2 weeks of top balancing finally complete! 16 280ah cells

Firstascent

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Mar 7, 2020
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149
Finally, after two long weeks my 16, 280aH cells are finally top balanced! I've had my cells for about a year now unused because I had been waiting for the new MultiPlus II 120v to come out. Now that I have one I'm getting the rest of my system ready which means time to top balance my cells.

All my cells were at about 3.29v at the beginning of the balance, they sat connected in parallel for 5-7 days before the balance as well. I purchased one of the recommended power supplies will recommended from Amazon, 30v/10a. I tried to find a high amp model but nothing was readily available at that exact moment.

The hardest part I think doing this for the first time is the amount of time it takes and wondering...is anything happening!? I did make my own power supply leads as most recommend with much larger cables than needed but it's what I had spare cable of, 4 gauge! haha.

For the first 10-11 days or so my power supply looked to be chugging along at just a little over 9amps. I know it's recommended to adjust to about 80% to prolong the power supply but I didn't care if this only lasted long enough to finish my top balance :)

Towards the last couple days I started having issues the with PS, my individual cells from my Fluke meter was about 3.36v but the power supply went into CV mode and was showing 3.6v and maybe 2a. I didn't think that would be correct and did lots of searching but mostly found people resolving this by making their own cables, which I already had done and I was confident in them. However, my crimped lugs were a little oversized physically compared to the PS hookups, all I did was simply just barely adjust the contact point of the lug to the PS and BAM, 3.5v, 9a, and back in CC mode. I probably lost about 1-2 days from this error.

This was all done in the "garage" of my RV 24/7, day night, awake or asleep. I knew it was going to take awhile so I kept a close eye on it until the end.
The last evening I checked on it and to my surprise it was showing CV mode, 3.6v and less than 1a. So at some point in a single day it went from 3.4v to 3.6. Very quickly as one of Will's post suggested. Also, my original plan was to do the latest recommendation of a stepped approach where you balance to 3.4, then 3.5 then 3.6. But with the issues I had at the end I got a little impatient :( oh well.

That last evening I kept a close eye on it, I didn't know how long it would take. I set my alarm every 20 minutes until 4am! it was a long evening haha. I pulled the plug when it got down to 0.05a.

Important not, I manually set the PS with my Fluke meter while detached from my battery pack. even though the PS only will show 3.6v, it is an infinite adjustment you just have to carefully set it. I was able to get mine to 3.648v reading off my Fluke.

The final measurement when I pulled the plug was 3.645v across each cell. I'd say yes, top balanced. About 8 hours later after resting each cell only dropped slightly (still paralleled) to 3.633. It was at this point where I re-assembled my pack into it's final 12v config. I have new copper busbars I'll be cutting and making but the pack is assembled.

Current state final photo attached is very temporary, I was using what I had in my RV :) When I'm back to my apartment/storage in a week I'll be able to finalize things with proper wire etc. But there is no real load on them so I wasn't too concerned about wire size. I have my MultiPlus II inverter connected along with my Batrium BMS and Cerbo GX. I don't really have anything large enough to do a good capacity test but in the meantime the Batrium is tracking all the usage which is minimal. I also set my Batrium so it knows the current state is 100% SOC. But in a 12v config with 16 cells I'm at 1120aH, that's gonna take awhile to dissipate. but I would like to do a test before any further charging is done (the inverter isn't connected to AC so it won't charge).

I'd say the most important part of this for me, was having a clear understanding of CV and CC and when it's supposed to be in which mode and what to look for if it isn't in the correct mode.

Unfortunately I didn't have my cells compressed during this but I will most definitely have a compression case made of aluminum. I'll begin working on building this shortly and will do the final compression when cells have dropped to around 50% SOC. part of me wishes I did a quick temporary wood plate and threaded rod assembly, but that's now in the past.

Things are coming together and this is a big step forward knowing that I knew it was going to take awhile. Thanks to everyone on here for all the good info.
Next big hurdle to tackle will be proper charge settings etc for Inverter, MPPT, and BMS and make sure they all play nice. That's for another post though as I have lots of questions :)
 

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HRTKD

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Apr 24, 2020
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Somewhere South of Denver
It's about time!!

Glad you got it done.
thumb_up.gif
 

DJSmiley

Solar Addict
Joined
Aug 13, 2020
Messages
409
Well... 16 x 280Ah = 4480Ah
Assuming 40-50% SOC on arrival = 2240-2688Ah to charge. Using 10A, thats 224-268 hours.

Add 1-2 days lost due to the the cabling issues (not pulling the full 10A) that's pretty spot on with your results.

Congrats on passing the 1st hurdle

will do the final compression when cells have dropped to around 50% SOC.

Do you have a load, or eg the commonly used capacity tester, to get the cells down to 50% SOC?
That's going to take another 10 days, assuming you have a 10A 3.2V load
 

Firstascent

Solar Enthusiast
Joined
Mar 7, 2020
Messages
149
Well... 16 x 280Ah = 4480Ah
Assuming 40-50% SOC on arrival = 2240-2688Ah to charge. Using 10A, thats 224-268 hours.

Add 1-2 days lost due to the the cabling issues (not pulling the full 10A) that's pretty spot on with your results.

Congrats on passing the 1st hurdle



Do you have a load, or eg the commonly used capacity tester, to get the cells down to 50% SOC?
That's going to take another 10 days, assuming you have a 10A 3.2V load
Yup pretty much spot on with timing even though I was secretly thinking “well maybe mine came extra charged and it’ll only take a week” haha wishful thinking.

I never did get a common capacity tester, I was going too but never did. Since my inverter can only be hardwired directly to the terminals I need to wire up a 110 receptacle so I can plug something in. Still trying to think of what I have that will draw a continuous large load though. All my power tools are battery powered so I can’t use a heat gun like I’ve seen Will use. Maybe my gf blow dryer haha I believe those are energy hogs I’ll need to look.
Now, quickly pluck out the Grey Hairs that popped up while painfully waiting for them to Top Off.
Psst... don't let spouse see !
😂😂 the struggle is real haha
 

Firstascent

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Joined
Mar 7, 2020
Messages
149
I was drooling over looking at your shop. In the nicest way possible...I hate you! LOL I just finished 12 days of anxiously watching the volt meter myself last night.
Haha thanks! I just did all the cabinets about a month ago so I’m def still in the honeymoon stage with it 😂 such a huge difference from having things on the floor everywhere.
Oh man 12 days, that’s a good amount of time too, congrats! The wait is over!
 

trougnouf

New Member
Joined
Aug 15, 2021
Messages
37
Unfortunately I didn't have my cells compressed during this but I will most definitely have a compression case made of aluminum. I'll begin working on building this shortly and will do the final compression when cells have dropped to around 50% SOC. part of me wishes I did a quick temporary wood plate and threaded rod assembly, but that's now in the past.
Did you notice any expansion or negative effect?

I will also be doing the top balance before they are put into the final compressed case, because there is no way I can move the whole battery (24 * 310 Ah cells; 150 kg?) from home (where I have power) into the houseboat (which doesn't yet have an electrical system) pre-assembled. I will have to (re)assemble the battery there with the balanced cells.

I don't know if I should make a temporary compression setup (either with two planks and very long threaded rods, or assemble, take apart, and reassemble the final case) or just do the top balance without compression.
 

Firstascent

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Joined
Mar 7, 2020
Messages
149
Did you notice any expansion or negative effect?

I will also be doing the top balance before they are put into the final compressed case, because there is no way I can move the whole battery (24 * 310 Ah cells; 150 kg?) from home (where I have power) into the houseboat (which doesn't yet have an electrical system) pre-assembled. I will have to (re)assemble the battery there with the balanced cells.

I don't know if I should make a temporary compression setup (either with two planks and very long threaded rods, or assemble, take apart, and reassemble the final case) or just do the top balance without compression.
Hey sorry I was out of town all week.

No negative effect but maybe some slight expansion which is to be expected at full charge. If you've seen any of Will's recent vids on the bloating he saw on the 320ah cells, this was NOTHING like that.

a temporary setup would be nice, but not required I don't think. But I believe what is recommended is to do the final compression at 50-60% SOC for best results. So once you do your top balance you'd want to drain them down before finalizing your compression case.
 

Shale MacGregor

Solar Addict
Joined
Sep 5, 2021
Messages
291
Well... 16 x 280Ah = 4480Ah
Assuming 40-50% SOC on arrival = 2240-2688Ah to charge. Using 10A, thats 224-268 hours.

Add 1-2 days lost due to the the cabling issues (not pulling the full 10A) that's pretty spot on with your results.

Congrats on passing the 1st hurdle



Do you have a load, or eg the commonly used capacity tester, to get the cells down to 50% SOC?
That's going to take another 10 days, assuming you have a 10A 3.2V load
120 amp meanwell could have knocked it out in a day or so :)
 

Brett V

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Joined
Apr 5, 2021
Messages
213
Location
South Central Pennsylvania
Hey sorry I was out of town all week.

No negative effect but maybe some slight expansion which is to be expected at full charge. If you've seen any of Will's recent vids on the bloating he saw on the 320ah cells, this was NOTHING like that.

a temporary setup would be nice, but not required I don't think. But I believe what is recommended is to do the final compression at 50-60% SOC for best results. So once you do your top balance you'd want to drain them down before finalizing your compression case.

I had a piece of 3/4" plywood at either end of the cells bookend style and cinched them down with a ratchet strap during the top balance process. After the top balancing was done, I left the cells connected and cinched for a few days. My install doesn't have room for any kind of compression so I wrapped them as tightly as I could in packs of four using filament tape. They're not compressed but I'd call it "restrained". So far I've put as high as 85 amps load on discharge and 60 amps on charge and have seen no signs of swelling.
 

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