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Charge Controller Settings Lead Acid to LiFePO 4
#1
Hi All

I have been extremely fortunate to pick up the pictured batteries which were unbelievably found at a rubbish tip by my battery supplier.



I want to reprogram my EPever Tracer 4210A solar charge controller from lead acid to the correct settings to run my LiFePO 4 26.5 nominal voltage bank. Charging voltage is listed on the pack at 28.5. I would be grateful if anyone could suggest the best voltages for maximum cell life and also the safest charge settings, the manual is here https://www.epsolarpv.com/upload/cert/fi...L-V1.0.pdf


I have the following options

Battery charging settings



Boost Charging Voltage 
Float Charging Voltage
Under Volt. Warning Volt.
Low Volt. Disconnect Volt.
Discharging Limit Voltage
Equalize Duration (min.)  0~180
Boost Duration (min.) 10~180
Over Voltage Disconnect Voltage
Charging Limit Voltage
Over Voltage Reconnect Voltage
Equalize Charging Voltage
Boost Reconnect
Charging Voltage
Low Voltage Reconnect Voltage
Under Voltage Warning
Reconnect Voltage

Note:
1) When the battery type is sealed, gel, flooded, the adjusting range of equalize
duration is 0 to180min and boost duration is 10 to180min.
2) The following rules must be observed when modifying the parameters value
in user battery type (factory default value is the same as sealed type):
a. Over Voltage Disconnect Voltage > Charging Limit Voltage ≥ Equalize
16Charging Voltage ≥ Boost Charging Voltage ≥ Float Charging Voltage >
Boost Reconnect Charging Voltage.
b. Over Voltage Disconnect Voltage > Over Voltage Reconnect Voltage
c. Low Voltage Reconnect Voltage > Low Voltage Disconnect Voltage ≥
Discharging Limit Voltage.
d. Under Voltage Warning Reconnect Voltage > Under Voltage Warning
Voltage ≥ Discharging Limit Voltage.
e. Boost Reconnect Charging voltage > Low Voltage Disconnect Voltage.

can anyone suggest what settings I should modify?

many thanks
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#2
Wow! nice find!

LiFePO4's are practically a drop in replacement for lead acids. So you should be fine to run with default settings without worry of damaging the cells.

2 LA's would about 28V fully charged as well.


I'm sure daromer or one of the other LiFePO4 guru's will chime in shortly Wink
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#3
28.5 volts should be fine, that comes out to 3.56 volts per cell (max is 3.65 volts per cell). 

But with lifepo4, you will need to try different bulk settings until you find the sweetspot. If you have voltage drop from controller to battery, 28.5 might be too low and you won't get a full charge. The lower the bulk voltage setting the less amps your battery gets and if you have a .5 volt voltage drop the controller will switch from bulk to float too soon.

I would verify the controller voltage reading and bounce that with what the voltage is at the battery terminals. Compensate by increasing the bulk voltage setting by whatever the difference is. 

Float can be 26.5 volts or lower, when in float the controller should be charging at less then 1 amp. Adjust it accordingly.
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#4
Should I be disabling equalization charge?
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#5
Yes, disable equalisation charge - that's only good for LA & will likely charge too high & damage a LiFePo4 pack.

Re the full charge max voltage ("absorption voltage" in LA terms), you should watch the pack balance above ~3.45V/cell, I found in my LiFePo4 packs that some cells would start going high even with a Batrium BMS bypassing. So I settled to approx 3.45V/cell max for my pack & 2 years in, so far so good, nice & stable system.
Your input charge current is always going to be way higher than a balancer in a BMS can cope with.
I'd suggest cell max approx 3.45 - 3.5V/cell for full voltage.
For float, I'd suggest only a little less, eg 3.35V/cell.

Trick with LiFePo4 is to hold at the full voltage until the current drops away, then switch to float.
Running off solar, DIY & electronics fan :-)
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#6
Ive been busy today setting up the panels and getting the cable runs ready. I have got coms running with the charge controller and when I get some current from the panels I will get some screenshots going and do some voltage measurements at the battery and at the charge controller. At this point the batteries are a complete unknown they may be faulty so I will take a careful look at what they are doing. I want to pick some cycling voltages that strike a balance between power available and cycle life. All my batteries are very evenly loaded. I basically pick a draw that will take overnight to reach my desired SOC and also supply that wattage during the day so the load draw is very consistent. We shall see what happens tommorow when I start feeding them some power. I may be that they have failed BMS or cells and then I will have to pull them down and rebuild them into a bigger cell with a custom BMS. I think they are thunder sky individual cells. What would you suggest as the lowest voltage I should draw down to under load. I am anticipating a constant draw of around 230 watts.
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#7
When you look at the voltage vs state of charge curve for LiFePo4, it's pretty flat & kicks up/down at each end.
For longer life, I don't like my system off the flat bit....
2.9V min is my low end.
Running off solar, DIY & electronics fan :-)
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#8
Should I disable thecharge?
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