Isuzu Repair: battery light and brake light on, isuzu rodeo, honda passport

Question
I have a 98 honda passport-isuzu rodeo.  One day, I noticed the battery light was on and we took care of it by going to Sam's club and have it replaced with a new one.  WHen we drove home that night, it was still on.  I thought that was weird but maybe it will go away later on.  Then the brake light would come on when it's cold but it got worse with both lights on at the same time.  Two weeks ago, the car won't start and we had to jump it to start the car.  We called someone to take a look at it and he said it was the spark plug.  We paid him $130 for labor, towing and spark plug after he changed it.  The following day, we drove it and noticed both lights were on again esp. when i pass 70 mph on the hwy.  Is there anything else we need to do?  I really wanted to get my passport fix as soon as possible.  Any advice would help a great deal.  Thank you for your time.

Answer
WEll it sounds like your battery light is coming on due to a faulty starting and charging sytem, you could have a slow drain, or what you call a phantom drain on a car, something might be slowly draining your battery down overnight. Also check your battery cables, if they are stiff and corroded then replace them, also have your alternator tested(they do it for free at auto zone or oreilly's auuto parts. Your brake light is your abs module probably going bad(this is very very common on passports and rodeo's cause they are the same thing with different badges.