Trouble finding an affordable LiFePo4 charger

[kmxtornado]

With LiFePo4 having a full cell voltage of 3.65 and Li-Ion of 4.2v, I understand I definitely cannot use a Li-Ion charger to charge my LeFoPo4 pack natively. However, if I'm able to set a charge of 80%, would that theoretically work?

In fact, I just noticed that the charger that comes with my battery says 80-85% charge, which makes me wonder if that's what the manufacturer is already doing. Limiting a Li-Ion charger to only charge up to 80-85%. Technically should be 87%, right?

A full LiFePo4 battery is 3.65v per cell. Whereas a full Li-Ion battery is 4.20v per cell. The difference is 13%, meaning the LiFePo4 has voltage of 87% of that of a Li-Ion battery if I'm doing my math right.

To confuse myself further, I'm noticing 48v Li-Ion chargers charge up to 58.8v and 48v LiFePo4 chargers charge up to 58.4v which goes against everything I understood up top. Ugh. Maybe someone smarter than me can explain this to me please?

UPDATE: okay, I think I understand why now. 48v Li-Ion is made up of only 13 cells whereas 48v LiFePo4 is made up of 16 cells. So this explains why the full voltage is so close together for a 48v battery even though the full volts per cell are vastly different between the two chemistries.

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Maybe all this stuff isn't that simple and I'm making it out to be. Educate me. I've run LiPo batteries on RC cars and FPV quads for years, but new to LiFePo4. It just makes me nervous to use a charger where I'm only looking for a green light and not actually knowing the voltage of the battery at any given time. Maybe I'm just paranoid. I'm the guy who storage charges all LiPo batteries when not in use and stores them in fire proof bags inside an ammo can in a metal cabinet off the ground in a concrete garage floor. I know the LiFePo4 batteries are a lot more stable than even Li-Ion which is my reason for selecting it on such a large battery (48v compared to my little 1-4S toy batteries).

Would love to know how you guys are charging LiFePo4 batteries.

ONES I'VE FOUND SO FAR:
There are a couple I found on Amazon by a company called WAOUKS for about $50-60 apiece. They have choice of an alligator clip so I'll need to cut those off and put on a proper connector. Another one has an XLR connector so that's my reason for considering an XLR connector for the charge cable on the battery itself. Neither of those have screens and aren't adjustable from a 5A charge rate (0.5C for my 48v LiFePo4), but at least they're metal shielded and looks like they have a decent fan.

What worries me about this charger though is that it says it's for Li-Ion, Lead Acid and LiFePo4 but is not adjustable. Sounds sketchy. Can't possibly be charging each one correctly that has different voltages for full charge.

 

[harrisonpatm]

With LiFePo4 having a full cell voltage of 3.65 and Li-Ion of 4.2v, I understand I definitely cannot use a Li-Ion charger to charge my LeFoPo4 pack natively. However, if I'm able to set a charge of 80%, would that theoretically work?

In fact, I just noticed that the charger that comes with my battery says 80-85% charge, which makes me wonder if that's what the manufacturer is already doing. Limiting a Li-Ion charger to only charge up to 80-85%. Technically should be 87%, right?

A full LiFePo4 battery is 3.65v per cell. Whereas a full Li-Ion battery is 4.20v per cell. The difference is 13%, meaning the LiFePo4 has voltage of 87% of that of a Li-Ion battery if I'm doing my math right.

Maybe all this stuff isn't that simple and I'm making it out to be. Educate me. I've run LiPo batteries on RC cars and FPV quads for years, but new to LiFePo4. It just makes me nervous to use a charger where I'm only looking for a green light and not actually knowing the voltage of the battery at any given time. Maybe I'm just paranoid. I'm the guy who storage charges all LiPo batteries when not in use and stores them in fire proof bags inside an ammo can in a metal cabinet off the ground in a concrete garage floor. I know the LiFePo4 batteries are a lot more stable than even Li-Ion which is my reason for selecting it on such a large battery (48v compared to my little 1-4S toy batteries).

Would love to know how you guys are charging LiFePo4 batteries.

ONES I'VE FOUND SO FAR:
There are a couple I found on Amazon by a company called WAOUKS for about $50-60 apiece. They have choice of an alligator clip so I'll need to cut those off and put on a proper connector. Another one has an XLR connector so that's my reason for considering an XLR connector for the charge cable on the battery itself. Neither of those have screens and aren't adjustable from a 5A charge rate (0.5C for my 48v LiFePo4), but at least they're metal shielded and looks like they have a decent fan.

What worries me about this charger though is that it says it's for Li-Ion, Lead Acid and LiFePo4 but is not adjustable. Sounds sketchy. Can't possibly be charging each one correctly that has different voltages for full charge.

It depends on what the voltage of your final battery is, and you can pick out a charger suitable. If you want one charger capable of charging several different batteries at several different voltages, it's gonna be more expensive. But there's always a solution. I was looking for a high amp charger for my 24s LiFePO4. It was harder to find, maybe I was running into the same issues as you because LFP is a less common option so the available chargers are more expensive as a result. So, since max voltage for 24s LFP is 87.6v, and I didn't actually want it charged that high ever, I just got a 20s Li-ion charger, max voltage 84. So it'll never top off my pack, which is just fine by me, and it was cheaper than the 24s LFP options anyway. The charging profiles between those two chemistries are the same, or at least close enough for my use.

 

[kmxtornado]

Okay, I see. That does help. Thanks for your feedback.

 

[amberwolf]

FWIW, you can even use LED PSUs as chargers, if you have a BMS on your pack that will shut off the charge input once the pack is full. (LED PSUs arent' exactly the same as an actual typical charger, in that they don't shut off once current drops below a certain very tiny amount, but they do everything else a charger does).

For my traction pack (not LFP, but chemistry isn't relevant in this case) I use the Meanwell HLG series (HLG-600H-54A for 12A charging at ~57v) built onto my SB Cruiser trike, because it is sealed, potted, waterproof and vibration proof, fanless, so it has survived years on the bottom of the trike, even at least two flashflooded rides home from work where it was completely submerged along with the rest of the wiring and electronics under the trike.


The main difference between LFP and LI chargers used to be that the LFP charger never shut off it's output (so it's just like the LED PSUs) while the LI charger did. In some models of charger there were even versions where you just broke off a little board inside that did that shutoff function to make it an LFP charger. (see some of Dnmun's old posts from several years ago for examples).

What the difference is these days, I don't know (I suspect it's not any different than it was then).