My first build 2014

Joined
Jul 4, 2017
Messages
221
This was my 1st go at a DIY pack. The larger bank is 2300mah cells and is 17 x 10, the two smaller banks are 2600mah cells and are 10 x 15. Gives me right about 12V @ 400Ah. Not a bad first pack. I damaged many of the heat shrink wrappers taking the laptop cells apart so I so even had to buy new heat shrink and wrap a bunch. Then I was going to wrap them all but that was more time than I wanted to spend in addition to the rest of the build. Its still in service today. I've had to swap out a few bad cells but no major rebuilds. 470 cells total.

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This is the batch I am testing as we speak. Its going to become a 12V 1000Ah pack. Ill have 6 packs that are 8 x 30 with 2200mah cells (avg) just under 1500 more cellsthat we can add to the cell counter!(There are about 2000 in the pics but some are unuable) and all the1400-1900 cells wont go into any builds.


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Nice work

Thats massive packs in terms of 1000Ah :)
 
daromer said:
Nice work

Thats massive packs in terms of 1000Ah :)

Its big.Edit* Its actually a 12Vnot 24V,it will be two 12V 500Ah packs in parallel. It was late here of the fireworks last night and I was a bit sleepy.

So I checked out a few of your videos mate, pretty cool. I wish I had done the Opus chargers instead of the Turnigy Quad. I like the Turnigy but Opus are so much easier! I ordered 10 Ardiuno Nano boards that should be here today and I plan to built my own little charging/discharge station with them. If it doesn't work out, I may sell the Turnigy Quad and just buy the Opus anyway.
 
daromer said:
Nice work

Thats massive packs in terms of 1000Ah :)

I am curious what is the nominal Low voltage cut off on lithium ion cells... and what would you advise to set your inverter to cut off voltage ?

and what safety method is advise for High voltage disconnect on charging devices AC chargers and solar charge controllers ?

John
 
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Pack #2 of 6. This one is only 8 x 27 because I used 2600mah cells. Its a bit over my target of 500Ahs but that's better than being under. I tried it with just 25 cells and it looked too odd. I had to extend the copper lug wire on the ends a little bit to make sure it still lines up with the other packs, but I'm stoked how it turned out. Loving this twisted wire busbar thing.

I have a bunch of 2200mah cells that are going into the next pack so it will be 8 X 32. Once its done I'll wire them up and put a charge in it for some testing. Stoked to have a place to share this stuff because as anyone who builds these things knows, it takes a lot of your time and sanity and its feels awesome to have a community to share it with. So thank you to everyonefor all the comments and likes!

@john mcCoy
Each manufacture is a bit different with their recommended low cut-off voltage per cell. Some makers say its safe to go as low as 2.5V, while other use the 3.5V figure. For my testing I use 3.0V cut-off. I've tested a few down to 2.5V but the curve drops off so dramatically below 3.0V that the power your getting out of the cell is not worthless compared to the stress its putting on the cell...if that makes sense.You might getan extra 50-75mah'sof energy but thedamage it can do to the cell is not worth it.When you push a li-ion to its max ( in either direction) it stresses the cell and can greatly reduce the life cycle. Since many of these cells are repurposed already, I don't want to degrade the cell any further an never go below 3.0V. If one of the cells I get from a laptop pack is already below 3.0V, then I charge it at just .050mah until it reaches the 3.7V mark and then slowly increase the current. If it holds the charge then I will cycle it three or four times to make sure it doesn't overheat or act up before I put it in the 'good' pile.

Safety for High Voltage (HV)disconnect: I havedisconnect switches (madeby SMAwhomake SunnyBoy Inverters) installedbetween my panels and the inverter (on each string), between the battery and the inverter, & betweenthe inverter and the fuse panel box. I only have the SMA branded switches because I got an amazing deal on thembut I'm sure any HV disconnect will work.I think a switch that can handle the high CURRENT is more important for most of our applications,butit depends greatly on how your array is setup. I'll post a pic of the switches shortly so you can see the one I am using.

Thanks again everyone and I'm stoked and honored to be a member of your community.



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SMA disconnect


AvgRageJoe..dude I built the bars based on your video. I love your humility man, who else would splice in the bloopers and out takes. I dig it. I'm going to check out some of your others now. I'm at the bench soldering for a few hours so I'll run your playlist. Thank again for the busbar idea.
 
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Another happy "camper". Literally! Installed this one in an RV under the fold away couch. The bank tested out just over 550Ah's and bounced back up to 10.5V after being discharge down to 9.0V for the load test. Pretty stoked...

I'm planning a new design for my next build. It's a blend of the old and the new and some things that havenever seen/ done before with18650 builds. I'll keep ya posted.

Cheers
 
10.5 down to 9V sounds alot! Either you pushed the cells way to much or you have huge voltage drop in the wires. But with that amount of cells it sounds like either HUGE load or actually to small wires :)

Neither less it's an impressive build.
 
No it's absolutely normal. Discharging a 12V pack down to 9.0V is exactly 3.0V per bank which is what I've been doing for years. The pack is tested on a Turnigy Quadcore Reaktor battery tester and when the discharge test is complete, the Voltage of the entire bank automatically pops back up from 9.0V to 10.5V which indicates a good battery bank. There is nothing at all wrong with my test, the math, or the battery.

Edit* I think you misunderstood. I charged the pack to 12.6V ( actually 12.55 to be exact), then put it on the machine for a 20A load/discharge test. The test took just over 28 hours nonstop because it's such a large pack. I set the cutoff voltage at 9.0V. When the pack hit the cut-off, and the test ended, the voltage popped back up, like all healthy cells do, to about 3.5V per bank or 10.5V for the entire pack.

I load test all my cells ( when I first get them) at 2.0A and this is why I get a higher final capacity than I plan for. I expected the battery to be 500Ahs, it was actually 550Ahs. If I tested the cells at 1.0A (after I remove them from their former laptop packaging) I would probably get a more exact number and be about to more accurately predetermine the final output capacity, but I feel like a 2.0Ah test is more realistic and helps get rid of, or weed out, any cells that may be close to their end of life cycle...it's just my preference because I sell these batteries and have to be sure that they will at least perform as I state...no one ever complained when paying for 500Ah and getting 550.
 
Im not saying its not normal :)

Im just trying to figure out what limit you have hit.
How much current per cell are you pushing when testing? I have not had many cells that bumps from 3 to 3.5 v when resting after a test unless i really stress the cells with high C numbers. Lets say atleast 2C or higher is when i see it happen on laptop cells.

Only real time i get that dramatic voltage drop currently is on my quadcopters. But then we talk about 50C :)
 
What voltage drop are you thinking mate? These cells are under a steady load the entire time until they get down to 9.0V. I don't think I understand. I want them to go down to the 3.0V (9.0V for the pack) so that I can record the result and ensure the battery is functioning.

There are no other wires or anything between battery and tester. With about 240 individual 18650's in each bank and the total discharge current set to 20A's, the load per cell is tiny. I built all 3 banks, connected the busbars in series, and put it on the tester.

At any rate, late here in TN. Chat later.
 
:)

Yeah at 20A on so many cell thats why i think it sounds weird that it bounces back to 3.5V. Did you meassure the voltage on the pack and compare it to the chargers voltage? or did you have the balance leads hooked up and checked that?

Because it do sound like the drop of 0.5V is way off to me. I have never had that much drop unless i push the cells with like 10A per cell or more. Thats why im just asking.

For instance when i run the test with my iCharger i get this issue easily due to the contacts on the wires going into the charger. i have to have the balance leads also hooked up even when i do single cell testing. And for high current i also add another volt meter.

Ie i think you might have like 0.3V drop between the charger and the batteries? just a guess since im not sure where you meassure.

Get to bed! It was just question for me to understand. Everyones setup is different and im eager to learn how it works for everyone.
 
Hey Mate,

I'll make a little video for ya. I also saw a couple of your videos and would like to chat about a project I am working on. My background is a BS in EE with a concentration in electronics and I will begin my Masters program for power electronics next month...( fingers crossed!). I've been building laptop based powerwalls long before it was cool and before there was any hype around it but I sell mine to paying customers so I typically don't record the builds. Not sure what YouTube money is, but I get between $2000 - $5000USD per battery bank...which I am happy with. I sell, on average, 9 per year, and have done so for just over two years. This year I have already made and sold 9 so I might have a record year! Again fingers crossed & if I keep getting battery orders, I may put off my studies for another semester.

Send me an email or message and let's chat about my new project. I want it all to be open source in the end, but need to finish it before I release too many details.
 
How much did you end up paying per pack?
 
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