Puerto Rico Powerwall

riveracc1

Member
Joined
Dec 16, 2016
Messages
9
Hi everyone !
I've been her for a while...looking, asking and learning.
I think I had introduced myself before but here goes my powerwall presentation. I am a small business owner fromSan Juan, Puerto Rico. In September 2016 there was a complete power grid failure due to a lightning strike on one of the main power generation plants. The whole island (100 miles long x 35 miles wide / 3.8million people) wasleft in the dark for 3 days until the grid could power back up.


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I own a 6 seatbarber shop and a car audio repair shop. By luck I had a Trace power inverter in the shop for repair (from a client that had problems charging but the inverter part worked. I hooked up 4 12v AGM 112ahbatteries I had at the shop and wired in half my breaker panel. To my surprise, this worked great for 3 whole days buy my batteries drained completely down to 21 volts. Had a hard time recharging but decided to have some kind of electrical backup permanentlybuilt for the shop. Hey, It's my money maker!
I ended up buying a 6.5kw diesel generator for the barber shop but I want something more silent, less smelly and less maintenence.

Some how, some way I started looking for ideas, info and very soon ended up here. Learned a lot and I'm still learning. Most of the people in the youtube videos are part of this forum.
My first bite on the 18650's came when I won an auction on ebay for a big lot of Ryobi 40v mower packs. I "recon" (caught that grom Peter's videos) y got about 600 cells on that lot. All Samsung/LG 1200~1400 cap cells in great condition, just dead in voltage. I devised a holder (4 cell) with a 20w / 20 ohm resistor in series to a 12v battery in order to "wake" them. Put them in the cradle and switch the 12v for 10 to 15 seconds while "handmonitoring" temp. The ramp up to 1.XX volts, enough to go to a string of 4056's and fully charge them up. From there to storage for 2 or 3 days and recheck voltage for drops. If they hold up, I send them to the Opus. So far, about 20 rejects in total, all shorted, only 1 open. For now I have them sorted by brand but marked from 1100 to 1460'ish.

(Gonna add some Charge Station pics soon)

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Have not decided on pack shape but playing around with some buss bar ideas, case/enclosure ideas, monitoring/BMS/fan cooling and others before I build.


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I need these INSIDE the shop for security purposes so I chose a "spot" and in the process of building the case for them. Apart from being my power backup at the shop (I open 6 hours a day, 6 days a week) I hope to extend or enlarge the battery bank so I can maybe last my 6 day work week using everything Iuse now including A/C. I will be using a 7s setup with electrical (grid) recharging as I only need this as a powerbackup. Aa soon as this is all running smooth I will start adding more packs and solar panels for recharging.


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My wife says that this is a new "hobbie" for me and I agree. I enjoy the skill learning and thebuilding process more than the actual usage for witch it was intended. Now all I need to figure out is how to "deviate" more funds without the wife getting upset about it. I will keep uploading more pics of my build on this same thread.


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A little bonus... this is my passion, what I do for a living... Car Amplifier repair.
Thanks for reading!
 
Nice build you got there m8!
 
Very nice. I like the green fade you got goin on there :) Too bad you didn't have good enough dark green cells to put in the very center to have 3 color fade. Maybe on the next batch ;)
 
looking good, how mnay cells in total ?
 
not2bme said:
I noticed you posted your first powerwall right before the hurricane! How did the wall performed after that?

I was tinkering with 18650's before Irma & Maria. I already had about 1000 unharvested cells to tackle. When the hurricanes hit I got up and running on my old AGM 450ah bank but it was old and failing. I stepped up the cell game and put up a 3S 12v system to get by and worked great. I just kept adding from there.


June 2018 updates.
Settled on 2800 cells 7S400p in 4 banks of 175ah. Got the Batrium up and running on 2 banks and rearranging the other 14 packs with better cells. Hope to have the other 14 packs up by the end of the month.
Total MAX power draw is around 2100W with everything running so my inverter is capable and more. I still have solar issues, getting some wiring re-done on a higher gauge and a new Charge controller for some extra panels.
Here's some progress pics.

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Just boosting my cell count... ??


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3100 and counting.
 
Dam dude - that's looking awesome!
 
Some updated pictures. Just added one more 7S100P battery for extra storage and reconfigured my solar to a higher voltage level (3S strings).
Doing a lot of "One year later" tests for degradation and it all boiled down to an average of 13% degradation of 12 months, about 200 full cycles, complete off grid use for the last 2800 cells. All from unknown sources, fully tested, no failures. I'm happy with the results.
 
It's hard to judge with old cells, but 13% capacity drop over 200 cycles seems pretty bad? At that rate you'd probably need to retest and rebuild all your packs every few of years?
One form of degradation can be reduced a lot by lowering the max voltage. For powerwall usage, around 4.1V~4.0V / cell seems to be the sweetspot re lifespan vs usable capacity.
High temperature kills cells, too.
Another form of degradation can be mitigated by drawing less amps/cell.
What voltage do you charge/discharge to, at what temperature, and at what amps/cell?
 
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