Class C Motor Home

cyperpc · November 2018

My Class C Motor Home need 120 Volts at 30 Amps.I was looking at Samlex America PST Series 24 Volts, 3000 Watts Pure Sine Wave Inverter. The Output Power is 120 Volt @ 25 Amps. Because the Motor Home setup for 30 Amps and the inverter is 25 Amps can I still use just one inverter or do I need two inverters?

I was also planning to use a car alternator with a fan motor to charge the batteries. The Fan Motor would be run by a 2nd inverter system with solar cell and a battery.

Estragon · November 2018

Having an inverter with less ampacity than the RV is fine.

A 3000w inverter is a bit on the large side for a 24v system. Do you actually need 30a AC? What size battery bank will be used with the inverter?

Not sure what you have in mind with the fan motor. Normally you'd charge the bank from solar panel(s) using a charge controller designed for that purpose.

mcgivor · November 2018

Measure the loads before jumping to conclusions , just because the shore power connection is rated at 30A maximum, it not nessersary what one would use. When using batteries to power anything, conservation is by far the less expensive option, perhaps a smaller inverter could be used, all speculation at this point in time. Not sure what the fan motor charging thing is about.

bill von novak · November 2018

cyperpc said:

My Class C Motor Home need 120 Volts at 30 Amps.I was looking at Samlex America PST Series 24 Volts, 3000 Watts Pure Sine Wave Inverter. The Output Power is 120 Volt @ 25 Amps. Because the Motor Home setup for 30 Amps and the inverter is 25 Amps can I still use just one inverter or do I need two inverters?

I was also planning to use a car alternator with a fan motor to charge the batteries. The Fan Motor would be run by a 2nd inverter system with solar cell and a battery.

A few notes.

1) There is a lot of value in an RV in sticking to 12V since your best charging source (the engine) can then charge the battery. At 24V you need some more expensive solutions - a voltage doubler, a second alternator etc - to support the 24V battery.

2) Do you really need 3600 watts? I would guess no. Add up all your loads and see what they total. Are you trying to run an A/C? If your loads end up as less than about 1800 watts you can do that with 12 volts.

3a) Move all possible loads to DC. That means lights, fans, phone and computer chargers etc that run on 12 volts, not 120 volts. This will help with reducing your load.

3) Make sure your battery bank can support that. If you go with 1800 watts, for example, you are looking at a 400-600ah battery system at 12V.

4) The solar -> inverter -> fan motor -> alternator -> batteries thing is just nuts, sorry. Makes no sense whatsoever. Are you trying to figure out a way to charge a 24V bank from solar? There are plenty of charge controllers that will do that.

cyperpc · November 2018

I thought by using a 24 volt systems it would be lest strain on the battery. My thought is that a alternator charges the battery. Not sure what RPM or speed the alternator need to spin but was going to us a 110v Fan motor from a ceiling fan and adjust the voltage for the right speed. So I was think of having a 100 watts solar cell power change a 12 volt battery which is connected a small 800 watts inverter which will then run the fan motor which will turn the alternator to change the Main batteries.

RV Microwaves	1000
A/C	1750
Refrigerator	300
Hot Water (Elec)	1,400
TV	100
Coffee Maker	100

Total 4600 watts

This is the maximum watts

I would like the Refrigerator and A/C on 24/7

littleharbor2 · November 2018

The fan motor to run an alternator is a no go. One other point, If you plug your shore power cord into an inverter powered by the house batteries you had better disable the voltage converter. If not you are going to be trying to charge the house battery bank off of the HOUSE BATTERY BANK. Eventually you end up with dead batteries.

mcgivor · November 2018

The ceiling fan idea is impossible as described, the source must always be greater than the than the end output, there will be losses in every step so from the 100W panel you may, if it were possible, see ~35-40% at the end.

With air conditioning, refrigerator and hot water you're looking at an extremely large system, especially a mobile application, the watt figures are what each will drew, the figures needed are the actual run times, for example the refrigerator 300W at 30% duty cycle or 8 hours equals 2400Wh or 2.4 kWh. Complete this with all the loads to arrive at a total, from this the battery requiments can be calculated, after which the PV or other source to charge them can be calculated. To get a better understanding I suggest getting w power recorder such as a Kill-a-watt, log each load for a week, this will give a more accurate figure of daily needs.

stmoloud · December 2018

@bill von novak Agree Bill if you are going 12v get as much of your power loads running off that or less. Prior to getting everything I could onto the DC, my system gave me 48 hours of normal use battery store. Now I get nearly double that amount.
A major draw was my Dell laptop and I had another monitor attached to it. Ouch! So I got googling and discovered the raspberry pi 3 needing only 5 volts. Now I am internet surfing on it, watching youtube, and making comments on forums!
For sure, cyperpc be kind to your batteries . Just look for anything connected to the AC with plug pack or wall wart, and they are very likely to be good candidates for transferring the power requirements directly to your DC.

cyperpc · December 2018

stmoloud said:

"wall wart"

Had to look that up!

ScoobyMike · December 2018

Motor homes come pre-wired with inverters that will power select outlets. They are typically 1500-3000 watt inverters capable of running things like TV, microwave, computers, coffee maker. etc (larger loads one at a time). Your coffee maker estimate is low, probably more like 800-1200 watts. Your TV estimate is high, probably more like 20-40 watt with DVD player (40" TVs are now 6-10 watts). Allegro Bus makes 100% electric class A motor homes that have 8 deep cycle batteries, no propane tanks. These are RV Park queens but when they are boondocking the generator automatically comes on when battery voltage gets low. Microwaves, toasters, coffee makers and hair dryers will cause the generator to start pretty much every time. Air conditioner will only work when the generator is on.

I have not yet heard of an all electric class C motor home,so whatever you buy will have propane (for heater, water heater stove and probably the refrigerator). I cannot even envision an RV house battery that will run the air conditioner for any length of time.

You do stand a chance of running everything but the air conditioner and water heater however even this will require at minimum 4 deep cycle house batteries, probably more like 6-8. I have never had a 2 or 4 house battery RV that would run the microwave for more than 1-2 minutes before the inverter goes into low voltage shut down. Small class C moror homes will come with 2 house batteries, 4 in the larger units. I do know of people that have added additional house batteries, most stick them under the bed in the master bedroom.

Are you on any of the RV forums? iRV2 is one of the better ones. If you really are serious about an all-electric class C they will help you to understand what is out there.

Class C Motor Home

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