Slow charge for 1999 Suburban

Maintenance/Repairs
1

The car has 2 batteries. The headlights were left on last night. Although the lights appeared bright this morning indicating the battery is probably good enough to go and change off the engine I’m wondering two things:

  1. Would it be better to hook my trusty slow charger to the battery to be certain?

  2. If I did, given the two batteries, does it matter which battery I attach the charger to?
    Mark

2

Using your charger will save the alternator from having to work extra hard to recharge the batteries.

If you have a diesel engine then the batteries should be tied together and both will charge up together, so it shouldn’t matter which you tie the charger to.