[Sunking]

Originally Posted by Jan

Add a 12V battery to your system, if you not already have. Charge this one with solar. And if you want to charge the main pack: add an 12V-220V inverter, and connect it to your onboard charger. With some simple electronics you could start the inverter if the 12V voltage raises eg 13V. And stop it when it reaches 10 or so. Sometimes they allready have such a battery protection system built in. So with a z-diode and a relais you could start it. It's like a bucket you fill up under a dripping tap, and pour into a big tub.

Jan I think I follow you but not to sure that would work very good.

First problem I see is the built in charger. I assume it is some type of constant current or constant power supply assuming the batteries need a charge. So for example it needs a solid 3 Kw source. Wel that means you need about a 4 to 6 Kw inverter which would be very expensive if you could even find one. But just how long do you think a 12 volt accessory battery could supply a constant 3 Kw load. Most likely outcome is the inverter tripping off-line immediately from under voltage supply. Not to mention all the losses along the way. I just do not see that as being practical or workable.

[green caveman]

Originally Posted by meanderingthemaze

Cool, although he must get a lot of drag in that setup. I'll probably be able to fit half of that, just to cover the backend, but hopefully I'll be able to find higher-density cells so I can get close to what he is getting, but over less area...
Thanks for sharing

If you're only going to use it while parked, you could improve efficiencies significantly by angling the panels. Gary Reysa's BuildItSolar has some great resources. Information on angles is here (and in some of the links from there too). Of course, that adds a level of complexity, since you'd either always have to find parking spaces oriented N->S or have some way to tilt the panels based on the parking space orientation.

[Jan]

Originally Posted by Sunking

Jan I think I follow you but not to sure that would work very good.

First problem I see is the built in charger. I assume it is some type of constant current or constant power supply assuming the batteries need a charge. So for example it needs a solid 3 Kw source. Wel that means you need about a 4 to 6 Kw inverter which would be very expensive if you could even find one. But just how long do you think a 12 volt accessory battery could supply a constant 3 Kw load. Most likely outcome is the inverter tripping off-line immediately from under voltage supply. Not to mention all the losses along the way. I just do not see that as being practical or workable.

Yes, I wouldn't take a inverter of more than 1 kW. Something between 600 and 800 watts would be enough. Not all chargers need 3kW. A manzanita (?) can be adjusted to a lot lower amperage. And a Brusa can be controlled with a pot meter.

[green caveman]

Originally Posted by meanderingthemaze

This is where I need help. I don't know what the available or necessary electronics would be to execute a custom panel for my pack.

If I'm doing 108V (18 x 6V), then the appropriate voltage should be about...
18 * 9V = 162V [I'm getting 9V from the 12V example given earlier ie: 6V:9V as 12V:18V, right or wrong?]

If so, and solar cells are rated at .5V each, then that would require...
162V/.5V = 324 cells

Otherwise, I'd have to step up the voltage, which would require other electronics. Does anyone know if the parts required to do the job would be specialty or off-the-shelf radio shack stuff?

What's the downside to splitting the pack? It's usually much easier to find electronics rated for, say 40V than for 160V. Or even charge each battery individually?. Someone suggested that this might not be a good idea, but assuming that the panels are match and have equal solar intensity on them is there really a problem.

I'm starting to like this idea in general, although I don't think I'm willing to take this on as a project just yet - at least until the car is finished! It occurs to me that most of the time the car will do, say, 6 miles per day. With some (easy) scheme to pull out the panels whenever it's parked it might not be too difficult to cover most of this from panels.

Unlike adding them to a house, you don't need the permits/grid tie/inverters, etc. which significantly lowers the cost of installation.

[meanderingthemaze]

Jan,

Thanks for the ideas. I'm not sure I completely understand, mostly because I've never done a conversion, so I don't have a lot of hands on with these components. But I'll read it a few more times.


green caveman,

I'm trying to think of a practical way to tilt but also have it be secured while stationary (to carry load), and also have some semblance of an anti-theft feature. I'm thinking of a telescoping ball joint...I don't know. If I want the right angle, I'll need control in all axes. Thanks for the links.


I'm going to call around to some solar companies and see what they say.

[Sunking]

Originally Posted by Jan

Yes, I wouldn't take a inverter of more than 1 kW. Something between 600 and 800 watts would be enough. Not all chargers need 3kW. A manzanita (?) can be adjusted to a lot lower amperage. And a Brusa can be controlled with a pot meter.

Ok 3 Kw was more of a guess on my part because there would be no reason to have 240 VAC charger for such a light load of 800 watts. I mean my little 48 volt golf cart charger uses more than that on 120 vac. If you have say a 16 Kwh battery pack and want it charged from 100% DOD in 8 hours you are going to need 2000 to 3000 watt input, and that can only come from a 240 VAC 30-amp circuit.

[Jan]

Originally Posted by Sunking

If you have say a 16 Kwh battery pack and want it charged from 100% DOD in 8 hours you are going to need 2000 to 3000 watt input, and that can only come from a 240 VAC 30-amp circuit.

I though we allready agreed that charging completely from onboard solar is impossible. So, to make some use of onboard solar with just radio shack stuff, this could be an option. You don't need a DCDC converter for your 12V circuit anymore. What helps a little. And in excess of solar energy this mechanisme charges the main pack too. Not full in 8 hours. But a few extra miles a day. And maybe full in a sunny week for a short weekend trip.

[rmay635703]

http://ecomodder.com/forum/attachmen...8&d=1202049916
http://ecomodder.com/forum/showthrea...cap-583-4.html

I had a nice point by point long post worked up but then I got a blasted spyware attack and crashed, everythings reinstalled now, bleh.

Anyway I would strongly consider making a lightweight aero flatbed/belly pan with wheel covers, Then repeat what bondo did above making a tiltable angled cover, I would keep the line of the cover just below the rear window. Since this would be a true boattail you could easily gain 20% more range just from the aero improvement, likely closer to 50% depending on your speed.

I would also attach the panels securely to that cover so although possible to remove eventually it would be big boxy, bulky and downright heavy making it almost impossible to steal.

Having a lightweight bed and cover on the back would allow the batteries to have a nice place to be put out of the weather and accessible. Also they would give you a bit more traction.

As for having separate MPPT systems to charge that is PERFECTLY fine so long as they are equally sized. You will have to do more maintenance on the batteries to keep equalized but you should do that anyway. Also remember panels run separately usually put out more power in total then when run in series but they also put it out unevenly.

Next don't bother building panels from solar cells, If I could still find the individual cells for $0.50 a watt I personally would build a custom panel but remember homebuilt have some major issues
1. Cost of ownership, solar cells die rapidly exposed to any form of moisture and the RTV like compounds to seal correctly are very expensive.
2. Complexity, there are literally thousands of solder joints to make in your project, meaning thousands of chances to get a cold one lighting fire
3. Lifespan as I mentioned most homemade panels, even those done correctly are indoor only and die within about 5 years outside.

So just find panels that will both fit within the area you have and also meet the voltage requirements needed when added together.

Solar panels have two voltages, one is the lower rated voltage that provides maximum amperage output the higher voltage listed is the open circuit voltage.
Generally the minimum voltage panel you need must have ideal amperage output at around your floating voltage, however if you don't want the panels to overcharge you can build an unregulated array that only goes up to the max voltage you want the batteries to see but then they are much less efficient.

I had a much better writeup earlier, ah well.

Cheers
Ryan

[meanderingthemaze]

Ryan,

What a drag about the computer. I just had to a wipe a computer the other day. Might I suggest you take a disk image of your newly configured system, just in case it happens again. You can revert back to a clean install in minutes. Don't mean to distract from the forum, but any time you're spending fixing computers is time you're not spending on EVs.

I was definitely planning some aero-mods...
http://ecomodder.com/forum/showthrea...ept-12206.html

However, I think the custom bed shell would violate principal #1 of building an EV, namely, that you must like the vehicle you will be driving, otherwise you won't want to drive it.

But the belly pan, and possibly some ducting to route the cooling air through the motor compartment is definitely a must.

I wonder if you would have the same opinion about custom solar panels if a solar company built it for me? I would totally agree that it is a manufacturing process that could lead to more headaches than help, and for a beginner probably will. But, I would prefer to have it fit the bed properly. I'm staying open to whatever option makes the most sense.

Too bad we missed your 'better' first post, but thanks anyway for reposting.

[rmay635703]

Well to build your own best to use tempered glass and slyguard, thats how they did them in the 70's and many of those panels are still operating.

Avoid any wood products. Plexi and plastics can work but don't pass light as well and also have issues with aging in the sun, unless of coarse special measures are taken.

and check out
http://solarpaneltalk.com/

They have several threads outlining what people have done, what they have used and how long they have lasted. Generally you need to get the cells encapsulated on both sides fully with slyguard after everything is tabbed, soldered and load tested. I believe you can also buy laminated cells which are more resistant to weather out of the box but they come at a premium costing almost as much sometimes more than the various panels on the market.

Also If you go around asking about DIY solar panels be prepared for backlash, many of the solar sites are hostile to that and I haven't even been able to coax any lower cost bulk sources of plain cells out of anyone. I find it very strange that cells cost more now than 5 years ago when I priced them out. Must be a lot of vested interests holding out on me.

Next step is to start bothering manufacturers. Needless to say with panels costing between $1.50-$3 a watt from many sources cells have to be in the $0.50-$1.00 a watt area for the panel to be priced that low.

Interesting reading here
http://www.builditsolar.com/Projects/PV/pv.htm (though not entirely on topic)