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How to Program Charge Controller for Lithium Batteries (MPPT v PWM | LiFePo4)


5 min read

When you’re setting up your solar panels and batteries, it can be a bit overwhelming to figure everything out. Look, I know, I was right there with you. Don’t worry though, let’s walk through one of the simple steps to set up your charge controller. This process works for both deep cycle and lithium batteries.

Lets do a brief refresher of charge controllers, A solar charge controller is needed in virtually all solar power systems that utilize batteries. The job of the solar charge controller is to regulate the power going from the solar panels to the batteries. Overcharging batteries will at the least significantly reduce battery life and at worst damage the batteries to the point that they are unusable.

PWM type charge controllers are simpler and less expensive than MPPT type charge controllers. MPPT type charge controllers have the ability to convert excess panel voltage into higher charging amps, which means that they will produce about 15% more power than PWM type charge controllers.

What charge controller should I use?

Charge controller selection is based primarily on the panel wattage and corresponding charging current. For every 100 watts of solar panels, assume that there will be about 6 amps of charging current. The charge controller’s current rating needs to be greater than or equal to the total panel charging current. For example, a system with four 100 watt panels can use a 25 amp charge controller. I have 400 watts of solar coming so while 25 amps works, I opted for the 35 just in case there is a spike or I want to add more panels down the road.

It is very important that your charge controller system is properly tuned for your battery bank. An improperly set charge controller can destroy an expensive battery bank.

Where do I get the settings for my own batteries? you may ask.
Well your batteries should come with a guide or you can check on the manufacturers website for the exact voltages and settings. Let’s take a look through my paperwork.

(Now’s a good time to check out the video link above to see what I’m pointing to)

Tuning for lithium battery banks is the easiest because they do not require equalization nor do they need regular full charges. The BMS (Battery Management System) handles most of the thinking for you. But if your charge controller or converter are configured incorrectly, and the battery bank gets too high of a voltage, the mistake could be very costly.

Unfortunately there are not a lot of lithium specific charge controllers. There is just no demand for them yet and thus no one is manufacturing charge controllers targeted at Lithium batteries. Regular charge controllers will work for lithium batteries, if they have certain options.

You can buy BMS charging systems but they are designed for the Electric Vehicle markets and require a very hard power source, and solar systems are not hard power sources and never will be. I recall one manufacture that has a Lithium setting, but I would not recommend using it because it is not accurate enough.

So we’re back to the good ol’ PWM and MPPT controller.
The MPPT is always more efficient when you have a higher voltage PV array. BUT, that’s not what Lithium batteries care so much about, as they need a very precise way to balance the charge to each cell in the battery, and not to overcharge. So being able to set precise voltage set points is the most critical thing. So as long as you have that option in your charge controller, it should work.

If you are not wanting to spend much money you can use a PWM charger with an adjustable end of charge voltage.14.8v that also allows you to turn off the “equalize ” setting.

I’ve heard someone say that they preferred PWM batteries for lithium batteries, because they didn’t believe the 30% increase in efficiency of the MPPT controllers. But, I’ve also seen real life data match the theoretical gains of the Mppt controllers. If you have the extra money, I suggest going with the MPPT.

Whichever solar controller you go with, the most important thing is that they can set voltage points.

While I was researching some more info for this video, I came across a video specifically about a new mppt charge controller designed for lithium batteries. Now, I haven’t used this one and can’t vouch for it’s quality, but I’ve included a link to that controller too if you want to check it out yourself. My system is 12 volts but they also offer a 48 volt model for a bit more.

If you’re looking to buy any of the gear here, I’ve got links below to some of the best priced options. And links to the specific gear I’m using for my AGM batteries. Consider clicking those because it gives me extra points and makes you feel extra good. Plus most things have free shipping in those links if you spend over $50.

As always, if you have any questions, hit the thumbs up icon and leave a comment and I’ll answer it as soon as I can.


Lithium Charge Controller Genasun GV-10L

100 Watt FLEXIBLE Solar Panels
40amp MPPT Solar Charge Controller
40amp MPPT Solar Charge Controller WIFI
Pure Sine Wave Inverter
AGM Deep Cycle 12v 310ah Batteries
Inverter Cable kit w/ Fuses
Blade Fuse Box
Inline Fuse Holder
Inline Fuse

LED Lights (Best I’ve found)
Romantic Christmas Mood Lights
12 Volt Dimmer Switch
Female pigtail connector
Switch project box (Different sizes too)

Wiring Diagram Slides

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