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w0ss semi DIY powerwall V2
#51
Turns out battery has a bad cell. Took it apart and tested. One cell was at .5volts. Battery hookup is taking it back. End of story, i think. I am going to go with Valence lifepo 138ah. I have a source. Will be selling the watchmon 5 and shunt.
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#52
(05-16-2020, 12:44 AM)evangarber Wrote: Turns out battery has a bad cell. Took it apart and tested. One cell was at .5volts. Battery hookup is taking it back. End of story, i think. I am going to go with Valence lifepo 138ah. I have a source. Will be selling the watchmon 5 and shunt.

Bummer.
Curious...if you don't mind, when you send it back, how is the shipping/cost handled to BatteryHookup?  Also, will you be selling your breakout board?
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#53
Just a heads up, if anyone is looking to order one of these breakout boards (thanks again w0ss for sharing the design and info!), JLCPCB is sold out of the fuses. I don't have any prior experience with ordering through them, so I'm not sure how long they take to restock. Given supply chain disruptions with the virus, I'm willing to guess it might be a while. However, LCSC has them in stock so I've ordered the fuses from them, the CN1 connector from Allied, and the U50/U51 terminals from Amazon. So, I guess i'll just order the boards from JLCPCB and assemble them myself. I know CN1 and U50/U51 are through hole and pretty straight forward. Anyone know about the fuses.. anything tricky to be aware of? This is a bit more round about than I was expecting, but as long as the assembly is fairly straight forward.. it seems like the best option right now.
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#54
The Fuses are surface mount but they are actually a decent size so probably doable. It would be pretty easy to redo the board with through hole if that would be valuable to folks.
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#55
w0ss, will you be addressing thermal protection for these modules?

Also, do you know the reason for the -8 pin being the same as the +7 pin?
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#56
My board is just a breakout board no protection at all. I only added the resetable fuses so I didn't burn up a balance lead if something got plugged in wrong/shorted.

The -8 and +7 is because the factory board is 2x7s monitoring sections. Not sure why LG laid it out that way but I am guessing they had a reason.
Sojourner likes this post
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#57
(05-19-2020, 08:50 PM)w0ss Wrote: The Fuses are surface mount but they are actually a decent size so probably doable. It would be pretty easy to redo the board with through hole if that would be valuable to folks.

Thanks, that's what i figured.  I've already ordered the surface mount fuses and will order the board as is.  Would it be possible to get a close-up photo of one of your boards so I can get a good view showing how the fuses should look when installed properly?  That would be a big help. Thanks!
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#58
Would 2amp fuses be okay on the balance leads?
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#59
I'm a long way from being able to hook up these modules and do any testing on them, so I'm curious to know from you folks who are using them, what sort of capacities are you seeing and how many kWh's are you estimating per module? BH was claiming 90% based on their testing so I'm hoping people are seeing something near that.
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#60
I never measured the wire so I can't say for sure. 2amp might be ok but I don't want to say yes and have it break something.

Here are a few closeups with a penny for scale.


My test earlier in the thread showed the following.

Discharge test of the bank from 4.08(3.57) to 3.40(2.98) volts per cell was ~425AH. Nominal is 550ah(378 LiPo/172ah LifePO4).

So I had ~78% capacity from 4.08 to 3.40. Since I had the LifePO4 pack in as well not sure how mush capacity it really has. I was also discharging it at probably .05c. Maybe I should isolate the Lifepo4 and do another test.
Thanks,
Will
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