2010 Yukon XL 2500 - Want to add 2nd battery and a hi-amp alternator

[calsdad]

Looking for some advice and or experience with doing an install like this.

I have a 2010 Yukon XL 2500 (6.0L gas 4WD) - and I would like to add a second battery and a high amp alternator.

I've been doing my research , and I think I've got most of the details down , but I've run into a few sticking points.

Basic system layout:

Odyssey deep cycle installed on the already-existing battery tray in the driver side front corner.

I would like to keep the 2nd battery isolated in some fashion so that I'm not drawing down the start battery.

I intend on adding a 12v to 120v inverter along with some extra lighting - these would be one of the main reasons to add the 2nd battery.

I've got a number of options for adding a high amp alternator, including buying one from a place like Mechman - or going with a factor 220amp from a later year GM truck

The alternator seems to be one of the sticking points. I haven't been able to determine yet whether my truck has a "smart" alternator. I've talked with Mechman - and when I laid
out my plans - they highly recommended against using a high amp alternator with a 2nd battery system that is isolated . The response I got from them said:

I would never run an isolator with an RVC controlled system. Parallel the batteries charge and ground. And then install the alternator according to the instructions we send. Your truck being a 2500 might not have an RVC sensor on the stock negative ground wire but if it does look at the type two instructions in the attached document.

Back to the isolator, there is no good that can come from it with a high output alternator. First most of them have significant resistance through the isolator which results in a high voltage drop and that is even worse with a potent alternator. If the point of the isolator is to allow you let one battery or batteries heavily deplete while making sure the other can start the vehicle then a high output alternator would be the last thing you want as it will put power back in way to fast and smoke a battery or if the bank is big enough even its own rectifier.

Now I do not believe my truck has an RVC "smart" alternator - I haven't found the negative ground sensor - and I've run the test to see if it exhibits the behavior of a RVC system - but Mechman's assertion using a high amp alternator with an isolator is a really bad idea - is something I've only heard from them. So that is one of my sticking points. Because I'd like to be able to run an inverter from the 2nd battery - I think I'd like to be able to have full alternator charge going to that battery. My other option is a DC to DC type charger like ones sold be RedArc to keep the secondary battery charged. I believe this would avoid the issue of the alternator having an issue if the secondary battery was really depleted.

But putting that secondary battery on a DC to DC charger - would restrict the potential charge going to that battery to the rating of the charger. Which might cause restrict my ability to run an inverter from it.

 

[rayra]

Back to the isolator, there is no good that can come from it with a high output alternator. First most of them have significant resistance through the isolator which results in a high voltage drop and that is even worse with a potent alternator. If the point of the isolator is to allow you let one battery or batteries heavily deplete while making sure the other can start the vehicle then a high output alternator would be the last thing you want as it will put power back in way to fast and smoke a battery or if the bank is big enough even its own rectifier.

They're full of excrement. I* and several other GMT800 owners are running all sorts of isolators, from the simplest key-on solenoids to high dollar isolators / combiners from Blue Sea and other companies. Get ye to the 12v / solar subforum and the '$50 dual battery' topic, which is chock full of all sorts of solutions, proven by many members in the real world.


But may I ask what sort of demand / draw you are anticipating, that makes you believe you'll need such a high output alternator? Many (most?) folks are running dual battery setups with their stock alternators and it's working well enough.

Know too that factory alternators aren't generally generating their max rated output at idle RPMs. Nor are they cranking out high amps unless your battery(ies) are low. It's more of a 'potential'.

Maybe see if you can get this topic moved to the 12v forum, there's a much higher potential state of wonkishness there about power issues.


* I'm running a deliberately simple 200A solenoid that combines my batteries when the key is on. Using standard group 74(?) batteries in the factory under-hood trays. I further added a pair of 1/0 cables to the rear cargo area, where I have a 'power module' setup with all sorts of converters / charging ports, rooftop solar connection, and a 1,000W inverter. I've also added some LED light strings and a lot of additional USB charging ports, etc etc. Seemingly everything you want to do and then some. Some info and related topics in my build topic in my sig.

 

[rayra]

well 'inefficient' maybe in a permanent living or motorhome scenario, but dual batts, high amp alt, roof solar, occasional glamping use, who cares / worries about 'efficiency' in the conversion? Too, you beat most of that by right-sizing your inverter(s) to better match the demand. I used the hard-wired 1000W for running corded power tools. I keep a cig-lighter / PowerPort plug-in 300W inverter for stuff like charging laptops, electric razor etc. Hmm, I wonder it it would work with my blender?

 

[RedF]

So why not try it with the stock alternator, and see how it works?

 

[DiploStrat]

Another vote for the 12v Forum. These horses have been beaten to death many times.

FWIW:

-- The post from Mechman is bizarre, but it appears to assume a diode based isolator and is correct in dismissing these as terrible bits of kit.

-- Many (most?) GM trucks of the vintage of your 2010 have very sophisticated charging systems designed to keep lead calcium batteries happy. They are prime candidates for use with a simply relay or intelligent relay. As long as your cabling is sized correctly for load and distance, you should get great performance with a second lead acid battery. You should not need a battery to battery charger.

-- Assuming a single second battery, mounted under the hood, any factory alternator of greater than about 100A rating should be more than you can use.

Again, peruse the 12v forum and start with the $50 thread. It covers the basics. This stuff has been argued to death.