Battery charge

[Laredo60]

Looking to take a dry camping trip end of October here in the mountains of NJ in a state park. First time doing this.i have installed a brand new battery for the rv. My question is how long can I expect the battery to last with minimal light use and the furnace and gas refrigerator on.it is a 27 battery. It will be for 2 nights. Also was wondering how long a Honda 2000 will take to recharge the battery? Thanks for the info on this.

[bsmith0404]

You may be able to get through 2 days of minimal use...MAY. Why not add a second battery? A 27 series battery will have about 70 amp hours, two wired in parallel will give you roughly 140 amp hours. That should be more than enough to get you through a weekend on minimal usage. If you did dry camping for longer periods and more often, you would want to consider switching to a double 6 volt system, but not worth the expense for what you're talking about.

As for how long will it take a gen to charge them, I'm guessing here, but I'd say at least a couple hours for a full charge if drained down pretty low.

[chuckster57]

The fridge will draw the entire time. Your biggest draw is going to be the furnace. The fan has to spin fast enough to push the "sail switch" closed to allow gas to flow. Are your lights LED or incandescent? Incandescent lighting can eat up amp hours depending on how many are on and for how long.

If you charge a couple of hours in the morning and again in the evening you should be fine.

[drdarrin]

Your refrigerator will draw approximately 1.2 amps 24/7. (1.2 x 48 = 57.6 AH)
Your furnace will draw approximately 8-11 amps every time the blower runs for as long as it runs. (you'll have to do the math on this one)
Incandescent lights draw approximately 1.2 amps; LED's about .2 amps. (1.2 x 4 hrs x 2 days x 1 light = 9.6 AH, adjust the # of lights as necessary)

I don't know how many Amp Hours your battery is capable of providing but it would be wise to find out. As a rule of thumb, you don't want to draw it down below 50% of capacity; it will dramatically shorten it's life.

The converter in your trailer will not use 100% of your generators available energy to charge your batteries and it will likely not fully charge your batteries unless it is run for a couple days (no practical). The converters in most RV's are crappy battery chargers. They don't get the voltage high enough to fully charge your batteries.

You would be better off with a seperate battery charger connected between your generator and battery. Or an alternative I've used is to use jumper cables connected to my tow vehicle (engine running) and connected to your RV battery. This won't fully charge it either but it will charge it faster. There is no 120v to 12v conversion losses this way.

BTW, a fully charged 12v lead acid battery with no loads is fully charged when its voltage = 12.7v. A trickle charge is about 13.2v, charging voltage is approximately 14.7, equaling charge is approx 15.3. These values assume the battery is at 70 degrees. More voltage is necessary as the battery gets colder.

[chuckster57]

Wow, lots of math!!
Our mantra "if it doesn't have full hook ups we don't go there". Thank you taking the time to post a detailed answer.

[Laredo60]

Wow that's is a lot of math. Not sure this dry camping stuff is worth it. Sounds like having a second charged battery with me is my bet option. I will have my friends generator with me in case I need it. But I was hoping to not have to run it that much. One question on using the battery charger off the generator do I have to disconnect the cables fron the rv while I am using the charger? Thanks again for all the info. No I do not have LEDs in the rv. But I will not be using more then one or 2 lights. I also did not realize the fridge would draw 24/7 either. Good to know that. Mostly worried about the heat to keep wifey warm.

[24v]

Wow that's is a lot of math. Not sure this dry camping stuff is worth it. Sounds like having a second charged battery with me is my bet option. I will have my friends generator with me in case I need it. But I was hoping to not have to run it that much. One question on using the battery charger off the generator do I have to disconnect the cables fron the rv while I am using the charger? Thanks again for all the info. No I do not have LEDs in the rv. But I will not be using more then one or 2 lights. I also did not realize the fridge would draw 24/7 either. Good to know that. Mostly worried about the heat to keep wifey warm.

This isn't as crazy as it sounds.

Just buy another 12 volt battery that matches the one you have and install it next to the first one. Connect the positive together, and connect the negative together. (wired in parallel)

For the charger, you can leave the trailer wires connected. Just connect the charger to the battery posts directly.

[bsmith0404]

You should have room to install a second battery and wire it parallel. Just stop by your local parts store, get a second battery and 2 battery cables, 12" is usually sufficient. Most people can get through a weekend with 2 batteries without any problems.

[Desert185]

When we had a single, group 24 batt and incandescent lights we had to run the gen at least a couple hours a day. We installed two, 6V GC batts and LED lights. BIG DIFFERENCE. Now we run the gen in the morning for coffee, microwave and the fireplace when cold to remove the chill and then a bit at night if we need AC power.

Staying in a park with power is a real convenience, but boondocking has it's own special attractions. Two batts and LED lights goes a long way in enhancing the experience.