So, I hooked my “fried” DieBieMS to my battery and could connect to it through Serial port using a TTL USB converter.
Pack voltage is OK.
All temperatures are OK.
All cell voltage are OK BUT one (C0) which is off by 0.28V (confirmed with a voltmeter).
Start with continuety meassurments, From C0 group, via cable to connector to resistor, to see where the drop is. if you end up with 4,08V at the LTC IC then I’d say you prob looking at swaping it for a new one.
Could also try apply some preassure to the connector to see if the crimp is crap or not
Thanks for the tip.
I finally found the culprit : C0’s R36 resistor is 18 kOhm instead of 100 Ohm.
This resistor is inline with the LTC cell voltage reading input, so it explains why it’s off.
The microscope also confirmed he was probably the smoker one :
Oh sure you can! Just power it of first and its pretty risk free
You just need two soldering irons or if you’re really quick you can do it with one.
I think one resistor is 100Ohm and the one next to it is 3.3k
I am having an issue, my board does power on but as soon as I apply any acceleration, even without me standing on it. Diebie shuts down with the following error shown in the diebiems tool: “errPreCharge”
Any idea what that error should mean or what would be the cause of it?
I’ll bypass bms later today just to confirm that it is diebie that’s shutting down.
Can you check on your PCB for any signs? like missing resistor or burnmarks.
From what I can tell from the datasheet of bq76200, the precharge is meant for a deeply depleted battery to set a lower current to not harm the battery. Its controlled by the MCU however. So not an automatic function.
In settings to my BMS I have the precharge output on true for discharge as well. Not entirely sure what it does while discharging since the series resistor R33 only handles around 3-5W. Maybe its used as kind of a softstart/inrushlimiiter before you can utilize full current.
Thanks a lot. I’ll do a visual inspection later today, I don’t have a multimeter with me since I am on a vacation but surely I’ll update you once a take a look at it tonight.
On further inspection I think that the precharge condition from the BQ76200 in Diebiems case Isn’t used as described in the datasheet at all(trickle current), but implemented precharge for the discharge if that makes sense.
This is it. This is why there is a timeout paremeter.
ERROR Precharge is triggered when the BMS is in Precharge operation and the load voltage hasn’t match the battery voltage * a precharge percentage (“Minimum precharge factor” parameter).
This is pretty strange as normally this error occured at the startup…
Could you hook a PC to the DieBieMS for reading its state ?
I was riding really slow… Like 8-9km\h. Stopped to let some cars go by, and the board was off… Turned it again on pushed the acceleration just to see it off again…
