Interstate Battery System of St Louis

Replaced factory original battery in my Charger just before five years, with a 75-​month Interstate battery. It started to fail after about 21 months, getting weaker and discharging several times. At least I was prepared.
My mechanic tested the battery for voltage and voltage loss, as well as for cranking power. The alternator and serpentine belt were good. He believed it was bad and recommended I return it.
Pulled the battery and took it to Interstate. They tested it and found it was no good. They cheerfully gave me a brand new one (now 72 month instead of 75), no money needed and not pro-​rated as within 30 months. Warranty starts over again! Wow!
I have installed Interstate batteries in all of my vehicles for years. This is the first time I have had any problems, and this is minor. I will continue to buy and recommend them.
John Q