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Help me understand Batrium Balancing
#1
Question 
Hi everyone,

I'm putting my powerwall through it's first days of trial (and error, I guess?).
Right now I've set the charger/inverter to go to 'float' voltage at 57,6 V (4,11 V per cell).

The Batrium Watchmon4 is set to start balancing at 4,05 V per cell and a high cell cut-off of 4,15 V.

Does this mean the longmons will start bypassing current at 4,05 V?  Is this an active or passive balancer?

In the assumption it is passive, this would mean that as soon as my cells reach 4,05 V the longmons will be burning energy until it drops beneath 4,05 V again?
That would be a quite some wasted energy...

Could anyone shed some light on this?
Batteries harvested: 2500+ / Cells tested: 2266 (Average: 2357 mAh)
Usable 1800+ mAh batteries: 1943 (78 %) / Cells in production: 14S 60P -> soon 1680 =14S 2x60P

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#2
I Guess you bought passive version since only they exist...


You need to set Up when to balance. This is done in several ways. Il attach Link to a yt video i made for it.

Next step is critical bleed. This is when a cell goes above set threshold. This should be above max Charge voltage and Will only happen IF a cell falls out of balance.

The normla balance routines have many settings.
And no you dont waste ton of energy.... Only whats needed to Keep Them in balance.... IF you think thats alot you should reconsider to rebuild your battery Wink

https://youtu.be/qNNffhusbXQ
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#3
I run Batrium. Thanks to @Daromer and other comments and now actual experience - I've come to understand that balancing need not become an obsessive end goal by itself. What I mean is that a well tuned battery bank in fact does not need a lot of balancing all the time.

I run my pack in the range of 56v(4.0v/cell) high/float and 48.5v/(3.46v/cell) low/inverter-off. Each pack/cell 260ah@3.7v nominal and I have 42 of them (42 longmons)

When I first got my Batrium I used the direct balancing to top balance 4.0/cell at 30mv max difference. Then I fooled with daily auto-level (excellent youtube by @Daromer above)... but then... I turned it off and observed that for the next 4 months my pack ran very well with no balancing - e.g. 30mv-50mv most of the charge/discharge cycle and then a divergence to 70mv during the last portion of the discharge curve to 3.46v/cell.

A 30-70mv pack difference is OK! Over obsession with balancing is not needed!

After 4 months - it started drifting to 80mv and then 90mv difference at the low end so I re-enabled auto-level balance for 3 days and right back to 30-70mv different it went. So again, I have no balancing at all enabled at the moment.

The point I want to make is that a well 'turned' battery bank does not necessarily need strong balancing every day.

If your pack is well tuned and if you stay 'more gentle' in the charge/discharge range of your battery bank (assuming its big enough etc) - you might find that light balance is all that is needed. One thing that helped me was to find the 'discharge knee' and set my low point just above it (thanks @Sean for that).
100kwh-hunter and Headrc like this post
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#4
Thanks for the quick response and the video, Daniel!
I had somehow never seen that video before (and I've watched quite a few of yours  Wink )

So do you think starting the top level balancing at 4,05 V is too soon? 
I'm trying to set the battery bank to be used between 3,1 V and 4,15 V
Batteries harvested: 2500+ / Cells tested: 2266 (Average: 2357 mAh)
Usable 1800+ mAh batteries: 1943 (78 %) / Cells in production: 14S 60P -> soon 1680 =14S 2x60P

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#5
I run top balance just 0.05v above My max voltage and as soon as any cell is above its bleeded down again. Its rare to happen....

And it only happens when the battery bank is toppen Up and i got excess energy.... That mean i wouldnt call it waste of energy Smile

IF you going to use to 4.15 you should have max voltage in batrium att perhaps 4.17.

Autolevel balancing i would set above 4.05v for sure. It wouldnt happen oftwn since basic setup require Idle load as well and a spread above xx mV. All based on ur settings.

Whats more important is that you have protection against IF a cell goes above lets Day 4.22V

Hope that Helps. It isnt that advanced as soon as you tried it out.
Headrc likes this post
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#6
To add to daromer's comments, having balancing enabled at 4.05 and the charger set to 4.11/cell will push the cellmons into working hard & hot, not really good for them.
When the pack is full at 4.11v/cell the cellmons will be constantly in bypass.
It's better to have similar balance voltage & charger max voltage.
I have auto balance enabled when the packs is over 90% SoC & this seems to be keeping things pretty nicely balanced for me.

Like daromer says, make sure you have trips set to disconnect the pack when any cell goes too high or too low.
Running off solar, DIY & electronics fan :-)
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#7
It seems that when I was still figuring this out, the batrium threw a critical condition for the first time and tripped the battery bank.

Thanks again, Daromer, since your help with figuring out the right resistor made it all work as intended.
Switching the battery back on sent the MPP Solar inverter into a critical fault, so the whole house went dark. Not a good move...

I got it back working again after a while, and changed the parameters around to:
- Bypass volt: 4,10 V
- Hi Cell Voltage: 4,15 V
- Bypass Current Limit: 1,5 A
- Bypass extra mode: Auto Level (with standard parameters)

My battery bank is limited to 14S 60P for now (with one pack likely with some blown fuses), so at 57% SoC I now have a 0.14 V difference.
Time to start soldering again, but with your help, at least I have the balancing pretty much figured out!

Thanks everyone!
Batteries harvested: 2500+ / Cells tested: 2266 (Average: 2357 mAh)
Usable 1800+ mAh batteries: 1943 (78 %) / Cells in production: 14S 60P -> soon 1680 =14S 2x60P

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#8
Another item to consider is "Bypass Temp Limit" (right below Bypass Current Limit). The idea is to 'go easy' on the longmons if they are burning off a lot of amps every day so they last longer. Either cool them with external fans or limit how hot they get thru this setting. I use 55C for this.
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#9
Bypas temp should be where its set... 55c wont get you snywhere. Instead change bypass current down to 0.96a

Set high cell voltage to 4.2 instead. You need the headroom you can get
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#10
To follow up, the trip seems to be working as intended. I had some blown fuses on pack 3 and based on the low pack voltage, the battery bank disconnected automatically this morning.
Some more soldering to do before we switch back to the battery then.

I have the limits on the PIP5048-GK set to 57,6 V float and 44 V low cut-off, which is 4,11 V high and 3,14 V low per cell.
Balancing starts at 4,10 V now, with the auto level feature enabled.

Next is figuring out if the Charging / Discharging parameters are needed at all, since the Batrium can't send a signal to the MPP Solar.
Batteries harvested: 2500+ / Cells tested: 2266 (Average: 2357 mAh)
Usable 1800+ mAh batteries: 1943 (78 %) / Cells in production: 14S 60P -> soon 1680 =14S 2x60P

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