Renogy LIFEPO4 charge profile not working for SOK battery

[joebob25]

I’m using a Renogy 30 amp DC-DC/MPPT charge controller to charge my SOK 206 AH Lifepo4. The “lithium” setting on the controller bulk charges fine, but when it hits the boost setting it seems to hold the battery at 14.6v indefinitely, and stay in “boost”. The charging amps drop to zero/near zero, but the battery doesn’t ever drop down to the usual 13.8ish resting or voltage. Is this a problem? It doesn’t seem that the controller is trying to cram more voltage into the battery, but I’m not used to seeing my battery sit at 14.6v all day either (coming from AGM batteries so still learning about lifepo4 charging) This happens when my camper is sitting outside in the sun while not being used. When I apply a load to the battery it rapidly drops to 13.7v or so and the charger returns to a bulk charging mode until it hits 14.6v again. Am I damaging my battery by letting it sit at 14.6v for an extended period of time? I can pull the fuse on the solar and stop the charging (which returns the battery to a normal resting voltage of 13.8v), but I don’t want to have to mess with this every time I let my camper sit idle in the sun for a few days.

I have tried to input the manufacturer recommended SOK charge profile as a “user” defined profile with similar results. The SOK profile calls for a 15 minute boost at 14.6v and then a float charge of 13.8v. I know lithiums don’t really require a float charge but that is what SOK reccomends. Even with these settings the charger stays in “boost” and holds the battery at whatever I have the boost voltage set to.

After researching it seems that Renogy recommends their lithium batteries be charged to and held at 14.6v.

The TLDR is that I’m looking for recommendations that won’t damage my battery but also won’t require me to manually adjust the boost voltage every cycle to fit SOK’s charge profile.

Thanks for any advice!

I have attached my settings below:

 

[mikefitz]

The problem with charging at 14.6 is that the BMS will detect overvolts and prevent charging, thus the zero charge current you are seeing.

Since you are able to adjust user settings, set boost volts to 14.2 and float to 13.5.

It's possible setting time duration to zero causes confusion in the softwere, set equalisation volts to same as boost, 14.2, and duration to 15 minutes .

If the SOK battery cells are significantly out of balance, not unusual on low cost batteries, a lower charge, boost, volts may be needed to prevent cell overvolts, try 13.8volts.

 

[JWLV]

I have a Renogy Rover 30A MPPT charge controller. The problem I have run into with Renogy is overvoltage. When my LiFePo4 battery is under load (a DC refrigerator), the battery voltage drops slightly. When the Renogy is charging the battery and the refrigerator is drawing a load, everything is fine. However, refrigerators don't run all the time. They shut off when the desired temperature is reached. When that happens, the battery voltage goes up since there is no load. That causes an overvoltage condition on the Renogy and it shuts off. So I can't use the default LI setting on the Renogy. I use a user-defined setting with float, equalize, and boost set to 13.8V. If it is set to anything higher, eventually it'll go to an overvoltage condition.

 

[JWLV]

For your reference, here is a screenshot of my Renogy settings.

 

[joebob25]

The problem with charging at 14.6 is that the BMS will detect overvolts and prevent charging, thus the zero charge current you are seeing.

Since you are able to adjust user settings, set boost volts to 14.2 and float to 13.5.

It's possible setting time duration to zero causes confusion in the softwere, set equalisation volts to same as boost, 14.2, and duration to 15 minutes .

If the SOK battery cells are significantly out of balance, not unusual on low cost batteries, a lower charge, boost, volts may be needed to prevent cell overvolts, try 13.8volts.

I don’t think it’s the BMS shutting off the charge necessarily, because the charge watts/amps will taper to zero in the same way if I have the boost voltage set to 14.6 or 14.0 or 13.8. I’m just confused because the charger never exits the boost mode into an idle state or into a “float” stage (I know lithiums don’t need to be floated but I have it set that way because SOK recommends it) regardless of what I have the boost duration set to. I’ve tried 0, 5, 10, 15 and 120 minutes and it stays in boost indefinitely (for days if I let it) no matter what. Good idea to play with the equalization settings and see if that changes anything. I'll give it a whirl when i get home tomorrow!

 

[joebob25]

I have a Renogy Rover 30A MPPT charge controller. The problem I have run into with Renogy is overvoltage. When my LiFePo4 battery is under load (a DC refrigerator), the battery voltage drops slightly. When the Renogy is charging the battery and the refrigerator is drawing a load, everything is fine. However, refrigerators don't run all the time. They shut off when the desired temperature is reached. When that happens, the battery voltage goes up since there is no load. That causes an overvoltage condition on the Renogy and it shuts off. So I can't use the default LI setting on the Renogy. I use a user-defined setting with float, equalize, and boost set to 13.8V. If it is set to anything higher, eventually it'll go to an overvoltage condition.

This is exactly the work around I have been using. My battery rests at 13.8 when it settles out under no load, so if I charge to 13.8 My battery is basically full. However I was under the impression that occasionally charging to a higher voltage like 14.4 (or 14.6 as recommended by SOK) helps the battery stay balanced and cycle properly. This why I have the boost return voltage set to 13.2 so if I discharge my battery that low it should (but doesn’t) trigger a charge to 14.6 for 15 minutes on the next cycle and then stop applying a charge. (At least that is how I understand the whole thing is supposed to work.) I can manually trigger a “boost” by changing the settings on my phone, but I was hoping this would all be seamless and automated.

 

[fratermus]

The charging amps drop to zero/near zero, but the battery doesn’t ever drop down to the usual 13.8ish resting or voltage. Is this a problem

If we are using a lead-profile to achieve different setpoints (or the USER profile without altering the Boost Duration setpoint) those will hold that voltage for 2 hours, which would behave the way you describe. If you drove for >2 hours with this setup I suspect it would drop to Float. Exception: Renogy Li profiles don't have float setpoints, so voltage would fall until it hit the Boost Reconnect setpoint.

Am I damaging my battery by letting it sit at 14.6v for an extended period of time?

IMO 14.6v is too high, and is likely triggering overcharge protection as others have said. I agree with the @mikefitz recommendation to "set boost volts to 14.2 and float to 13.5"

I usually charge even lower (13.8v), but that is with solar where available charging time is much longer. With a charger that runs a limited time (while the engine is running) 14.2v should deliver good current without encouraging runaway cells. We're looking for a balance that gets the desired amount of Ah back into the bank in the allotted time without triggering BMS overcharge protection.

 

[joebob25]

If we are using a lead-profile to achieve different setpoints (or the USER profile without altering the Boost Duration setpoint) those will hold that voltage for 2 hours, which would behave the way you describe. If you drove for >2 hours with this setup I suspect it would drop to Float. Exception: Renogy Li profiles don't have float setpoints, so voltage would fall until it hit the Boost Reconnect setpoint.

This is what I thought at first as well, but I've left the Renogy in boost for well over two hours while driving and charging via DC-DC, and over two days while charging via solar (after lowering the boost charge voltage to avoid damaging the battery) and it never exits "boost" mode to a float setting. I have never seen the display say float. It's either in "bulk" if I'm below the boost set point, or in "boost" if I'm at the boost voltage.

I don't think it's the overcharge protection because it behaves the same way whether I'm boosting at 14.6, 14.0 or 13.8. I think the programming on the Renogy is faulty and won't enter a float stage. Unfortunately I've contacted their customer support and they just told me that 14.6 is a safe charge voltage and the battery will protect itself. Unfortunately I think I'm just going to have to constantly fiddle with the settings to force it to do what I want it to. I'm fine setting the battery to charge to a lower voltage (13.8 or so) but the SOK battery specs state the balancing voltage is 14.4 and a recommended charge voltage of 14.6. I just don't want the battery to sit that high indefinitely and risk shortening the life span.

 

[mikefitz]

Have you tried adjusting the equalisation duration?
I think the SOK statement regarding balancing at 14.4 is an error In the documentation. Most BMS start the balance when cell voltage exceeds 3.4 volts, 13.6 volts for a 4 cell battery.
It's possible the Renogy charger is not working as expected.

Could you try a lead acid battery out of a car and see if the unit still stays In boost?

 

[SoakedUp]

Raise the Equalize Charge Interval to 185. If it’s 0 the controller won’t ever come out of Boost/absorption mode and drop voltage to your set float voltage. I just had this issue and found the solution from this thread.

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