I picked up 20 used solar panels about six months back, and now seem to have some time on my hands. I’ve played with single panels in the past, and have a basic understanding of electrickery.
I’ve got room on the roof of the bus sitting in my driveway to fit 12, 18, or possibly all 20 panels. I could also throw them on the roof of my shop. both spots have the same orientation, and are facing ~35degrees east of ideal.
I’m assuming 2-D tracking is too complicated to try and implement (without purchasing it solved), and it seems much easier to change the tilt on a rack on top the bus twice a year than figure out a tilting mount for the shop that doesn’t cause leaks (the bus came with a 30ft rack on the roof ).
I don’t have a solid grasp of all the pros/cons of “grid tied” vs not. given that I’ve got to throw money at the problem to get a controller and an inverter, this is probably the first place I need guidance. part of that is going to be picking an array voltage. I’m leaning towards 48V, but that’s probably because I think I’ve got a 2kW 48V UPS buried in the shop somewhere…
I have two electric vehicles with 400V 24kw lithium battery packs. which seems relevant, but I’m not quite certain how.
I need to double check nominal panel ratings.
EDIT: 165W 36V panels. derated for age, I’m guesstimating 150W each. so 3kW array, not 4kW.
The most important lesson I’ve learned over the last 5 years with an offgrid farm, is to invest in the proper batteries up front.
6v golfcart batteries are designed to get drained fully without being damaged, and are cheaper and more widely available (less/no shipping cost)
Also, run as high voltage as possible to minimize cable costs. Plan up front for that because your charge controller and inverter will be based on that voltage as well
to me it looks like 48V lithium might be the right response at this time.
having 48kW of lithium on wheels seems like an important piece of the puzzle, but I haven’t found off the shelf solutions for accessing that.
I’d take lead if it was free, but if I’m paying for it, I’d rather scavenge Li at this point.
what I think I’d like to build would be grid tied, with the cars as the battery bank when the grid was down… but ripping apart a 400V car battery and rebuilding it at 48V seems like a viable alternative for a non-tied system.
a nominal 400V array straight to the car has crossed my mind. but I’d need another 20 panels.
edit: 36V panels not 12V!
so theoretically I could get stupid and try charging a 400V battery with DC…although wrapping my head around the comm the battery wants when doing this is a whole different can of worms.
It doesn’t take many photons for the panels to generate a voltage, probably safest to do this indoors with artificial light instead of using sunlight, for safety’s sake.
Lithium batteries are expensive, and you have to manage them properly. They aren’t like the deep discharge batteries most solar systems use. The charge controller needs more brains.
Price is key; wrecked leaf batteries can be had by purchasing totaled nissan leafs; if you do it right you could probably get the battery for free and sell the chopped used car parts to pay for everything.
Here’s a source of crunched nissan leafs (don’t buy cars with water or fire damage, and don’t get screwed by fake auctions and add on fees)
How big are these suckers? Do they have a model #?
What application is this for? This will determine battery, controller and inverter needs. Your power company might even give you your hour by hour usage.
Does your municipality buy back power?
It’s the amps that do the work(kill you), but it’s the volts that hurt and the higher the voltage the less amperage needed to do the work. 99% of the time the path the current takes is the most important part. Without enough voltage the amperage doesn’t matter because there isn’t enough voltage to push the current through the resistor (you).
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