Charging LiFePO4 Batteries

AnOldUR

Off topic, but hoping someone here has an answer. I have a Ryobi riding mower that has four 12V lead acid batteries. The batteries are shot and I'm thinking of switching to LiFePO4's like I did in our T@B. The T@B's WFCO will not fully charge the lithium, but doesn't cause any harm. Does anyone know if this is universal to all lead acid chargers? Do you think I can use the Ryobi lead acid charger without damaging the batteries if I'm fine with less than a 100% charge?

elbolillo

My understanding is that lead acid chargers generally can be used without causing damage to LiFePo4 batteries. But as you mention you won’t be able to fully charge the batteries and for optimal charging and care of LiFePo4 batteries they really need that absorption charge.  A number of different manufacturers state that lead acid chargers shouldn’t be used and may cause damage. Possibly they are just covering themselves. I think much would depend on the parameters of the Ryobi charger.

enzo86

You could just charge them with one of these:

https://www.victronenergy.com/chargers/blue-smart-ip22-charger

AnOldUR

I didn't mention that the batteries are in series, so I'd need a 48V charger. There are golf cart type chargers with the correct plug, but I was hoping to avoid the expense. I have a NOCO Genius10 that could be used to charge one battery at a time, but that's not a practical solution. I was hoping to use the Ryobi charger for normal use and periodically use the NOCO to fully charge and balance the cells. Similar to using the older WFCO to charge a T@B's LiFePO4, but occasionally topping off with a compatible charging source.

I'm waiting for a response from the battery manufacture, but though that one of the battery gurus here might have an opinion.

B0atguy

You can get a NOCO 4 bank charger that would work . Either a Genius 2x4 (2 amps each x 4 bank= 8amps ) , or a Genius GENPRO 10x4 (10amps each x 4 bank= 40amps ).
The 2x4 is pretty cheap (like $199.95) and for a slow charge like a trickle .
The 10x4 is more robust and more expensive ($424.95) and more like a fast charger . 

You can hook these up to 48volt systems that use 4 - 12v batteries x4 in series , and they work perfect . We use these all the time in the boat industry , also with a lot of Lithium battery conversions. (48v trolling motors, large stereo systems , etc) . 

Horigan

I’d be concerned about the Li individual cells becoming unbalanced over time, with some getting over charged. Cell balancing happens near full charge by the internal battery management system.  The concern could be exacerbated by charging multiple batteries in series. 

Grumpy_G

Keep in mind LiFePo batteries limit output current via the BMS, and there are limits on many batteries can be used in series. Besides charging there might be other pitfalls. Do you know how the batteries are configured and what the power demand of the motor is ?

AnOldUR

@Horigan My plan is to fully charge all four batteries individually with my NOCO Genius10 before installing and then again possibly at the end of the season. Thinking this should be enough to keep the cells balanced.

@Grumpy_G I've watch a few videos about doing this switch from lead acid to LiFePO4 with positive results, so I'm pretty confident it will work.

The mower came with four 75Ah sealed lead acid batteries. Even if I don't get a full charge with the Ryobi charger, I'll still be ahead with the 100Ah LiFePO4's. Epically considering that the lead acid should only be drained to 50% and is probably the reason they died.