Overvoltage from AIMS Power Inverter/Charger with (2) SOK 206aH batteries

[OffTheWall503]

Hey everyone! Having an interesting issue with my two 12v 206Ah batteries wired in parallel. I am using an AIMS Power 2500w LF Inverter/Charger (PICOGLF25W12V120AL) set to charger profile #4, which is within range of the recommend bulk/float settings from SOK. Once at full charge, the inverter will switch to float and then beep continuously, troubleshooting has indicated that it’s telling me it’s “over voltage.” Also running a Renogy solar charge controller from panels to the batteries and the indicator light is also telling me the same when this occurs. Doing some further testing with a multimeter, voltage would get to 14.4, spike to 16v briefly then go into a float state. I’m not sure if this is how it’s supposed to behave, but I have a feeling the BMS is getting tripped somewhere. This also makes me wonder if I need to change my solar controller settings for these batteries, however I am switching to a Victron SmartSolar MPPT 100/20 this weekend.

After doing some research, people have started that the “AGM 1” may be the better choice of a profile, however it’s on low end of the recommended specs and I’m not sure how long absorption works in this profile.

Two other threads I found for reference:

Aims Power inverter/charger with SOK 206ah batteries - will these charge properly?

I'm looking at building a power system for a travel trailer. I am comfortable with almost everything in the system, but have some questions on an AIMS Power inverter/charger and their use with lithium batteries. Essentially, this 2500w AIMS Power inverter/charger looks attractive due to the...

diysolarforum.com

Charging LiFEP04 with AIMS inverter/charger

Hi, I'm using an 2000 watt AIMS inverter/charger that was made before LiFEP04 batteries became popular, circa 2013. It doesn't have a setting for LiFEP04 batteries. Here are the available profiles, from a photo of the unit: In response to a similar inquiry, @snoobler suggested using the AGM1...

diysolarforum.com

Thanks!

 

[sunshine_eggo]

I agree with your conclusion and would also recommend AGM 1.

Also worth checking the battery with a meter as well. Could be a measurement error on the AIMS.

Also worth checking all connections/components between inverter and battery.

The BMS shouldn't be tripping at 14.4V, but there might be a cell imbalance. If AGM 1 works for you, I would try #4 again after a few weeks of use.

Lastly, the AIMS and similar chargers are pretty crap for LFP charging. Their T0 and T1 computations usually results in very long absorption times especially for LFP. Note the 1h min and 12h max on the chart. LFP rarely needs even an hour @ absorption when charging to 14.XV.

@snoobler had it right.

 

[time2roll]

I would go with the GEL USA and see if the issue improves. IIRC this might be a common issue.
AGM 1 would be a better choice for use if it resolves the issue.

 

[Samcat]

If you can adjust tail current to 0.05 C it will not matter what your absorption tome is set for once it hits tail current it will go to float.
Tail current depends on manufacturers and types of chemistry ( what are cells you have originally designed for)
But 0.05 C is usually good set point for tail current.
Good luck.

 

[mikefitz]

BMS shut down of charge path is occurring. SOK, along with many other producers of low cost batteries are not using balanced cells.
The voltage you are seeing may not be float volts , but the battery volts following BMS shutdown.

Charging at lower voltages may solve the issue. Absorbtion is not usually an issue unless charging at low volts , ( below 13.7), or very high currents, ( above 0.5C). Provided the cells are well balanced a short or no absorbtion is needed. Where there is a balance problem, holding the charge volts just below the trip voltage for a long time, with a long absorbtion, may be useful.
There is no advantage in many systems from having a charge voltage over 14.0 volts.

Mike

 

[LouFromDetroit]

Have a similar issue with my same AIMS inverter/charger 2.5kw green monster. When the BMS does stop the charging (due to slight imbalance of cells) the AIMS inverter charger will spike to mid 16V and trips its own overvoltage warning. It does not happen all the time but only certain times. My VICTRON Solar Charger does a good job of capturing the peaks in the history settings.

I also charge with an IOTA 45A AC to DC charger sometimes and it does not exhibit the overvoltage issue when the BMS turns off.