Adding 3rd Battery on Duramax...

[Elite130]

I am wanting to add a 3rd battery to on my 2022 Duramax. This battery would be mounted in the bed of my pickup inside my truck box. The purpose of this battery would be to power auxiliary items while camping without worrying about discharging the two starting batteries. The items would include:

- Inverter (800watts max) - Running/charging a laptop or TV, 120v air inflator for lake toys (i.e. tubes, stand-up paddleboards, etc) and/or running Traeger Tailgater Smoker (400watts for first 5 minutes, 50 watts to run). 

- Air compressor - Viair 300P portable air compressor or future air-on-board air compressor 

 

I'm thinking I'd run a positive cable from the alternator back to the battery. I'd have a breaker with an isolator inline within the engine bay. The battery will be mounted in a battery box that is vented out of the truck box. The inverter and compressor will be connected to the battery and mounted within the truck box. 

 

Has anyone done this? Does anyone have comments, tips or tricks? Again, the purpose of this is to run items off the auxiliary battery instead of the main starting/running batteries. 

[Another JR]

Based on the loads you described I think you will be much happier if you go with a lithium (LiFePO4) battery and a DC to DC converter charger instead of a lead-acid battery. 

 

To size the battery you’d want to estimate your daily energy usage and how many days you’d like to be able to go without running the truck to recharge.  One of the nicest accessories to have camping if you have the space and the power is a 12 volt compressor fridge, so consider adding that to your sizing calculations.
 

The DC to DC charger I’d recommend is the Victron Orion XS 50 amp charger. 

[bruceb58]

5 hours ago, Another JR said:

Based on the loads you described I think you will be much happier if you go with a lithium (LiFePO4) battery and a DC to DC converter charger instead of a lead-acid battery. 

 

To size the battery you’d want to estimate your daily energy usage and how many days you’d like to be able to go without running the truck to recharge.  One of the nicest accessories to have camping if you have the space and the power is a 12 volt compressor fridge, so consider adding that to your sizing calculations.
 

The DC to DC charger I’d recommend is the Victron Orion XS 50 amp charger. 

Exactly what I would do. I have lithium batteries and the that same Victron XS DC to DC converter on my trailer.