Thor Forums - View Single Post - Lithium Batteries and Factory Charge Controller

Beau388 · 09-26-2020, 10:29 PM

Quote:

Originally Posted by LowOnCash

Hello the above statement is not correct there are different voltage protocols for charging lithium batteries, therefore in most cases standard flooded / AGM chargers are not to be used. Inverter / Chargers such as (Xantrex, Magnum, other) must have a lithium charge program to properly charge lithium batteries, most come with the proper selection for lithium.
Mike Mas

Please do not confuse lithium polymer, lithium cobalt or lithium nickle batteries with LFP (lithiumferrophospate or LiFePo4). LFP batteries are less dense have a lower charging and output voltages than the other common types of lithium-ion batteries. The reason LFP batteries are used in RVs is their stability and similarity to lead acid batteries.
LFP cell voltage at 100% charge is 3.2 volts, 3.28 volt min charge, but the charging voltage can not be greater than 3.65 volts. That is 12.8 volts resting for 4 cells in series and 14.6 volts (max) four cells in series, charging.

The charging profile for LA and LFP batteries is exactly the same: bulk (constant current), absorption (constant voltage) and float (trickle charge). For a flooded deep cycle, the max cell charge voltage (resting) is 2.13 volts. The min charging voltage at 70 F degrees is 2.22 volts with a recommend charging voltage of 2.35 to 2.45 volts. That's 12.78 volts for 6 cells in series and 14.1 to 14.70 volts for 6 cells.

So any voltage above 3.28 volts will charge a LFP cell or for 4 cells in series 13.12 volts will charge the battery. Admittedly it will take a fairly long time at 13.12 volts. The higher the voltage the shorter the charge time and so it is with LA batteries. The slower you recharge a battery the longer its life. For 400 cycle life, Lifeline recommends 10 to 13% charge in amp-hp. So for 400 amp-h LA battery bank, that would be a current of 40 to 52 amps. The recommend max charge current for Battle Born's LFP battery 50% charge in amp-h, so for the same 400 amp-h LFP battery bank that would be 200 amps and that would equate to aprox 2,000 cycles from 100% down to 20%. Again less current will lengthen the cycle life of the battery.