New TV chevy 2500HD with aux battery

[dnd]

Hello I bought a 16 chevy 2500 with plow prep pkg that came with aux battery. My sales person was unable to answer my questions. My understanding from some web reading is that both batteries are charging when running. With ignition off only the aux battery power is used so not to kill the starting battery. So is 7 pin hitch plug being powerd by the Aux battery and if so could you dry camp off of the 7 pin hitch plug then drive vehicle to recharge or is 7pin being powered from main batt while driving and powerd by Aux batt when shut off. Anyone have any experience with similar truck

[Grumpy]

Look under the hood, does the positive run from battey to battery? If it does then they both power the 7 pin.

[dnd]

looks like positive cables from batteries connect to a relay block

[Camping Couple]

Originally Posted by dnd

Hello I bought a 16 chevy 2500 with plow prep pkg that came with aux battery. My sales person was unable to answer my questions. My understanding from some web reading is that both batteries are charging when running. With ignition off only the aux battery power is used so not to kill the starting battery. So is 7 pin hitch plug being powerd by the Aux battery and if so could you dry camp off of the 7 pin hitch plug then drive vehicle to recharge or is 7pin being powered from main batt while driving and powerd by Aux batt when shut off. Anyone have any experience with similar truck

When I purchased my 2013 2500, I didn't have 12volts at the 7pin connection. The dealer has to connect a wire and install a fuse. Make sure that got done. Mine also had the snow plow prep as well. Congrats on the new TV.

[dnd]

Originally Posted by Camping Couple

When I purchased my 2013 2500, I didn't have 12volts at the 7pin connection. The dealer has to connect a wire and install a fuse. Make sure that got done. Mine also had the snow plow prep as well. Congrats on the new TV.

Thanks ill have to check that with a meter

[Grumpy]

Originally Posted by Camping Couple

When I purchased my 2013 2500, I didn't have 12volts at the 7pin connection.

Both my 2011 1500 and now our 2015 2500 HD DURAMAX came with that pin hot with the key off. They did however have the towing package

[SouthCo]

All Duramaxs come with two batteries. They are wired in parallel. Both batteries are charged and discharged at the same time. They function together and not like separate aux and starter batteries. So if you run accessories with the engine off, you'll eventually drain both batteries and will not be able to start the engine.

[TCNashville]

All Ford, Chevy, Dodge HD diesel trucks come with 2 batteries. One of the main reasons for this is to assist cold weather starting because diesels usually have over 3 gallons of oil in the crankcase and glow plugs need to be heated. That takes a lot of CCA's. [cold cranking amps] The other main reason is the compression ratio of a diesel engine is around 17/1 where a gas engine is around 9/1. Sounds like your salesman needs to educate himself.

[dnd]

Truck is a Gas 6.0 Plow prep pkg & integrated brake controller, 2 1/2" receiver

I do have 12.86 VDC at the 7 pin connector with the truck off and 14.86 with truck running so there is power at all the times and it is charging. Trailer brake pin is 0vdc with truck off .95 VDC with truck running so I assume the brake controller is searching to see if a trailer is connected

[dnd]

Both positive battery cables are connected to a Gm part 12135194 aux batt relay/ isolator. I need to find the function of this part

[bigmeaux12]

My 2015 DURAMAX does not have power to the 7 pin and have been unsuccessful at finding how to connect it on my own.

TV- 2015 CHEVY 2500 DURAMAX
TT- 2015 JAYCO EAGLE 314BHDS

[dnd]

found this online gm trucks.com


Not such an odd ball option.
This battery is isolated. That means it is only connected to the main battery when the truck is on. This allows it to charge but not to drain the main battery. It is very usefull if you have a high power sound system and listen without the truck running. It is usefull if you run an inverter for your laptop or power tools. It is used most with trailers. If you have a camper you can run your lights, refridge, etc. and still start the truck in the morning. If you have a trailer package it is wired to the 7 pin connector already.
I have a 2800 watt inverter hooked to mine with 110v outlets at the rear of the bed. I can operate my miter box and planer and still start the truck at the end of the work day.

[SouthCo]

I did some looking as well dnd. I've never heard of the battery isolator. Turns out it is only on the gas models. I'm familiar with the diesels and wrongly assumed that's what you had. Here's a post I copied from another forum. I don't know if the RPO codes are still accurate as they were discussing a 2011 in the other forum thread...

"TP2 is the RPO for dual batteries in the diesel. These are just hooked together all the time for increase starting power.

8BO is the RPO for dual batteries in most gassers. It is an isolated option for trailer usage and power usage when vehicle is not running.

Either option is available for gassers."

Sounds like on your isolated gasser, when the key is on both batteries are used and charged. When the key is off only the aux battery is used. I learned something new as I don't follow the HD gassers. Good luck with the new truck!

[dnd]

Thanks SouthCo the artcle I read was also 2011-2012 I assume they haven't changed. I think the only way to tell would be to put a 12vdc load on the 7 pin overnight @ HOME and measure the batteries with meter in the morning to confirm

[TCNashville]

Originally Posted by SouthCo

I'm familiar with the diesels and wrongly assumed that's what you had. I learned something new as I don't follow the HD gassers. Good luck with the new truck!

X2, just assumed he had a diesel.

[SouthCo]

Originally Posted by dnd

Thanks SouthCo the artcle I read was also 2011-2012 I assume they haven't changed. I think the only way to tell would be to put a 12vdc load on the 7 pin overnight @ HOME and measure the batteries with meter in the morning to confirm

No problem, and I'm sure it hasn't changed since 2011. Testing it out at home is smart. Another thing I'd want to know is at a certain voltage is the power from the aux battery cut? Running down a regular starting type battery too far isn't good long term as opposed to a deep cycle battery. And you shouldn't have two different types of batteries charging on the same charging circuit, I think lol... again congrats on the truck and pls post up what you find. There isn't much info on your setup so it'll help others for sure.

[Wireman]

Very similar to class A RV's with the house batteries isolated from the chassis battery when shut off.

Both are charged by the engine alternator when running. House batteries are used for RV 12 volt stuff with the engine off and isolated therefore not discharging the cahassis battery.

[dnd]

found another article on silveradosierra.com aux battery 2013


"The neat thing about this isolator is it is not a diode type so charge voltage isn't dropped by .7v on the batteries. It is a relay type with sensing circuit. The isolator monitors the voltage of the main battery, when the voltage reaches 13.8v it kicks in and begins to charge the Aux battery while maintaining the starting battery. Once the voltage drops to 12.8v ( which happens pretty quickly due to headlights and cabin lights staying on for a minute after the engine is shut down, the float voltage is bled off pretty quick) the isolator disengages. The benefit to this is it prevents the alternator from potentially charging 2 low batteries at the same time and over working itself. The starting battery has to reach full charge with a 13.8v float before the Aux battery will begin to charge."