Firstascent
Solar Enthusiast
- Joined
- Mar 7, 2020
- Messages
- 265
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
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