My DIY 300A cell amp hour tester and cycler

Maast

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Finally got it done, if it looks like a kludge it's because it is - but it still works, and pretty well at that. It'll charge up a cell, then discharge it to a load and then charge it again and just keep doing that until I interrupt it. Unfortunately my data collection is having to manually write down the amp hours from the meter. I need a much better solution for that.

Three of small relays are to deal with the behavior of the lipo battery alarm I'm using as my low voltage signal and the fourth is to trigger an increment in the counter.
The big power supply is just a 12V megawatt I had laying around the small one is a 60a 3.3V meanwell I bought for this and the cc/cv adjustable power supply is my bench power supply. I've got about $130 into it that I bought specifically for it and most of that is the big 400a normally closed contactor and the meanwell power supply.

P1030916.JPG
 

Woggs1

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Finally got it done, if it looks like a kludge it's because it is - but it still works, and pretty well at that. It'll charge up a cell, then discharge it to a load and then charge it again and just keep doing that until I interrupt it. Unfortunately my data collection is having to manually write down the amp hours from the meter. I need a much better solution for that.

Three of small relays are to deal with the behavior of the lipo battery alarm I'm using as my low voltage signal and the fourth is to trigger an increment in the counter.
The big power supply is just a 12V megawatt I had laying around the small one is a 60a 3.3V meanwell I bought for this and the cc/cv adjustable power supply is my bench power supply. I've got about $130 into it that I bought specifically for it and most of that is the big 400a normally closed contactor and the meanwell power supply.

Nice! You should do a YouTube video to show it in action.
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
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Well done and personally, I would not say "kludge" with your kit, you set it up very nicely I have to say. As you noticed Cell & Battery testing IS an issue people are tackling and Will's Forensic Investigations are pushing more folks to check things out. See my ShunBin Thread as one example of how it is evolving. I mentioned / suggested (I believe in that thread) about how many cannot do any serious testing as they lack the gear or knowledge to do so. Heck some folks are lucky enough to have a DVOM that they can use, properly and who has a Fluke equipped test bench.

Maybe yourself and a couple of the others here who are great at whipping up a test suite as such, could create a simpler DIY "Test Bench" thread / article which show what to get, how to put it together to test cells etc. "note I said simpler, not simple" as it's never really just "simple" is it. unless you buy a big buck commercial cell tester and you, me and the everyday some won't do that or afford that either.

My new pack arrives next week.... I am indeed hesitant as it is an "unknown brand" to me and so far what Delta-V and a couple of others have discovered, warrants further inspection & testing prior to installation & running. I want to test these to some extent, unfortunately I no longer have any of the gear I used to and budget is very tight, so I need to assemble a "testing rig" on a budget that can test the cells and completed pack. I prefer not to test using my live solar system until I have complete confidence in the pack.
 

Woggs1

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Maybe yourself and a couple of the others here who are great at whipping up a test suite as such, could create a simpler DIY "Test Bench" thread / article which show what to get, how to put it together to test cells etc. "note I said simpler, not simple" as it's never really just "simple" is it. unless you buy a big buck commercial cell tester and you, me and the everyday some won't do that or afford that either.

I second that notion! Unfortunately it won't be me to start the thread because I am clueless on the issue, but want to learn.
 

Bob142

Build more, learn more.
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I second that notion! Unfortunately it won't be me to start the thread because I am clueless on the issue, but want to learn.
Maybe yourself and a couple of the others here who are great at whipping up a test suite as such, could create a simpler DIY "Test Bench" thread / article which show what to get, how to put it together to test cells etc.

Let's skip the member vote and go right to motion carried. @Maast and others: great work - a DIY test bench blueprint would be very helpful to so many people.
 

grizzzman

Some say "Why" and some say "Why not?"
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Could you share the low voltage alarm you are using? ( behavior of the lipo battery alarm I'm using as my high voltage signal )
 
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Maast

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Washington State
Could you share the low voltage alarm you are using? ( behavior of the lipo battery alarm I'm using as my low voltage signal )
I just used these Amazon link, they're common and cheap, surprisingly its really difficult to find a inexpensive low voltage alarm for 3.2v cells until I stumbled on those.
There are two generations of them, I used the newest because it has better voltage resolution. Desolder the pizeo noise makers and use the left hand pair to trigger a signal, I had to put in a 100uf capacitor to smooth out the signal enough to reliably trigger the time delay relay. The alarm can be set in .1v increments between 2.7 and 3.8 volts. The far left pin is ground, 1s is pin two and 2s is pin three, etc. They have some PITA behaviors though: beep on power up, you have to have power applied to pin 3 for the alarm to work (used the 12v), if you leave the battery connected when you turn off the 12V supply it detects that and annoyingly it wont redetect power being reapplied so it shows "2s" (and you need 2s for the alarm) until you cycle power to it on both the batt and 12v rail.

I also had to do a common negative for the battery and the power supply to feed the 3rd pin with voltage.

Which lead to it own problems - I ended up with a 12v bias coming from the alarm circuit going to the time delay relay trigger which would activate the relay constantly, so I had to isolate the TDR with its own power supply; a USB phone charger which the relay just happened to have a input for.

I'll try to do a diagram, but I just kind of laid it out in my head and started putting things together, ordered whatever I didnt have on hand, and modified as I went to get it to work. I tried to be tidy but the wiring still ended up a mess.
 
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grizzzman

Some say "Why" and some say "Why not?"
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Ya, I have been looking for a replacement for the Junsi Celllog 8 M and S series units. I would like to find a cell level volt trigger to set up as a charging disconnect. The issue with what you are doing is I need to have the unit reset when the voltage is above the trigger threshold.
 

Maast

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The issue with what you are doing is I need to have the unit reset when the voltage is above the trigger threshold.
Oh yeah that was another annoying thing about these, even if the voltage goes back up above the trigger threshold it wouldnt STOP alarming.
 

Johan

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@Maast Great work! I agree: Dump that electrical energy in water, having one of the highest heat capacities available and dirt cheap. Oh, and you are not alone with tedious non-automated cell measurements - The famous Jack Rickard does it too.

Here is (a tiny fraction of?) blue prismatic cell "supply chain" info, followed by a question:

Factory name: ETC | Check this ETC energy density roadmap graph :p!
Reseller example (Switzerland, EU, has datasheets :)):
https://www.lithiumstorage.eu/Joomla/images/Produkte/ETC-Series/ETC-LFP277AH.pdf

Factory name: CATL
Reseller example (Zaozhuang , China, limited datasheets):
http://www.evlithium.com/catl-battery.html

Reseller with unknown factory, sold under the name "XCell" (Utah, USA, limited datasheets):
https://www.electriccarpartscompany.com/Lithium-Battery-277Ah-LiFePO4-XCell
Also see this thread.

Reseller with unknown factory, sold under the name "Venom Industrial" (Idaho, USA, has datasheets :)):
https://www.vpwllc.com/prismatic-cells

On Alibaba, the company named "BLS" sells blue cells from both CATL *and* ETC: in at least this instance they use the same listing for both factories. More discussion here.

👉Any idea which factory made your cells?

Also here you observe an internal DC resistance of 0.075V / 20A = 3.75mΩ. Where along the SoC did you see that? Only toward 100% and 0% or everywhere? Did the cell get hot? Maybe also nice to fully thermally insulate the cell to simulate being embedded in bank while (dis)charging, and measure the max temperature and compare to theory.

Also you work with (expensive?) time delay relays. What about using this programmable timer in combination with a standard relay?
 
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Maast

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Not sure where you're getting the DC resistance value, I haven't measured it, if you're looking at a picture of a display I wouldnt set any value on it, the meter is only attached to the shunt and main power supply so any other readings are spurious.

The relay is cheap, its a simple DROK I got on Amazon for $14 and if you look around you can find digital time delay relays even cheaper than that, I just liked its interface - I got lucky w/ the USB power input it turned out I needed. The other relays are even cheaper than that, I think I paid 12 bucks for a bag of 5.

Of the 5 batteries I got, one is a ETC, three turned out to be the same GFB battery from three different vendors, one is a ETC battery, and one is a real turkey thats supposed to be a "Lithtech". What happened is I put out a RFQ for 270-300AH batteries without specifying brand names and this is what I got.

Of the three types, initial capacity testing at .25C gave me consistent 286AH for the GFB batteries, 279AH for the ETC and 273 for the turkey. I have to say I like the GFB batts quite a lot and those are probably what I'll be going with. None of them have gotten warm, but then I havent discharged at a 1C rate yet either. I'm still working on the adjustable load bank.

Until I get a decent cycle sample size I can't definitively say which battery I'll be going with. Cycling these from 3.65V down to 2.8V is taking forever. I can discharge in 2 hours, but charging is taking me 10 hours so I'm only getting two cycles a day. I just put out a bunch of RFQs to more vendors at alibaba for a 120A constant current power supply; meanwell HRP-600-3.3

BTW, here is the spec sheet for the GFB batts
GFB.jpg
 

Maast

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BTW, if anybody is in the Tacoma WA area and want to test a cell please PM me. I'd be glad to. The load bank can handle up to 12V but the minimum amp draw at that voltage will be 120A and it'll probably make the stainless wires boil the water immediately around them. I can do 30, 40, 70, 140 and 280 amp loads or any combination thereof @ 3.2v - or at least I will when I get the load bank done this week.
 

mzoid

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I have the pleasure of resurrecting this great old thread!
@Maast - any further insights from the cells that you can share?

Specifically, I'm wondering if you would be willing to post a photo of the top of the 'turkey' cell that underperformed compared to the others.
Lithtech are currently offering some CATL cells that I'm interested in. With all the time that has gone by since you ordered that under-performer from them, I'm sure they've sold many other batches from many manufacturers, but I would still be keen to do a visual comparison.
 

Maast

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I have the pleasure of resurrecting this great old thread!
@Maast - any further insights from the cells that you can share?

Specifically, I'm wondering if you would be willing to post a photo of the top of the 'turkey' cell that underperformed compared to the others.
Lithtech are currently offering some CATL cells that I'm interested in. With all the time that has gone by since you ordered that under-performer from them, I'm sure they've sold many other batches from many manufacturers, but I would still be keen to do a visual comparison.
It's sitting on a shelf somewhere, I'll see if I can find it. I ended up going in a completely different direction with used BYD modules - which turned out to be a huge mistake and almost a year of labor. I should have stuck with the 280AH cells. I think I might have been the first to get interested in them.
 

mzoid

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It's sitting on a shelf somewhere, I'll see if I can find it. I ended up going in a completely different direction with used BYD modules - which turned out to be a huge mistake and almost a year of labor. I should have stuck with the 280AH cells. I think I might have been the first to get interested in them.
Hey - don't worry about it if it's a hassle.
Really sorry to hear about the wrong turn you took.
In what way did the used BYD modules disappoint?
 

Maast

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Hey - don't worry about it if it's a hassle.
Really sorry to hear about the wrong turn you took.
In what way did the used BYD modules disappoint?
The BYDs were badly under expected capacity but worse than that the individual cells in the modules are horribly capacity mismatched and I had to figure out a way to even them up. Required a shitton of testing and cycling per module and then adding booster cells to the weak ones. Rinse and repeat for 18 modules. Took me forever.
 
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