Propane question

[herk7769]

Originally Posted by Taranwanderer

Couple points here: it would not be running "all night," just a few minutes before everyone turns in. Also, were not in a real campground, it's a dirt parking lot with a wooded edge at an off-road park. It gets pretty rowdy at times and a Cummins at idle will be one of the least noisy things going on! But I get your point, I may just plug into the truck and draw from all 3 batteries, and if they're dead in the AM, have one of my jeeping buddies give me a jump start.

Due to the way your converter charges your battery, you will not replace many amps by running your vehicles alternator "for a few minutes" (or even a few hours). The converter cuts back on amps as your battery fills.

Also there are "drain preventers" that prevent your truck batteries from discharging into your camper (or any other load) without the engine running.

Most trucks' Vcc line to the trailer plug are fused through the ignition circuit so the line is dead without the truck running (or at least the key in the ignition and switched to "on")


Now, to solve your problem. Buy a SMALL generator; say 1000 watts from a discount house (like Sportsman's Guide or Northern Tools) for a hundred bucks or so.

Plug in a battery charger to the generator.

Remove the positive terminal wire and all the vent caps from the camper's battery. (WEAR OLD CLOTHES and safety glasses. You will get splashed)

Connect the charger to your camper's battery (watch polarity)

LEAVE THE HATCH OPEN - using a car charger will cause huge amounts of Hydrogen to be released.

WEAR EAR PLUGS and run the generator till the battery says "full" (about 2 hours if dead or very low)

ADD DISTILLED water to replace electrolyte you boiled out with the car charger. (This is not a worry with the camper's multi-stage converter as it is designed to only pump in the amps the battery can take for the level of charge. That is why it takes forever to charge with the converter)

[Taranwanderer]

Herk, thanks for the ideas. I think if I'm going to do a generator, I'm just going to have to bite the bullet and do a Honda or Yamaha.

A few other points: The converter should be a non-factor here, because it won't be plugged in--are you saying that the converter has the ability to limit charge applied to the battery from an external source (like a running alternator or a small smart charger/maintainer) even when it's not plugged in? There will also be no load limiter, as I did the large gauge cables from one of my truck batteries back to the bumper and then the same type of pigtail (plow-type) to plug the TT battery right into the TV battery (ie, not using the 7-pin.) The alternator's voltage regulator should prevent overcharging. And since it's plugged directly to the TV's 2 batteries, I should have a good amount of battery time/amp hours before all 3 run down. And even if they do, I can get someone to jump start my TV in the morning. Of course, a small genney (2000 to 2400W) would eliminate all this fuss. But I spent enough money today already.

[herk7769]

Originally Posted by Taranwanderer

A few other points: The converter should be a non-factor here, because it won't be plugged in--are you saying that the converter has the ability to limit charge applied to the battery from an external source (like a running alternator or a small smart charger/maintainer) even when it's not plugged in?

<sigh> Tired is my excuse. If you are charging from the truck's alternator you are absolutely correct. The converter is a non issue. So many variables to this issue they sometimes run together in my head.

Your limitation in the alternator case is the alternator/starting battery system. It is designed to recharge a "starting type battery" and not a deep cycle one.

The starting type of battery has thin plates designed to release their stored up energy rapidly and take a recharge quickly.

Deep cycle batteries on the other hand have thick plates designed to release its charge slowly over time and it takes a nearly correspondingly long time to replace that charge. See the attached info on battery types.

Originally Posted by Taranwanderer

And since it's plugged directly to the TV's 2 batteries, I should have a good amount of battery time/amp hours before all 3 run down. And even if they do, I can get someone to jump start my TV in the morning. Of course, a small genney (2000 to 2400W) would eliminate all this fuss. But I spent enough money today already.

I am not sure how you wired all this. My GMC Duramax has two batteries in the TV as well. There is a fairly complex battery isolator/charging system that separates the two batteries so you should never need to worry about running your primary battery dead.

If I read what you are saying correctly, what you will need to worry about is battery service life. Paralleling a starting battery and a deep cycle battery will cause "working - loafing" issues where one battery (the stronger one) does all the work.

I am explaining this badly and I apologize. I will attach some reading on deep cycle batteries and some graphics on how to parallel them.

[Taranwanderer]

Lou, thanks again for the ideas. I guess ideally what I should do (if I don't permanently mount a second, identical deep cycle battery in the TT) is to get an identical one, keep it charged up in the garage, then throw it in the back of the truck and plug it in (parallel) when the primary TT battery runs down. In a case like that, the "loafing" battery would be the one that's discharged (the primary TT battery,) so that would pull charge from the "working" one. Does that sound right? And if so, wouldn't the same be true by plugging the primary TT battery into parallel with the TV batteries, even though they're different types?
Hell, I should just buy the genny...

[herk7769]

Originally Posted by Taranwanderer

Lou, thanks again for the ideas. I guess ideally what I should do (if I don't permanently mount a second, identical deep cycle battery in the TT) is to get an identical one, keep it charged up in the garage, then throw it in the back of the truck and plug it in (parallel) when the primary TT battery runs down. In a case like that, the "loafing" battery would be the one that's discharged (the primary TT battery,) so that would pull charge from the "working" one. Does that sound right? And if so, wouldn't the same be true by plugging the primary TT battery into parallel with the TV batteries, even though they're different types?
Hell, I should just buy the genny...

Well, there are folks here who do the "carry a spare" technique. They don't use the long jumper cable routine that I am aware of, though. They just swap em out when the first one dies. IMO, jumpering the two after the first one is dead will discharge your second into the first and both will be below any useful capacity.

The graph I posted earlier on capacity remaining vs. discharge voltage will show why that is the case.

When parralleling, both batteries need to start at the same level of charge. To ensure this, they need to be not only identical in type; but identical in AGE (number of cycles on the plates).

Most people you will poll, will tell you that what you are trying to accomplish (longer dry camping times on battery) is best handled by two or four brand new identical deep cell batteries wired in "cells" of identical internal (and external - meaning equal length battery cables) resistance and recharged at 50% remaining capacity.

Parallel or Serial for your Battery Bank? has a long discussion on this topic.