My wife has a 2008 Xterra that is having some battery issues and am hoping that someone out there has seen similar issues and can provide some advice.

issues:
- Dealership reported battery was bad 11/2016 after I informed them that car was having trouble starting (taking 2 or more tries & needing help - pumping gas pedal to get it to start - wouldn't start without that)
Battery died about 2 weeks later, replaced battery 12/1/16. Battery was only 4.5 years old (rated for 7 years).
-New battery died 2 weeks later
- Dealership unable to find source of battery drain. Got 2nd opinion at another clinic, they tested for several days, thought they identified issue as body control module. After disconnecting fuses & cleaning them, they could not reproduce the draw. It started fine for 2 days, then the issues resurfaced. It takes 2 tries to get the car started on most occasions whether it has been sitting for 3-5 min or 12 hours or sometime in between. I cannot get it started without helping it - battery not powering fuel pump among other things to get it started.
-Of note, body control module system has never been right since I bought the car in Aug 2008. VCD/slip light would come on intermittently. Dealership unable to resolve this.
-Car also appears to accelerate sluggishly at times, but not always.
-Dealership also stated that drive belt is cracked. Car has been making a grinding sort of sound - kind of like sand going through the engine. This has only happened while accelerating uphill at higher altitudes

Car info:
2008 Nissan Xterra off-road package
78K miles
battery just changed
spark plugs still original
after market radio (because one shop thought the stock radio could cause battery drain)