Beginners Guide to Processing 18650 Cells | Cell Database


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Bob's Powerwall Project
#31
2x14s450 is 600kg... Not many modern raid cabinets that like that weight Big Grin

RAIB5+0 ?

I have spare pack. But its manual labour. No use at all to have one spare that is automatically gets inserted if you got 2 or more strings. I run 4 main strings and 3 secondary so i can easily just swap out 1 string until i have fixed the faulty pack.
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#32
While I like the idea of a redundant pack to be able to put in the switching needed to be able to put it where it is needed automatically would be nuts. I'd rather have it sitting partially charged for when a cell has a problem and then it can be swapped out to keep the rest of the batteries operational.
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#33
I agree, I guess I was having a maxi-zoom-dweebie moment and try to figure out how to automate something that does not need it..... thanks for the advice.... I suspect I will just keep am extra pack available i needed.
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#34
There is however somethink you could use a spare pack for:
Active balancing. I have been think about it, and perfect (but slow) active balancing could be achieved using a spare "flying" pack and some relays (14S-pack would need 14*1+5 relays to be precise).

There are different algorithms for this, but I would use:
Step0: Log all cell-levels
Step1: Select Higest and Lowest.
Step2: Connect flying to higest for x minutes
Step3: Disconnect for x ms
Step4: Connect flying to lowest (from step1) for x minutes
Step5: Disconnect for x ms
REpeat, and keep doing this as long as system is operational. Under charge, under load, allways.

Has it been done before? yes. Its called flying capacitor balancing - but this uses solid-state and caps and can therefor not overcome a minimum voltagedrop through the FET-switches for balancing - I would use mechanical relays, with a specific loadconnecting relay (protected with freewheeling diodes), and the rest as normal. 12V auto-realys cost nothing and are good for millions of swithes under no load, and balancing would converge to 0.00V difference.

Try a google for "flying capacitor balancing"

Main advantage - active balancing "for Free" since we allready have some spare batteries :-)

[Image: energies-07-02897f5-1024.png]
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#35
Maybe you need almost the same sytem to read voltage separately of every cell.
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#36
Greetings All, after dealing with some major health issues I am back, not sure how back yet, but back. Anyhow, in the next 3 weeks I expect that Tesla will be out to install 9.1 kw of solar panels, I refused their power wall for reasons you all are too aware of.... I have begun emptying my Dell rack in my basement, need to sell my blade centers, this project is more fun than the 25 servers I have in my rack. The joke in my neighborhood was that when I turned all my systems on the lights would dim. Needed to water cool my electric meter, well now I hope to get it to spin the other way and I placed my computer lab on my 24 core 128gb MAC. For years I have been sucked into over clocking while heating the house. Now I have found you guys with Pete being the king pin and now I have a new hobby. 

Today I finished my first PAK, finished as in all the batteries have been tested over and over. I re skinned them, I know it does nothing to the function, but it is like OCD or something. I have decided to buy 6 rack shelves for my 42 Dell rack shelves which are 19" x 39" and place 7 packs on each shelf. My packs are 240p, so I will be 14s 240p with the goal of having 14s720p x 2500ma x 3.7v. Since Tesla will not allow me to directly access the PV system they will be installing, I am going to have to go the AC Coupling route. So I am watching all the videos and reading all the white papers I can. So right now I am trying to determine the best bus bar design to use. After watching Darrel's video on the 906a spot welder, I think I am going to buy one to use because the Fast Axial Glass fuses are so small and their is not a lot of real-estate. I also am using Mike's suggestion of 6 awg copper wire. 

  

Perhaps if I am successful with the AC Coupling I will start a thread of my build..... for now, looking for advice on my pack deign.

-Bob

Just got off the phone with Tesla aka Solar City and they scheduled my install Sept 9. Guess I am going to have to hide all my DIY stuff Smile Thus far I like the Magna Sine 48 volt inverter.... hoping to get some input on that from someone who has experience.... Also, the electric company has to install a Net Meter and they say that can be 6 to 8 weeks..... ouch....
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#37
Looking awesome Bob
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#38
Huge packs! Good work m8 Smile
Follow me! >> YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#39
Amazing man! Those packs are gigantic! What do you expect your capacity to be?
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#40
I am just finishing up on testing to full a second, I have an idea of a bus bar design, just waiting for the spot welder because I want to use the Glass Fast Axial fuse. Each pack will be 240P with average of 2.5 giving me like 2.22 kWh each
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