LiFePO4 120 Volt Battery Charger

[06RKguy]

I'm new to lithium batteries and am replacing the AGM battery in my cargo conversion camper with a LiFepo4 battery. The old charger I have is a "Battery Tender" 1.25 amp trickle charger, but it does have a LiFepo4 setting. It has been my experience that Battery Tender makes pretty good chargers. The battery I'm buying has a recommended charge current of 20 amps 0.2C. I understand that a 1.25 amp charger will take forever to charge the battery, but I'm more concerned that not using the manufacturers recommended 20 amp charge rate will somehow damage the battery? I'm not living in the camper, and I plan on buying an adequate solar setup in the near future for when I am on the road. The camper just sits next to the house plugged in 75% of the time so fast charging it isn't much of a concern. I do want to buy the proper 120 Volt charger eventually, but would like to know if the Battery Tender I already own will be ok for now?

 

[sunshine_eggo]

the recommended is an alternative to the maximum charge current, which is typically 0.5C or 1.0C.

Charging at lower current is not a concern.

The bigger concern:

The camper just sits next to the house plugged in 75% of the time so fast charging it isn't much of a concern. I do want to buy the proper 120 Volt charger eventually, but would like to know if the Battery Tender I already own will be ok for now?

Unlike lead-acid, LFP deteriorate when stored at full charge, particularly in warmer weather.

 

[50ShadesOfDirt]

As camper currently sits "idle" in between uses, possibilities might be:

- run an extension cord from RV system to a load in the house, and power that load, exercising the RV's battery bank
- design the RV battery bank to be more mobile, and put it in the house when not RV'ing, such that it services (12v?) loads
- camper becomes "office" when at home if you can set it up that way
- one of your children (if old enough) uses it as a bedroom

Efforts would pay their way by reducing grid bill on the house side of things, and your RV components don't sit idle ...

Hope this helps ...

 

[Solarcabin Channel]

You can use that charger BUT it isn't recommended to store LFP full or leave them on a charger when full.

The charger will keep trying to read the battery and the BMS will keep trying to check the cells even after it is full with the charger connected.

I would suggest charging to 80 or 90% and then just checking it in 4 months and only charging it to full before you plan on using the camper.

Overcharging is not as much of an issue with LFP because BMS should prevent that but it is with Lithium Ion and not recommended to leave an LI battery on the charger for extended periods after it is charged. Only time you can do that is if you are balancing the battery and are right there to watch for any over heating.

Most Ebike and Escooter battery fires are from leaving a battery on the charger after full, using cheap blackmarket or DIY batteries, damaged battery or trying to fast charge with the the wrong charger.

You can fast charge an LFP but most batteries have a recommended rate of charge and 20 amps will charge a 200Ah LFP from empty to full in 10 hours.

 

[06RKguy]

As camper currently sits "idle" in between uses, possibilities might be:

- run an extension cord from RV system to a load in the house, and power that load, exercising the RV's battery bank
- design the RV battery bank to be more mobile, and put it in the house when not RV'ing, such that it services (12v?) loads
- camper becomes "office" when at home if you can set it up that way
- one of your children (if old enough) uses it as a bedroom

Efforts would pay their way by reducing grid bill on the house side of things, and your RV components don't sit idle ...

Hope this helps ...

The camper is wired for 120 volts, and I do have a few 12 volt items like 2 LED RV lights, water pump and television. Could I maybe just put some kind of a 12 volt load through a 12 volt timer to come on for an hour everyday?

 

[Brett V]

Just charge them to maybe 90% - 95% and turn everything off.

 

[06RKguy]

Just charge them to maybe 90% - 95% and turn everything off.

How often should I check them?

 

[50ShadesOfDirt]

You should be able to put anything on a power on/off (digital) timer, and "exercise" the batteries ... this could be useful if you want to do work inside the camper. If the camper batteries:

- supply the camper fridge, then you can store things from the house in the camper fridge, and get value
- supply the camper heater, and keep things warm over the winter, possible value in florida
- drive the landscape lighting, and get value

I like the idea of moving the batteries into a mobile solar generator for use in your home, such as:
- UPS for critical electronics. simple plug swap, and batteries go back into rv.
- emergency power for critical loads, as in, run the house fridge until grid comes back up

Anything to get value out of batteries, vs sitting idle, and possibly risking degradation, or calendar death without value received. RV's have year-round value in being ready to go camping anytime, but you might be able to wring out more value than that, if you utilize the batteries in some way ...

Hope this helps ...

 

[Solarcabin Channel]

You should be able to put anything on a power on/off (digital) timer, and "exercise" the batteries ... this could be useful if you want to do work inside the camper. If the camper batteries:

- supply the camper fridge, then you can store things from the house in the camper fridge, and get value
- supply the camper heater, and keep things warm over the winter, possible value in florida
- drive the landscape lighting, and get value

I like the idea of moving the batteries into a mobile solar generator for use in your home, such as:
- UPS for critical electronics. simple plug swap, and batteries go back into rv.
- emergency power for critical loads, as in, run the house fridge until grid comes back up

Anything to get value out of batteries, vs sitting idle, and possibly risking degradation, or calendar death without value received. RV's have year-round value in being ready to go camping anytime, but you might be able to wring out more value than that, if you utilize the batteries in some way ...

Hope this helps ...

I agree and my camping system comes inside the cabin to expand my main system in winter for low sunshine days.

 

[Brett V]

How often should I check them?

Checking them as in voltage? That’s not easy because the discharge curve is so flat. The difference between 95% and 75% is around .05 volts per cell. There’s nothing wrong with floating them but the charger you have is going to hold them at or near 100.%.

 

[sunshine_eggo]

Just charge them to maybe 90% - 95% and turn everything off.

How do you propose he stop his alternator charging them at 90-95%?

 

[Brett V]

How do you propose he stop his alternator charging them at 90-95%?

I was referring to charging from shore power. Wasn’t the original question about a battery tender?

 

[sunshine_eggo]

I was referring to charging from shore power. Wasn’t the original question about a battery tender?

My bad. Went cross-eyed with another thread.