Solar Panel Charging

[JoeWawaw]

Hi, i bought a solar panel along with a charge controller to charge a 12V car battery. The battery will basically always have a small load, occasionally driving a bigger load. What i was wondering was whether the solar panel needs to be physically disconnected while there is a load.
During a higher load (400W), will my small 20W solar panel get damaged? I dont know much about whether they have a shutoff when the leads are short-circuited, or if its ok to short circuit their leads. I don't know if charge controllers can sense whether the battery is driving a load, or even if its possible for them to know. I quickly drew up a rough schematic for this situation. Thanks

 

[MikeMl]

The panel will be fine.

Since you should never allow a lead-acid starting battery to discharge below about 12V (as low as you should ever go), the panel will always see a load voltage somewhere between 12V and about 14.5V (just prior to reaching full charge).

You really should have an auto-load disconnect to prevent deep-cycling the battery. An automotive starting battery is only good for a few (less than ten) deep discharges, and then you might as well recycle it. In a car, a starting battery lives its whole life between fully-charged and maybe 80% charged. It is normally only discharged below 80% if you do the dumb-shxx thing and leave the lights on when parked.

 

[NorthGuy]

The load will not damage the panel.

Although 20W panel will probably not produce enough to maintain the loads you describe.

 

[JoeWawaw]

There's a cutoff circuit in the charge controller. Also, my 400W load is handled by the battery and only going to come on for short periods of time in long intervals, so i don't think the battery would go through a deep cycle charge.