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The Outhouse Powerwall
#21
(08-12-2018, 12:11 PM)Korishan Wrote: Interesting BMS.

Can you tell me the numbers on these two ICs? Curious as to what brains they are using for the logic

It's an ATMega8. The J2 headers leads to the programming ports so I presume it can be reprogrammed through that. What I would really like is for it to balance to .02v and then stop balancing until it reaches over .03v difference and not to balance at the bottom, ie. below 3.6v. Anything below that is pointless as there's not much capacity left in them leaving it trying to work hard balancing it when it's not needed.

Did another test with a few varied voltages this morning. This is a single cell so I doubt it's moving more than 100ma between them.
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#22
ahh, thnx. Not exactly what I was thinking it was. But, it does make sense. It uses the ATMega8 to do the brains work, then uses the DeMux to trigger the FETs to enable/disable the discharging.
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#23
Hooked the BMS back up to my battery pack and can now watch my packs in grafana! The USB to TTL was fine while testing on my bench but when running it along power lines it picks up some interference and not getting a good reading. So I ended up running around the power lines and seems to be better now. Setup is ugly but I'm just eager to get back to solar production after over a month of hiatus! What the hell, as long as it works!

I have another 7 packs tested, ready to be assembled and spot welded. So should be going in this month or so. Then I have to ground mount my solar panels, whenever it stops raining every friggin weekend!

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#24
Took that long weekend and slaved away stripping romex wires, twisting, bending, crimping, heat shrinking, zip-tying, sorting, spot-welding and soldering. All that equals to another row of batteries in my Outhouse!!

Now up to 10kwh!!! 



This is a 7s60p configuration, but since I link the batteries together, they essentially are a 7s180p configuration. I have them linked in between with some 12ga jumpers. I think should be plenty as I would never expect to see more than 20A transfer between cells. . And because it's not fixed, I will be shifting the packs around so they're more even. Once the batteries settle down after a week I'll see which ones are the weakest and the strongest and swap the packs.

Before the update Cell 2 was always the lowest at full charge and highest at the low charge, so it's the strongest. The difference between the packs always stay under 20mV. Right now my Cell 2 seems to retain a higher charge, but since my BMS doesn't really balance unless it's over 30mV, it'll take a while for it to bring down. Anyone have ideas on depleting a pack? I can hook up my charger to it, but thought there might be an easier way, like a resistor or something that is just a parasitic drain?
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#25
to balance a single cell manually I use a 10W 3Ohm resistor to pull just over 1A out of a cell. I have one of my cells that has had some dead cells and therefore popped fuses and that one gets high during charge and I don't go anywhere near empty so it's fine. After a few charge cycles it gets close to 4.2V so I pull it down but it takes a few hours to come down to where I like it. (7s56p)
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#26
(09-05-2018, 12:26 AM)jdeadman Wrote: to balance a single cell manually I use a 10W 3Ohm resistor to pull just over 1A out of a cell.   I have one of my cells that has had some dead cells and therefore popped fuses and that one gets high during charge and I don't go anywhere near empty so it's fine.   After a few charge cycles it gets close to 4.2V so I pull it down but it takes a few hours to come down to where I like it.   (7s56p)

Thanks!! Simple enough for me to do. I just ordered a 100W 1Ohm resistor off amazon to add to my list of tools! That should pull about 3-4A and bring that pack down enough that it'll stay more in line with the rest of the pack.
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#27
Yea Ive put 3 in parallel and pulled just over 3A . Just watch the heat
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#28
fantastic work bud - shared on fb - https://www.facebook.com/photo.php?fbid=...ater&ifg=1
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#29
Thanks Pete! It's all thanks to discovering your youtube channel, then watching hours of your videos and browsing everyone's build this website that made me decide to get to this point!!

Appreciate the share on fb too! (though I'm not on fb...)
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#30
(09-06-2018, 11:26 PM)not2bme Wrote: Thanks Pete! It's all thanks to discovering your youtube channel, then watching hours of your videos and browsing everyone's build this website that made me decide to get to this point!!

Appreciate the share on fb too! (though I'm not on fb...)

You're welcome bud! Gota get this stuff out to as many in the community as possible
If you'd like to support the forum please feel free to use my affiliate links to purchase all kinds of stuff for your projects 
Amazon - https://amzn.to/2qURmH2
eBay - https://goo.gl/6mrQHH 
Aliexpress - http://s.click.aliexpress.com/e/bNLW537E
Banggood -  https://goo.gl/FF2v6W
Battery Hookup - http://bit.ly/2Oe9PLW 
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