Hi all, I'm curious about the Prius electrical system, primarily about where the boundaries of the low-and high voltage systems are. The Prius has a lot of electronics onboard, how much current do these subsystems draw? As I understand it, the 12V battery recharges from the HV battery via a DC-DC converter. The onboard electronics then draw from this 12V bus. Relays, controlled by the 12V system, connects and disconnects the HV system. The reason I'm asking is that if the onboard low voltage electronics (computers, MFD screen, NAV computer, sound system) all draw say 1A from the 12V subsystem, isn't it possible to supplement that current with current from a roof mounted solar panel thereby reducing the power demands on the 12 battery and DC-to-DC converter. Such systems exist I know, but how far do they go? It's obviously easier to supplement energy on the low voltage side than to mess with the HV systems. Thanks
There was a post on the Prius Technical Stuff Yahoo group a while back with typical current draws for the 12 volt system. And yes, it would be possible to supplement the 12 volt system with a solar panel if you connect at the 12v battery so the inverter sense wire can see the voltage. Wayne
Sorry to be needy, but could you point me in the right direction? Google comes back with all kinds of rubbish on the topic.
Keep in mind if you are trying to help with overall fuel consumption, it is better to put a real PV array on the roof of your house and forget about carrying one around on your Prius. If you want to do it for fun or show, then that's a different story. Tom
Fair enough. You are correct that any 12V power supplied by a PV panel is power not drawn from the HV bus and ultimately from gasoline. The amount is small at best, and probably does not justify the cost and weight of a PV panel. Several of us have talked about just this idea in regard to the new 2010 and the integrated PV panel. If you have it on the car anyway, it might be fun to tie it into the 12V system. Tom
Perhaps the most practical use for an integrated PV on the car, asides from ensuring the 12 vdc battery is kept fully charged, is to power a fan. That way, when the car is parked in the boiling hot sun, at least it won't be a solar oven inside As far as overall "footprint" a home PV makes a lot more sense, and has more potential to make a difference. Say when small desirable EV commuter cars are finally mainstream :flypig: You could charge the batteries with the home PV system
I disagree with your assertion that the onboard electronics cumulatively draw 1A from the 13.8VDC bus. That implies that the ECUs in total require 14 watts of power. Recall that power steering/brakes are also powered by this bus, as is the rear window defroster, the cabin ventilation fan, two PTC electric heaters, and vehicle lighting. Although I haven't measured the current draw, my guess is that the ongoing power requirement would be more like 20A-30A without having the defroster, cabin fan, and lighting on. Remember that Prius has many ECUs: engine, hybrid vehicle, traction battery, skid control, power steering, air conditioning, transaxle gear select, immobilizer, body, smart, etc. With all electrical accessories on, the cumulative current draw might be as high as 70A-80A. Therefore, the contribution that a roof-mounted solar array might provide is quite minor compared to the ongoing electrical draw upon the system and the cost of such array. The only use that Toyota can make of its 2010 roof-mounted solar array is to spin the cabin ventilation fan when the car is IG-OFF, which probably requires current of 3A-5A.
That's incredible! A 15W 3x1 foot panel would still only contribute less than 5% of the total power demand for the onboard electronics. I wonder if increased integration in the 2010 model could've potentially have reduced the power demands from the onboard electronics.
That would be the base load while operating. The best a 15W panel could do would be to top off the 12V battery when parked in Sunlight. The MPG savings would be negligible, surely much less than 1%.
Anyone with a scangauge can see the hybrid battery current with the car in READY and stopped. Between 1.2 and 1.5 amps, if I remember off the top of my head. [I monitor my current with an analog meter and so rarely see a fine-resolution figure.] Do the math to translate from ~ 230V to 13.8, and there's your watts in the 12V system. . If you feel the top of the MFD after everything's been on for a while and *not* in the sunlight, it's easy to believe that all those little boxes taken together, and the inverter pump and whatever else, is pulling 350+ watts all told. . _H*
