has anybody made up this set up? what do you think about permanatley attaching a cable the same size as the battery cables to the altenator and run a ground? keep them coiled up under the hood and run them out to the camper when the battery dies, run the truck for a bit, should be the same as boosting a vehicle wouldn't it. or is there a better way?

 

Your 7 pin connector should already be set up with 12 volts to the camper to charge the batteries.

Denny

 

Because of the size of wire used to supply the power through the seven way plug,(12 Ga. over at least a 20' run) don't be in a big hurry trying to charge the batteries this way, it will take most of the day. Durtybird has a nice idea, but the tow vehicle system will detect the voltage of the starting battery and cut back the charge long before the alternator charges the coach battery. On an older pickup I had, I put a switch in the circuit between the alternator and starting battery, turn this off when charging coach batteries and the alternator will stay at full charge.

 

If your truck isn't charging the battery make sure the relay was plugged in under the hood to allow this

 

ok mechmagcn, that makes sense. help me understand the battery setup for the diesel. is the main reason for the two batteries because of the extra power needed for starting these high compression engines? the term you used "starting battery", does the starter only pull from one battery or are both available? ie one for starting, one for accessories
i don't have my truck here to look over or it might make a little more sense. i understand what you are saying, just wondering exactly where to put the switch. and how long would you expect to run the truck for with this setup to fully charge the camper batt. thanks.

 

Gasoline engines have a compression ratio of about eight or nine to one (9:1) which results in the cylinders developing pressures of about 90 to 110 lbs per square inch before they start and run.

A diesel engine fires from compression, and the pressures in the cylinders are more like 300 PSI. This is why two batteries - twice as much current (AMPERAGE) is needed to turn a diesel starter motor.

To get that, two batteries are connected in parallel to double the amperes while keeping the voltage the same.
If you have a pair of 700 CCA (cold cranking amperes) batteries connected in parallel you have 1400 CCA, and still only 12 volts for example.

It is still only twelve volts, and if don't have any kind of special power managing module installed (One I can think of is called "Charge Wizard" or something like that) it should only draw on the alternator when the engine is running (important point!) and only a percentage of the alternators current output (it gets divided between the truck and RV).

IF THE RV pulls too much - you can blow an alternator in the blink of an eye, this is why circuit protection is needed to do this.

What you are proposing might get real expensive unless a self-resetting breaker of about 30 amps is in line with it. A regular fuse would just blow and need replacing, self resetters blow, cool off, and then reset all by themselves.

Figure about a buck and a half apiece...

*See the consolidated tips list at the top of the forum for more detail

 

ok, something to chew on.

so for simplicity sake, how about a set-up which has the switch to isolate the tow veh. batt. from the altenator. Using a long set of jumper cables with the 30 amp self-resetting breaker spliced in, one clamp onto the altenator, on clamp grounded and the other ends clamped to their posts on the camper battery. Run truck to recharge camper batt.
Remove cables when done, reset switch to connect truck batt. to altenator....done deal. does this sound like a feasable idea?

 

Isn't the camper set up with a charging circuit already and you could just plug in the cable? If the cable's too short, make an extender cable. You can get replacement pigtails with the 7 prong plug. Make an extension cable from that using one of the plugs that would be installed on the truck to plug in the cable.
Or they may simply sell the whole setup all ready to go.

 

yes, its all rigged up with its own 7-prong cable, but like mentioned above once the battery is drained it takes quite awhile to recharge through that setup.
last weekend it drained after one day and night, i beleive the fan in the forced air furnace used alot of juice.

 

How many batteries does your RV have ? I would look into having atleast 2 that way you can use one as a reserve. Yes the furnace fan draws alot and make sure your fridge is set on propane not 12v .

I can run my set-up all weekend from Friday night till Sunday on the batteries I have . The only thing I run on 12v is the furance besides the lights but they don't stay on that long. I plug it in when we get home and let it charge all week .

 

i have one batt., and the fridge was on propane. not a bad idea having the second battery. i have a week long trip coming up here, so was still wondering if my jumper idea sounded right.

 

It will take a while to recharge a battery and there is no way around that. A typical deep-cycle marine-RV battery is around 100 amp-hours. At a 20 amp average charging rate, thats five hours. Just because your alternator is rated for 100 or so peak amps, does not mean that the battery can absorb that much current. The voltage regulator is just that, it regulates voltage to between 13.5v and 14v, not current. The battery will charge at a tapering rate with constant voltage.

Jim

 

durtyburd,

You need to add more batteries to your trailer, a vehicle alternator was never designed to charge dead batteries and will shorten its life considerably. A vehicle alternator was designed to top off your batteries after starting the vehicle and keep them fully charged, in addition your alternator supplies the vehicles power when the engine is running.

If you need to charge your trailer batteries in camp, get one to the small hand carried Honda generators (ie EU1000 or EU2000), they come with clips designed to hook to your batteries and charge them.

www.hondapowerequipment.com/gensup.asp
http://www.hondapowerequipment.com/A..._Chapter_5.pdf
www.campinglife.com/output.cfm?id=1047547

These can be purchased for under $800/$1100 respectively and will be much more versital and not prematurely wear out your vehicles alternator.

Hope this helps

 

good points, i don't want to screw with my altenator out in the bush. an extra battery will do for now and maybe a generator in the near future. thanks guys.

 

The charge circuit in the truck is to charge the battery only, while in transit. Everything in the trailer should be shut down. If you are drawing on it to run things - I see no way the alternator could produce enough to keep up with it.