Unbalanced LifePo4 batteries

[mattonthesea]

Can you set bulk, absorption and float on the B2B or doesn't just have a generic lithium setting?
Ditto the MPPT?
Monitoring SOC without a smart shunt may be problematic. Inbuilt BMS are notorious for inaccurate readings. You may find each battery gives you a significantly different value of SOC

I can set these but, until I've got my head around it I'm using one of the two genetic settings. Bizarrely for LifePo4 they still have a float period! Of Grid Garage points out that this is wasted uncharge time.

The B2B displays battery and input (solar, alternator, shore) voltage but by LEDs on a scale - not too easy to read.


I'm also about to connect up the battery monitor

 

[geem]

I can set these but, until I've got my head around it I'm using one of the two genetic settings. Bizarrely for LifePo4 they still have a float period! Of Grid Garage points out that this is wasted uncharge time.

The B2B displays battery and input (solar, alternator, shore) voltage but by LEDs on a scale - not too easy to read.


I'm also about to connect up the battery monitor

What are the generic lithium settings you are using? A float period of 1/2 hour is not a problem but your voltage settings maybe. The idea is to set up the system so the BMS is not doing shutdowns because of high voltage charging. The B2B and MPPT charge settings should be such that they stop charging before the BMS detects a high voltage cell and shuts off the battery.
The BMS should have a balancer that will balance the cells but this isn't normally activated until 3.45v per cell. A short absorption period gives an opportunity for the BMS to carryout some cell balancing.

 

[mattonthesea]

Thanks Geem. The newly fitted battery monitor suggests that the widely held view, that the Renogy Bluetooth app is unreliable, is correct.

The B2B settings I'm using at best close to the batteries'. I'm using these to test everything and then I'll do some adjusting on the custom setting.

Of I can believe the app then the cells are nicely balanced and far more indicative of the correct voltage.

 

[geem]

Thanks Geem. The newly fitted battery monitor suggests that the widely held view, that the Renogy Bluetooth app is unreliable, is correct.

The B2B settings I'm using at best close to the batteries'. I'm using these to test everything and then I'll do some adjusting on the custom setting.

Of I can believe the app then the cells are nicely balanced and far more indicative of the correct voltage.

The cell voltage and battery voltage in the app will be accurate. The SOC is the thing that goes haywire. If you charge both batteries up to 3.55v per cell. So 14.2v, then do a reset on the Victron battery monitor to show 100% you can then use this to monitor SOC of the battery bank.
Then work on the basis that you only occasionally, maybe every few weeks, need to get the battery up to 100%. The life of the batteries will be longer if you don't routinely go above about 90%. To do this, set the mppt to charge to no more than 14v. Set absorption to 1/2hr and float to 26.8v, effectively off. I use 0.2v rebulk in the MPPT