I've had so many troubles with carts over the years. I'm slowly learning more and more.

At first, it seemed like ALL of my carts would break before they were used up. I got a better battery with a display screen, and knowing for sure when the battery is dead/dying or if it's not connecting to the cart has helped me stretch the life of my carts.

Also, overheating the coils seems to be a huge issue. Don't take super long hits, or pass it between people quickly. Hitting it over and over before it can cool back to room temp, will cause your oil to leak into the battery or up into the sucking tube(? I don't know what to call the part you put your mouth on).

During last week's heat wave I left one in my car and found half the oil in my cup holder. Stickiest, messiest stuff I've ever dealt with!

Oh! If the cart hits really hard and even the tiniest hit causes you to cough, unscrew the cart and get a qtip dipped in rubbing alcohol to clean out both the male and female parts of the cart and battery. I just learned that one, and it worked wonders!