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Planning The Off Grid King Power System

CJGing

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Jul 14, 2020
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Good day I am in planning stages of "The off grid king power system" (https://www.mobile-solarpower.com/the-off-grid-king-power-anything.html) and I have a few questions. Thank you in advance for any help you can provide!

1. The system will be installed in to a travel trailer (30amp w HVAC) and I'd like to keep the ability to keep my existing shore power hook-up. BTW, I don't plan on running the HVAC unit on Solar.
1a. The 120v AC to DC converter that comes with most travel trailers, to my understanding, is very cheap and basically is on or off when charging the batteries. My question here is does this need to be upgraded or no?
1b. Is it best practice to install a "auto switch" in such that when I plugin to shore power or a generator it switches off the inverter feed to the shore power feed?

2. I don't plan on buying everything and installing at once, instead I'd like to do this over time, starting with the battery bank conversion (Lithium) and building the system up from there. What do you guys recommend I do as far as the "order of conversion"? My reasoning for starting with the battery bank is this would give the the ability to run off grid with little to no generator time (only run generator as needed). Since this build isn't quit big enough to run a 13,500 BTU unit for any extended amount of time the generator will still be needed.

Also, sorry for the non-technical terminology here, I hope this makes sense..

Again thanks in advance for the advice.
 
Starting with the battery seems like a reasonable approach. Is your goal to run off of solar "as much as possible" and then augment with shore power and generator? Or??

Have you done an energy audit to get a feel for how much power you use each day?
Running your HVAC is probably out as you indicate with only 800w on the roof. But with sufficient sun exposure and battery its feasible to run a smaller window unit (there are some recommended ones that folks swear by for small to medium sized installations).

Do you have a feel for how many AH of lithium (assuming LiFePO4?) you need? Then see if 800w x solar hours is enough to replenish battery(s). Then a charge controller that works well with panels and batteries.

I think i would make this all independent of your existing electronics. I'd defer to someone else's opinion/recommendations on how to install a transfer switch(es).
 
Starting with the battery seems like a reasonable approach. Is your goal to run off of solar "as much as possible" and then augment with shore power and generator? Or??

Have you done an energy audit to get a feel for how much power you use each day?
Running your HVAC is probably out as you indicate with only 800w on the roof. But with sufficient sun exposure and battery its feasible to run a smaller window unit (there are some recommended ones that folks swear by for small to medium sized installations).

Do you have a feel for how many AH of lithium (assuming LiFePO4?) you need? Then see if 800w x solar hours is enough to replenish battery(s). Then a charge controller that works well with panels and batteries.

I think i would make this all independent of your existing electronics. I'd defer to someone else's opinion/recommendations on how to install a transfer switch(es).

Thanks for the reply....

Yes, my travel trailer is very small and in my calculations (leaving out the HVAC) 800w solar with 400 amp hour of Lithium and yes the LifePO4, should be enough to run my needs, including about 45 minutes or so a day with the microwave if needed.

Thanks for the suggestion to keep it separated, only issue if I was to do this I would need a separate converter to charge on the extended cloudy days with shore power and/or gen. However, I am trying to avoid the need to install separate outlets, etc.. in the RV.

If I was to start with changing over from one AGM batter (came with RV) to two 100amp LiFePO4 batteries, would the AC to DC converter that comes with RV need to be replaced? I am a little concerned with trying to charge the LiFePO4 batteries with the "house converter".
 
Thanks for the suggestion to keep it separated, only issue if I was to do this I would need a separate converter to charge on the extended cloudy days with shore power and/or gen.

2 things I'd like to point out.

You need to ensure that your inverter and converter don't create a power loop.
In other words you don't want your inverter creating ac from dc and your converter using that ac to make dc power.

When you are connected to shore power the neutral/ground bond must be somewhere between the pedestal and the power company transformer.
When you are not connected to shore power the neutral/ground bond must be within your domain.
That means it must be switched.
Many inverter/chargers can take care of this by design.
@mapguy525 can site you relevant UL standard.
The inverter/charger will make the converter redundant btw.
 
The 120v AC to DC converter that comes with most travel trailers, to my understanding, is very cheap and basically is on or off when charging the batteries. My question here is does this need to be upgraded or no?
I am/was in this boat too. In 2011, i swapped out the crappy RV charger with a wire-for-wire swap compatible unit from Progressive Dynamics (PD4645) for about $225. Made a world of difference. I am still using this with my LiFePO4 batteries (which it is not compatible with). It charges to around 13.25v so around 85% SoC.
Their newer models know about LiFePO4 so would be a much better option than what I have. If I planned on keeping my RV for a long time (we're 5 years past where we thought we would upgrade!), AND if i used shore power more than rarely, i would get a newer one.

My solar panels (2) run to a Victron 100/30 and to the batteries directly and do not mix with the RV electronics. So even with shore power, generator power, engine power and solar power, they each contribute to charging the batteries as necessary (and as they are programmed).
 
2 things I'd like to point out.

You need to ensure that your inverter and converter don't create a power loop.
In other words you don't want your inverter creating ac from dc and your converter using that ac to make dc power.

When you are connected to shore power the neutral/ground bond must be somewhere between the pedestal and the power company transformer.
When you are not connected to shore power the neutral/ground bond must be within your domain.
That means it must be switched.
Many inverter/chargers can take care of this by design.
@mapguy525 can site you relevant UL standard.
The inverter/charger will make the converter redundant btw.


thanks and was the path I was thinking... Any recommendations on a AC switch and inventor/charger ?
 
thanks and was the path I was thinking... Any recommendations on a AC switch and inventor/charger ?

I assume you mean an automatic transfer switch.
Have a look at the samlex evo line.
Btw most inverter/chargers have a built-in transfer switch.
 
 
Thanks guys, after a bit of digging I found this:

Which is exactly the missing peace I was looking for, thanks for your help.
 
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