If it is not a battery problem, then the voltage regulator is going out in your alternator. It regulates the amount of voltage that goes to all of your appliances. Our alternators ususally last around 100-120k miles, but somehow mine got about 200k before having issues. A new alternator will run you 140-200$ and you can easily do it yourself. Barely loosen the serpentine belt, remove the bolt that holds the alternator on, take it out, put the new one in place, put the bolt and belt back on, tighten the bolt and belt and bam you are good. Unplug battery before doing any electrical work on your vehicles. I am about to do mine here when I get the money together. Also I believe the ESV uses the 160 amp alternator versus the 145 on the base models, I could be mistaken though. Make sure you get the right alternator.