LFP charge profile for BMS, battery monitor and inverter etc...

[TommyDKY]

Looking for help with the Charge profile and other items when I get the new batteries. Any help would be greatly appreciated.
Thanks in advance.

Current setup in 2000 Foretravel GV320 RV:
1120W of solar in parallel
2- Victron 100/50 MPPT solar controller with 560W each
Xantrex FSW3000 inverter Model #815-3000
Battery Monitor—Victron BMV712
Current 3-8d agm 245AH
On order not arrived yet 8 —271AH CATL cells from Michael group buy
Will eventually do 4s2p so I will have 542AH @ 12v
120A overkill BMS on each 12v battery
I will top balance and do a capacity test when I receive them

Assumptions:
Capacity test gets 542AH
I would like to cycle between 10% and 90%

How will the BMV 712 work??
Do I put 542AH in the setup? or .90*542=488

If I only charge to 90% or 13.4V how will it calibrate?
Will it think its at 100% if it stops/goes to float at 13.4V
When I store the RV I usually turn my disconnect to off on house and start batteries
Thus the power to BMV is off how will that affect the SOC on the BMV?

What charge profile do you use/recommend for BMS?
(Will Prowse #’s)
12V 4S LiFePO4 Battery w/ BMS
Absorption: 14.5V
Float: (13.6V) 13.4=90%soc
Inverter Cut-off: 12V=9.5%soc (10.7-12V depending on size of load and voltage drop etc)
BMS cut-off 12V

Should I use the same profile for the inverter?

Not sure how much voltage drop from actual when using a load with LFP say the toaster oven 1800w or Hair dryer1500w? My current AGM’s voltage drop can be 1+ full volt. I am assuming not much since charge curve is so flat?

My generator has a low voltage autostart feature and it starts when the voltage goes below 11.2V for 1m. This seems like the proper setting even for LFP, what do you think? The generator uses the house batteries to start

 

[HRTKD]

How will the BMV 712 work??
Do I put 542AH in the setup? or .90*542=488

If I only charge to 90% or 13.4V how will it calibrate?
Will it think its at 100% if it stops/goes to float at 13.4V
When I store the RV I usually turn my disconnect to off on house and start batteries
Thus the power to BMV is off how will that affect the SOC on the BMV?

What charge profile do you use/recommend for BMS?
(Will Prowse #’s)
12V 4S LiFePO4 Battery w/ BMS
Absorption: 14.5V
Float: (13.6V) 13.4=90%soc
Inverter Cut-off: 12V=9.5%soc (10.7-12V depending on size of load and voltage drop etc)
BMS cut-off 12V

Should I use the same profile for the inverter?

Not sure how much voltage drop from actual when using a load with LFP say the toaster oven 1800w or Hair dryer1500w? My current AGM’s voltage drop can be 1+ full volt. I am assuming not much since charge curve is so flat?

My generator has a low voltage autostart feature and it starts when the voltage goes below 11.2V for 1m. This seems like the proper setting even for LFP, what do you think? The generator uses the house batteries to start

I entered 280 Ah into my BMV-712. The Victron 100/50 MPPT solar charge controllers are charging to 14.40v. There isn't a whole lot of Ah at the end of the charge. The closer you get to 14.6, the fewer Ah you get. I stuck with the Victron 14.40v default on the MPPT. I'm charging to over 90%, but I'm not charging to 100%, and I'm good with that for now. For this first winter with the system, I'm not going to change it. Next winter, I'll likely reduce the max charge point to somewhere well below 90%. Even in the storage lot, I do use 12v power in the winter when I work on projects.

The Inverter should follow a similar profile.

I haven't looked at the volts at the battery when I draw a heavy load. Since the curve is flat, I'm not sure it matters. I've yet to go much below 60% state of charge also.

I think your generator will never kick in if you don't discharge to a very low number. I rarely turn on my generator to actually charge the batteries. It's mostly on to run the microwave or high load space heaters. My generator control does not have an auto start feature installed.

 

[TommyDKY]

I entered 280 Ah into my BMV-712. when your bms stops charging does the bmv indicate 100% soc? Or something lower? The Victron 100/50 MPPT solar charge controllers are charging to 14.40v. There isn't a whole lot of Ah at the end of the charge. What did you use for your float voltage? The closer you get to 14.6, the fewer Ah you get. I stuck with the Victron 14.40v default on the MPPT. I'm charging to over 90%, but I'm not charging to 100%, and I'm good with that for now. For this first winter with the system, I'm not going to change it. Next winter, I'll likely reduce the max charge point to somewhere well below 90%. Even in the storage lot, I do use 12v power in the winter when I work on projects.

The Inverter should follow a similar profile.

I haven't looked at the volts at the battery when I draw a heavy load. Since the curve is flat, I'm not sure it matters. I've yet to go much below 60% state of charge also. I don’t think music will get very low either but what did you use for LVDC?

I think your generator will never kick in if you don't discharge to a very low number. I rarely turn on my generator to actually charge the batteries. It's mostly on to run the microwave or high load space heaters. My generator control does not have an auto start feature installed.

 

[HRTKD]

Tommy, don't edit the quote of a reply. It's hard to reply to your post.

My BMS has never encountered a High Voltage Disconnect. The BMS has the HVD set to 14.6, maybe 14.61. So the MPPT cuts off charging long before the BMS will ever cut off.

Float is whatever the Victron default is.

I don't recall what my Low Voltage Disconnect is. Whatever the app/BMS defaults to for LiFePO4.

 

[BattMan]

Hey Gents - there is a bunch of info here : https://diysolarforum.com/threads/which-charge-profile-is-ok-for-lifepo4.12966/page-5#post-220747 and I'm going to be doing some testing. I don't have all of the gear you have, but as far a charging profiles go, you might want to read through.