High Output alternators?

joe&julie81 wrote:
I'm thinking about getting a 2 or 3k amp power inverter to hook to my truck batteries and running a heavy ext cord to the shore power of the camper, in lieu of a generator. This would replenish my camper batteries after sitting awhile running fans, furnace, lights, etc. I could crank the truck for 20 or 30 min occasionally with a high put alternator to replenish the truck batteries. Anything wrong with this thinking?

A couple things to consider; a) Powering a 2-3K watt inverter from your truck batteries is wishful thinking unless you've done some serious upgrading to your batteries. b) There are a lot of losses going from 12Vdc to 115Vac, then back to 12Vdc again... and then unless you have a high current converter or charger in your camper you won't be able to do much charging in 20-30 minutes. c) You stand a very good chance of discharging the truck batteries to the point at which you can't start the truck.
You may be better served by a small generator or a solar charging system.

HMS Beagle wrote:
You also have a large battery bank of AGMs, which will absorb much more charge, for longer, than the typical one or two flooded cells, and added the cabling to feed them. If you are going to do this it should be part of a complete system....

This is a good point HMS. Although the OP's question was about alternator swapping, when considering any electrical system upgrade it is important to look at the system holistically. Otherwise, any one weak-link will severely limit charge current.

theoldwizard1 wrote:
Did you have to do anything to your charging system to get it to deliver that kind of voltage ?

3rd gen' Ram trucks regulate the alternator output to 14.6V (temperature dependent), so I did not need to make any changes. There are aftermarket regulators available, but since most alternators are PCM/ECM regulated, changing the voltage not as simple as it used to be.

Cheers
-Mark

joe&julie81 wrote:
I didn't realize I already had a 135 amp alternator. I'm thinking about getting a 2 or 3k amp power inverter to hook to my truck batteries and running a heavy ext cord to the shore power of the camper, in lieu of a generator. This would replenish my camper batteries after sitting awhile running fans, furnace, lights, etc. I could crank the truck for 20 or 30 min occasionally with a high put alternator to replenish the truck batteries. Anything wrong with this thinking?

Trouble is where to put the inverter that does not like heat or moisture or to be too far from the power source.

I would try to go a little smaller to power maybe PD9130 or PD9140 converter with a 1000 watt inverter.

If you get any sunshine consider 200 watts of solar. This works driving or parked as long as the sky is clear.

Yeah I would use 2gauge from the truck battery to the external inverter and then a heavy ext cord from that inverter to the shore power. I figure that will at least transfer some of the full charge of the truck batteries to the charger of the camper batteries. Is there some kind of terminal adapter I can put on my truck batteries to accommodate the additional cables?

msiminoff wrote:
Of course in order to charge at this rate I also had to install a dedicated pair of 2ga cables from the truck (passenger side) battery all the way to the camper's batteries, and put a lift-gate connector in the wall of my truck bed.

THAT IS HOW IT IS DONE !

Did you have to do anything to your charging system to get it to deliver that kind of voltage ?

joe&julie81 wrote:
I didn't realize I already had a 135 amp alternator. I'm thinking about getting a 2 or 3k amp power inverter to hook to my truck batteries and running a heavy ext cord to the shore power of the camper, in lieu of a generator. This would replenish my camper batteries after sitting awhile running fans, furnace, lights, etc. I could crank the truck for 20 or 30 min occasionally with a high put alternator to replenish the truck batteries. Anything wrong with this thinking?

For that size of an inverter, you need 6 gauge or less (fatter) wire and keep it as short as possible. Most alternators will not put out their full power until about 2000 RPM.

I recommend a good quality 2,000W SINE WAVE inverter. Your microwave will work better. Also, install a hard start setup on your A/C. If the A/C is on, forget about the microwave, coffe pot and hair dryer.

joe&julie81 wrote:
Is it still accepted that 2, 4, or 6, 6v battery are better than the same number of 12 v, even if series 31?

The most important thing about batteries for your trailer is that they are TRUE deep discharge batteries. Not car batteries or marine dual purpose.

The easiest/cheapest way to get deep discharge batteries is buy golf cart batteries. Very reasonably priced at Costco or Sams Club.

A quick and reasonably accurate way of comparing 6V vs 12V batteries (assuming they are deep discharge) is by total weight. The more weight the better.


BTW, the proper terminology is "Group 31" not "series 31".

GordonThree wrote:
Sometimes I'm tempted to beef-up the charge line running to my trailer, but that's next to pointless because of the computer controlled regulator.

Upgrading the charge line (to say 10 or 8 gauge) would help SOME, but not a lot !

As you stated, any US vehicle built after about 2000 has a "smart" charging system that will cut back the charging voltage to 13.6-13.8. By the time that gets to your trailer batteries it will keep them from discharging further, assuming there are NO LOADS in the trailer.

The bottom line Joe is, it is not the amps at the alternator it is the volts AT the trailer battery.

One thing to remember is any alternator is a parasitic load on the engine and impacts fuel mileage..adversely.

I may briefly run a small microwave or even a small a/c for short spurts. Is it still accepted that 2, 4, or 6, 6v battery are better than the same number of 12 v, even if series 31?

joe&julie81 wrote:
I didn't realize I already had a 135 amp alternator. I'm thinking about getting a 2 or 3k amp power inverter to hook to my truck batteries and running a heavy ext cord to the shore power of the camper, in lieu of a generator. This would replenish my camper batteries after sitting awhile running fans, furnace, lights, etc. I could crank the truck for 20 or 30 min occasionally with a high put alternator to replenish the truck batteries. Anything wrong with this thinking?

I had 40 amp alternator on my boat and was powering 1500W oven from 1200W inverter with small, single battery.
The inverter would overheat after about 12 minutes, but that was all I needed most of the time.
Point is that on boat we did not have 100F heat, but too often we tend to overkill the design.