adding a second battery

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by dougtexas, Aug 22, 2013.

  1. dougtexas

    dougtexas New Member

    I want to add a 1000 watt XANTREX inverter into my 08 suburban. Before I start completely diving into this project, I was thinking that it may benefit me to add a second battery to assist with the electrical load that I'll be working with while towing and having a bunch of kids gadgets/ laptops charging. I know adding the battery isn't hard, especially with a vehicle that is physically set up already, but do you guys know if I need to upgrade the alternator too? Any other pitfalls along the way that I need to look out for? Thinking of mounting the inverter under the second row seat.
  2. So, have you thought about portable solar charging systems?

    I've seen a few set ups with solar strips to power the accessories in the car/truck (usually it's a truck that has it)
  3. steved

    steved Former Member

    If you have the second battery tray its cake...takes a hold down, cables, and a battery.

    I didn't upgrade my alternator, but its a 160A already. If your alternator is more than 100A, I'd say leave it alone; it would likely be fine.


  4. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    you might want to look into running an isolator on the second battery. That way when the truck is parked you will not drain both batteries. You will still have one to start the truck with. I believe that @PantheraUncia has a really nice dual battery setup. Maybe he will give some suggestions here.
  5. Jamm3r

    Jamm3r Member 2 Years 100 Posts

    I added a second battery to mine. There are a few Facts to Consider.

    1) You can order the tray at any dealer. It's a common mod around here since the snow plow guys do it. The rubber battery hold down, and the metric bolts and washers, all must be ordered separately. You will end up throwing away the existing fender support, that's ok, battery tray provides the same stiffness

    2) If you want to fit in a deep cycle battery then that will have to be a group 24 and go where the stock battery is now. The second battery location doesn't have enough vertical clearance for a group 24 and there's no way to get it. You will spend around $100 on heavy copper wire to do this mod properly since you will have to move the group 79 starting battery to the 2nd tray (passenger side) and wire it up to the distribution block on the driver's side.

    3) The output wire from the alternator is a problem area since it is too small and will tend to overheat. On the other hand if you upsize it you run the risk of breaking the output stud. Pick your poison or shell out $300 for a custom wound alternator with an oversize stud. I put on a bigger wire and tried to bend it first in such a way to minimize stress

    4) I put in an isolator. You might want to as well. On the other hand at full load a 1000 watt inverter will draw more amps than one battery can be expected to put out for very long. Rule of thumb is C/4 -- divide the amp hour capacity, typically around 90 or so for a group 24 deep cycle, by 4 for the max sustainable long term output. So maybe around 20-25 amps max, that will give you 200-250 watts output from the inverter. You can go over that for tens of seconds but if you do it for minutes at a time then eventually it will cause thermal runaway especially as the battery gets older and the internal resistance increases.

    I think I made a thread with photos on it. If not I know I put one over at airforums.

    Looking at your post again you have an 08 nnbs so some of this may not apply.
  6. DrumBound

    DrumBound Member

    Adding a second battery will help with draining your primary battery when the engine is not running. So if you're planning on running your electronics with the engine off it will give you more play time. Also adding a second battery adds more workload to your alternator. So depending on whether or not your charging system is already at its max would want to be something you look at. A battery isolator is a good idea to add as not to drain your starting battery, but make sure it can handle the amperage. $100 on wiring is a bit much for updating wiring. I tend to install alot of aftermarket stereos and I always upgrade the big three (a google search will net you the instuctions). A car audio shop should have all the wiring and connectors you need.

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