Charging LiFEP04 with AIMS inverter/charger

[Daybyday]

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 profile. (14.1 fast, 13.4 float). Apparently on newer units AIMS suggests the SLA profile for lithium batteries (14.4 fast, 13.6 float).

The AIMS will charge at up to 30 amps.

I'm running two 24v 50ah LiFePo4 batteries in parallel. Here's the specs on them re charging:

Power and Energy
Nominal Charge	25.6v
Charge Voltage	30.0v
Continuous Charge Rate	20 Amps
Continuous Discharge Rate	50 Amps
Peak Discharge Rate (<2 minutes)	70 Amps
Capacity (Amp Hours)	50 AH
Capacity (watts)	1280 Watt-Hours

Can you please tell me which profile you recommend, and how to use it? Following @snoobler's lead, I'm guessing set it to AGM1, keep an eye on the battery voltage, and then turn it off when the charge maxes out. I understand that LiFEP04 don't require a float. Thanks for your guidance.

 

[chrisski]

Mostly interested to see what others have to say, and I am trying to figure out the voltages to charge my packs to.

Here is the charge voltages for the newest AIMS COnverter Charger 12 / 24 volt 75 amp model that Will recommeds:


In his videos, I see him charge, but not maintain batteries. I bought this to put in my RV so when I have cloudy days, I can push 35 amps back into my batteries, and I will shut this off when charged. I’m not sure that 14.4 volts going into the batteries at all time is healthy.

For most of the time I will charge my batteries at 28 - 28.5 volts, which is under the 29.2 max for my batteries. THat keeps my batteries pretty close to fully charged (95%?) without going to point where I risk a runaway cell. If your cells have the same charge curve, I like the 14.1 because its in the range.

I’m still trying to figure out float voltage, but I think it will be between 26 and 27.

 

[John Frum]

@Daybyday I suggest option 2 AGM 1 14.1V bulk and 13.4V float
14.1 is enough voltage to get your battery full in a reasonable amount of time but not so much that you are likely to trip the bms.
13.4 volts is the lowest float available and will therefore minimize voltage stress on your batteries.
Its the primary reason I suggest that profile.

 

[John Frum]

@chrisski all those floats are too high for my taste.
If you have some raspberry pi skills I have an idea how to make your charger work a treat.
Actually you can do a reasonable facsimile with a Victron smart battery protect and a solid state relay.

 

[chrisski]

If you have some raspberry pi skills I have an idea how to make your charger work a treat.

I don’t have those skills now, but that is something I’d like to start in October.

I seem to remember reading somewhere that Victron is fairly open source for its coding, so my thought would be to delve into that in October to see how true that is. I think I may need to use Ve networking, but at this point I’m just guessing. Goal is to have integrated stats from four victron devices and two overkill BMS systems displayed on a tablet. I’m a long ways away from that.

For my charger, I intend only to turn that thing on on the rare occasions where the solar is not recharging the batteries, and I’m not even sure that will happen once I get this battery upgraded.

 

[John Frum]

I update my post to above to mention that a Victron smart battery protect can drive a solid state relay to control the charger via its battery temperature sensor.
Anyway I think it should work.
Some brave soul would need to short the bts leads to see if it terminates charging

 

[Daybyday]

@Daybyday I suggest option 2 AGM 1 14.1V bulk and 13.4V float
14.1 is enough voltage to get your battery full in a reasonable amount of time but not so much that you are likely to trip the bms.
13.4 volts is the lowest float available and will therefore minimize voltage stress on your batteries.
Its the primary reason I suggest that profile.

Thanks @smoothJoey So what is the charging practice? Can I use the AGM1 profile and not worry about turning off the charger at any given time?

 

[John Frum]

Thanks @smoothJoey So what is the charging practice? Can I use the AGM1 profile and not worry about turning off the charger at any given time?

I have a converter/charger controlled by a raspberry pi.
I charge with constant current until I hit target voltage, target amp hours or target temperature; whichever comes first.
Then I let the pack discharge until I hit all 3 of target voltage, target amp hours and target temperature.

Even a float of 13.4 volts will sequester some lithium over time.
This is according to people who know far more about this than i do, specifically @RCinFLA.
However for applications where float is required 13.4 volts or 3.35 volts per cell is considered the optimal compromise of high state of charge vs cell degradation.
Hopefully RC will set me straight if I got anything wrong.

 

[John Frum]

@Daybyday In all of the above I forgot to say that lifepo4 batteries like to be cycled not floated.

 

[Daybyday]

@Daybyday In all of the above I forgot to say that lifepo4 batteries like to be cycled not floated.

Thank you sir

 

[TLayne]

I have a newer model 24v AIMS inverter and the charging profile for lithium on the unit itself states 28.8 fast, and OFF for float, yet the green float indicator light comes on as if it actually were floating??...trying to crack that nugget, because leaving it on this LiFePo4 setting seems fine

 

[chrisski]

deleted

 

[chrisski]

Hope I'm helping here.

I’m not helping. I’m going to delete that post to avoid detailing the thread.