Lost on Battery/BMS wiring & config

[MisterSandals]

Really important:
3.65v as high cell voltage.
2.5v as low cell voltage.

That's a good catch (there was a lot of data in all those pics!).

You can of course use more conservative settings,

Agreed. Unless you need to squeeze every bit out of your cells on a daily basis, i recommend conservative settings like 2.7V and 3.63V. 2.8V and 3.62V wouldn't be wrong either, adjust for YOUR level of comfort and battery needs.

 

[HRTKD]

In post #42 I pointed out that the BMS parameters needed to be changed.

 

[MisterSandals]

In post #42 I pointed out that the BMS parameters needed to be changed.

Yea, i see that I did too in post #51. So many threads, they get jumbled sometimes...

 

[myersfamilyhome]

This look better

You really need to change these settings.

Really important:
3.65v as high cell voltage.
2.5v as low cell voltage.

After you top balance:
3.4v as balance turn on voltage.

What you are showing here is really terrible and will eventually damage your cells. You can of course use more conservative settings, but these will ensure your BMS is doing the job of protecting your cells from damage.

Thank you for pointing out ?. This looks better? Also should these settings be a percentage higher or lower that the recommended long life charge profile in the DIY LifePO4 forum?

 

[myersfamilyhome]

Ok, I also made the adjustment to my SOC cell parameter to 73.3% to prevent swelling/bloating of cells at any point. Shocked at all how quickly they charge up with just the 3 320w panels....what do I do with the other 15 I have lol. Not sure if I can use the active balancing feature for top balancing but it has yet to turn on. Here is the status page.

 

[HRTKD]

If your cells never get charged above the "Balance Start Volt" then balancing won't happen. Looking back, you had it set to 3.2 volts. Most of us use 3.4 volts. Aim for charging a bit above whatever you use for the balance start voltage. On my 12 volt system, I use 14.4 volts when the system is actively being used and 14.2 volts when in storage. These are the bulk voltages, not float. Float is 13.6 or 13.5.

 

[MisterSandals]

active balancing feature for top balancing but it has yet to turn on.

your pic shows balancing is turned off.
Your cells are very well behaved at that voltage so that's good.

 

[myersfamilyhome]

your pic shows balancing is turned off.
Your cells are very well behaved at that voltage so that's good.

I tried to turn it on but it's not letting me

 

[Just John]

I tried to turn it on but it's not letting meView attachment 122802

Balanced open start voltage - set to 3.4v.
Balancing below that is counterproductive.

 

[HRTKD]

You don't turn it on. The BMS turns it on. If there is no charge then there won't be any balancing. If the cells are balanced close enough, then there won't be any balancing.

 

[myersfamilyhome]

My battery SOC of 73.3 is I believe preventing the cells from reaching that

Balanced open start voltage - set to 3.4v.
Balancing below that is counterproductive.

My battery SOC of 73.3 is preventing the cells voltage from reaching 3.4v. I have it set to 73.3 to reduce any chance of swelling/bloating from occurring. I chose this for piece of mind that regardless of temp I would not risk any swelling and would extend cell life as much as I possibly can.

 

[MisterSandals]

You don't turn it on. The BMS turns it on. If there is no charge then there won't be any balancing. If the cells are balanced close enough, then there won't be any balancing.

Are we talking about 2 different things? Isn't the switch thingy a user toggle?

 

[myersfamilyhome]

Are we talking about 2 different things? Isn't the switch thingy a user toggle?
View attachment 122822View attachment 122823

That is a visual representation of the state/status, there is a switch on the active balance parameters page at the bottom that doesn't turn on. Maybe because of the settings

 

[HRTKD]

Are we talking about 2 different things? Isn't the switch thingy a user toggle?
View attachment 122822View attachment 122823

Depends on the BMS and the situation. Sometimes you can turn it off, sometimes you can't. Like said above, it's a way to show that balancing is "On".

 

[Just John]

My battery SOC of 73.3 is I believe preventing the cells from reaching that

My battery SOC of 73.3 is preventing the cells voltage from reaching 3.4v. I have it set to 73.3 to reduce any chance of swelling/bloating from occurring. I chose this for piece of mind that regardless of temp I would not risk any swelling and would extend cell life as much as I possibly can.

If you don't let your cells exceed 3.65v then they won't swell. At least mine haven't.

 

[myersfamilyhome]

If you don't let your cells exceed 3.65v then they won't swell. At least mine haven't.

So I believe I have some bad cells in the bank. I want to do an effective test to see which need to be replaced but at 4am I lost power due to low cell protection. Any suggestions? I'm going to wait till the bank gets to the same voltage as the replacement cell and swap it out. I am hoping it's a simple as remove bus bars and BMS lead, swap, reconnect.

 

[MisterSandals]

Any suggestions? I'm going to wait till the bank gets to the same voltage as the replacement cell and swap it out.

At this SoC with one cell at 2.510V (absolutely empty), and the top cells at 2.853V (less than 5%??), they are not horrifically out of balance. Your entire battery is pretty much empty and one of the cells was going to reach low cutoff first.

With that, yes, cell 15 looks to be the weakest link (or has a problem connection). It would be interesting to swap cell 15 and 14 (chose because its also high and convenient to swap) and see if the problem follows "cell 15"*.

* you should label your cells (I like letters A, B, C... because numbers are in use with the cell location) and take good notes so you can keep track of this and other cells. It is vital to managing a bunch of cells.
My notes might be "Cell O in position 15 LVD at 2.5, while Cell G at 2.853"
Swapping Cell O in 15 with Cell N in 14 to see if LVD follows Cell O or position 15.

 

[myersfamilyhome]

Please tell me what I'm doing wrong with my settings. Feel like I'm so lost on this. Included latest status before I swap out the cell.

 

[MisterSandals]

Please tell me what I'm doing wrong with my settings. Feel like I'm so lost on this. Included latest status before I swap out the cell.

Your settings look just fine. I am a little conservative (to extend battery life, or so i hope) and have the cell low voltage protect at 2.7V and cell high voltage protect at 3.63V.
This is not affecting what you are seeing, it would actually make it cut out a little earlier.

Your battery looks pretty good to be honest. Its just that your battery was empty and the BMS did its job and prevented it from being over discharged.

I'd look at your battery use and figure out why you are running your battery to empty. Is your battery too small for your use? Is it never getting charged full? (this is my guess but without any info)

I see you have very few cycles on your battery (BMS says 0). How high are you charging your battery in terms of volts? Were your cells top balanced? Happen to have a BMS screenshot of your cell voltages when fully charged?

 

[HRTKD]

Your Balance Open Volt of .05v may be the same thing on my BMS that I believe is called Balance Differential. Mine is set to .015. Consequently, my BMS will initiate balancing when A) cells are over 3.4 volts and B) the differential between cells is greater than or equal to .015 volts.

Your setting would prevent balancing when the cells are at a larger differential value, up to .05 volts. In your latest discharge, the cells may not have balanced, so while the battery may have been at 100% state of charge, the cell could have been at a large difference.

We top balance with the expectation that the cells/battery will spend more time close to 100% state of charge than 0%.