Using a propane generator to charge batteries

Welcome to the forum Lois,

In general, it is a good thing to start with understanding your loads. For example, a Kill-a-Watt type meter is very helpful. Plug your AC load(s) into the meter, measure the average Watts (power requirements--Like Miles per Hour). And measure you loads as they operate (hopefully, on a cold day for 24-48 hours, such as when you need to run the heating while the Mains are out)--Watt*Hours -- sort of like Miles Driven.

https://www.amazon.com/s?k=kill+a+watt+meter

There are "whole house" energy meters too--Here is one example:

https://www.theenergydetective.com/

Say you have 5 water pumps that take 0.9 amps each @ 115 VAC, and run for 12 hours per day. And guess that the rest of the system (electronics, fan, etc. that run the boiler) takes another 2.0 amps (pure guesses, just to show how the math works):

• 5 pumps * 0.9 amps * 115 VAC * 12 hours per day = 6,210 Watt*Hours per day (pumps)
• 2 amps * 115 Amps * 12 hours per day = 2,760 Watt*Hours per day (balance of system)
• Total = 8,970 WH per day (that is a lot of energy)

Lets guess your Golf cart takes 6 volt @ ~220 AH batteries of some sort... To run the above load for 1 days with 50% maximum battery discharge (for longer battery life), the minimum number of batteries needed would be:

• 8,970 WH per day * 1/0.85 AC inverter eff * 1/24 volt battery bank * 1/0.50 max discharge = 880 AH @ 24 volt battery bank.

Or, the number of 6 volt @ 220 AH battery required would be... 4x 6 volt batteries in series (for 24 volt bank) * 4 parallel strings (for 880 AH), or 4s*4p= 16x 6 volt @ 220 AH golf cart batteries...

In general, that is probably a) many more batteries than in a typical golf cart, and b) many golf carts are wired not natively wired for 24 volt operation.

The above is a bunch of guesses, and may be wildly wrong... But on the surface, it would appear that such a battery system to run a radiant heat system of your size would not be very practical--Relatively large battery bank, does not use your "native golf cart" batteries optimally, and you may be better off just running the heat, refrigerators, etc. on the genset using your normal schedule (may be six hours in the morning and six hours in the evening)... And make a much smaller AC power system that can run your LED lighting, LED TV, cell phone charger, perhaps an RV Water pump (if you pump from a cistern or similar), etc...

A "small" battery+inverter system may run 1,000 WH per day (1/8th the size of the mythical radiant heat system) during "quiet times). and use the genset to recharge the battery bank during the morning/evening.

• 1,000 WH * 1/0.85 AC inverter eff * 1/12 volt battery bank * 1/0.50 max discharge = 196 AH @ 12 volts
• or 2 series * 1 string = 2x 6 volt @ 220 AH "golf cart" batteries for a 12 volt @ 220 AH battery bank

Such a system with a ~300 Watt AC inverter would let you have enough AC power for LED Lighting and odds and ends, and just continue to run your 6 kWatt genset for your main loads.

An alternative would be to look for a smaller AC genset if your average loads are much less than ~3,000 Watts (most gasoline/propane gensets are most efficient at 50% or larger rated loads--Below 50%, the fuel flow remains close to 50% as loads drop to 25% to near 0% loads). Oversizing a genset can be a real fuel hog.

Generally, Solar (and genset) supplied AC power is something like $1 to $2+ per kWH vs whatever your utility rates may be (typically $0.10 to $0.40 per kWH--Those high rates are usually found in Hawaii and California--You are are up in BC Canada area?).

Conserving power (and fuel usage) during off grid operations can save you a bunch of money. May not be a big deal for a couple days of winter outages--But for Weeks+ at a time, besides the simple expense of fuel (6 kW propane genset may take something like 1-2 GPH of propane--Just guessing), the cost of fuel and fuel storage is more of an issue:

• 1 gph propane * 24 hours per day * 14 days = 336 gallons of propane for 2 week outage

A much smaller eu2200i Honda gasoline genset may run your home on 2-5 gallons of gasoline per day vs the (again guessing) 24 gallons of propane (or more) per day. And there are propane conversions for some of the smaller generators.

Add storage and delivery issues (getting truck, typically higher costs during winter for fuel, etc.), "freezing" the propane take (if pulling vapor from tank in cold weather, smaller tank... Can drop propane pressure to zero PSI at times)--All come into play here.

I am sorry I did not answer your question directly... Really need to understand your power needs first to do a paper system design first, then figure out what hardware is needed to run it.

-Bill

Leaving the Batteries+charger+AC inverter etc. in the garage / basement (hopefully, >~45F as warm batteries have more apparent capacity), and just run the 120 (or 120/240 VAC) power from the garage to the house AC main panel. And use either a manual or automatic transfer switch to power your "critical" circuits.

It is much easier to wire 10-15 Amps of 120 VAC, then to transfer batteries and/or wire long distance low voltage DC power long distances (such as batter bank to AC inverter).

https://www.homedepot.com/s/generator%2520transfer%2520switch?NCNI-5 (manual transfer switches)
https://www.solar-electric.com/pomaxpmautrs.html (auto transfer--Just start the genset or AC inverter and relay will transfer 120 VAC power)

The Honda euXXXXi family of gensets are very quiet and can be very reliable (should last >>2,000 Hours with oil changes). An eu2200i or eu3000 would probably run your home on 2-3 gallons of gasoline per day.

Some of them can be converted (change to a "syphon type fuel cap" to draw fuel from an external fuel tank. For short term power outages (suggest less than a couple weeks a year), generators are generally a better solution vs solar/battery banks.

If you have natural gas or propane, getting a compatible genset saves the issues of getting, storing, and persurving gasoline (or even diesel).

-Bill