Not that it has happened yet , but say one battery goes bad , will the truck start? if I had to jump it, whats the best way, and finally, if I had to help someone, which battery is best to jump a 12 volt car, thanks in advance.

1. Depends on the Temp, both engine and ambient.
2. With a jump pack
3. Whatever is closest to the vehicle.


Tom

1. Also depends on how fast the bad battery drags down the good battery.
2. My preferred method is have the other vehicle running, connect the jumper cables (positive/red first, then the ground, last connection not directly on a battery), then let it run for 10 minutes or longer to charge up your batteries. Even the bad battery should hold a charge for a short while. Then try to start while still being jumped, and immediately disconnect the ground that isn't on the battery, and carefully disconnect the others.
3. As above. There are lots of variations. The only important thing to avoid is a spark near a battery (sparks happen on last connection made and first disconnection made). Charging batteries can produce hydrogen and oxigen gases, which is explosive.

I just had my pass side batt die on me, bubbeling gas from the vent. I disconnected the ground post on that batt and drove my truck on one batt until I got both replace this weekend. When I pulled the batts the pass side had 4vDC and the driver side was at 12.4vDC. If I left the bad batt connected it would have killed my good batt when sitting, with it out of the circuit my good batt was able to keep it's charge.
So yes you can run on one batt but I wouldn't call that a solution just a workaround until they are BOTH replaced.

As for jumping I use the + terminal and the gound tab, I don't connect directly to the battery...seams to work fine.