Toyota Prius: solar cell battery charger

We bought our '04 in Oct '03, and a couple of weeks later the
lines were six months long. As a charmed engineer, I bought and
did everything you can imagine, including building a solar
charger as a backup for the 12V system - which is what the
cigarette lighter socket would be connected to if it were ON
when the car were OFF (it must be modified to achieve that).

Useless. Unnecessary. And for the high voltage system, the
difference in vehicle performance would be unmeasurable unless
you used the entire outer area of the car, and even then it
would be tiny. The way to improve mileage is to

(1) accelerate smartly when nothing's in front of you
(2) avoid using the brake

That's right, keep your foot off the brake... with that mindset,
you drive properly and can get more than the average.

Great car, isn't it?


Bill wrote: 

"Bill" <com> wrote in message
news:googlegroups.com... 
You don't say whether it is the sedan or the hatchback. I don't know about
the hatchback (I think it's the same) but in the sedan the lighter socket is
disconnected when the car is off. It can be modified to be live, and some
people have used the solar charger you describe to keep the aux battery
charged when they have to park (as in long term parking at an airport) for
more than a week or two. Most modern cars have the same problem - the alarm
system slowly drains the battery.

This affects only the aux battery so no change is seen in fuel economy.

Mike

Bill:
Charging thru the cigarette lighter only charges the 12 volt battery, and
this would have no effect whatsoever on the 273 volt main traction battery.

Dick


"Bill" <com> wrote in message
news:googlegroups.com... 

On Jun 30, 8:56 am, Bill <com> wrote: 

On the Prius (doesn't matter the model year), the 12v accessory outlet
(aka cigarette lighter) is switched off when the car is off. So, if
you want to use this battery charger, you'd have to either modify/
rewire the outlet to always be on/hot, or you'd have to wire a 12v
cigarette outlet directly to the 12v accessory battery.

for the power outlet mod:
http://www.coastaletech.com/powermod.htm
http://www.coastaletech.com/power_outlet_mod.htm

Such solar cell battery chargers as you describe are used by people
who do not use their car very often, or are planning on leaving their
car undriven for quite a while (such as at an airport parking lot).
There are various parasitic loads on the 12v system, most notably the
alarm or SKS system if installed, that will slowly drain the 12v
battery during extended periods of non-use (besides the natural self-
discharge). The solar charger would keep the 12v battery charged up,
so that you wouldn't need a jumpstart when you return to your car.

When the car is off, the hybrid traction battery is electrically
disconnected from the car. So no solar charger will directly affect
the charge level of the hybrid battery.

Would there be a benefit to fuel economy by using a solar charger?
Well, once the Prius is started the hybrid battery wouldn't have to
recharge the 12v accessory battery as much if the 12v battery is
already recharged by the solar charger (and therefore the gasoline
engine wouldn't have to run so long to recharge the hybrid battery if
needed). But I doubt that you'd see a measureable change in fuel
economy. Mainly, you'd just be able to start your car because you
didn't let the 12v battery get flat in the first place.