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Charge Lifepo4 using MPPT SCC and a car battery charger?

Skid

Solar Enthusiast
Joined
Oct 26, 2020
Messages
202
Location
Nicaragua
I bought two 12v 50ah Lifepo4 batteries and a 30a MPPT a year ago for a project that never happened. They have sat, forgotten, until now. I checked the voltage and one at 13.2v and the other at 12.9v. Can I use the MPPT to charge the batteries from the cheap dumb charger? There are no smart or lifepo4 chargers available here.
 
Instead of risking things with some cheap kludge of a charging setup, why not just buy a small panel to accomplish the job as designed without a lot of risk?

I'm assuming you'll be buying panels at some point, but here just to accomplish a small maintenance task, you don't need to go all out with some huge panels. Just something large enough to charge them up with using your existing controller in the meantime.
 
I'd love to but there's nothing within 6 hours (by chicken bus) from here. When my system arrives it is 48v so that's ruled out.
 
Well, I guess it's cheap dumb charger time, hoping that your LFP batts are using a BMS of some sort and that it doesn't exceed the capabilities of the SCC. Which is really meant for solar panels, but in a pinch some have hooked chargers to them and crossed their fingers.
 
Yes, they do. Thank you. The charger is only 10a and just want to take them to 13.3v.
 
is not recommend to do that way, mppt charge controller only connect able with the panels.
 
Use your battery charger direct on the battery, monitor the volts and stop when they get to 14 volts. After a rest they will sit at about 13.4 volts. If you want to store for some, time pull the charge down with a car headlight bulb.

Mike
 
An MPPT charger can only decrease the voltage while increasing current - it can never increase the voltage.

I have a modification in my RV Trailer and Tow Vehicle, to take low-voltage "Tow Vehicle" power (at about 13.5V) and boost it to 36V as input to my MPPT controller. From there, it charges my LFP batteries great. But you'll need a "Boost Device" for your charger, and there are 3 rules:

#1 The MPPT must not overrun the boost device - you must limit its maximum charge current to something less than 80% of the maximum power of the booster in the middle.
#2 The Booster must not overrun your original low-voltage charger.
#3 You must re-program your MPPT to a profile which matches LFP batteries (if you have not already done so).

With that said, this IS workable, and would be like my configuration in this Thread - except that you won't need any of the Relays and switches: https://diysolarforum.com/threads/r...rs-of-mppt-charge-solar-in-the-trailer.20730/
 
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