DIY RV LiFePO4 24v 100ah solar setup - help with configuration parameters for Epever Tracer4215BN & Victron BMV-712

[randybobandy]

Equipment (already installed and running):

• Batteries - qty 2 Roypower PowerUrus 12v 100ah LiFePO4 wired in series for 24v (rated for 50A continous charge / 100A continuous discharge) [user manual]
• Inverter/Charger - Sungoldpower 24v 4000w w/ built-in 50amp charger [user manual]
• SCC - EPEVER Tracer4215BN 40A 150V w/ MT-50 remote display [user manual] [MT-50 user manual]
• Solar Panels - qty 4 BougeRV 200w CIGS wired in series [user manual]
• Battery Monitor - Victron BMV-712 500A shunt w/ optional temperature sensor [user manual]

Assumptions:

• I will occasionally have relatively high discharge rate (60-70amps max...most of the time much lower)
• I will frequently fast-charge at the max rated continous charge rate of 50amps.
• I need to squeeze out as much battery capacity as safely possible - meaning charge to 100% SOC and discharge deeply. (this is due to weight constraints, my batteries are undersized but I can't add more batteries as I'm almost exceeding payload capacity of my RV)
• I will only use the system for approximately 40-50 days per year, so 40-50 charge/discharge cycles. I don't expect to keep the RV for more than 10 years so as long as the batteries last that long I'll be happy. So 50 days per year x 10 years = ~500 charge/discharge cycles.

Questions:

1. Given my planned usage profile, do you think I can realistically expect the batteries to last >10 years without substantial capacity loss?
2. What Depth of Discharge target should I choose to meet my requirements/goals without risking damage to the batteries? Can I go to 100% every single time if needed (or maybe 95% target is safer, to avoid triggering the BMS low voltage cutoff repeatedly)? What's the max you'd choose in my situation?
3. When we're not actively using the RV I plan to put the system into unattended storage (could be from 1 week to 3 months). I plan to discharge batteries to 50-70% SOC, then fully de-energize the system and leave the batteries disconnected. Is that a good storage SOC target?
4. Which charging profile should I pick for the AC fast-charger? (Sungoldpower inverter/charger - more info below)
   1. Sungoldpower Inverter/Charger Charge Parameters:
      There are 7 different charging profiles to choose from that allow you to adjust 2 parameters - "Fast mode" and "Float mode". Preset #7 is for LiFePO4 and has fast mode 14.0 / float mode 13.8 which seem kind of low for my use case? Preset #4 is for Lithium/Sealed Lead Acid and has fast mode 14.4 / float mode 13.6 which seems to be better suited. Would you agree Preset #4 is better for my use-case where charging as quickly as possible is important? More info about how the charger works on pg.7-8 of the user manual.
5. I need help in choosing the appropriate settings for my solar charge controller (EPEVER Tracer4215BN) and battery monitor (Victron BMV-712). I filled in the tables below based on my best guess with all the information I could find but I'm really not super confident with most of it....most of the recommended/example settings that I have seen online seem to be designed to maximize lifespan of the battery (at the cost of usable capacity) so I don't think I can use those values for my nonstandard scenario. Please review tables below and let me know if you think I should change anything.
   1. I'm also not quite sure if/how my AC charger's behavior should play into the config for the solar charge controller and/or battery monitor. Is there any concern here that the two chargers won't play well together?

EPEVER Tracer4215BN Settings:​	Config 12v (24v)​	Notes
Temp comp. coeff	0 mv / C / 2V	Setting based on PowerUrus battery user manual recommendation
over volt disconnect	14.7 (29.4) ?	Setting based on PowerUrus battery user manual recommendation
charge limit	14.6 (29.2) ?	Setting based on PowerUrus battery user manual recommendation
over volt reconnect	14.4 (28.8) ?	Setting based on PowerUrus battery user manual recommendation
equalize charging voltage	14.4 (28.8) ?	Setting based on PowerUrus battery user manual recommendation
boost charging voltage	14.4 (28.8) ?	Setting based on PowerUrus battery user manual recommendation
float charging voltage	13.6 (27.2) ?	Setting based on PowerUrus battery user manual recommendation
boost reconnect charging voltage	13.2 (26.4) ?	Setting based on PowerUrus battery user manual recommendation
low voltage reconnect	12.4 (24.8) ?	Setting based on PowerUrus battery user manual recommendation
under voltage warning reconnect voltage	12.4 (24.8) ?	Setting based on PowerUrus battery user manual recommendation
under voltage warning voltage	12.0 (24.0) ?	Setting based on PowerUrus battery user manual recommendation
low voltage disconnect voltage	11.2 (22.4) ?	Setting based on PowerUrus battery user manual recommendation
discharge limit voltage	11.0 (22.0) ?	Setting based on PowerUrus battery user manual recommendation
equalize time	0 min to disable	PowerUrus manual says 120min but I think 0min to disable makes more sense
boost time	120min	Setting based on PowerUrus battery user manual recommendation
Battery Charge SOC	100%	Epever says "The setting is some spare setting, will not effect on your system, please ignore it." so I guess it doesn't matter what I put here. I think maybe this is only used if you select SOC charge mode instead of Volt.Comp. charge mode.
Battery Discharge SOC	5% ?	Epever says "The setting is some spare setting, will not effect on your system, please ignore it." so I guess it doesn't matter what I put here. I think maybe this is only used if you select SOC charge mode instead of Volt.Comp. charge mode.

Victron BMV-712 Config Parameter	Config 12v (24v)	Notes
Battery Capacity	100AH
Charged Voltage	14.0 (28.0) ?
Discharge Floor	5% ?
Tail Current	4% (4 amps) ?
Charged Detection Time	3min ?
Puekert Exponent	1.05
Charge Efficiency Factor	99% ?
Current Threshold	0.10A
Time to Go Averaging Period	3min
Zero Current Calibration	ZERO
Synchronize	SYNC​
Relay Mode	DFLT​
Battery Starts Synchronized	Disabled​
Low voltage alarm/clear	12.0/12.4 (24.0/24.8) ?
High voltage alarm/clear	14.7/14.6 (29.4/29.2) ?
High temperature alarm/clear	45°C / 43°C (113°F / 109°F)	The battery manual says max operating temp for charge cycle is 113F and discharge 131F...I settled on the lower of the two since I don't expect it to get that hot anyways and this is just a warning for unlikely edge-case scenario.
Low temperature alarm/clear	2°C / 4°C	Going with this so I have some heads up when it's getting close to danger level. The batteries have low-temp protection built-in but with this alarm I can have some notice to get them warmed up before it gets to that point.
Temperature coefficient	0.5°C ?	Victron recommends 0.5°C but PowerUrus manual says to turn off temperature compensation on charge controllers so not sure what to choose?

Thank you in advance!!

 

[12VoltInstalls]

Can I go to 100% every single time if needed (or maybe 95% target is safer, to avoid triggering the BMS low voltage cutoff repeatedly)?

I would try not to hit the floor everyday and maybe ‘leave’ 10-15% on the bottom

batteries are undersized but I can't add more batteries as I'm almost exceeding payload capacity of my RV)

While I understand your point, the additional weight of two more batteries is not enough to worry about imho. Weight-save on something else.
There’s a LOT of weight you can take out of most RV’s anyway: if you have a ‘proper’ setup with an ATS you can save most of the battery weight deleting the factory ‘converter’ by itself. This can be more complex sometimes if a 50A system vs 30A but still doable.

Propane / “multi fuel” fridges can be deleted and replaced with an appropriate “residential” fridge for weight savings.

My point is that you are battery starved and I think less battery cycling and more capacity is going to be way less of a pain in the neck on the road imho. Solar is pretty seamless when it doesn’t run out of battery.

Is that a good storage SOC target?

I’d settle on 75/80% for storage but it’s fine.

Given my planned usage profile, do you think I can realistically expect the batteries to last >10 years without substantial capacity loss

Likely, but then they’ll start fading from age eventually

most of the recommended/example settings that I have seen online seem to be designed to maximize lifespan of the battery (at the cost of usable capacity) so I don't think I can use those values for my nonstandard scenario. Please review tables below and let me know if you think I should change anything.

do what the battery mfgr recommends
Don’t overthink this.

 

[mikefitz]

Much of the Tracer settings relate to the load output and warnings, and have no protection effect on battery charging.
The settings you need to consider are,
Boost, this is the charge volts, no need to exceed 14.2, 28.4 volts
Boost duration, 30 minutes , this is the absorbtion period.
Equalisation, not needed set same as boost or set equilisation duration to zero.
Float volts, idealy this should be battery resting volts, 13.5, 27.0 volts
Boost reconnect, 0.2 volts lower than boost for 12 volt system, 26.6 volts
Temp coeff , set to O

BMV 712, charged voltage, set to 0.2 volts lower than boost volts.

Don't worry about chargers playing together, there will be no issues

Having two batteries in series will eventually cause issues with balance. A mid point battery ballancer will be useful.

Depending on battery quality, its very possible there will be cell inbalance. Charging the batteries separately, ( that is needed anyway before connecting in series) will identify this. ( the battery BMS cutting off charging before the charger reaches target volts). This could influence the actual charge voltage used for the series

 

[billybala494]

When we're not actively using the RV I plan to put the system into unattended storage (could be from 1 week to 3 months). I plan to discharge batteries to 50-70% SOC, then fully de-energize the system and leave the batteries disconnected. Is that a good storage SOC target?

Storage Conditions of battery: Temperature 0 ~ 35℃, humidity ≤ 60%, state of charge 15% SOC ~ 40% SOC.
If the interval between two charges of the battery exceeds 2 months, the standard charging mode should be adopted for 2~3 times before the battery performance can reach the best state.