How much solar needed to improve MPH

i dont' think they're even considering the solar for mpg.. I thought it was just to help run a fan or something to cool the interior while the car sits in the hot sunlight..

 

All those panels are going to provide, say they are rated at 15 watts output, it will go thru the charge controller and give you around 14 volts DC at about 60 to 75 ma. All it really will do is make sure the 12 volt low battery will not discharge if you let the car sit parked for extended time!!!

I use one to top the battery in my 4Runner off as it now sits for extended periods of time due to obvious reasons.

How ever as a battery maintenance charger, IT WORKS GREAT!!!

Putting it on a Prius full time would be a waste of money if all you are trying to improve is your MPG!!!!

IMHO!!

73 de Pat KK6PD

 

all the solar chargers out there, even the ones for the Prius is NOT meant to be charging the hybrid batteries. It's only to keep your 12 volt battery in good condition.. so it has almost no effect on MPG.

I've been pondering about it myself because I often commute 1 mile or so all over the place on campus.. (from lab to lab.. im a grad student), so if i can use electric mode, and then have the sun charge the hybrid battery.. all my 1 mile runs can essentially be "gas free"

but what I've come to find out is that the hybrid battery is NOT easy to charge.. u can't just slap on a 237 Volt battery charger..
I thought about connecting one 7.4 volt solar panel to each battery inside the battery bank, that'll work.. BUT i don't know how that'll affect the onboard prius charger.. and its risking charging the batteries unevenly.. and damage them prematurely.

conclusion? I give up, i don't think its an easy home mod... probably would be more worth it to go plug-in method...

 

Your question has been answered several times. Solar panels (current technology) do not provide enough power to be of any practical benefit for your intended purpose.

 

In theory, you could get perhaps 40W out of panels on the current Prius.

IF it was nice and sunny, and
IF you could convert that power to the 201V level, and
IF you could add that power to the system power,

THEN you would be adding 40 W to the car that gasoline wouldn't have to supply.

That's 0.054 HP. Let's assume you use 15 HP cruising on the highway (level road, no wind) to overcome air resistance, tire friction, and running gear friction. You will improve your economy by 0.36%. So if you were getting 50 MPG without solar you would get 50.18 MPG with solar added in.

Is it worth the $1500 or so to implement such a system?

Lets assume you could do an "economy of scale" installation (by Toyota for example, when they design the "next generation" Prius).
Solar panel - $300
Electronics upgrade - $50
Roof modification/sealing - $50
Cabling - $25

Is 0.18 MPG on sunny days worth an extra $425 on the base price?

 

The capacity of the larger conversions is something over 200 watts. They use a 70 to 48 volt converter, and charge a secondary lead-acid battery bank. There is another DC-DC converter to charge the traction battery. I do not think that you would install something like this expecting it to pay itself off, although it will get a lot more attractive as gas prices go up.

Pat

 

Unless you are considering adding additional batteries, typically the Prius can't make it much more than 2 miles in EV mode. This means that, even with a fully charged battery, the Internal Combustion Engine (ICE) will still need to fire up at some point in your 15 mile drive.

The 15 HP numbers quoted by David Beale assume constant velocity on flat roads with minimal wind and an already warmed up ICE. You are talking about a commute that would at least involve accelerating, likely involve wind, and potentially involve less than perfectly flat roads, with a cold ICE.

Therefore, you are probably going to be using quite a bit more than the 5 HP hours you calculated.

Assuming that your idea is to charge the existing battery, the NiMH battery in the NHW20 Prius has a capacity of about 1300 Watt hours. Assuming that you will not be charging the battery beyond the 80% that the Prius maintains as a maximum charge, you will have an adjusted capacity of about 1040 Watt hours. Assuming you will allow the Prius cancel EV mode and start up the ICE and charge the battery using its current programming, you won't be able to use the last 40% of the charge in the battery. This gives you a potential usable storage of approximately 520 Watt hours.

So to ensure a maximum charge over 8 hours you would want 520 / 8 = 65 Watts.

Assuming that you get 48 MPG for your 15 minute drive when you start with an empty battery display on the Energy screen, and that you can get 1 mile from a full battery display on the Energy screen before the ICE kicks in, you'll add a bit less than 1 mile for every 15 mile commute to your MPG.

48 / 15 = 3.2

So you might bump your 48 MPG to 51.2 MPG, an improvement of 6.67%

30 miles per day for 5 days per week for 52 weeks per year = 7,800 miles per year.

7,800 miles / 48 MPG = 162.5 gallons per year

7,800 miles / 51.2 MPG = 152.3 gallons per year

A potential savings of 10.2 gallons per year.

 

I am interested in where the 15 hp per mile came from. One horsepower is about 740 watt-hrs. Ignoring efficiency issues, 11 kw-h per mile would give a battery capacity of about 650 feet.

The numbers I have seen are around 250-500 watt-hours per mile.

Pat

 

This has been done. See the white paper.
Solar Electrical Vehicles - Articles

The claims have been debated previously on this site. But you can check out the numbers for yourself and see what you think.