Recharging batteries: genset vs. chassis alternator

[jillhop]

Please bear with me--I'm new to the RV world (purchased my first RV this past summer). 🙂

I am planning a trip to Wisconsin this coming April where I will be dry camping in a hotel parking lot for 7 nights. This trip is for a dog event, and I will have access to the hotel for showers, etc, but no electrical hookups. The weather averages for the time I will be there is for low in the upper 30's, high in the upper 50's, so I am concerned about recharging my single 85AH battery after using the furnace overnight.

I've been doing some experiments to try to learn what it takes to recharge my battery here in the driveway. After fully charging the battery (12.83V) from shore power, I ran the furnace from 4pm to 8am the next morning. This depleted the battery to about 50% (12.11V). After 24 hours with the battery disconnected (no charging or use) the reading rebounded to 12.25V (about 60%).

I then ran the generator several times, taking readings 24 hours after each "run":

2 hours generator increased battery to 12.35V (70%)

Another 4 1/2 hours brought it up to 12.54V (~85%)

Another 3 1/2 hours brought it up to 12.75V (100% on my chart, but still not back to the original 12.83V charge from shore power).

So, that was 10 hours of generator use to bring the battery back to full charge from one night of furnace use. This was on a colder night (low 20's) than I'm likely to need on my trip, but still...

I'm wondering if running the truck engine (Ford V10) would charge the battery more quickly? I have been doing some research on solar, but I wouldn't be comfortable installing myself, so that would be a pretty big expenditure for me. While I do dry camp regularly, except for this trip doing so for more than 2-3 nights in one spot (without a day of driving in between) isn't likely to happen.

My coach has pretty much original equipment, so just a basic 1998 converter. I know from what I've read that I could benefit from a better converter, and probably adding a second battery would be helpful. But, if I don't have charging capacity to charge the single battery I have, I'm not sure how helpful that would be.

So, does my 7 nights of dry camping sound workable with the equipment I have now? I'm interested in any and all suggestions!

[Fishinghat]

The alternator on your engine is designed to bring the battery back up to 80% faster than the generator and converter. That said, the alternator on the engine can overheat if you don't run the engine at 1200 rpm or so. It just wasn't designed to recharge an almost dead battery at low rpm.

The suggestion to use your generator for two hours in the morning and two hours in the evening is a good one. That's what we've done. It won't bring your battery up to a full charge, but good enough. Adding a second battery is also a good suggestion.

[BFL13]

Some 1998 MHs have a PD 9100 converter. If your Class C does, then just get a Charge Wizard for it so you get decent amps while charging on Generator.

Otherwise you need a higher amp portable charger like the VEC1093DBD or a deck mount converter that will do more amps in the 14.4 volt range or better. You can leave the existing 13.6v converter in place either way. Your charging is taking so long now because it only goes to 13.6 instead of 14.4 or higher.

A second battery would be a good idea too.

[youwillforget]

...

[2oldman]

It's difficult for any of us serious boondockers to ever get fully charged batteries. It just takes a long time.

I'm sure there is someone more familiar with truck alternators to answer, but I'd like to know the amperage rating of your convertor.