RV Help with concept especially fusing

[-TX-]

A 7-pin trailer connector will already have a 12V line that provides charging while hooked up, no need to purchase and install anything else. The issue is that this is connected to the vehicle's 12V power source via a long skinny wire that doesn't allow a whole lot of current to make it to the battery for meaningful quick charging. If you're driving/towing the camper regularly as part of normal use, then it is a good investment to beef up this charging path. But I think most people interested in solar for RV use are trying to avoid firing up even a generator for battery charging, much less a several hundred horsepower vehicle engine.

I did a limited search for a 12-->24v step up but couldn't find a reasonably priced one that supported higher amps.

As far as firing the truck up to charge bank, it's not a bad option if we confront a week's worth of heavy clouds. Quieter than a generator too.

[Sunking]

I did a limited search for a 12-->24v step up but couldn't find a reasonably priced one that supported higher amps..

Wrong direction. 24 to 12 is easier and less expensive.

[-TX-]

Sure, and I have one, but my truck is 12 and my bank is 24. In order for my alternator to charge my bank I need 12 --> 24v

[Wrybread]

> You need either or both a Generator and/or Alternator to save your butt from solar.

Ha, that's a very surprising thing to read from someone on this forum.

I personally disagree. I'm now outfitting my 5th RV over 20 years with solar, and I lived for 3 years fully off-grid, and solar has always worked great for me, especially for RVs. And as a fellow boondocker, I'm always grateful when people want to minimize noisy generator use. The first thing I do with every new-to-me RV is rip out the generator. In my opinion the only thing you need a generator for is air conditioning, if you use it. Everything else can be made to run off batteries.

Your specs look perfect to me, and are pretty much identical to mine. I currently have half that (a 300 watt 36v panel feeding into four T105 batts) and its just fine, so I expect my upgrade to two 300 watt panels will be that much better.

One thing I've found helps a lot, by the way, is to get an alternative to the blower-based furnaces in most RVs. On mine that thing pulls 80 watts, and is horribly inefficient with propane. I got a Little Buddy heater for my 24 foot Class C, and if you go that route with your 27' you might consider the step up from that (the "Big Buddy"), and plumb it into a bigger propane tank (either your onboard or a 5'er) and you reduce your need for the generator even more. I still use the blower for a quick temp boost in the morning, but other than that its the Buddy whenever I need heat.

Anyway, awesome on the system. Post pics!

[-TX-]

With all due respect:

>I currently have half that (a 300 watt 36v panel feeding into four T105 batts) and its just fine

>I'm now outfitting my 5th RV over 20 years with solar, and I lived for 3 years fully off-grid

How are you pulling off fully off-grid? My setup will be 6 times that and I can't even dream of being fully off-grid all year.

[Wrybread]

> How are you pulling off fully off-grid? My setup will be 6 times that and I can't even dream of being fully off-grid all year.

Sorry that was confusing, the off-grid living situation wasn't in my RV. I'm now setting up my RV, which is technically off-grid, but I'm not in it full-time, so it doesn't count.

And I'm boosting it up to 600 watts not because I need the extra power, but because I'm trying to run my fridge off an inverter part time (as opposed to propane).

[SunEagle]

With all due respect:





How are you pulling off fully off-grid? My setup will be 6 times that and I can't even dream of being fully off-grid all year.

It is amazing how some people have the ability to live off grid using very little in the way of electricity. Different culture and different life styles.

My hat is off to those that can manage a simple and enjoyable life without being tethered to the electronic world that most people that live in the US or are custom to city life are slaved to.

If you can live with little electricity, then I say go for it. If not then I say try to reduce what you use and if you succeed then try to help others find a way to learn how to do the same. Even if they are still connected to the grid because anything saved helps us all.

[ewarnerusa]

Sure, and I have one, but my truck is 12 and my bank is 24. In order for my alternator to charge my bank I need 12 --> 24v

What are you running in your camper that requires 24V?

[-TX-]

Nothing, I need to step down from that 24v. But my system is too large to run at 12v.

[ewarnerusa]

Ok, I'm just asking because it is unusual for a camper to be 24V. If you have no need for 24V, then just wire your batteries in the normal configuration as parallel 12V and you won't need a step down device? There are balancing issues to consider with parallel 12V batteries, but it is also the typical way it is done on a camper.

[-TX-]

You need to talk to SunKing

[ewarnerusa]

No thanks. His views on RV solar are readily available. I see you have a large thread dedicated to your large system install. I didn't look through it though.

[-TX-]

Sorry, the point of 24v in my case is to manage my PV and battery bank outputs. At 12v my controller would have to push 158 amps to charge my battery bank, and then that bank would send the same dangerous current to my inverter. 24v is a compromise, I coulda, shoulda but not woulda went with 48v.

[SunEagle]

Sorry, the point of 24v in my case is to manage my PV and battery bank outputs. At 12v my controller would have to push 158 amps to charge my battery bank, and then that bank would send the same dangerous current to my inverter. 24v is a compromise, I coulda, shoulda but not woulda went with 48v.

It was a smart move to go with a higher battery system voltage.

[ewarnerusa]

Sorry, didn't mean to threadjack or derail by asking about a topic unrelated to the OP. From just the first couple posts of TX's large system install I can see that it is over my head and beyond my knowledge level! My experience level is with basic RV systems and using a small solar array to maintain/charge a small battery bank. 12V, clearly.
As for the OP, I think his system looks like it will do great. And he already has an onboard genny and upgraded charger to make it through the cloudy spells.