12V/12Ah Solar Generator Charging

[Solothurn]

This is my first DIY solar project: Nermak model 12V12A LiFePo4 battery and Renogy 12/24V 10A PWM solar charge controller. It's going to replace a Bluetti EB3A for charging HT radios, running LED lights, and powering an HF radio.

I'd planned to charge it with a 12V/10W solar panel and cigarette lighter car charger. The solar panel works ok when it gets above about 18 volts, which requires almost full sunlight. The car charger, at 14.4 volts, doesn't put any power through the charge controller. So reading here and other places I find that's the way it's supposed to work: I need about 5 volts more than battery voltage going into the controller.

https://www.amazon.com/dp/B09235DJ1...AU6FJEA15&ref_=list_c_wl_lv_ov_lig_dp_it&th=1

Will this 12V to 24V step up converter charge my system with around 14 volts input, without harming my charge controller? Would there be a danger of it putting out too much power with the solar panel in full sunlight?

Or is there a better solution that I haven't found yet?

 

[Rednecktek]

So you're starting out at a disadvantage with that 10w panel. That battery is about 144wh which will take about 15 hours of direct perfect conditions to recharge that little battery. At 14.4v you can probably just connect the car charger directly to the battery and skip the PWM controller all together as 14.4 is a good charging voltage for a LFP battery and let the BMS cut off the charging when it gets full.

 

[Solothurn]

Will the battery BMS protect the battery with a solar panel directly to the battery putting out 18 or more volts?

 

[Rednecktek]

The car charger, at 14.4 volts, doesn't put any power through the charge controller.

The car charger is the right voltage, you'll only need the controller for the solar panel.

 

[Techman Solar]

PWM solar charge controller

Switch to an MPPT charge controller.

The car charger, at 14.4 volts

As @Rednecktek suggests, connect the 14.4V car charger directly to the battery. The BMS will protect the battery.

 

[Rednecktek]

Switch to an MPPT charge controller.

On a 10w panel that would just be a waste of money.