Solar Panel Mod charger

"If it was easy to do, i'd literally rather cut the power wire to the fan and run it to an aftermarket outlet"
You can do that. You won't be happen in the summer though when you get in the hot car.
You can also switch the wires on the fuze for the 12V outlet so you have power all the time.
I couldn't find the post for it. But you can also get a fuzed wire adaptor and and install it on an empty fuze
to an outlet you install/

 

Thanks. I did see that post about the small modification to allow the,existing 12v outlet hot at all times, and was seriously going to do that, but I know the small 12v battery doesn't last very long and I don't want to take a chance of getting stranded. That already happened to me once while using the outlet with the car on the accessory position for about 15 minutes. Probably the main reason why I have such a bad attitude about the solar panel situation.

 

The solar is independent of the of the battery.
I've run a walfart fan for 2-3 hours and had not problem with starting.
I also carry a battery jumper. You can get them for about $50.00.
I don't know what you are planning on running, but if it's just your iPhone or iPad, you won't have a problem.
It's a simple mod, just moving 1 wire. I will see if I can find it.
Here it is:
Power Outlet Mod

 

I don't know what you are planning on running, but if it's just your iPhone or iPad, you won't have a problem.
Here it is:
Power Outlet Mod[/QUOTE]
Thanks. I would be using it to be charging a camera battery, possibly for 8 hours, and occasionally my cell phone. I have done the same thing in 3 other vehicles previously (often times while sitting in the car with the radio playing) without ever having a problem.

 

Just got started on a similar project using @Michael Cline's approach here (a simple adjustable buck converter, rather than a fancy solar MPPT controller). In my case, the more adjustable converter is useful because I also have a low-voltage disconnect in the car, that detects when the car is READY by seeing the voltage above 13.2, so I need the solar controller to be adjustable to a voltage just below that. The MPPTs I've seen have higher output targets.

But I've run into one snag: the very nice small buck regulator I bought has all the features I wanted: adjustments for voltage and constant-current limit, no fancy display, just a red/green LED.

However (comma!), it measures the current for CC mode using a shunt that is between its IN− and OUT− terminals. Because in the Prius the solar panel and the 12 volt system share the body as a negative ground, current is not forced to flow through the shunt, and this regulator's CC mode will not work in this application.

So, that's a thing to pay attention to in selecting one of these. The seller offers a crazy number of slight variations on it, so I have a question in, asking if they have one that is almost the same but bases CC mode on current sensed in the + path.

Fingers crossed....

 

Mppt does a much better efficient job at taking varing voltages and keep it steady to a set voltage than a bucker. It may cost more but you can set it to stop sending charge to a battery at a set voltage like pmw.

 

I hear that, but I'll also acknowledge Michael Cline's earlier comment, "Either way it is only wasting a small amount of free energy."

In my case, I have a specific additional requirement I have to meet, the output must be adjustable to a limit below 13.2 volts. None of the MPPT controllers I browsed briefly on the web a week or so ago met that requirement. If you know of one, I'd be grateful for a link, considering I have to repeat the shopping step anyway. There are way too many products around to pretend my search was exhaustive.

And, of course, any candidate will also have to allow the input and output to share a common negative, which is where my current bucker falls short.