Charging Lithium Off Mains Power

**d2dave** · 21st March 2025, 11:45 PM

I am ditching my gas fridge in the caravan. I have purchased a compressor fridge to replace it.

I have also purchased a 200 AH lithium to power it.

I am currently running this in my shed to test it.

The battery states that it should be charged at 14.6 volts.

I have a Projecta battery charger which has a setting for lithium. https://www.projecta.com.au/ts166173...issue-8_v7.pdf

It does however only charge at 14.2 volts.

Should I consider something like this?

https://www.aliexpress.com/item/1005...293769291300_6

**drivesafe** · 22nd March 2025, 12:42 AM

Hi Dave, the 14.6v charging voltage is the MAXIMUM safe voltage for that specific battery.

The 14.2v is both safe and OK to fully charge your battery.

BUT NOTE, the battery charger must have a Lithium Battery setting.

This is more important than the 14.2v as a lithium battery can only tolerate a constant charge voltage for a short time once the battery is fully charged and at that point, the charger should not go into FLOAT but should turn off.

This is where charging a Lithium battery differs from charging a Lead Acid battery.

All types of Lead Acid batteries, whether they are Wet Cell or AGM, can have a constant FLOAT voltage applied to them indefinitely, but this type of constant FLOAT voltage will destroy a Lithium Battery.

**d2dave** · 22nd March 2025, 08:28 AM

Originally Posted by drivesafe

BUT NOTE, the battery charger must have a Lithium Battery setting.

This is more important than the 14.2v as a lithium battery can only tolerate a constant charge voltage for a short time once the battery is fully charged and at that point, the charger should not go into FLOAT but should turn off.

Thanks Tim. Yes the chargers does have a lithium setting.

However, as for floating, my understanding is that when the lithium is full the BMS shuts off and no more charge can go in.

**drivesafe** · 22nd March 2025, 11:06 AM

Originally Posted by d2dave

However, as for floating, my understanding is that when the lithium is full the BMS shuts off and no more charge can go in.

Your battery may be different, but I have never seen that in any of the lithium batteries I have worked with and it is actually an OVER-VOLTAGE shut down.

Again, a proper lithium battery charger will turn off once the battery is fully charged.

This type of operation is based on the amount of CURRENT being absorbed in the final stage of the charge cycle.

As the amount of current being absorbed by the battery drops while charging at the maximum voltage stage of the charge, In your case, at 14.2v, the charger determines that the battery is fully and turns off.

There should be no FLOAT cycle for a lithium battery.

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