Single cell voltage drop for no apparent reason
- Thread starter Philtao
- Start date
The BMS knows the battery configuration so it corrects cell IR for the number of cells in parallel. But in the manual calculation I did earlier I did not and you are right: the individual cell IR is 0.50 mOhm (twice nominal value!).
The difference is that the BMS only calculates IR under load (for exemple going from a 5A to a 50A load) and in the manual calculation above the starting point is a 10A charge current. I will have to review the IR algorithm as it might be a transient / timing problem...
Yes, I cannot be sure about that. In the future the PCB's will be manufactured and assembled in France, close to where the TAO Performance company is now located. So being close to the manufacturer might give us more understanding (control?) over the manufacturing process. We are also considering increasing the IP rating...
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,682
You need to specify the process. We hadn't, just assumed. So analog and power boards were just no-clean flux. Only the guy doing 10 fA electrometer has the sense to specify cleaning.
No-clean is fine for 3.3V logic. And it makes the manufacturing process green, by distributing waste over landfills worldwide, rather than collecting flux residue at the point of PCB manufacturing.
But maybe it has nothing to do with your problem.
If you have spare channels, you could include self-test of surface leakage.
I've found some customer interface personnel to sometimes be compulsive liars. I asked how many parts in the lot were hand placed. he said none. I said to have no assembly defects requiring rework on our first batch of prototypes, they would have had to have a 10 dpmo process. He said they did. On a first prototype? A part was used 10 places on each board, 20 boards, and exactly one site was stuffed with a different tolerance part of similar value, that was used elsewhere on the BOM? (Turns out parts fell off the SMT machine, so the operator picked one up and hand placed it.) I wanted the board shop to give us a list of all defects spotted and corrected, because that's the first place I would look if a board malfunctioned.
No-clean is fine for 3.3V logic. And it makes the manufacturing process green, by distributing waste over landfills worldwide, rather than collecting flux residue at the point of PCB manufacturing.
But maybe it has nothing to do with your problem.
If you have spare channels, you could include self-test of surface leakage.
I've found some customer interface personnel to sometimes be compulsive liars. I asked how many parts in the lot were hand placed. he said none. I said to have no assembly defects requiring rework on our first batch of prototypes, they would have had to have a 10 dpmo process. He said they did. On a first prototype? A part was used 10 places on each board, 20 boards, and exactly one site was stuffed with a different tolerance part of similar value, that was used elsewhere on the BOM? (Turns out parts fell off the SMT machine, so the operator picked one up and hand placed it.) I wanted the board shop to give us a list of all defects spotted and corrected, because that's the first place I would look if a board malfunctioned.
Marinepower
Solar Enthusiast
- Joined
- Apr 24, 2020
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- 224
I don't think Winstons have aluminium terminals (tinned copper i think) with big beefy M10 bolt.
I used the Winston bus bars in a marine environment for 2 years and they were nothing but trouble - as they are made of un-tinned copper.
I switched to Weber busbars which fixed a lot of voltage spiking cells issues i was plagued with while using the Winston bus bars. Just not good in a salty environment IMO
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