D/A Drivers - Montana Owners Club

Cat320 · 10-09-2006, 07:58 AM

I was reviewing my owners manual today and it states: "If you are charging a remote (non-vehicle) battery, press the tow/haul button located at the end of the shift lever. This will boost the vehicle system voltage and properly charge the battery. If the trailer is too light for the t/h mode, turn on the headlamps as a second way to boost vehicle system voltage and charge the battery."

bsmeaton · 10-09-2006, 08:13 AM

Wow CAT - that must be a GMC exclusive and a nice feature.

There is a problem with keeping charge on the RV batteries from the vehicle. Essentially the TV alternator is regulated by voltage, such that around 14V the amperage output from the alternator is minimized to prevent overcharging. When the Monty is plugged in, this voltage is measure across all three batteries as one. It is common that your TV battery is freshly charged and overcompensates for your RV batteries causing the alternator to stop charging even though your RV batteries are not fully or deeply charged (they obtain a surface charge). My class A had a three battery isolator system that ensured each battery was measured independantly and recieved a full charge. I've often wondered why trailers didn't use something like that, or if it would help to add one. It sounds like your GMC has a feature to overcome that.

bsmeaton · 10-09-2006, 08:17 AM

Actually CAT, your TV probably has 2 batteries, so the total would be 4.

Cat320 · 10-09-2006, 09:50 AM

It does have two batteries, I think all the diesels do.

Native Tex · 10-09-2006, 01:28 PM

Pretty nice feature. It would be nice if all diesels had this feature, especially if you have one of the dual-alternator trucks.

OntMont · 10-09-2006, 02:35 PM

Hey Bert, thanks for reading the manual for me! That is a good item to know about. I guess I really should read mine.

Montana Sky · 10-09-2006, 04:40 PM

Wow! Learn something new everyday. I guess I should read my owners manual as well. LOL! Thanks for the tip Bert.

RKassl · 10-10-2006, 12:48 AM

I have the book out right now, where is this info located about the the T/H mode and battery charging? Does it apply to a 2004?

Thanks

Cat320 · 10-11-2006, 01:48 PM

In my '07 Classic manual it's on page 452, in the section called "Heavy Duty Trailer Wiring Harness." Don't know if it was available in the '04s or not.

sreigle · 10-13-2006, 08:03 AM

That is a nice feature.

Brad, the Fords do have an isolator. Exactly how all this works is beyond my understanding. If I understand this at all, the charging circuit for the trailer battery is isolated from that for the TV batteries so this would not be a problem for the Fords. But, I'm not very well versed in this so maybe I'm wrong.

bsmeaton · 10-13-2006, 08:17 AM

Steve,

You might be right and I just don't know. Perhaps that is why they provide separate circuits in the factory trailer hookups for the charging. It might be more sophisticated than I thought. I do know I have not had problems charging off the new truck, but I have with previous vehicles where once the truck is charged it just stops charging and the RV batteries never get a full - good charge.

If you hear anything more, please drop me a line. I would be real curious to know.

Brad

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