components/ERA-3AEB393V/P39KDBCT-ND/1466090

Are you sure on that? If raw battery voltage were going into that pin the MCU would probably blow. The GPIO pins are only tolerant to 3.3V.

Blasto · February 24, 2020, 10:44pm

if that res was very high impedance, the mcu would see close to 0V. so the mcu should be fine. change that resistor

fallingdown · February 24, 2020, 10:58pm

Measured a bunch of times now and its 12mohm so definitely broken. Higher Ohm should mean that the MCU sees less volts if I’m not mistaken (rookie on this lol) so really odd that it shows 61v but might be that its so far out of spec that the MCU goes nuts. Will pick up a new resistor tomorrow they ‘‘only’’ had 9559 in stock at my local electronics shop so should be all good lol. Will report back here what happens when its swapped will do it first thing when I get home tomorrow.

Thank you all for the help so far much appreciated!

BluPenguin · February 24, 2020, 11:30pm

Curious to find out what happens too. Deodand basically designed that whole thing so he’s pretty qualified on troubleshooting it.

fallingdown · February 25, 2020, 5:54am

yea really great that we got him specially now that enertion have gone under.

Gerrycorrado · February 25, 2020, 7:21am

@Deodand what does c17 do?
Seems that one blew in my unity

fallingdown · February 25, 2020, 5:02pm

Didn’t help Still the same error. When measuring C23 mounted I get 3mohm now and when measuring the resistor lose it get 39kohm…

Blasto · February 25, 2020, 5:10pm

I assume you meant R23 (not C23)

make sure it’s soldered properly, the resistance would not increase like that unless your meter is low battery or the resistor is badly soldered