w0ss semi DIY powerwall V2

w0ss

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Oct 15, 2019
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Glad the other one is working :)

I just bought one of the cheap 48v to 24v converters. Although I might try to figure out a new plan. The MM8 needs 12v to run. I was planning on running everything off that converter but the MM8 has me thinking of other ways I could do this since now I have my WM5 and MM8 running off 12v.
 

evangarber

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Apr 21, 2020
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if I can get this battery working well and safely under control with my SMA sunny islands When they show up at Battery "Whatever", I am going to buy two more and go off grid. I'll need to consider what I am going to do when I add the mm8. It's unfortunate there isn't a site for Batrium Watchmon users to share approaches.
 

Sojourner

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May 7, 2020
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Hi guys. I have one of these batteries as well. Actually, it's the only component I have so far for my system.

Can you tell me what chemistry this module uses? Someone said "Lithium Polymer"...not sure what thatmeans exactly. Others say NMC...etc.

Following the thread with great interest.
 

Sojourner

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w0ss said:
They are filled with LG JH3 pouch cells.

Thanks. What I actually need to know is which general chemistry (class of battery) this is, so when I select a BMS/charge controller/etc to use, it will be able to work with this battery...for example, have the proper setting available in a pulldown menu in its setup utility. For example, if a BMS says it will work with Li-ion, or Li-Po, will it work with this battery? Hope I explained that well enough :dodgy:
 

evangarber

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Apr 21, 2020
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I have gotten my batrium bms to pass the testmon. However After installing into the watchmon 5, Iam getting some very strange readings from the watchmon 5. 11 Ofthe dells are showing 3.75 volts but the 8th cell is blank and the 6th and 7th are showing a blinking tower with excessive voltage, the Blinking on and off tower shoots up to 5.5 volts. I do not think this is a real measurement The battery is cold. My battery also is showing when i test at the terminals 49.1 volts as if one cell is not functioning. At all.
I have yet to charge or put any load on this battery.
I Am thinking may have a defective battery..

Is there any advice you can give? I am thinking of returning the battery. It is Nowstored outside BetweenHardibacker board
 

w0ss

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Oct 15, 2019
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That doesn't make much sense to me. If it passes the testmon then that means it saw all good voltages. If the 8th cell was blank then it shouldn't have passed the testmon. Perhaps you have a loose connection? I guess it would be possible one cell is bad, but again it should have failed on the testmon. These cases come apart real easy and you would have access to the connections on the sides to double check at the battery.
 

evangarber

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Apr 21, 2020
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Turns out battery has a bad cell. Took it apartand tested. One cell wasat .5volts. Battery hookup is taking it back. End of story, i think. I am going to go with Valencelifepo 138ah. I have a source. Will be selling the watchmon 5 and shunt.
 

Sojourner

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evangarber said:
Turns out battery has a bad cell. Took it apartand tested. One cell wasat .5volts. Battery hookup is taking it back. End of story, i think. I am going to go with Valencelifepo 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?
 

HydroGeo

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May 7, 2020
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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.
 

w0ss

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Oct 15, 2019
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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.
 

Sojourner

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w0ss, will you be addressing thermal protection for these modules?

Also, do you know the reason forthe -8 pin beingthe same as the +7 pin?
 

w0ss

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Oct 15, 2019
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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.
 

HydroGeo

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w0ss said:
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!
 

HydroGeo

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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.
 

w0ss

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Oct 15, 2019
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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.

image_aoarrn.jpg

image_dewvto.jpg



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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