Hacking the solar?

[rachaelseven]

Okay, so I'm reviving an old thread here, but for good reason. Seems that there might be a real possibility the 12V battery is only good for 2-3 weeks of inactivity before it becomes too dead to boot the computer and engage the main contactor for the traction battery.

http://priuschat.com/forums/gen-iii-...=hacking+solar

It seems improbable, but if the 12V battery is really that weak, using the solar panel as a trickle charger sort of takes on a new urgency. So here's what I think the function of that panel ought to have been:

A.) In normal operation, the panel operates exactly as it does now, running the fans to keep the interior cool.

B.) The 12V battery voltage is monitored and the moment it begins to get low, such as after being stored for a week, the panel function switches over and uses all its current to trickle charge the 12V battery.

So then question one, does this make sense? Is it a good use of the panel's voltage? And two, how hard would it be to accomplish?

The charger circuit is readily enough available - been discussed already - and a solid state relay for switching the current from the present circuit to the charger circuit is easy enough. How difficult would it be to rig a battery monitor circuit and use that to drive the solid state relay? Almost seems like the monitor circuit from a commercially available battery tender serves about the same function, right? Only instead of turning on the charger, it could fire the relay and switch the solar panel output from the car to the new charger circuit. When we 'throw the switch', we completely disconnect the panel from the car's built in circuit, so the car will just think it's in the dark and getting no voltage from the panel.

Seems pretty straightforward to me... am I oversimplifying this?

[hobbit]

I've been mostly not tracking this thread, but a slightly sideways
idea occurred to me the other day: how 'bout hacking the circuit
that the solar plugs into, and be able to power it off the normal
12V of the car?? I'm thinking the overnight camping scenario
where you want to run the fan at a very low level for ventilation,
and given that the panel powers up the fan controller and feeds
it a low-speed control waveform, it would be the semi-obvious
way to do my fan hack in a 2010. Well, if it's got the solar
in the first place.. something else would be needed for cars
without, I guess.
.
_H*

[rachaelseven]

If the battery is as weak as some people are saying (only 10 days of inactivity before it needs to be jump started?!?), I'd be pretty hesitant to deliberately run anything off of it overnight. I'm still not buying the 10 day battery theory, to be honest, but if it's true...

[carz89]

Originally Posted by rachaelseven

If the battery is as weak as some people are saying (only 10 days of inactivity before it needs to be jump started?!?), I'd be pretty hesitant to deliberately run anything off of it overnight. I'm still not buying the 10 day battery theory, to be honest, but if it's true...

To be able to run the fan, you have to be at least in accessory mode. In this case, doesn't the 12v battery ultimately get its power from the HV traction battery via a DC-DC converter? If so, then you could probably run the fan an extremely long time in slow speed. At least overnight, and perhaps a whole day.

[carz89]

Originally Posted by rachaelseven

It seems improbable, but if the 12V battery is really that weak, using the solar panel as a trickle charger sort of takes on a new urgency....Seems pretty straightforward to me... am I oversimplifying this?

Yes it can be done and I'm sure someone will soon have a hack to provide the trickle charge from the solar panel. However, if you park your car in your garage while away on long trips, you are out of luck! For you "garage parkers" out there, like me, it's probably cheaper and simpler just to hook up a plug-in battery trickle charger.

[solarMD]

Where can I find the schematic involving the EV button, and the Motive Battery? Has anyone built a solar charger for the Motive Battery ? I would like to do it, if it does not void my warranty now.

Originally Posted by qbee42

It only runs the fan. Toyota was very clear on this issue.

Tom