Community Forums

rrtribble · 12-31-2018, 02:34 PM

2 part search for info

1. heat DP using the on board propane (27.5 gals when full)? My DO is 35 ft long with 2 slides. Nights will be below freezing with days slightly above. I replaced the inverter with a converter and run frig, stove, water heater and furnace on propane. When running generator I plan on switching to electric heat, frig, water heater and use microwave and tv (probably about 3 hours a day).

2. run on my batteries? I have 3 new 12v deep cycle batteries from Rexx. Not sure amph rating but supposed to be the best they offer. No inverter. Use gen for AC and to recharge batteries about 3 hours a day - Is that enough time?

Thanks for your assistance in planning so I won't run dry. Richard

Unicorn Driver · 12-31-2018, 02:40 PM

Propane has 91,600 btu's. My furnace is 40,000BTU. Yours is problay about the same.

If the furnace is going full belt it will burn .43gallons of propane an hour.

Unicorn Driver · 12-31-2018, 02:48 PM

Your electric heat will not work below 40f or so and will turn on your propane furnace.

I have 2 ceramic oil filled heaters which I run when the generator is running, I just turn the furnace off and back on when the genarator is stopped.

rrtribble · 12-31-2018, 04:24 PM

Thanks. So I can figure on about 55 hours of full heat. Spreading that out due to time on the road and when I'm using my elec heat I shouldn't have any problems with this area.

As to my elec heat. I've used my elec heat here at home while plugged in. I used propane to bring it up to desired temp then switched to elec heat and it ran fine. You just have to remember to keep elec within 5* of inside temp. I tested mine at 5* at a time and brought unit from 55 to 75 using elec heat. BUT can only use elec when on shore power or with generator. My generator is said to use approximately .5 gallons an hour of running so I could use it if necessary or when in the WalMart lot where everyone else is running their's overnight too.

Thanks for the info. My only concern now is how long will my batteries run the furnace is I choose to go that way. Not planning on spending more than 3 days at a time without shore power.

Unicorn Driver · 12-31-2018, 05:53 PM

You could test it out before you hit the road.

Do you have a battery monitor?

dons2346 · 12-31-2018, 10:39 PM

Why in the world would you replace an inverter with a converter?

Persistent · 01-01-2019, 09:37 AM

Quote:

Originally Posted by rrtribble

2 part search for info

1. heat DP using the on board propane (27.5 gals when full)? My DO is 35 ft long with 2 slides. Nights will be below freezing with days slightly above. I replaced the inverter with a converter and run frig, stove, water heater and furnace on propane. When running generator I plan on switching to electric heat, frig, water heater and use microwave and tv (probably about 3 hours a day).

2. run on my batteries? I have 3 new 12v deep cycle batteries from Rexx. Not sure amph rating but supposed to be the best they offer. No inverter. Use gen for AC and to recharge batteries about 3 hours a day - Is that enough time?

Thanks for your assistance in planning so I won't run dry. Richard

Sorry, I don't know what Rexx batteries are. If they are lead/acid then the following applies. If they are lithium then I don't know.

How long on battery? It is all about the amps both charging and discharging.
You need to know how many amp hours the three batteries store.
You need to know how many amps the furnace and other 12 volt appliances draw.
You can probably use 80% of the batteries deep draw amp/hr capacity if you are using AGM sealed batteries. The lowest 10% would be reserve. The highest 10% takes a long time to fill. You may need a little more reserve for flooded cell batteries. The only way to know is to check the manufactures web site for the charging profile.
Three large deep draw batteries should last 2 or 3 days. If each battery is rated at 100 amp/hrs, you can use 240 amp/hours of storage.

Is three hours charging enough? What are the maximum amps the new converter will deliver?
What is the charging profile of the brand of batteries you have.
When the batteries are down to 10% and you use a generator and a converter to charge them, the converter will limit the charge current. Current will flow at the maximum the converter can deliver.
When the batteries are charging in the middle of the charge cycle, charge current will be limited by the batteries and the charge voltage. The converter will probably provide 14.5 volts for the middle of the charging cycle then drop to 13.6 for the remaining period. Charge current continues to drop until it is very low during the last two phases.
Some deep cycle AGM batteries can get to 80% in 3 hours using a high capacity charger.
If you don't want to calculate all this, you can test it to find out.
1. Use the batteries until they are down to 10%. Measure the battery voltage when disconnected for a period of 30 minutes or more to determine % of charge. Flooded cell level of charge can also be determined using a hygrometer and measuring electrolyte specific gravity. Tables of charge % to no load voltage are usually available on battery mfg's web sites.
2. Continue to measure battery voltage using a digital voltmeter or a built in monitoring system while you charge the batteries using the generator and converter for three hours.

The period of time before the charging voltage reaches 14 volts is the time the batteries are taking the full current from the converter. So, 50 amps for 1 hour is 50 amp/hours. At this rate Three hours would provide half capacity of three 100 amp/hr batteries (150 amp/hours).

If the charging voltage drops to 13.6 volts within 3 hours, the batteries are probably above 70%, maybe even 80%. It depends on how the converter calculates when the last stage of charging has been reached.

Conclusion: 3 modern 100 amp/hr AGM deep discharge batteries will easily run furnace, lights, pumps, and fans for one day (probably 2 or 3 days.) 3 hours of charging using a modern 50 amp converter will not fully charge from 10% to 90%. The system will probably replace enough to get you through another day.

John Hilley · 01-01-2019, 10:59 AM

What Unicorn Driver is saying about your electric heat, is that if it is a heat pump, it won't work below 40F.

We use a heat lamp type electric heater with fan that works well when we use the generator.

your 3 12 volt batteries should easily carry you from one generator session to the next.

rrtribble · 01-01-2019, 06:35 PM

dons2346 - why would anyone want an inverter unless they loved to watch tv in rest areas. I found that my inverter, before it blew up, was good for only one thing - draining my batteries. If and when I want AC I use shore power or my generator.

Persistent - thanks for the info on determining my battery draw. The placard showing amph must be on the side facing the other batteries. I'll be pulling them to check when the weather breaks. I'm continuing to learn and I thank you for adding to my education. For more than 40 years of RVing I had only one battery and only ran it down once. Sure don't want to do that again.

John Hilley - I just tested mine a couple of weeks ago after the electricians put in my 50 amp plug. Temp was 28* inside DP. Set thermostat to 32* and elec heat started right up. Kept going up 4 or 5* degrees and it kept working. Switched to propane and brought temp up to 70* then back to electric and it held temp steady through the night. Reason I did this was to test it but also because I needed it to be heated so as electricians shut off electricity I would have a warm place for my wife and me to rest while they completed their work.

RoadDogYVR · 01-03-2019, 05:53 PM

Quote:

Originally Posted by Unicorn Driver

Propane has 91,600 btu's.

Per Gallon.

Quote:

Originally Posted by Unicorn Driver

My furnace is 40,000BTU.

DryCreek · 01-03-2019, 08:25 PM

Quote:

Originally Posted by rrtribble

John Hilley - I just tested mine a couple of weeks ago after the electricians put in my 50 amp plug. Temp was 28* inside DP. Set thermostat to 32* and elec heat started right up. Kept going up 4 or 5* degrees and it kept working. Switched to propane and brought temp up to 70* then back to electric and it held temp steady through the night. Reason I did this was to test it but also because I needed it to be heated so as electricians shut off electricity I would have a warm place for my wife and me to rest while they completed their work.

Just to clear things up - were you running the heat strips in your rig, or a heat pump. I think the statement about 32 degrees being the lower limit for electric heat is true for heat pumps, but not applicable to the electric resistive heating strips found in some units. I am not sure which type of heat the basement unit in your has.

rrtribble · 01-04-2019, 07:08 AM

Dry Creek,

I only have my basement AC heat pump and that is what I used. I don't remember anything in my manual about any reference to temps except for the 5* difference so when I turned it on I went electric heat and added 4* to the current temp and she started running. I know it was the heat pump rather than the default propane furnace because it comes out the ceiling (AC) vents while propane furnace comes out the floor vents.
Also tested setting electric heat to 70* while inside temp at 50 and it immediately switched from electric to propane.
Won't be using it much this winter except when I go out to do some work which I have to do, maybe next week as the temps here in Central IL are projected to be in the 50s.

Have a great day - Richared