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hgoudey
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Posts: 55
Joined: Fri Jul 08, 2011 6:39 pm
Delivery Date: 03 Jul 2011
Leaf Number: 5132
Location: El Cerrito, CA

Re: Solar Solution

Tue Nov 13, 2012 7:44 pm

AndyH wrote:A direct solar setup should be more efficient than a battery-based system anyway. Solar panels with a small MPPT board feeding a ~90% efficient inverter would provide electrons directly to the Leaf's charger. A battery-based system would require panels feeding a charge controller feeding a battery, which feeds an inverter and then the Leaf charger.

Sure, direct DC should be more efficient - but how many solar panels would one have to haul to hit 450-500VDC? Good luck with that on a portable system. ;)
While I wouldn't encourage anyone to run out an try it, it is entirely possible that the onboard charger will accept DC directly from a PV array. The input voltage of the onboard charger is reasonably wide (~100 to 250+?) and the first thing it is going to do is rectify AC to DC anyway, so why bother inverting power from a PV panel? It's not really necessary, but the intrepid among us could even implement a form of MPPT by monitoring the output with a microcontroller and adjusting the J1772 pilot signal for amperage to keep the panels at their optimal power output.

I was eyeing a bunch of Unisolar panels to roll up in the back of the LEAF for a mobile charge station. Turns out for ~4kW (down rate for ~3kW charging?) 28 144W panels would be an array of 18' x 36', weigh 450 lbs, and cost ~$5k. (I didn't even bother to figure out if they could be rolled small enough to fit reasonably). A potentially fragile and tedious, but less expensive and lighter weight approach would be to build a bunch of DIY PV panels from loose cells off ebay on light weight foldable/stackable backing. An array of 4kW would then be closer to $1500 in parts. A crystalline array would total about 400 square feet for 4kW instead of the 650sq ft above for amorphous.

Still, the charging time would be similar to the typical 3.3kW L2 rate, so you probably couldn't do more than one full charge per day (on a good solar day). It might at least be one way to leisurely and autonomously cross Nevada at a rate of 80-100 mi per day. I'm not sure how practical it is for other uses, given the size and setup hassle.

Howdy

Smidge204
Posts: 940
Joined: Wed Nov 24, 2010 1:42 pm

Re: Solar Solution

Wed Nov 14, 2012 2:52 am

AndyH wrote:Sure, direct DC should be more efficient - but how many solar panels would one have to haul to hit 450-500VDC? Good luck with that on a portable system. ;)
I could fit a 500VDC solar array in my shirt pocket. It would put out microamps of current... but at 500VDC. :P

=Smidge=

fooljoe
Posts: 646
Joined: Wed Jun 15, 2011 10:33 am
Delivery Date: 10 Jun 2011
Location: Seal Beach, CA
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Re: Solar Solution

Wed Nov 14, 2012 3:17 am

AndyH wrote:Sure, direct DC should be more efficient - but how many solar panels would one have to haul to hit 450-500VDC? Good luck with that on a portable system. ;)
Hence the DC/DC converter I mentioned before. I'm not saying anything about efficiency. My point is I don't see how it could possibly work any other way.

I guess hgoudey could be right that the onboard charger can accept DC at any amperage, but I haven't heard of anyone who's tried it. All I know is that it can accept AC at a *constant* 120v @ 12 amps or 240v from 12-16 amps, none of which can be effectively provided by a few solar panels. If anyone knows otherwise please chime in. Until someone demonstrates this, I strongly urge against anyone investing in equipment to try to set up some kind of portable charging apparatus.

I do know that others have successfully charged the battery via a direct DC connection, including Ingineer with his propane turbine trailer and Enginer with their add-on battery / DC/DC converter in the trunk range extender. So while I still think it'd be a bit silly to do it, it does seem that it could work this way if someone were really motivated to make it happen.
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