Low Power (10W) Solar Charger for LifePo4

[Panoramix]

Hello Everyone! First post, sorry if not in the correct thread, please let me know

I'm working on a small 12V system with a 10W panel and a 40Ah LifePo4 battery. (I know it would take ages to fully charge, but the goal here is to have a "portable" system with a small panel "always on", and having the possibility of connecting additional panels if necessary).

My issue here is finding a solar charger (possibly MPPT) able to work with a 10W panel.
I initially bought a Voltima SCD12 which is rated for 165Wp, but what it didn't say anywhere is that it needs about 80W minimum to actually start charging... I got this information after talking to the manufacturer, but I don't have any experience in this field, does anyone know if that is a general rule that would apply to all MPPT charger? Meaning I would need about 0.5 x Max power of the solar charger to have it actually charge the battery?

This is my first solar project and I am certainly lacking experience. Here's the main questions I have flying around my head in this moment:
Is there anyone here with experience on "low power" systems such as this one?
Do you have any suggestions on how to choose an MPPT solar charger?
Should I move towards PWM solutions?
Wouldn't there be a problem with using PWM to charge a LifePo4 battery? (Maybe the low power and low currents involved here would mitigate this issue?)

I'm eager to hear your feedback!
Please ask if anything isn't clear.

 

[justgary]

I'm charging a 230Ah 4S LFP battery with a 100W panel and a PWM Tristar SCC. The battery never really completes a charge cycle, but it has enough capacity to get close to full in the summer and somewhat lower in winter. The constant load I have is only a few watts.

I don't see PWM as a problem as long as the panel voltage is not too high. Putting panels in parallel rather than series can help raise the charge current but not the voltage.

 

[yodamota]

Personally I think you would be better off with an AC charger versus the 10w panel.

Here are some low wattage charge controllers https://www.eco-energy.us/products/solar_controls/

 

[Rednecktek]

At that size, you're looking to spend $100+ to get less than 1% more power. Stick with PWM until you're getting above the 200w range where the efficiency really starts to be measureable.