diy solar

diy solar

Charge controller, grid tie inverter all in one.

knowpistons

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Dec 15, 2022
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I have a converted school bus with 6 100ah flooded lead acid batteries charged by an 40a MPPT controller via 6 100w solar panels (more to come hopefully). I also have an AC to DC converter for "shore power", and of course a DC to AC inverter. I would also like to add a grid tie inverter to feed excess power back to the grid, so I could actually benefit from the solar panels when the bus is just parked at the house. Is there a box that does all of this? If there was a solar charge controller that could also feed power back to the grid, it obviously would have an inverter built in, right? This doesn't seem that far fetched but I cannot seem to find anything like this.

Here are my goals
  • When attached to "shore power"
    • Power flows directly to AC appliances, does not need to be converted to DC then back to AC
    • AC power and solar simultaneously charge battery bank
    • If battery bank is full, excess solar gets pumped back to grid
  • When "boondocking"
    • DC power is converted to AC for appliances
    • Solar is used to charge the battery bank
    • Excess power can power a motor that I can make do something cool?
 
Doing any kind of grid tie requires so many hoops to jump through with your utility that I would highly recommend just giving up on that idea. I don't think any kind of mobile setup will conform with the requirements for grid tie.

Other than that your setup is pretty easy to accomplish.

There are units that can back feed to grid from solar directly to the grid but they're not exactly legal from a utility standpoint and the second you generate more than you're consuming your utility may notice that and come calling.
 
Do you have any sort of examples? Even if they don't have a shutdown feature for when the power goes out, I could make that.
 
Ironically, my DC to AC converter broke this weekend, started charging the batteries at 18+ volts, luckily I caught it after only a couple minutes so I don't think any damage was done.

Needless to say, I am in need of another converter so I want to just upgraded the hole system. Any suggestions for what I am looking for?
 
I use a progressive dynamics 1800w inverter, it passes shore power through if it is available. has an automatic transfer switch built in.

Grid tie to sell back power is just about impossible with most utilities unless you have a special meters, and much much more.

Supposedly if you do send power to some meters instead of getting credit for the power, it reads as power used so you might be billed for the power you try to "sell".
 
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