Can I recharge marine/RV battery w/generator - How?

[VermontMeow]

Hi - I have been using a Respironics RemStar for six months and loving the result, if not the experience. I am going camping in the hinterlands of Maine. I bought a marine/rv battery and will have the Respironics DC adapter and power cord. There will be a generator available a couple of hours each evening. My question: What do I actually do to recharge the marine battery using the generator? Do I need a charger also? Will an auto battery charger work? It is not an option to run the cpap directly from the generator. Someone please explain exactly what I need to do - your know "Battery Charging for Dummies". Thanks for your help! Good sleep on ya!

[Guest]

most generators have a direct 12-volt DC output that charges 8-12AMPS, you would connect your battery to that output.

[BATPOO]

If you can recharge the battery each day you only need to be able to put one day's worth of power into it. (Not obvious to everyone).
Assuming your CPAP draws 1.5 amps for 8 hours every night you will need to pump 12 amp hours (AH) into the battery. Since battery charging is not 100% efficient (if you are checking my math I have assumed 70% charging efficiency) you will need to provide 17 AH over the charging period. If you can charge for 3 hours every night you will need a charger that can provide 17/3 = 5.7 amps (this is a simplistic but conservative calculation).
If the generator has a battery charging output (not just a simple 12v DC output) that provides 6 to 10 amps (many do) you can hook up the battery to this.
If the generator does not have a battery charging output you can connect an automotove battery charger to the generator's 110 v output. A Sears DieHard 10/2/50 amp. Automatic Battery Charger ($39.99) should do the job easily. Your battery should probably have a capacity of 35 AH or more to safely absorb the charge at this rate.

BATPOO

[Vermont Meow]

Hi Bat Poo - THANKS TONS! I'm too ignorant of the whole thing to know for sure, but I think you have told me just what I need to know. I'll check it out at home (working now) and expect I will find everything is fine. Thanks!!

[Grimace]

I'll make the same suggestion I made in another thread a second ago, portable jump starting unit. You can buy the unit for about the same price as a good battery charger, and charge it up by just plugging the included charger into a wall socket or a cigarette lighter plug in a vehicle. You can also use it to start your car if you tend to leave the lights on a lot the way I doe

[Sleepy-in-AL]

Grimace,

I don't think that will work too well for VermontMeow's stated purpose. Most of those units are designed for very slow charging. They want to charge in 3 hours and be able to run for several nights charging each day.