More Amps to the Trailer

[DonG]

I just completed a 5500 mile trip with trailer to California, Arizona, and New Mexico and back. The truck pulled very well considering a total combined weight of 21,500 pounds.

The one problem I had was getting sufficient power to the trailer to keep the trailer batteries charged. I run the refrigerator in the trailer from the batteries via an invertor, and on some legs of the trip, the trailer batteries were somewhat depleted.

I think I only need a little bit more juice at the trailer. Unfortunately, GM has installed a 105 amp alternator in the 2003 trucks instead of the 130 amp they first supplied.

1. Would going to the 130 amp alternator solve my needs?
2. Should I replace the GM wiring to the trailer plug with heavier gauge wiring? Or is that a waste of time?
3. Is dual alternators my only hope?

Any suggestions would be very appreciated.

Don

[RATDOC]

Don,
you should have ordered the factory duals like I did........anyhow, I think that the factory
145amp. is a direct bolt-in. I believe that it's the same one they use for the snow-plow package on the other trucks. If not, Summit racing and others carry aftermarket upgrades up to 200amps......
Tom

[breeze hotshot]

Hi Don
I can't help much but could you find out
how many amps. you're refreg. pulls?
My guess is a 130 amp alt. would do
the job but bigger wire never hurts.
You could go with 10ga. Direct from
acc. box under hood and 10ga.run in
trailer to battires.

[DonG]

RATDOC,
I never thought I would need the dual amps so I did not order them. I think upgrading to the 130 amp system should help a lot, but I am not sure if I need to tell the computer in the truck that I changed alternators.

breeze,
The refrigerator pulls about 32 amps when it runs, but it does not run all the time. It depends a lot on the outside temperature. I figure GM only put in the minimum size wire to feed the trailer, but I was not sure sure I would get enough by upsizing the wiring.

Don

[SoCalDMAX]

Don,

I can't imagine that the alternator couldn't supply power to keep it all going. What V were you seeing on the dash? If it was in the 13.8V -14V range, then there might be a connection issue.

If you end up changing alternators, go with the dual 100amp setup. Mdrag posted an interesting link showing that high cap. alts. actually produced less power at lower rpms and produced their stated power at high rpm. Conversely, the 100 amp alts. produce a great deal of their power at lower rpm, thus 2 of them could produce a lot of power at cruising speeds. Not to mention they cost less and you're not removing a good alt.

Do a search, Mdrag did the conversion to dual alts and there should be a complete parts list posted somewhere.

Regards, Steve

[SoCalDMAX]

Holy cow!

Just read your post, 32A!! Thats a lotta juice!

I'd add an extra wire in parallel with the existing wire to provide power and upgrade to the dual alts.

Good luck, Steve

[RATDOC]

Don,
while I couldn't justiy the NEED for duals, at only around $175.00(IIRC) for the option, I couldn't think of a reason not to.
Tom
P/S- as previously stated, duals provide a much better low rpm charge than a single H/O.

[rtquig]

Just a thought, why don't you run your fridge on propane? With my fifth wheel, I'll travel for 2 days, 8 hours each day and hardly burn any on the trips. That includes staying overnight at truck stops.

[DonG]

SoCalDMAX,
I know 32amps is a lot at one time, but the trailer batteries provide that just fine. Then when the refrig. shuts off the batteries can be recharged (in theory). Usually the refrig runs less than 1/3 of the time.

rtquig,
I think running with propane is too dangerous. If I pull into a fuel station, that refrig. burner may be all that is needed to send me too never never land. Also an accident could rupture propane lines and a bad situation could be a whole lot worse.

Thanks for all the suggestions. I will look into a dual amp setup. I read mdrag's post about dual amps a while ago but I believe he wanted ac power in his truck so I did not pay too much attention.

Don

[a5150nut]

Don,
If you run a new line to the back, use light welding leed. Finer straned wire carries more amperage with less line loss.

[BigLakeDMAX]

I just bought all the stuff I need to upgrade to dual alts for my '02. I got a new take-off alternator from truck and rv supply on ebay - they have several available for $89. It's a 130 amp Delphi. All other parts I ordered through www.gmpartsdirect.com for about $130. Should install it this weekend. Should have lotsa power then. I, too, will be running a heavier lead back to the 5'er.

Here's the link to a thread by Joe Pool that I used for my '02.

http://forum.62-65-dieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=003544&p=

Don

[Flyboy]

I just finished installing a second alternator on my truck. It is a single wire, and I wired it directly to the trailer plug. I removed the fuse and the factory wire from the receptical and replaced the wire with 6 gauge (probably overkill). Any trailers that I pull are completely isolated from the truck electrical system. The alternator does not put out any current unless a trailer is hooked up. So far, It has worked great. I will know more next week when I tow my camper to Daytona. I also made a cable to plug in with clamps to charge a battery.

[Seattle Steve]

Dan- If the truck was supplying power to your trailer and that battery was drained, your truck's batteries should have been low also... unless they weren't feeding power to the trailer. This makes me wonder if you have added the fuse in the underhood fusebox that sends aux power to the trailer. Perhaps no power from the truck is why your trailer battery was dead. There are some posts on wiring brake controllers that tell all about this missing fuse on the '03's if you need it. Good luck.

[a64pilot]

Bingo on what seattle said. If your wiring to the trailer was sufficent and your alternator was at fault then all three batteries would be low.
If you have the fuse installed measure the trailer batt voltage with all accesories running. Idle the truck up to 1800 rpm or so. If the truck batteries measure more than 13.8 V and the trailer less than 13.8 your wiring is inadequate. If all three batts measure less than 13.8 then your charging system is not up to the task.
P.S. don't forget you have to have a very good ground too. If you have to increase the size of the positive cable to the trailer, ensure you have the same gauge wire as ground too.

[mdrag]

To clarify SoCalDmax, the OEM 100W alt is rated @ 60A at idle. The 200A Powermaster that I have is rated 120A @ idle.

Here are measurements that I posted in a previous thread trying to confirm that both alts in a dual alt set-up are on-line all the time:

I took DC amp measurements of my '01 Dmax dual alts using a Fluke 337 digital clamp meter. All of the readings were taken after the truck had been running long enough to stabilize the battery voltage (14.4V), and temps up to normal operating range.

At ~625 RPM idle with all accessories turned off (interior dome light off, the under hood light was on for part of the time):

Primary alt Powermaster 200A: 23A max (range 18A to 23A) eventually decreasing to 2A*
AUX alt OEM Delphi 100A: 14A max (range 10A to 14A) eventually
decreasing to 7A* - I double/triple checked this reading

Then I turned on everything I could find (without restarting the truck) - 4 lamp high beams with 70W low/100W high (Kennedy Diesel heavy duty HL harness), PIAA 80 Pro XT driving lights (120W ea), A/C, seat heaters on HI, rear window defroster (and outside heated mirrors), OEM radio, scanner, power inverter, dome lights, running board lights, bed lights - and again measured at idle:

Primary alt Powermaster 200A: 75A max (range 66A to 75A)
AUX alt OEM Delphi 100A: 43A max (range 29A to 43A)

I then shut off all the accessories and after a few minutes took one more set of readings - this is where the 2A*/7A* numbers came from.

When I first started the truck, I obtained a max output measurement of 60.3A for the AUX alt (right on the mark according to the Helm's manual for the OEM 100A Delphi at idle). I did not get a measurement of the Primary alt (Powermaster 200A) at cold start up and will do that the next time I think about it, to see how it compares. This would be the time when the dash voltmeter is reading low from the draw of the starter, glow plugs, and intake heater.

Ronclyde got it right - both alts are on line all the time. :D


I've still not measured the Powrmaster's output immediately after start-up...

[FisHn2DMax]

Don G,

If your 110 Volt inverter is drawing 32A on the 12 Volt wiring, your trucks wiring needs to be beefed up to a minimum of 6 guage copper stranded wire. I've seen that small stuff that in the OEM harness. While it's rated for 40 amps, your really pushing it an probably heating up the existing 12 volt trailer battery wire! If your power inverter is pulling 32 amps then your trailer batt's are also drawing down, your peak load could easily be exceeding the max for the approx 10-12 guage wire in your OEM truck trailer harness, thus causing an (I*R) or voltage drop across the lenght of your trucks OEM harness. Beef up your 12 volt wiring!!!! A new or secondary alternator will not help a (I*R) voltage drop across you existing truck wiring. Once you've beefed up the wiring, (and as posted above) you note the trucks Alt can't maintain 13.7 volts measured at truck battery, then you'll also need to upgrade to higher output alternator.

Good Luck! ;)

[DonG]

I have installed the 40 amp fuse and I know the trailer batteries are being charged properly. I have also installed an isolating solenoid to insure my truck batteries are never depleted.

The last time I checked, the trailer batteries were down to 12.2 volts while the truck batteries appeared to be fully charged. My dash meter was indicating above the 14 volt mark slightly. It is usually right on the 14 volt mark when no trailer is hooked up.

I am thinking that this indicates the wiring is inadequate to carry the needed charge rate to the trailer.

Thanks for all the suggestions.
I think SoCalDMAX's suggestion of running a parallel line to my trailer plug is the best first step. If that is not enough, then dual alternators will be next.

FisHn2DMax, The inverter is pulling 32 amps from the trailer batteries with internal trailer wiring, not from the truck. I just need to replace those amps when the refrigerator shuts off. Fortunately, the refrig. runs less than 1/3 of the time.

Don

[Bruce T]

I'd first check if there is a fuse for the trailer accessory wire in the fuse box under the hood, and you're getting voltage at the plug. I had a similar problem last year with my 2002 D/A CC LB and our fifth wheel trailer. GM never put that fuse in the fuse box.


(P.S. I've been lurking for a year, figured it was about time to post. 16,000 miles so far, had the injector pump replaced at 5,000 to correct idle surge.)

Bruce

[BobW]

Check the voltage at the trailer plug to see what kind of voltage drop you are getting in the stock wiring. I'd guess you need to go to heavier guage wire with either your one alternator or an upgrade.

Check out the following website for some info on 12 V wiring.

http://bart.ccis.com/home/mnemeth/12volt/12volta.htm

There is a table there that gives wire guage for various current and length combos. For example for
20-35 A

16-22 ft use 6 guage
22-28 ft use 4 guage

[a64pilot]

Not trying to beat it to death, but make sure you upgrade your ground as well, grounding through the hitch is not enough IMHO.

[Lone Eagle]

I was sure we had an automotive electrician or two hanging around this sight that would mention resistance. Some that said to go with bigger wire were right on the money. The problem is I don't think you can put a big enough wire in to handle that kind of load. The power is going to take the path of least resistance and that is to the batteries under the hood. I haven't been following the dual alternator setup but if one is dedicated to the trailer that will solve the problem. Just MHO. later! Lone eagle