My first top balance and capacity test

Tlovell

New Member
Joined
Mar 28, 2021
Messages
12
I finally received my 12 Eve LF280K cells from Amy Wang a week ago or so. I've been busy, so haven't had the time to work with them much. This weekend I was able to top balance and capacity test 4 cells. I followed the instructions on this forum for top balancing by first putting the cells in serial, added the JBD BMS, that I also ordered from Amy, (4s 12v 120a), and charging with the benchtop power supply set to 14.2v and 10a. After one of the cells hit 3.65v, the BMS shut down the charging. The first picture is a screen shot from the app that I downloaded from Overkill Solar for the 120a JBD BMS. It shows the first cell in red to hit 3.65.

Screenshot_20211030-111359_xiaoxiang.jpg
After that, I arranged the cells in parallel and top balance with the power supply set to 3.60v and 10a.
IMG_20211030_113825.jpg

Once it would take no more amps, I put the cells back together in series and added the BMS. This is what the app looked like before the capacity test.Screenshot_20211030-203346_xiaoxiang.jpg

During most of the test, the voltage diff stayed around .007v. As the test neared the completion, the voltage diff began to widen until the end.
Screenshot_20211031-160337_xiaoxiang.jpgScreenshot_20211031-161129_xiaoxiang.jpgScreenshot_20211031-162508_xiaoxiang.jpg
The capacity test ended with the pack getting almost 281Ah, so I guess that is as advertised.

IMG_20211031_162611.jpg
I am now charging the pack back up and I've seem the BMS start to do some balancing, so the cells are starting to get back in line with each other. I am still new to this, but during the time I waited for the cells to arrive, I read a ton of posts here and watch a bunch of videos on YouTube. Does all of this seem about normal? This is my first battery build and I don't want to screw it up!
 

Diysolar123

Photon Sorcerer
Joined
Feb 28, 2021
Messages
662
those seem to be very nice cells if they only varied by 0.3v AFTER hitting the capacity mark...yea cell #2 is your "low capacity" trouble maker but the key thing is you did hit capacity.
I am sure you have seen the many posts from folks that have 1 or 2 low capacity cells in an order than die before hitting capacity hehe

congrats!!
 

DJSmiley

Solar Addict
Joined
Aug 13, 2020
Messages
470
And good job on reading and applying this to your setup

- Getting proper cells at Amy (and not go for the cheap Aliexpress shit and complain about bulging/damaging or fake tracking)
- Proper topbalance
- Use proper cables, crosswired to the + (and - on other side)
- Fast charge using the BMS before topbalancing to speed things up.

Much better job than some who don't read, topbalance by just paralleling cells and waiting for magic, or topbalance using crappy wires and complain the voltage hasn't gone up when they 'already have it running for 2 hours!!!'

If everyone starts doing it this way that would get rid of 80% of the topics regarding crappy cells, improper balance and scams.. which imho is their own stupidity :)
 

triplethreat

Solar Enthusiast
Joined
Oct 12, 2021
Messages
31
Just curious which bench power supply you have. I'm getting ready to order one and are you happy with the one you have.....and is this the first time you used it for the battery build? TIA
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
2,681
THe Power supply looks just liek the one I got off Will’s recommendation:


Although 4.5 stars, Read the three star and lower reviews. Like some of the reviews say, the power supply drifts more than I’d like. A couple times, it drifted above 3.65 when charging, just like some reviews say the voltage drifts. That just means to watch the thing. I top balanced my cells to 3.62 or 3.63 instead of 3.65.

Mine had a diode blow, but the company had me a new one in a week. SOmethign was shaking and when I took it apart, I found half a diode sliding in the bottom. When I posted this on the forum, someone else said they had the same diode go bad.

Works for most people, and I use the replacement Power supply the vendor sent out. This power supply is in a lot of pictures in posts here.
 

TomC4306

Solar Addict
Joined
Mar 2, 2021
Messages
201
This was my exact experience but with Lishen 150 ah from the group buy.
I bailed when the delta approached 150 at about the same place.
My intention at the start of production is to cycle from 3.45 to 3.15 and see where that leaves me as far as capacity goes.
Can always widen the bandwidth.
 

Tlovell

New Member
Joined
Mar 28, 2021
Messages
12
Just curious which bench power supply you have. I'm getting ready to order one and are you happy with the one you have.....and is this the first time you used it for the battery build? TIA


The power supply is called Kaiweets. It is a 30v 10a supply. It is basically the same one Will recommended. I got it on Amazon. There is a 20% coupon, so I went with it. I think they might be made by the same company, just re-branded for different retailers. As mentioned above, it does drift above the set voltage at times so I set the voltage a little lower. I charged the pack at 14.2v and top balance to 3.60v. That gave a little room in case it went over voltage and I wasn't right there watching. It's not the best power supply, but so far it is doing what I need it to do.

The cables that come with it are crap. Tiny wire with the alligator clips. When I first tried to top balance, it would only put out 2 or 3 amps. I made new ones with some nice 10g wire I had. I put ring terminals on them and got the full 10 amps. Much better.
 
Last edited:

Tlovell

New Member
Joined
Mar 28, 2021
Messages
12
The pack finished charging last night. The first screen shot is from right at the end of the charging.
Screenshot_20211101-204441_xiaoxiang.jpg
The next screen shot is from this morning after the pack had sat all night with no power supply connected. For those of you with more experience than me with these 280 Eve cells and the JBD BMS, does this look acceptable?
Screenshot_20211102-082343_xiaoxiang.jpg

Thanks
 

Tlovell

New Member
Joined
Mar 28, 2021
Messages
12
The test data I received with these cells showed that each cell tested between 287ah to 290ah during individual testing. After I did all the top balancing and put them back together in series, my capacity test on two of my batteries yielded just over 280ah. Right at about 281ah. Is this from the BMS managing the batteries? Would I see different results if I capacity tested an individual cell without the BMS?
 

smoothJoey

Hoop Dee Doo!
Joined
Nov 30, 2019
Messages
9,857
The test data I received with these cells showed that each cell tested between 287ah to 290ah during individual testing. After I did all the top balancing and put them back together in series, my capacity test on two of my batteries yielded just over 280ah. Right at about 281ah. Is this from the BMS managing the batteries? Would I see different results if I capacity tested an individual cell without the BMS?
What was your low voltage disconnect set to?
Both for the inverter and the bms.
 

Tlovell

New Member
Joined
Mar 28, 2021
Messages
12
Low voltage disconnect is the default setting in the JBD BMS at 2.5v. I was not using an inverter during the test. I used the capacity tester shown in one of my earlier post above.
 

meetyg

Solar Enthusiast
Joined
Jun 4, 2021
Messages
256
Just curious which bench power supply you have. I'm getting ready to order one and are you happy with the one you have.....and is this the first time you used it for the battery build? TIA
If you're in for something fancy, I just received this Wanptek 30v 10a.
I think it's their newest and most "high-tech" one for this rating.

I haven't charged any batteries with it yet but I did play around with it. It's got lots of features and is very compact! It fit perfectly under my laptop stand.

Here is a picture while it's connected to my SCC (charging a batter). I am testing the accuracy of the win500-MPPT SCC's bluetooth app.
The app does exaggerate a bit, but only a few watts off what the power supply displays.
20211118_203832.jpg

It's a bit pricey at $85 on Aliexpress, but maybe you can find it cheaper on Amazon or eBay.

I got mine from here:

They have a few models here. Mine is the APS3010H.
 

Tlovell

New Member
Joined
Mar 28, 2021
Messages
12
What voltage did you charge the pack to?
Did the bms trip at the top?
Yes, when I first put the battery pack in series the BMS shut down after one of the cells hit 3.65v. Then I took it apart and put them in parallel and charged them at 3.60v until they wouldn't take anymore amps to top balance. Then put them back together as a 12v battery in series with the BMS and capacity tested them.
 

Tlovell

New Member
Joined
Mar 28, 2021
Messages
12
One thing I did not do was to use the data sheet to group the cells together. I just grabbed 4 cells and made a battery. Is that a mistake? What data from the test sheet would you use to group them? Amp hours? High to low?
 

smoothJoey

Hoop Dee Doo!
Joined
Nov 30, 2019
Messages
9,857
One thing I did not do was to use the data sheet to group the cells together. I just grabbed 4 cells and made a battery. Is that a mistake? What data from the test sheet would you use to group them? Amp hours? High to low?
The pack should give have the capacity of its weakest cell.
Some reasons why you would not get the same results.
Measurement error on your part, their part or both.
Not an exhaustive list.
 

Cavendish

New Member
Joined
Nov 29, 2021
Messages
11
@Tlovell
Thank you for showing your results, I will read this a couple of times and hopefully recreate your tests. As they seem like solid examples to follow, along with many of Wills YouTube videos.
Really appreciate your attention to detail with this post.
 

Rogermija

New Member
Joined
Apr 12, 2021
Messages
18

The power supply is called Kaiweets. It is a 30v 10a supply. It is basically the same one Will recommended. I got it on Amazon. There is a 20% coupon, so I went with it. I think they might be made by the same company, just re-branded for different retailers. As mentioned above, it does drift above the set voltage at times so I set the voltage a little lower. I charged the pack at 14.2v and top balance to 3.60v. That gave a little room in case it went over voltage and I wasn't right there watching. It's not the best power supply, but so far it is doing what I need it to do.

The cables that come with it are crap. Tiny wire with the alligator clips. When I first tried to top balance, it would only put out 2 or 3 amps. I made new ones with some nice 10g wire I had. I put ring terminals on them and got the full 10 amps. Much better.
I have asked this question before...but... Depending on SOC my current, for example, would fluctuate between 5.15 and 5.70 rather randomly. I was expecting a constant charging current but current trending downward. I'm suspecting a bad ps. What was your experience? Thank you.
 

meetyg

Solar Enthusiast
Joined
Jun 4, 2021
Messages
256
I have asked this question before...but... Depending on SOC my current, for example, would fluctuate between 5.15 and 5.70 rather randomly. I was expecting a constant charging current but current trending downward. I'm suspecting a bad ps. What was your experience? Thank you.
What was your battery voltage and PSU voltage at?

Most of these PSUs are CC/CV meaning that as long as the battery voltage is lower than the PSU voltage, it will supply constant current. When the voltage it reached, they will go into CV, and current will go down as SOC goes up.

Did you use the original cables? I made that mistake... As mentioned they are too thin with too much resistance. Try getting/making some better ones that will handle 10A.
 
Top