Hacking the solar?

Call me gutless, but this sounds like a warranty breaker to me. I'll be disappointed if they don't already use the solar cells to top off both batteries. Seems like a natural to me to trickle charge the 12V battery and not much extra work to charge the motive battery.

Anyway, I'll help read schematics and make suggestions but I'll have to stop there. Even if I wasn't worried about voiding the warranty, my wife would kill me if she saw me cutting into and soldering up our new Prius.

 

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

Tom

 

Yeah, you've got to pay to play. As long as you don't break anything, then no warranty can ever be voided.

Rick - it is easy to prevent backflow with a diode. Charging the 12V would likely be quite simple. Charging the HV battery would be too complex (expensive and ineffective) to make any attempt worthwile. I think it should just power a propeller on the top of the car when it is doing nothing else. You know -like a propeller beanie. It does drive me nuts that around here that PV panel would only be put to use about five months out of the year - the rest of the time I WANT whatever heat is collected in the car to stay there! What a waste of product!

 

I could use it for a couple of days in August. The rest of the time snow would block the PV panel.

Tom

 

there is probably good reason on why it runs only the fan too .

 

Probably the main reason is that the PV array doesn't generate much power. Toyota probably figures that the cost and complexity of routing that power to the 12V battery is not justified. Routing it to the HV battery is silly.

Tom

 

It certainly is a natural fit. The car will tend to heat up when its sunny, and the sun angle is high (ie in summer). Part of the problem with utilizing it for something else the rest of the year is that the sun angle will be poor, which will not only limit hours of production, but also reduce peak production.

For example:

Average Wh/day for 80W panel at 0deg inclination in:

Month: -- 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12
Phoenix: 214 288 359 458 504 500 471 436 380- 314- 233- 188
Duluth:- 115 184 300 326 392 416 387 340 254- 173- 96 - 82
Seattle:- 49 105 196 281 375 409 411 330 251- 131- 66 - 36

I used the site below, with the following inputs: System size = 8kW (result divided by 100), DC/AC conversion 0.9 (higher than default 0.77 as we don't have to convert to AC), and array tilt angle = 0 deg.
PVWATTS v. 1

Ideally I would think running a block or battery heater in winter would be very desirable, but I don't see there being enough power available to do much. The OEM block heater is 400W, and takes 3 hours to heat the block using ~1200Wh of power. A trickle charge on the 12V battery is probably feasible though. You'd probably need something like the charge controller below, although this one would probably be overkill. The nice thing about ones like this is they function like a dc:dc converter, or buck/boost converter, taking whatever the solar panel voltage is and transforming it to the battery charge voltage while putting as much current into the battery as possible. This is much more efficient than an old school solar charger.

Blue Sky Solar Boost 2512iX 25A,12V 3 Stage Charg - Blue Sky Solar Charge Controllers (MPPT) @ AltE

Rob

 

Incidently, in Seattle in December, if you can find a south facing 47 degree hill to park on you can more than double your solar output. Maybe a jack of some sort is in order

Rob

 

Would have helped if they had hinged the solar panel, so it could be tilted to the best angle for max. power!
But given its low power output, I think it is as much a marketing ploy for Kyocera as for Toyota, with the former picking up much of the tab.

 

Why trickle charge a fully charged battery?
I think some people are starting to work out the solar panel is an expensive gimmick, nothing more.
The cost of the solar panel over the life and location of the car combined with the limited amount of time it would be useful mean the solar panel would never recoup the additional cost. It shouts GREEN to the world but it is quite black.

A PV array on the roof of a house has a life of productive power conversion of +25 years, even a Toyota Prius won't live 25 years on average due to collision damage, corrosion and wear.
The PV on the roof of your home collects power when ever the sun is shining and if it makes more than the household is using at that moment pushes the left over into the grid for someone else to use, the Prius panel only works when the car is parked in the sun and it is going to get hot in the car, otherwise it's a decorative item.
The PV on the roof of a house is carried from factory to final location once, the PV on the roof of a Prius will add weight to that Prius for its entire life, meaning that the panel will be responsible for transport costs of the journey from factory, via Toyota's factory to the dealer then another 300,000 miles of travel until the end of the vehicles life. Carrying that additional weight will cost in fuel consumption.

I think if you want the solar panels to be green, don't.
If you want the solar panel to look green, go ahead but keep the truth quiet.
If you want the moon roof and it only comes with the solar panel, what can you do?

These are just my thoughts, no science to back it up, just dead reckoning and gut reactions.
I'm not trying to force my opinion on anyone and if a friend gets a solar panelled Prius I will praise it like a grandmother would a baby grandchild but if you are out to reduce your carbon footprint you would be better off putting the added cost of the solar roof Prius toward a home mounted PV array, it would be a better investment for the planet..

 

It is very hot here in summer too but we are talking a 5 minutes per drive benefit from the solar panel, the remote AC to me makes sense.

Good point but a costly way to do it. A solar battery charger which cost about $25 on the cargo blind during long periods parked in the open would do the job just as well I suspect.

Anyone remember the accessory solar powered fans that went in the side windows?

Maybe my mind is just rationalising for me why I won't be getting the solar panel roof? Never been a sun/moon roof fan myself.

Evan, for cabin heating a double glazed roof would be more effective. Let the sun in but keep it in too. Of course if you can't cover the glass you have cabin heating in spades in hot sunny weather, when you don't want it.

 

Another way the solar could have been used, this is after all a cutting edge vehicle.
Charge the traction battery and run a small transmitter. When the key fob is within a predetermined distance, user defined within hardware limits the AC comes on to adjust the interior temperature toward the preset comfort level selected by the driver when last driven. An electric inverter controlled AC could be reverse cycle for this purpose.

The only charge you could put into the traction battery is from the normal state of about 60% charged up to 80% full charge and once this state was reached the AC fan could be powered if the interior temperature was further for the preset temperature than the outside air.

I still would see the solar panel as a look good feel good item of little practical use. Hard to please hey?

Edit, I suspect you are right Rick, damn UV reducing glass.
I agree with what the solar panel is meant to do and it will reduce the overall load on the engine for recharging the traction battery after remote cooling but when considering the added weight of the solar panels and that the added weight is on top of the car inducing more body roll so requiring more speed reduction for corners, I suspect the solar panel uses more energy over its life particularly in its current part time role than it contributes.