What am I missing?

[user4572]

So I'm putting together a little system to run a fan and light to get my feet wet in the solar thing.
I have (4) 5 watt solar panels connected to an OOYCYOO 40A charge controller and I have (3) 12v 7Ah LiFePo4 batteries (w/BMS) connected to the charge controller and a 12v fan and light connected to the batteries.
Before I power this up am I missing anything? I know the 20watts for the panels aren't much but again it just to start learning with.

here is a quick drawing

 

[BentleyJ]

What is the operating voltage on the 5W solar panels? They probably need to be connected in series as the incoming PV voltage typically must be higher than the output charging voltage of the battery. 12V battery would suggest the PV voltage should be about 20V minimum.

 

[Hedges]

Load control. The loads will continue to drain batteries past minimum, relying on BMS to disconnect. Better to have loads disconnected at some SoC or voltage. Some SCC provide a control signal or port for small loads.

How many watts to the loads draw? They may draw all your 20W of PV can produce, so no charge ever occurs.
Or maybe you only turn them on briefly. This might work for something like bathroom fan and light only run occasionally.

 

[user4572]

What is the operating voltage on the 5W solar panels? They probably need to be connected in series as the incoming PV voltage typically must be higher than the output charging voltage of the battery. 12V battery would suggest the PV voltage should be about 20V minimum.

21.4v

 

[user4572]

Load control. The loads will continue to drain batteries past minimum, relying on BMS to disconnect. Better to have loads disconnected at some SoC or voltage. Some SCC provide a control signal or port for small loads.

How many watts to the loads draw? They may draw all your 20W of PV can produce, so no charge ever occurs.
Or maybe you only turn them on briefly. This might work for something like bathroom fan and light only run occasionally.

right now I've got the load to 1 -2 watts

 

[Texas-Mark]

What is the operating voltage on the 5W solar panels? They probably need to be connected in series

I agree for this charge controller. However, 20W total is pretty low (given actual output will be less), may barely replace what the charge controller uses to operate.

 

[Hedges]

0.28A Imp, 0.31A Isc.
Assuming PWM, four of these will deliver 1.12A into 12 ~ 14V battery, 14.6W
In summer you may get 5 to 7 hours effective sun if oriented well and not shaded. About 90 Wh/day.
2 watts load sounds it could run 24 hours/day in the summer (but winter maybe 2 hours effective sun). Need to see what SCC consumes as Texas mentioned.

A larger panel should work better over seasons and poor weather. Don't exceed recommended charge current, and protect batteries from freezing unless BMS has low-temperature charge cut-out.

With PWM SCC, stick with panels having suitably low Voc, like up to 20 or 25V (watch out for max SCC voltage rating and PV panel voltage increase when cold.)

If you get MPPT SCC, then the higher voltage panels can be used too.