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Old 08-01-2018, 10:42 AM   #1
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Need some guidance with 12v and 120v systems

Hey everybody! Ive been doing my dardest to read up, but i think im more confused than when i started. Everyones electrical needs and wants are different and i suck at electrical. My wife and I have been making progress on our conversion and we're about ready to start on the electrical system. But alas, electricity is a weird form of magic that I don't quite understand. It hurts my brain a bit. So any help would be greatly appreciated. Bear with me, I'm going to try to go over this as best I can.

What we have:
3x 12v 100 watt Renogy mono panels
Renogy Rover 40a mppt controller
4x Trojan T-105 6v 225ah flooded cell batteries. Will be wired in series/parallel 12v 450ah
Powermax PM4 45a 4 stage converter charger
Blue sea 5025 12v fuse block

What we plan to get:
Predator 2000 watt gen
Inverter: need help
120v panel: need help

What I'd like to accoplish:
Install battery bank to run small load 12v items. Led lights and phone chargers/laptop charger. Water pump.
Be able to run 115v refrigerator with a 126 watt load from battery bank to inverter, to panel to appliance.
Be able to power 3 120v outlets from battery bank, to inverter to panel. Phone charging and other small load.
Be able to charge battery bank with generator and simultaneously power 120v panel, bypassing the inverter.
Same as above, but through shore power hookup.
Not burn down the bus. That's a biggie.


Now for some questions. Is my fridge plan even realistic?
If so, how would I go about accomplishing it? What panel should I be looking at? What inverter would be best to hook up to panel?

If I'm running the generator to the converter/charger, will the solar controller freak out? Or can both systems get along?

What else do I need to shore power hookups?



Fyi. Everything can be returned with the exception of the fridge. I know it's not ideal, but my wife loves that fridge and I'd love to make it work for her. I'm sure there are things that I'm forgetting.

Any and help is greatly appreciated!
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Old 08-01-2018, 11:16 AM   #2
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Welcome,

Your basic concepts are reasonable. I would be concerned about supporting the refrigerator with the solar /battery combination.

To get a realistic idea of what the refrigerator consumes in normal operation I would suggest that you get a "kill-a-watt" meter. Plug the refrigerator in and fill it with stuff. Open the door periodically.

This will give you a much better idea of what the refrigerator actually consumes over a 24 hour period.

With that you can better gauge how your system will support it.

With what you spec'd above, I can see daily generator runs to bulk charge your batteries.
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Old 08-01-2018, 11:28 AM   #3
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Is my fridge plan even realistic?
Yes.

Quote:
Originally Posted by TheNewblyweds View Post
If so, how would I go about accomplishing it? What panel should I be looking at? What inverter would be best to hook up to panel?
You first need to ensure that you have adequate battery capacity to run the fridge for x period of time. 450 Ah gives you 225 Ah usable.

I would suggest a pure sine wave inverter for a refrigerator.

Your refrigerator probably does not draw 126 watts continuously (if it does, get a different refrigerator), let's assume 50% duty cycle - probably a very inaccurate guess. That would equate to 1500 watt-hours (per day) or 120 Ah (per day). That is more than half of your usable battery capacity. So, if it is the only thing running, you would have slightly less than two days of running for the refrigerator. That isn't too terrible.

I'm not sure what the start up loads are for your refrigerator so only guessing here but perhaps an inverter as small as 500 watt would run it? However; since you are going to run more than just the refrigerator, get a 1500 watt or so. Best option is to add up all the 110VAC loads that you may want to run from it and size from there. The negative is that the larger the inverter, the more power it "wastes" when not working (generally).

To bypass the inverter (when on shore/generator power), you either need an inverter with a built in transfer switch or an external transfer switch.

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If I'm running the generator to the converter/charger, will the solar controller freak out? Or can both systems get along?
No, they get along.

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Originally Posted by TheNewblyweds View Post
What else do I need to shore power hookups?
The "ideal" way is a shore power cord that runs to an automatic transfer switch. The generator is also wired into this switch. The output from the switch goes to your 110VAC distribution/breaker panel. The transfer switch has a "default" or "preferred" input which is usually shore power.
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Old 08-01-2018, 01:37 PM   #4
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Thanks very much! Ill plug her in tonight and get that info.
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Old 08-01-2018, 01:55 PM   #5
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JDOnTheGo and PNW_Steve, Thanks so much! With my solar hooked up will the batteries be charging while also powering the refrigerator during the day?
Also, any recommendations on an automatic transfer switch, 120v panel, and whatever else im not thinking of? Im going to total up all possible appliances that might be running off of the 120 system. would it be worthwhile looking into charging battery bank from alternator when on the move?
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Old 08-01-2018, 02:08 PM   #6
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Quote:
Originally Posted by TheNewblyweds View Post
JDOnTheGo and PNW_Steve, Thanks so much! With my solar hooked up will the batteries be charging while also powering the refrigerator during the day?
Also, any recommendations on an automatic transfer switch, 120v panel, and whatever else im not thinking of? Im going to total up all possible appliances that might be running off of the 120 system. would it be worthwhile looking into charging battery bank from alternator when on the move?
Depends on the fridge requirements. If you're putting more into the batteries than the fridge requires, your batteries will continue to charge. If the fridge requires more, while the solar is charging the batteries the fridge is slowing discharging them.
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Old 08-01-2018, 02:48 PM   #7
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I found that my refrigerator (chest freezer actually) took about 50% more wattage to operate from my inverter than it did when operating from residential AC power. That was with a modified sine wave inverter, so a pure sine wave unit should do a bit better.
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Old 08-02-2018, 06:11 AM   #8
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With my solar hooked up will the batteries be charging while also powering the refrigerator during the day?
Yes, maybe. 300 watts of solar is VERY minimal, IMO. Depending how they are mounted and where you are location (solar insolation), you'll probably only 200 watts or slightly more. Assuming a charging voltage of 13.5VDC, that means something around 14 amps under the best of conditions. If your refrigerator is running at the stated 126 watts, most of that power will be consumed by the refrigerator which doesn't leave much going into the batteries. Obviously lots of "conditions" to all this (like sunny or cloudy, fridge duty cycle, etc.) so few certainties. I would certainly increase the amount of solar (more/larger panels) if possible. If not possible, any is better than none, of course.

Quote:
Originally Posted by TheNewblyweds View Post
Also, any recommendations on an automatic transfer switch, 120v panel, and whatever else im not thinking of? Im going to total up all possible appliances that might be running off of the 120 system. would it be worthwhile looking into charging battery bank from alternator when on the move?
Transfer switches aren't very complex. The only trick is deciding if you are going to wire your system for 30 amp or 50 amp. I don't see air conditioning listed so 30 amp is probably sufficient. In that case, something like this will work.

All the other stuff is pretty common. A 120VAC distribution panel (called a variety of things) but it contains circuit breakers for each 120V circuit running thru your rig. Most folks install something like 12/2 romex "house style" wire but 14/2 might be plenty sufficient (that is a smaller wire size, can carry less current). Electrical sockets/plugs, boxes, etc... All of that is wired up exactly like a traditional house.

Steve is way more familiar than I with the 'charging house batteries from alternator' bit. My only warning is that there is much more to it than just connecting the house batteries to the alternator.
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