Good point to start balancing?

Is there any rule when we should start with balancing. At the moment I want to charge my 14S100P setup, around 280 Ah, to 4.0V max. Is it good to start balancing at 3.95V? Charging current should be max. 50A and I use Batrium with Longmons.

Maniac_Powerwall said:

Is there any rule when we should start with balancing. At the moment I want to charge my 14S100P setup, around 280 Ah, to 4.0V max. Is it good to start balancing at 3.95V? Charging current should be max. 50A and I use Batrium with Longmons.

Click to expand...

I balance when I add new packs to my powerwall and then - turn off balancing. Balancing isn't needed for healthy packs. My system runs between .04v and .06v 'max delta' during full charge/discharge cycle each day. After 9 months - I had drift up to .09v as the max delta and simply did a touch up balance when I added a new pack recently.




If you have Batrium - you can
- "Auto Level Balance" - which you can set to run thru-out the charge/discharge cycle. Its a lighter touch and nudges 260ah packs to within .04v over a couple of days.
- pick a voltage level and turn off charge/discharge - and just 'balance at that voltage' and then turn it off (set it so high it won't kick in)
- you can pick a top level voltage and it will balance as it charges above that voltage - each time it goes up. *This isn't needed for healthy packs once they are balanced.

A max delta of .04v - 06v (40-60mv) is perfectly OK. The pic above shows 40mv diff right now. No need to obsess on .01v max difference across all the packs.

The key I want to emphasis, that I learned by *listening* to @Daromer (one of top experts)and confirmed by hands-on experienceis that healthy packs just don't need much (or any) daily balancing.Daily balancing is an indication of a troubled pack and that you should fix/replace it

+1 to OffGrid's comments above.
You don't want the balancers working hard eg when your charger is pushing 4.0v/cell & the balancers have been bypassing hard from 3.95v/cell, they'll just get hot & stressed.
+1 to Batrium's auto balance function - you can set this to run from say 80 or 85% SoC & let it tweak the pack for you.
I've set my longmons to bypass at the same voltage as "full" max v/cell (I'm LiFePo4), equivalent to 4.0V or (a fraction higher) for you.

Ok, I'll change that. But could you explain what auto balance does in difference to normal top balancing? I don't understand that feature. Already watched Daromers video on that but still confused...

Already thought that 3.95V could be to early. Thanks for your thoughts on that.

Basically, auto balance looks at the cell voltages & bypasses the higher voltage ones for up to 25 seconds each & cycles/loops slowly through the pack - it jumps past/ignores lower cells.
With time, your cells end up pretty close.

Maniac_Powerwall said:

Ok, I'll change that. But could you explain what auto balance does in difference to normal top balancing? I don't understand that feature. Already watched Daromers video on that but still confused...

Already thought that 3.95V could be to early. Thanks for your thoughts on that.

Click to expand...

>what auto balance does in difference to normal top balancing?
For top balancing, you have to wait till your battery bank gets to the top balance voltage - and it balances at the top only.
For auto-balance - you can set it tooperate over the entire voltage range... and it will reduce the max differences as it goes. In a healthy battery, this will let you achieve a reasonable 'max difference' over the entire voltage range of operation. For me, I have a 0.05v goal and OK with <= 0.10v max difference as I operate between 4.0v and 3.5v / pack.

For example, I rarely get to 'top balance voltage' as my goal is to consume all the PV power as it's produce and minimize battery use. So top balancing won't work for me 'operationally' as I don't ever get to the top and/or I have to set the 'top' artificially low for that day. OR I would have to shut-down power consumption and let the battery fill and then wait till it balanced. I prefer Auto Balance because it works without me having to disable the system or force it into an abnormal 'top voltage' situation.

Onedown side of auto balance is that's its a 'lighter touch' than full-on top balancing - e.g. it takes longer to balance, maybe twice as long with my settings. I've never needed to run it more than a few days because 0.05v max difference is fine for me... so I'm not sure how far it would actually go. I should preface the 'couple of days' with the context that I've done pack voltage matching before putting a new battery online... so things are usually within 150mv max difference to start with. And I have used an X8-Charger directly on a new/mis-matched pack to lower or raise it to assist the balance process.


Here's my auto-balance settings.




Notice that 'normally' I have it disabled - e..g "Bypass Extra Mode [None]v More" - and I just turn it on for few days when I want to add a new packs or do a touch-up.

When enabled...
-"Different Gap" at 0.01v (this is the goal it tries to achieve - a max of 0.01v difference across all packs)
- "Bypass Banding" at 0.03v - it will select groups of cells that are 0.03v (or more) different to focus on. In my case (0.04v -> 0.06v max diffs) this lets it balance 'all of them' eventually.

----- Set low enough so the feature works 24/7 regardless of where I am in charge/discharge cycle -----
- Cell Volt Low Cutout 3.50v - my inverter off is 3.54v.
- SoC% Low Cutout 0.0% - I never get this low
- Shunt Limit - Charge/Discharge - again, high enough that it never stops working

----- Some throttling so it doesn't just go crazy while cells are charging and discharging
- Bypass Extra Time - Not sure what this is.. maybe the length of time it performs the bypass?
- Cell Volt Stable Time - Cells must have same voltage for 120seconds before bypass will initiate - e.g. you don't to bypass(balance) cells with rapid voltage changes.
**I have a a large system so 120secs (2 minutes) is fine for me - you might need something smaller**