Solar panels to starter batteries

[Rucker]

Originally Posted by rossvtaylor

It's too late to add an edit, with addition information in my previous post. But I looked up that Grape Solar charge controller, as I'm not familiar with it. The load/output terminals are rated for 20A. It appears that he used that to power a 2000W inverter. 2000W/12V=166.6666666666666666666666666666666 amperes. Despite my extreme depth of precision here, I'm not that good with math. But I think that's bigger than 20A.

Agreed on all points, crankypants :-')

To your point, while it's physically possible to connect a 5,000 watt inverter to load terminals rated for 20 amps, even with a steady 20 amps of solar any actual inverter load over about fifteen amps will make the inverter beep, or worse.

I haven't watched the video. Sounds like they were shooting for sound advice on charging options, with some pretty shaky execution.

[Rock-N-Ruth]

Originally Posted by rossvtaylor

Please, don't follow that plan. I just started watching and gave up at the 5 minute mark when he bragged about using 8 gauge wire out of the charge controller. He said the incoming wires from the solar array are 10 gauge so he could use 10 gauge on the output, but he wanted to be safe (and didn't have enough #10) so he used 8 AWG. He clearly doesn't realize that the voltage on the input is anywhere from 35-120 volts but it's 12V on the output. #10 would not have worked, so I'm glad he didn't have any more. #8 would be fine, with a 3% voltage drop, for a 6-foot run...but he'd need larger cable for anything longer.

I started to doubt him when I saw that he laid the flooring first and screwed things down to it. He, or the buyer, is going to be mighty sad when that buckles or gaps...

Okay, I had to watch more.

When he describes using #4 wire to run back from the DC>DC charger, I'm guessing that's about 20 feet and he'd need a #2 for that with a 3% loss.

And...I watched the rest...

Perhaps I was a bit harsh at first, but seeing folks demonstrate wiring when they don't show a clear understanding of the design considerations bugs me.

I do like (and am a promoter of) the simple "charger as shore power" design. And he makes good points, with which I agree, about using 12VDC as much as possible and turning off the inverter when not needed.

But he does or says lots of things I disagree with. First, the execution of his system...I see no disconnects. And, true, a fridge only runs for a fraction of the day...but certainly not 2 minutes a day. And why are the USB charger plugs in the AC power strips, which require keeping the inverter on just to charge a phone? Put those on the 12VDC circuit.

And, finally. It sure looks like he describes connecting the inverter to the load terminals on the charge controller. I believe that is what he advocated and it looks like that's what he did. This is not recommended. Here's one manufacturer's comments on the charge controller load terminals:

Some loads should not be connected to the controller’s load terminals and instead connected directly to the battery. Highly inductive loads with high inrush currents may damage the controller’s load terminals. DC motors and inverters are examples.

And here's another:

...you might consider connecting an inverter to the charge controller’s terminals. But is that right? This is it, you should never connect an inverter directly to a charge controller.

It might be acceptable with a small inverter draw, compared to the charge controller capacity...I see 50% bandied about...but, personally, I don't do that.

EDIT to add: I just re-read my post. Man, I'm getting cranky in my old age. But I'm seeing so much bad electrical advice and work that it just irks me.

You may be cranky, but you aren't wrong. When it comes to electrical in a bus, efficiency is important but safety is even more important. Undersized wires are inefficient, but can also be dangerous. No disconnects multiplies the danger.

[mmoore6856]

--yes rossvtaylor makes some excelent points. people that take shortcuts with eletricity is why we can not get insurance. some of what i seen online scares me to the point i wont park within 100 feet of another schoolie

[Booyah45828]

That, and wood stoves installed in a wood enclosure, with the firewood/kindling packed around it, without a proper flue or chimney. And roof decks attached with drywall screws through the sheet metal and no rails. And just the general poor mechanical condition used school buses can be frequently found in.

I'm honestly happy that there are companies out there that would take the risk. Insuring a group of skoolies would be like insuring the space program. Something is bound to fail, and do so expensively.

*I'm not a fan of insurance or an advocate by any means. Don't take the prior comment as such. Insurance is a necessary evil to protect from loss and litigation.

[Rucker]

I did watch the video to the end.

It's a nice video for inspiration. At best. IMHO.

Shorty22, apologies for crankilatin' on, I hope you're not driven away by the dumping!

[rossvtaylor]

Originally Posted by Rucker

Shorty22, apologies for crankilatin' on, I hope you're not driven away by the dumping!

I think Shorty took all this in the spirit we meant it. I reached out via DM to offer some phone help and we might be talking today. If we helped someone avoid following bad guidance, we've all done our good deed for the day. So, karma points to everyone here!