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replaced lead acid with LiTime lifepo4 batteries and power goes off and back on

aburt

New Member
Joined
Dec 7, 2024
Messages
4
Location
Missouri
I have a 6 year old Aims 48V inverter/charger and just replaced my lead acid batteries with twelve 12V 300aH LiTime lifepo4 batteries. They are in 3 banks of 4 wired series/parallel for 48 volts. I called Aims and set the inverter where they said to. I also have 2 Outback Flexmax 80s. I called Outback and set them where Outback recommended. I have 30 250 volt solar panels that charge the batteries. When the inverter comes on, my power blinks off and back on and my tv and some small appliance turn off. Can anyone help me figure this out? Thank you.
 
Do you have any communications (wires or Bluetooth or anything) with your batteries, so you can tell what’s going on inside of them?

Do you have any inter-battery equalizer/balancer boxes to keep your lithium batteries in balance? I suspect you do not and if you were to measure the voltages across your batteries, you would discover that they are not all the same. Hence, the common recommendation to not build battery voltage is up by putting batteries in series, but to buy 48 V batteries in the first place.(I know, too late, but this is why.)
 
If the Aims Inverter does not have a pre charge built in it may be necessary to wire one in. to much inrush causing an overload on inverter input.
search this site for inverter precharge. I have had this problem with other brand inverter, this is a maybe. Hopefully some more knowledgeable will chime in.
 
I agree with the suggestion to precharge.
Also note that it's frowned upon to wire 12V LiFePO4 batteries in series. Hopefully you charged each one completely, 14V, before wiring them in series.

Welcome to the forum.
 
Thanks for all the comments. I do not have communication with the batteries. The batteries do have BMS built in. I charged and balanced them when I first got them. I disconnected them just now and checked the voltages in each group of 4. One group measured 53 volts and the other 2 groups measured 52. Is that enough difference for me to recharge and balance them again? The inverter has never been serviced. I'm going to research "pre charge". I'm not familiar with that term. Since I have the batteries already, I need to find a way to make them work.
 
You can use a resistor or light bulb to pre charge.

They sell balancers / equalizers for the 12V packs in series.

The BMS doesn't even have bluetooth?
 
Thanks for all the comments. I do not have communication with the batteries. The batteries do have BMS built in. I charged and balanced them when I first got them. I disconnected them just now and checked the voltages in each group of 4. One group measured 53 volts and the other 2 groups measured 52. Is that enough difference for me to recharge and balance them again? The inverter has never been serviced. I'm going to research "pre charge". I'm not familiar with that term. Since I have the batteries already, I need to find a way to make them work.
Don't measure the banks, measure the individual batteries when you are having the problems.
 
Thanks, I will measure each one individually. The LiTime batteries do have bluetooth. I'm not familiar with bluetooth, but will try to figure it out. Also, the light bulb to pre charge is interesting. Is that just for the initial connection of the inverter and batteries? Because each time the inverter comes on is when our power goes off briefly and back on. From what I've been reading, it might be the BMS in the batteries is causing this.
 
Thanks, I will measure each one individually. The LiTime batteries do have bluetooth. I'm not familiar with bluetooth, but will try to figure it out. Also, the light bulb to pre charge is interesting. Is that just for the initial connection of the inverter and batteries? Because each time the inverter comes on is when our power goes off briefly and back on. From what I've been reading, it might be the BMS in the batteries is causing this.
Bluetooth is good, it'll let you see if the cells are out of balance when the battery is "full charged".

And yes, get the battery balancer.
 
Yes, the precharge should only be needed for the initial connection. Are you using a disconnect to turn it off or just the power button the on the inverter?

I'm not familiar with what app they use for BMS comms, it should just be a matter if installing the app and connecting to the BMS.

The balancer would be a good idea.
 

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