Hello, I am new to truck camping and thinking about needing my furnace overnight while boondocking overnight as we head south. My question is, if running the furnace and a few other small items were to drain my house batteries to a 50% charge overnight, would driving for 8 hours the next day fully replenish the batteries?I have two new flooded batteries and my diesel has dual alternators. I will start the trip with fully charged batteries.

Battery charging is not linear, so that is a bit difficult to answer, but roughly you will get about 80% of battery charge after 1 hr of charging(drivng). To top-off the rest will take about 2hr.

8 hr x 10 a = 80ah. If your batteries are 160ah, then yes.

You will not drain to group 27 battery's to 50 percent in one night just by using the furnace and some lights. I think you will be fine.

It looks like 80 amp/hours each.

hondaone wrote:It looks like 80 amp/hours each.Sounds like 12v batteries.

Charging House Batteries while Driving | Good Sam Community

Kayteg1
Explorer II
Dec 12, 2015
Battery charging is not linear, so that is a bit difficult to answer, but roughly you will get about 80% of battery charge after 1 hr of charging(drivng).
To top-off the rest will take about 2hr.
2oldman
Explorer II
Dec 12, 2015
8 hr x 10 a = 80ah. If your batteries are 160ah, then yes.
Old_Days
Explorer II
Dec 12, 2015
You will not drain to group 27 battery's to 50 percent in one night just by using the furnace and some lights. I think you will be fine.
hondaone
Explorer
Dec 12, 2015
It looks like 80 amp/hours each.
2oldman
Explorer II
Dec 12, 2015
hondaone wrote:
It looks like 80 amp/hours each.
Sounds like 12v batteries.
deltabravo
Nomad
Dec 12, 2015
Depends on the size of the charge line. If it's 10 or 12 awg, the voltage drop at higher amps will be limiting the amount of charge.

I upgraded my charging system to 4awg wire, which needs replaced, because some rats, marmots or rabbits chewed up my wiring.
hondaone
Explorer
Dec 12, 2015
My thanks to all of you for your input. It sounds like a win-win; the batteries won't drain to 50%, and the truck charging will be more than adequate. Good news; I will rest easier.
2oldman
Explorer II
Dec 12, 2015
hondaone wrote:
It sounds like a win-win; the batteries won't drain to 50%, and the truck charging will be more than adequate. Good news; I will rest easier.
Don't put away your voltmeter just yet. Charged batteries at rest will be around 12.7. And with just two, and depending on your actual use, and how cold it is, you may not make it through the night ( 12.0 in the morning.)

The only way to answer your question is for you to measure them.
jimh406
Explorer III
Dec 12, 2015
Keep in mind that the amount of time that the furnace fan runs it he biggest determination of whether you will drain your batteries or not. Putting the thermostat lower so it won't run as much will help. Winterizing your camper by adding reflectix in the windows etc will minimize heat loss.

As far as lights go, the normal 12v bulbs use a lot of power. You should consider changing to LEDs if you are worried about batteries lasting. It makes a huge difference.

Finally, make sure your antenna amplifier, fantastic fans, water pump, or anything else that uses 12v is off.

The amount your vehicle charges depends on the vehicle and circuit. There are some vehicles that don't charge without adding a fuse, etc. You want to check to see if your vehicle is truly setup for charging.
Old-Biscuit
Explorer III
Dec 12, 2015
OEM factory tow package charge line is just big enough to maintain RV battery and charge them minimally so if charge circuit is 10 or 12 awg it's a gamble