Cargo trailer solar build

[eXodus]

I'm not too worried about water just sitting. The top is metal and water will evaporate as there's air plus the heat and such from the panels

I am a little. The Unistruts are galvanized, which is fine when I can dry - but when sitting submerged for an extend time it gets galvanic corrosion.
Further a pool of water on the roof - will eventually grow some algae and collect dirt out of the air.

 

[littleharbor2]

The trailer inverter is just for things like drill battery chargers or maybe jump packs or something that doesn't really matter.

I ruined all my Makita tool batteries charging with a MSW inverter. Replacing them cost more than a decent PSW inverter would have.

 

[justinm001]

I ruined all my Makita tool batteries charging with a MSW inverter. Replacing them cost more than a decent PSW inverter would have.

Thanks. Didn't think it would matter but guess you're right. Dull sinewave only then... Unless I can find a huge DC charger for them all

 

[justinm001]

I am a little. The Unistruts are galvanized, which is fine when I can dry - but when sitting submerged for an extend time it gets galvanic corrosion.
Further a pool of water on the roof - will eventually grow some algae and collect dirt out of the air.

Yeah but they should last a few years at least and they're easy to replace if they get bad. Just inspect annually.

You could plastidip spray them too. I'm surprised that stuff isn't used a ton more for things like this.

 

[0truck0]

The video above.... It is the AMPS not the voltage that kills. The video leaves out the amps! ...A little deceiving in that regard. 12v or 24v is NOT 220 volts either.

I would not worry too much about galvanic corrosion. When it rust through then just replace it. I would worry about anyone with a thin painted aluminum RV roof who has sitting water as the corrosion will eat through that thin garbage quickly.

Side note: I have a 7 pin trailer plug that is always connected to the camper battery. Though the pins in the plug do not touch, they are close. I call it - electrical potential. It will not arc like the 220 volts in the video, but something electrically happens still. When I disconnect the battery so that the plug is not connected to 12 volts when stored (often humid days) then I DO NOT get terminal corrosion as fast nor as often, if ever. The 12+ and the 12- are in the same plug and are very close and the 12+ will be first to corrode when voltage is present. The other pins are in a way still grounded in that the light bulbs are grounded on the negative side and through the filament they are connected to the positive side which is what is at the pin. Im not an expert, but that might be why they corrode. Same issues can apply to other areas where voltage is around, like your solar panel frame....

Disconnect your battery from the trailer plug when in storage!!! For whatever reason, this causes the pins to NOT corrode.

 

[12VoltInstalls]

I ruined all my Makita tool batteries charging with a MSW inverter. Replacing them cost more than a decent PSW inverter would have.

That’s interesting since the transformer and circuits in the chargers sorta isolate the batteries from the AC wonkies.
It’s usually the chargers that I’ve seen die from MSW on job sites.

 

[12VoltInstalls]

It is the AMPS not the voltage that kills

I debate that.

but something electrically happens

I had a poor-man’s terminal lug in a boat ~1995-ish. Basically I bolted a bunch of 12V+ wires and the battery feed together through a piece of plywood under the bow. There was also a neg(-) terminal done the same way.
The rack and pinion helm had an issue so I was under there working on it and noticed the plywood looking wet. I touched it- it was dry, but there still appeared to be water/water stains. I didn’t understand- couldn’t see how it could get wet.

Got looking at it with a flashlight to see how and what was going on and realized that the tinning from the ring terminals had migrated along leaving hairline silver traces following the wood grain over the several years since I’d done the wiring.

That was eye opening. Electricity never sleeps.

 

[littleharbor2]

I ruined all my Makita tool batteries charging with a MSW inverter. Replacing them cost more than a decent PSW inverter would have.

This was older technology, if that makes any difference. All I know is all my batteries lost 98% of their capacity.

 

[eXodus]

I would not worry too much about galvanic corrosion. When it rust through then just replace it. I would worry about anyone with a thin painted aluminum RV roof who has sitting water as the corrosion will eat through that thin garbage quickly.

yes, my cargo trailer roof is a thin not painted aluminum.

Putting a galvanized strut on it and letting it sit in water for extended times seems like a good receipt for creating corrosion issues. - I decided to space my rails of the roof - just a quarter inch. Found some square nuts which are going to elevate the Unistruts.

 

[HarryN]

I have used 8020 extruded aluminum on vehicles to mount solar panels.

Not exactly cheap, but the parts are all aluminum including brackets.

 

[eXodus]

I have used 8020 extruded aluminum on vehicles to mount solar panels.

Not exactly cheap, but the parts are all aluminum including brackets.

On the top of my trailer I would need 2x 14ft long pieces (or 3x 10ft) . So those are getting expensive in 8020

https://www.grainger.com/category/electrical/conduit-fittings-strut-channel-framing/strut-channel-components/strut-channel?searchQuery=strut+channel+aluminum&sst=4&cpnuser=undefined&searchBar=true&suggestConfigId=6

But I may have found something better.

Aluminum strut channel. It is slightly more expensive $41 vs $31 per 10ft stick - but should eliminate the corrosion issue altogether.

 

[0truck0]

As far as a modified sine wave inverter, I would just say NO! The pure sine wave inverters are so cheap now that it is not so painful to throw out the MSW and replace with Pure sine wave.
I would never even own a MSW nowdays given the potential for device damage.

Some transformers will be fine, some can get hurt. Transformer being the "brick", or big thing you plug into the wall to charge your phone or other item, or to power an electronic item. keep in mind that most electronics actually run off of DC power, not AC power, they have built in AC to DC transformers.
Light bulbs, motors, fans, heaters, vacuum cleaner (basically a fan) are all AC, but
TVs, radios, phones, computers, music amps, most all electronics that use chips... all run off of DC power (provided by an AC to DC transformer).

Also fwiw, even the cheapest of cheap PSW inverters give a very clean, very neat sine wave. I checked with an oscilloscope. It is better than your house, way more clean therefore safer.

 

[Vigo]

Ideally I'd be able to easily switch 5 panels from series to parallel then use a cheap 12V PWM controller for the trailer which I already have and then I could switch from using 1500w to the RV and 500w to the trailer or all 2000w to the RV. Even better if it was a digital relay then I could have something digitally send a signal so when the trailer battery is under 80% it'll take the solar but when its above it'll send to the RV. Any thoughts?

So in general im not for spending 'nearly the same money as an mppt' on a PWM controller but i DID buy one of these a while back ( i got it for like ~$53) and it would do what you were suggesting. You could set your load port on/off voltages to correlate to the trailer battery's SOC curve and then feed that to the tow vehicle. Not every PWM controller can handle the same amps on its load ports as its battery ports but im 99% sure this one can because i opened it up and it has the same size fets in every position, plus the wire resistance is probably going to limit it to WAAY under 80 amps anyway. It's the beefiest PWM controller ive seen as far as the size of the fets and the wire terminals, and has an adjustable current limit that actually works.. it's honestly a cadillac of PWMs. Now that cheap MPPTs are down into the same price range it has little reason for existing but.. it would do what you mentioned.