Feedback on my settings

[BretS]

**Edit... made changes marked with **

My system so far consists of a DIY LiFePO4 bank of twelve 310Ah cells in 3P4S for 12V, a REC Active BMS, a Multiplus II 2x 120V, a Cerbo GC, and an Orion 12/12-30A DC-DC Charger. I am setting up with conservative charging settings to maximize cycles (based on Will's sticky post). I would appreciate any feedback on the below settings (in order from highest to lowest):
charge:
-REC max cell 3.55V (14.2V)
-REC end of charging 3.52V (14.08V)
-REC balance end 3.50V (14.00V)
-Multiplus absorption 14.00V (3.50V)
-REC balance start 3.40V (13.60V)
-Orion absorption 13.80V (3.45V) **13.60V (3.40V)
-Orion float 13.50V (3.375V) **13.35V (3.33V)
-Multiplus float 13.50V (3.375V) **13.35V (3.33V)

discharge:
-Multiplus inverter low shutdown 11.00V **12.00V
-Multiplus restart/low pre alarm 12.60V **12.25V
-REC Min cell 2.70V (10.80V) **2.95V (11.80V)

I ran the pack down to 13.10V using the 15K Air Conditioner on battery - it ran for a good half hour, and nothing got even warm anywhere on my MP or busbars.

I then charged a bit using the Orion and my truck running to verify it worked well, and to check the engine not running function. It worked great.

I then started my generator connected to the 50A shore power with a 30A dogbone. The MP charged the bank back up in around 45 minutes. I was watching the BMS and it started and completed the balancing perfectly! It was really interesting to watch it all happen - I learned a lot about how the balancing function works. After the balancing was done, it reset to 100% state of charge and went into float.

Anyone see any issues with anything? I am also attaching some pics of my system and screenshots of the BMS under load and my settings. Thanks in advance for any input...

 

[John Frum]

Why are your multiplus and orion absorption voltages different?
As for the low cutoff I suggest you watch your cell deltas while you discharge the battery at a representative rate and set the cutoff to coincide with your weakest cell dropping off.
That assumes a decent top balance.
Also watch the cell deltas on charge to see how high you can safely charge without triggering a high cell cutoff.

 

[BretS]

Why are your multiplus and orion absorption voltages different?
As for the low cutoff I suggest you watch your cell deltas while you discharge the battery at a representative rate and set the cutoff to coincide with your weakest cell dropping off.
That assumes a decent top balance.
Also watch the cell deltas on charge to see how high you can safely charge without triggering a high cell cutoff.

I set the Orion lower because it is not on the Canbus and the REC can't control it for balancing. So, if I am driving it will cut off before the balancing and top off with balancing when I use shore power or generator (later solar)

I raised my cutoff to 12.00V on the inverter now.

 

[John Frum]

I just checked my cutoffs today.
I have it set to 24.8 volts which puts the lowest cell at ~3.05 volts and a 75mv delta.
bms cutoff is 2.9 per cell or 23.2 volts for the pack.

 

[GnrlPatton]

Hi Bret-
I just finished my install that's very much like yours (been following your setup for a while as I built mine out). Mine is 304aH, 3P4S with a REC Active BMS, Victron CerboGX, Multiplus Compact and MPPT solar. I don't have a DC-DC (yet). I got it all setup and powered up, it ran great for about 24 hours then disconnected the non-Victron side, likely because of an over voltage detection. The odd thing is my SOC on the REC wifi module shows 0%, but the pack voltage is fine at 13.78. I reached out to REC and they replied with "Set your End of Charge voltage and Balance voltage End to 3.55 V. If you have not performed the initial cell balancing you have to wait for the BMS to do it slowly." I did see the balancing happening while trying to troubleshoot, but I didn't see that it was successful.

I noticed your settings above, so wanted to see if you had made any changes or if you are still happy with them? Do you know how to manually override the BMS SOC? I had heard that it would reset itself after the initial charge, but mine doesn't seem to have done that.

Thanks,
Kevin