Paseo gets a solar sun roof

[Christ]

You might consider storing the voltage in a capacitor to use for starting the engine, the single largest momentary tax on your battery/charging system.

There are high current long-store, quick discharge capacitors out there, if I can find the stupid links again. You might be able to set up a circuit which allows for the 300 amp draw (most car starters don't require this even momentarily, I don't think) to occur over a 5 second period, more than enough to start a well-tuned engine. (And even some not so well tuned ones.)

[Daox]

That shouldn't be a problem though since the panel charges the deep cycle that starts the car.

[Christ]

Originally Posted by Daox

That shouldn't be a problem though since the panel charges the deep cycle that starts the car.

Just an idea, McGraw. :P (Reference to Quick-Draw McGraw, there... cartoons.)

If that's the case, though, why bother powering anything directly with it, when the deep cycle battery will power everything, and you can trickle the battery from the panel?

[Daox]

Good point, but if I use too much energy from the battery, I loose range. I do have some room to play of course, but not a ton. Its kind of an odd problem. I have excess energy, but not really enough to do anything really useful with.

[Christ]

Originally Posted by Daox

Good point, but if I use too much energy from the battery, I loose range. I do have some room to play of course, but not a ton. Its kind of an odd problem. I have excess energy, but not really enough to do anything really useful with.

Ok, so lets analyze -

You have a solar panel array that can do ~35w at 12VDC, right? (In full sunlight, by the way.)

What is there in a car that only requires >35W to run?

I'm thinking a second 12V battery would be the best way to go, something that could be used to power a fan or some lights in the car, or moved from one location to another in the event that it's needed. The extra weight might be justified by the mobility, and you can use the 12VDC battery to power things in your home as well, like a reading light at night, or a fan, during the summer, to help keep you cool w/o running the A/C.

Would it be enough to run the engine coolant fan all the time? I think you could run more of a grille block if you had the fan running by some input that didn't require engine power.

[Daox]

Yeah, I'm beginning to think the same thing. Darin agrees as he said above. Store the energy to use all at once. Using it as its produce just isn't enough to do anything meaningful with it.

Talking with Darin, we think that a remote block heater might be semi-possible to do. With 4 hrs @ 36W I'd have 144Wh to play with. That would run a 300W block heater for a half hour. Not sure how much that would raise coolant temps, but its a start.

Edit, I forgot Darin actually did block heater testing. What a swell guy!



So, it looks like 30 minutes on the block heater would get me 10°F. Not really a huge savings, but if I did run the additional battery, I could drain it further without worrying about range. As the car sat during the week it could recharge this aux battery fully. Then, I could probably run it for 1 - 1.5 hrs. THAT would be significant!

edit: I see Darin corrected his images. It is a 30F raise. Not bad.

[RobertSmalls]

Since the graph starts at 0:15, the way I read it, half an hour will give you +30°F. Not huge, but it's something.

How many solar panels would it take to make your daily commute alternatorless?

[Daox]

I also looked into that mppt circuit. It basically consists of 3 chips. However, one of those chips costs $45! Thats 3/4 what I paid for the solar cells unfortunately. So, I'm planning on going with this conventional and cheap DIY dump controller.

[Daox]

Lets see... I use roughly 25Ah to get to work and back. So, I use 12.5 on the way to work and that gets recharged by the time I leave with the 36W panel. Really, by the time I get home there isn't much sun left. But, I could easily make it back to work with that level of charge. So, I'd imagine that 8.5 hrs at work the next day would give me 25.5Ah effectively recharging my battery completely.

Of course, this assumes its never cloudy and always is light the entire time I am at work which is not the case in winter. There is also snow to contend with and headlight use which is a major battery drain. So, in winter I'll be in trouble, but summer I think I'll be in good condition. Perhaps a panel that put out 2x as much would suffice for winter, but I really can't say that for sure.


These are all really rough guesses though. I'm not even sure that my 36W panel will actually put out 36W.

[Daox]

I should add, I rarely use the car two days in a row. Normally, I use it once a week. That is why I'm putting the effort into thinking about capturing the excess energy generated.