So Power Switching...

[Third From Texas]

I'm starting to gather the bits I need for plumbing and electrical.

I'll have 1) shore power 120v, 2) generator pushing 120v to the hab (the gen also has 240v for my welder should the need arrise), and 3) battery/solar.

I have my mind wrapped around the concept of an automatic switch, but I need to find something 3-way I suspect (or possibly double up on switches). How are you guys addressing this?

*Example of a two-way:

Amazon.com: 110V 2P 63A Dual Power Automatic Transfer Switch Dual Power Generator Changeover Switch 50HZ/60HZ with Electronic Instruction Manual: Industrial & Scientific

Buy 110V 2P 63A Dual Power Automatic Transfer Switch Dual Power Generator Changeover Switch 50HZ/60HZ with Electronic Instruction Manual: Transfer Switches - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[TechnoWeenie]

Your 120V generator and 120V shore power should be the same circuits.

You'll have a switch that cuts from shore power to genset when either the gen or shore power is connected.

Don't make things too complicated...

Your 120V side should have a battery charger that charges the 12V side when it's hooked up.

Getting 'all in one' devices is generally not a good thing, because when they fail, they take EVERYTHING with it. You're better off keeping it simple.

Just about everything should be 12V if possible, so your shore power is only powering things that have to be 120V, like an air conditioner... There's a pretty big efficiency loss in using inverters. Laptop? DC->DC converter, don't use the AC brick that comes with it. Lights? 12V. Charging phones? Ditto, DC-DC converter.

With things like laptops and cellphones, they charge on DC voltage...

So, what you're doing is... 12VDC -> 120VAC ->5VDC (~19VDC laptop)..

Instead of 12VDC ->5VDC

Each step you add, adds losses.

You can lose up to 20% in each change, so by going DC/AC/DC you can increase your power usage by as much as 40%, vs the DC->DC conversion usually has power losses in the 2-5% range...

 

[TechnoWeenie]

Hopefully this clears things up.

 

[TechnoWeenie]

Or, if you are running an inverter, and want REALLY simple...

Amazon.com

 

[Third From Texas]

Or, if you are running an inverter, and want REALLY simple...

Yeah, this is what I was originally going with. Just a simple 3-way manual switch.

But then I got to thinking an automatic switch would be nice to incorporate. I figured it would either require a 2-way manual combined with a 2-way auto in some fashion. I've no idea if there is such a thing as a "3-way auto switch" but I could swear my old Winnie Brave was pretty much fire-and-forget once I was plugged in. If the batteries died, the gen would kick in before the lights went out. If shore power failed, the gen would start (to keep the AC running), etc.

What was throwing me for a mental loop was likely remembering wrong. I wasn't clear on what happened when the gen kicks in while the batteries were on and you were plugged into shore power. I envision much of the magic smoke escaping. LOL

I don't want to reinvent the wheel on something this common to the RV world.

I guess shore power and gen would never be online to the hab at the same time, so something like this perhaps :

 

[Third From Texas]

*the reason I think this is viable is that I rarely will be anywhere camping that has shore power

 

[TechnoWeenie]

*the reason I think this is viable is that I rarely will be anywhere camping that has shore power

You're adding more points of failure.

More switches = more to go wrong.

Also, you need isolate shore power and gen so you're not backfeeding the shore plug...unless you intend to do that...

A simple 4 position (Inverter, generator, shore power, off) would make the most sense, IMO. Those switches are rated for hundreds of thousands of cycles, generally speaking.

You'd essentially have 3 switches.. an A/B switch, an automatic switch, and an override switch.. Why would you do that when a simple, single, 4 position switch will do what you want, it's more reliable, significantly less expensive, and you can't screw it up . Not to mention, it gives you an OFF position so if you're working on things, you know for damn sure there's no juice past that switch.

As far as an automatic generator... That's a different ballgame altogether. Those are usually dual mode 12VDC/120VAC generators with a voltage sense circuit. When the DC voltage gets below a preset point (usually ~50% SOC (state of charge)), the generator uses its built in batter to turn on, switch over to the generator's 120VAC, thus removing the 12V load (110V inverter) and allowing the generator to recharge the house batteries quicker.

That's an entirely different ballgame.

With enough solar, you CAN run A/C..The mini splits are super efficient and can draw as little as 300W....with most running about 550ish watts.


I would ask... What are your 110V loads gonna be?

 

[Third From Texas]

Rgr all.

I have a little battery and tray for my genset (it's actually a BAPU battery charger with a 6KW gen head installed...overkill I know, but I can power my house with it from the truck). It's hooked up to the truck batteries (being 24v).

Long ago I had settled on 24V in the hab but I cannot for the life of me recall the reasoning (I think it was efficiency). But that does limit what it runs w/o introducing a 12v step down (another thing to break). But my LEDs can run either. The fridge I was recently given is a brand new Dometic 12v/120v/butane (I won't be carrying gas though) so that shifts things towards 12 as well.

I really need to commit to either 12v or 24v so I can get my inverter.

Really the only 120v is the ac and the microwave. The little LED TV in there currently is 120v and I may just leave it in there as I'm please with it's low draw. Everything else can pull off 12v...

 

[TechnoWeenie]

Rgr all.

I have a little battery and tray for my genset (it's actually a BAPU battery charger with a 6KW gen head installed...overkill I know, but I can power my house with it from the truck). It's hooked up to the truck batteries (being 24v).

Long ago I had settled on 24V in the hab but I cannot for the life of me recall the reasoning (I think it was efficiency). But that does limit what it runs w/o introducing a 12v step down (another thing to break). But my LEDs can run either. The fridge I was recently given is a brand new Dometic 12v/120v/butane (I won't be carrying gas though) so that shifts things towards 12 as well.

I really need to commit to either 12v or 24v so I can get my inverter.

Really the only 120v is the ac and the microwave. The little LED TV in there currently is 120v and I may just leave it in there as I'm please with it's low draw. Everything else can pull off 12v...

No doubt 24V was to be able to charge from the vehicle's alternator, or to jump the vehicle using the house batteries as a spare set, essentially.

A good solar system makes that not needed, HOWEVER.........you have options

Option 1 is to put a small solar panel dedicated for the starter batteries to keep them topped off.
Option 2, use a 24V bank, run 2 separate 12V circuits, making sure none of the 12V devices connected are connected to chassis ground unless they're on the first, grounded battery, and run a battery equalizer.
Option 3, use a 24V bank,with 12V step down for the things you need, as mentioned.

If it was me, I would want to charge, and use the 2nd battery bank as an emergency jumper as well. Thus, I would have a battery selector, runs about $35, that allows Bank 1, Bank 2, BOTH, or NONE to be connected. I ran that in my M934. Thus you can start/keep it on Bank 1, but if you need to charge quick, you switch to BOTH, and it'll charge both. Bank 1 dead? Switch to Bank 2 and start it up, then switch back to both.

As I mentioned, the DC->DC process is fairly efficient, so running a 12V downconverter from 24v will use much less power than a 120V inverter.

I would buy a 12V LED TV. I did, actually, lol.. but at the time, the biggest you could get was 19".... Now you can get 36"+ that run on 12V.. and again, more efficient, because the TV is running on DC voltage anyway, so you're still doing the DC->AC->DC conversion, and all the losses associated with it, by running a 120V TV.


I would also make sure my inverter has a remote switch, then put the switch next to the microwave... Then keep the inverter off at all times, unless you need it.. Wanna microwave some popcorn? Turn the inverter on, use the microwave, turn the inverter off. Devices use juice even when 'off', parasitic drain, and the inverter also uses power even if nothing is connected.

 

[Third From Texas]

Appreciate all the input !

 

[Third From Texas]

No doubt 24V was to be able to charge from the vehicle's alternator, or to jump the vehicle using the house batteries as a spare set, essentially.

A good solar system makes that not needed, HOWEVER.........you have options

No, there was something about 24v solar and batteries being more efficient than a 12v system. I think I had been looking into 12/24/48 and settled on 24v. I'll have to see if I saved any links.

 

[chucky]

Appreciate all the input !

My truck always struggled on the batteries being hot enough to fire the truck up until i hooked the solar panels up . I put 3 315 watt solar panels on the roof to the gray epever in my build pics to 2 8d agm house batteries all wired in 12 volt (there are many ways and voltage options i just went with what i understood KISS keep it simple stupid but from the house batteries i ran a 2/0 hot and ground down to the 12 v side of the truck batteries and that keeps everything topped off all the time the solar controller will keep them from over charging i put a heavy disconect between the 2 sets of batteries to isolate if needed and i leave them on all the time and again there are many differant ways to switch from one power source to another ive had problems in the past with automatic switchers hanging in one or the other spot or the contacts welding themselves togeather . Ship shore switches are normally drama free at least my experiences with them but i wanted the most easy for anyone to understand electrical switching i put my hole house panel on to a 60 amp 4 prong range plug male then put 3 double gang boxes stacked with 2 of them being the female 60 amp 4 prong receptical one labeled shore power the other labeled generator so you have to unplug the house to go from one to another so they would never have the chance to take the other one out in a short or wire receptical you plug the shore chord into that you didnt wire ! This is why you have a shore power cable so at least when the truck is at home you can run off house current and not have to use your other equipment and if you lose power to your house for whatever reason go in the house flip your main breaker off then plug your truck up and back feed your panel to at least keep your fridges and freezers working lights what have ya . oh and the 3rd receptical box is for the inverter but i put it on a 3 prong 50 amp plug to feed the panel the rule being never but one tail pluged into a receptical at one time ever and at the end of the day it makes trouble shooting any electrical problem quick and easy to find so at the end of the day you have 1 solar power to run on and keep all batteries hot 2 you have a generator to do the same things 3 you have shore power and 4 you have the truck to crank up refill all the batteries to run inverter so if at worst case senario youve lost any 3 of the 4 ways to make power for truck or habitat this all sounds confuseing but as soon as i get more pictures of the electrical posted you can see it then you will get it.

 

[TechnoWeenie]

No, there was something about 24v solar and batteries being more efficient than a 12v system. I think I had been looking into 12/24/48 and settled on 24v. I'll have to see if I saved any links.

When putting up panels, you can run 96V of panels in series if you have a charge controller that can handle it. The advantage is, smaller gauge wires.

No real advantage going from 12V to 24V or 48V unless you're dealing with MASSIVE battery systems in multi-KW range with high draw, then the advantage is smaller gauge wire.

Which requires more power..?

1. A 12V winch drawing 100A
2. A microwave that draws 10A on 120V from an inverter (discounting any losses from conversion/additional power from inverter)
3. A 24V winch drawing 50A

Which uses 14ga wire and which one uses 2ga, or 4ga?

Spoiler: Answer

They're all 1200W, but the higher voltage and lower amperage of the microwave means you can use smaller gauge wire to do the same amount of 'work', ditto with the 24V winch using smaller wires than the 12V winch

Parallel adds amperage, series adds voltage.

5 - 100W solar panels... Normally around 5.5A output...18V.

So, if you string 5 together in parallel, it's 18V, 27.5A... So you'll need a wire that can carry 30A.
If you string 5 together in series, it's 90V @ 5.5A.. So you'll only need wire that carries 5.5A...

BOTH are 500W setups.

You absolutely can get a solar charge controller that accepts 100V in @5.5A and outputs 13.8V @ 36A....or 27.6V @ 18A.

BTW, GC2s are cheap, $100 at costco, and while 6v, are around 220AH, and designed for deep discharge. 2 in series gets you 12V, 220AH... fo $200....

 

[Third From Texas]

When putting up panels, you can run 96V of panels in series if you have a charge controller that can handle it. The advantage is, smaller gauge wires.

No real advantage going from 12V to 24V or 48V unless you're dealing with MASSIVE battery systems in multi-KW range with high draw, then the advantage is smaller gauge wire.

Which requires more power..?

1. A 12V winch drawing 100A
2. A microwave that draws 10A on 120V from an inverter (discounting any losses from conversion/additional power from inverter)
3. A 24V winch drawing 50A

Which uses 14ga wire and which one uses 2ga, or 4ga?

Spoiler: Answer

They're all 1200W, but the higher voltage and lower amperage of the microwave means you can use smaller gauge wire to do the same amount of 'work', ditto with the 24V winch using smaller wires than the 12V winch

Parallel adds amperage, series adds voltage.

5 - 100W solar panels... Normally around 5.5A output...18V.

So, if you string 5 together in parallel, it's 18V, 27.5A... So you'll need a wire that can carry 30A.
If you string 5 together in series, it's 90V @ 5.5A.. So you'll only need wire that carries 5.5A...

BOTH are 500W setups.

You absolutely can get a solar charge controller that accepts 100V in @5.5A and outputs 13.8V @ 36A....or 27.6V @ 18A.

BTW, GC2s are cheap, $100 at costco, and while 6v, are around 220AH, and designed for deep discharge. 2 in series gets you 12V, 220AH... fo $200....

I don't have the link that sold me on 24, but it was like this info...

 

[TechnoWeenie]

Whole house systems fall under the multi-battery and multi-KW setup I mentioned before.

A mobile setup for 12V is a COMPLETELY different animal than a 24 or 48V setup for home, where 99% of your electricity use is through an inverter and 110V.

A lot of these setups are relying on 110V inverters, and thus a higher voltage system makes more sense.

For a 12V system, with only minimal 110V use, it doesn't make sense to go 48V... Lots more precautions need to be made, you'll need more batteries, and the equipment is a lot more expensive since it's designed for commercial use and not as many people make it.

 

[Third From Texas]

Whole house systems fall under the multi-battery and multi-KW setup I mentioned before.

A mobile setup for 12V is a COMPLETELY different animal than a 24 or 48V setup for home, where 99% of your electricity use is through an inverter and 110V.

A lot of these setups are relying on 110V inverters, and thus a higher voltage system makes more sense.

For a 12V system, with only minimal 110V use, it doesn't make sense to go 48V... Lots more precautions need to be made, you'll need more batteries, and the equipment is a lot more expensive since it's designed for commercial use and not as many people make it.

I get ya.

But the first video specifically mentions RVs.

His whole series looks to be RV related material.

 

[TechnoWeenie]

I get ya.

But the first video specifically mentions RVs.

His whole series looks to be RV related material.

and as I said, most of these people are looking at taking their home, on the road.. Not making a vehicle, into a home.

They're STUCK on 'we need 110v'... since EVERYTHING runs off 110v in modern RVs.... because they assume they're gonna be at a park with power or something. Very different setup than boondocking and long periods off grid.