My 5-6 year old 12v battery in my 2011 gen 3 needs replacement. It would be probably still be ok, except I’ve left the interior light on a few times. The ICE starts almost straight away when I start it. I can’t afford to replace it at this moment. My car is parked in the open. I have a spare flexible 100 watt panel that sits nicely behind the windscreen when parked. I’ve bought a cheap $20 Renogy PWM solar controller. My question is would it be an issue if the Prius was started on a float voltage (13.5v ?) or even a charge voltage (14.5v?) or would I need to disconnect the panel before each start?
The solar controller will never send voltage upstream to the solar panel itself so you can start the car with panel still connected to the controller. Just remember to unplug the panel it as you drive away My solar controller is connected to the built in solar roof on top, the panel is always connected to the controller.
The car won't mind a bit. Anyway, if you move the solar panel away from the windscreen before starting the car (which you might have other reasons for doing anyway) it probably won't be putting out 13.5 or 14.5 volts right then anyway.
This is why I preemptively changed the factory incandescent interior lights to low-current LED models. While this doesn't prevent the problem, it very greatly extends the time to discover and remedy the problem before the battery drains enough to prevent starting. Though the degree of improvement will vary greatly depending on LED choices.
This would be my guess too. But since you don't know exactly how your "cheap" controller really works.......it will be somewhat of a gamble. Since the panel is inside the cabin, put the controller there too.......with a quick connector that you can unplug whenever the car is in use.
What's your usage of the car like? Do you drive it multiple times weekly? What's the trip length on average? Is your usage pretty steady, or are there some times it sits for a protracted time, say a week or more?
