house batteries & heat with 120v

we have a stand up electric heater fan built in works great.no batteries involed,

You might be overthinking this one. Remove the negative cables of the batteries. Plug it in and see if everything still works.

Since you have 120V shore power, have you thought about using an electric space heater instead of the furnace? It will save you propane.

If you need new batteries and you have 120 volts available then why not buy the batteries and plug it in from time to time to keep them topped off or leave the rv plugged in. Use the rv kill switch to prevent a drain.

Using your RV as it was intended…with a battery…is the safest route. Fully charged a wet cell battery won’t freeze. Why not buy a new one now?

valhalla360 wrote:
Should be fine. Typically a dead battery is not completely dead. The only downside is the charger will run pretty much continuously but if it's only for a stray night, it's not a big deal.

Actually, if the battery has a bad cell, and the converter is on 24/7 it could be a VERY big deal.

Charging what would amount to a 10 VDC battery (one dead cell) at 13+ VDC could cause severe overheating, boiling electrolyte, etc.

A battery with a bulging case and/or the smell of sulfuric acid are a dead giveaway that the battery is being dangerously overcharged.

Should be fine. Typically a dead battery is not completely dead. The only downside is the charger will run pretty much continuously but if it's only for a stray night, it's not a big deal.

The charger should put out enough to keep the furnace fan and brains working.

Generally yes, the furnace will work fine as long as you have 120v and propane.

Switch-mode converters made since about 1998- early 2000s do not need a battery to operate and supply the 12v to the rig. However some 12v things have their pos and neg paths connected part way along using the battery posts.

You can leave the cables off the battery bank, but do join up the same wire terminals as though they were on the battery posts. Vice grip pliers can do that or nuts and bolts. Don't let the pos wire collection touch any metal nearby or it will short and blow fuses.

cac43 wrote:
my 2 house batteries my class c are dead and Cales taken off. want to wait until spring to buy new ones, but want rv to be available for kids to sleep inside if needed during the winter. If I hook up to 120v shore power to use the furnace will the blower work all night without the batteries being hooked up?
thanks again.

Probably not, but adding year/make/model of RV will get better more relevant answers.