I am thinking of adding a second battery on my new truck. It is a gasser and has the space for a second battery. I am thinking about wiring the second battery to be hot all the time to the truck camper. I plan to put a isolator between the truck battery and this second battery. So the second battery will be a camper battery only. Now somewhere I read where someone said he had seen a lot of wiring burned up on vehicles because people put in batteries that are to high in cranking amps. I didn't even realize that was possible. Is it? Because when the isolater is powered and three batteries are all running in parallel isn't that going to be like a ton of cranking amps. So can somebody explain if this is a concern or not. and a second question is...I have a 150 amp alternator in my truck. When the two batteries for the camper run down to lets say 50 percent and the truck battery is 100 percent I start the truck. If I turn on the tow haul it makes the alternator put out more power. How does this all play out considering the full truck battery and the 2 half depleted camper batteries. This is on 2017 silverado.Now this is how I have always done it in the past and haven't noticed any problems but what really happens in situation like this. We only camp occasionally so this is nothing like a full time situation but I am curious. Thank you!

People also burn 5 kw transformers and the truth is that you can make horror story to every subject. As long as you do it right way, you will be safe. I do have mechanical degrees, so don't take me as expert, but that is what I learned mostly the hard way. -use battery combiner, or ignition-activated relay connection from alternator- put fuse or circuit breaker adequate to the cable you will be using -I understand this is going to be 2nd battery parallel with the one in the camper, so you might not need heavy cables, but nothing wrong with over-sizing.

I would just tap into the trailer charging line add a fuse and call it good.If Chevy charge line is not isolated I would add a relay so you can deplete the added battery independent of the start battery.No, you will not melt any wire from too many cranking amps available.The existing wire size and length will typically limit the voltage/amps that go into the house batteries. Worst case you need to replace a fuse.

dave17352 wrote:Now somewhere I read where someone said he had seen a lot of wiring burned up on vehicles because people put in batteries that are too high in cranking amps. Whomever said that was smoking some pretty good ganjaStuff doesn't burn up because a battery is too big.

My 2015 GMC 3500 HD has an auxiliary battery from the factory with a isolator from the starting battery. Stop over to your Chevrolet dealers parts department and see if they will print off the parts and wiring pictures so you can see how the factory did it.

Kayteg1 wrote:-I understand this is going to be 2nd battery parallel with the one in the camper, Maybe not.There may be only ONE battery now for everything.Anyway, if there ARE two individual batteries now, most people boost their house capacity by adding a battery in the house section, NOT under the hood of the truck.And that initial story about burning something up with a battery that is too high a capacity......is total bunk.

Adding another battery under the hood question | Good Sam Community

SidecarFlip
Explorer III
Apr 30, 2017
When installing a second batter under hood, Dell City Electronics is your friendly on line store for pre-made cables.
dave17352
Explorer
Apr 30, 2017
Grit Dog my manual on my truck says to turn on tow haul or the head lights to increase the output of the alternator. So in this case it does have something to do with it. I was surprised at this also. I have used a battery isolator many times with TC campers. I guess I didn't make what I was asking clear. Basically the two questions were with the two house batteries being separated by such a distance (the existing and the new aux battery would the charging work out ok?) The second question was about the wacky idea that too many cranking amps will cause melted wiring. The two many cranking amps didn't make sense to me but I wanted to be sure.

Not sure which way I will go yet, adding a battery right next to the existing house battery or putting one under the hood. Making some mods lately and have decisions to make.
This years mods include
solar
12 volt fridge
different truck
Its been busy time but fun time in the shop.

Thanks for opinions!
brholt
Explorer II
Apr 30, 2017
Here is a kit to add one for a Ford. There might be a similar kit for Chevy's

Gas Suoer Duty Second battery kit
Kayteg1
Explorer II
Apr 29, 2017
RoyB wrote:
In my world of OFF-ROAD CAMPING I would not want to do anything to interfere with the normal operation of my truck start system. It is designed for what you normally will use in your OEM setup... This is my only way to get back home on haha...

On the other hand almost all emergency vehicles do have dual battery banks for lights operation and they operate with no issues for generations.
Just for extra capacity, to boost camper battery I would be tempted to use plug charging wire, but on the other hand, those connectors do bring some maintenance problems, beside bad ground wire being pretty common issue. On my 2007 F350 the ground wire was having hefty size and had big bolt grounding it 4 feet away from the plug to the frame.
I tracked the bad ground to connection between the eye on the end of the cable and frame. That on truck who being CA all the years had no corrosion.
RoyB
Explorer II
Apr 29, 2017
In my world of OFF-ROAD CAMPING I would not want to do anything to interfere with the normal operation of my truck start system. It is designed for what you normally will use in your OEM setup... This is my only way to get back home on haha...

Adding things to the Truck Start systems might be too much load for your truck alternator, might run down your truck start battery along with the extra battery you have installed, might blow some fuses for the added DC current required for two batteries when being charged...

These are real issues to consider...

If you are convinced that the truck alternator is cable of charging two batteries at the same time then you might want to look into the SMART SOLENOIDS that are on the market that monitors your truck system system and will only switch in your extra battery when the truck start system is in its charge mode. It would not switch the extra battery into your truck system without the motor running i.e. Blue Sea SI-ACR 7610 and SUREPOWER 1315-200 comes to mind...

In the old days we used DIODE BASED ISOLATOR and those will not work with our present day of smart mode charging. The voltage drop across those high current diodes will keep your charging system to work with our modern day deep cycle batteries charging requirements.

I would look into these items from other sources to insure you know what you may be getting into...

No way would I just parallel another 12V battery to my truck battery terminal and wish for the best...

However this is just me saying these things...

Roy ken
Grit_dog
Navigator
Apr 29, 2017
Tow/haul has nothing to do with alternator output.
If you want another battery in the house bank (camper) but located in the truck, conceptually it's simple.
You'll need about 60lf of 2 or 4 ga wire. Check the drops but 4ga is probably plenty considering you won't be pulling large loads.
Hook the existing house bank to the new battery (in parallel) with the proper lugs soldered on etc and a winch plug to disconnect between camper and truck.

Now you have to connect it to the vehicle/charging source.
(Btw once you're done with this, the little 12v hot wire in the trailer plug is pretty useless for the camper.)

I would simply parallel off the start battery through an ACR/VSR like a Blue seas model used primarily for boats.
This will link the house bank to the start battery and alternator when charging voltage is present, vehicle running, and automatically disconnect once the system voltage gets below 13v or something. Basically when the alternator is not pumping out charging voltage.
From there out, it's completely hands off save for plugging the camper in.

The downside to this is when you don't have the camper on, that one house battery stuck on the truck will be charging all the time, although it will also act like dual batteries for the truck when the truck is running.
Sam_Spade
Explorer
Apr 29, 2017
Kayteg1 wrote:

-I understand this is going to be 2nd battery parallel with the one in the camper,

Maybe not.

There may be only ONE battery now for everything.

Anyway, if there ARE two individual batteries now, most people boost their house capacity by adding a battery in the house section, NOT under the hood of the truck.

And that initial story about burning something up with a battery that is too high a capacity......is total bunk.
GeoBoy
Explorer
Apr 29, 2017
My 2015 GMC 3500 HD has an auxiliary battery from the factory with a isolator from the starting battery. Stop over to your Chevrolet dealers parts department and see if they will print off the parts and wiring pictures so you can see how the factory did it.
deltabravo
Nomad
Apr 29, 2017
dave17352 wrote:
Now somewhere I read where someone said he had seen a lot of wiring burned up on vehicles because people put in batteries that are too high in cranking amps.

Whomever said that was smoking some pretty good ganja

Stuff doesn't burn up because a battery is too big.
time2roll
Nomad
Apr 29, 2017
I would just tap into the trailer charging line add a fuse and call it good.
If Chevy charge line is not isolated I would add a relay so you can deplete the added battery independent of the start battery.

No, you will not melt any wire from too many cranking amps available.

The existing wire size and length will typically limit the voltage/amps that go into the house batteries. Worst case you need to replace a fuse.