Off-Grid multi input / output power supply for RV - HELP!

Thread Starter

travellinglee

Joined Oct 3, 2017
7
OK, so the base or core system is supplied as part of the standard RV build which is:
  1. 120v 30 amp hookup input
  2. 120v 50 amp hookup input
  3. 12v input from tow vehicle
  4. Charge controller
  5. 12v battery
When the RV is not connected to a shoreline (30 or 50 amp hookup to mains) only 12v appliances will work but no TV, AC, microwave etc.
When connected to 30 amp shoreline the 12v battery will charge and I can use maybe 1 or 2 120v appliances depending on the amperage draw.
When connected to 50 amp shoreline the 12v battery will charge and I can use many 120v appliances.

This means that if you camp the RV on a beach, mountain e,g, no mains, you can;t use any 120v appliances. Obviously I could get an inverter to supply 120v from the 12v battery but to hook the 120v output from the inverter to the RV appliance oulets without a total internal re-wire so I would need to put the inverter 120v output into the one of the shoreline input, but this would cause great inefficiency as the battery would be supplying the inverter which would be supplying the shoreline feed which would try and recharge the battery.

Here's where I want advice, let me tell you my plan and please feel free to throw rocks at it or offer a better solution.

I'm going to leave the RV electrics 'as is' and have a totally separate system that simply feeds the 50 amp RV input as if it was hooked up in a trailer park.

So working back from the RV 50 amp input - this is fed by a 50 amp 10Kw 12>120v inverter - this is fed by the load output from a secondary charge controller - the secondary charge controller is fed by solar panels and as well as supplying the load output it also charges a large secondary battery bank that powers the inverter when solar is insufficient - Finally, I will program an Uno board to act as a volt meter relay so when the secondary (660Ah) battery bank drops to 11.5v the relay will start up a 6Kw 120v input to the charge controller from an electric start gas powered generator which will be shut off when the batteries get to 12.9v.

In theory this should give me 24/7 120v 6-10Kw 50 amp power as long as I have gas for the generator.

Thoughts & comments please.

Cheers

LeeCougar Electrics.jpg Cougar Electrics.jpg
 

DNA Robotics

Joined Jun 13, 2014
515
Arduino sensing voltage to start the generator is good.
Your battery charger will put out 13.5 volts or more as soon as it comes on.
Your battery charger will use less amps and put out less amps as the batteries get closer to fully charged.
A current transformer (CT) on the charger AC input and an Arduino could sense when the batteries are charged.
Or use a DC amp sensor on the charger output.
 
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Thread Starter

travellinglee

Joined Oct 3, 2017
7
Arduino sensing voltage to start the generator is good.
Your battery charger will put out 13.5 volts or more as soon as it comes on.
Your battery charger will use less amps and put out less amps as the batteries get closer to fully charged.
A current transformer (CT) on the charger AC input and an Arduino could sense when the batteries are charged.
Or use a DC amp sensor on the charger output.
Good catch, I didn't think about the fact that when the charger kicks in the whole circuit to the battery will show as 13.5v so the gen would just go on and off. I don't want to use amps as the 'off switch' for the gen as power usage in the RV would effect that. If I use Arduino for a relay to close the circuit between charger and batteries and then test battery voltage, would that work? In dumb DOS code it would look something like:

Line 1 start counting
Line 2 if count = 10 minutes then close gen to bat relay, else goto Line 2
Line 3 measure battery volts=x
Line 4 if X=>12.8v then gen off
Line 5 END

This would have the effect of checking the bat volts every 10 minutes without the charge voltage so should give a true reading of the battery charge in volts regardless of how many amps are being pulled to the inverter for the RV's AC consumption.

Does this work/make sense?

Cheers

Lee
 

DNA Robotics

Joined Jun 13, 2014
515
That would work.
You should check to see if the battery voltage drops as soon as you turn the charger off, or if you need to wait a few minutes for the battery to settle.
If lights or pumps are on, they would bring the voltage down.
That might start your generator often.
 

Thread Starter

travellinglee

Joined Oct 3, 2017
7
That would work.
You should check to see if the battery voltage drops as soon as you turn the charger off, or if you need to wait a few minutes for the battery to settle.
If lights or pumps are on, they would bring the voltage down.
That might start your generator often.
I think that the model is valid and I can fix timing issues by tinkering with Arduino code, my last concern is that if I close the circuit between the charge controller and batteries whilst the gen is still pushing out power is something gonna go BANG?
 
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