To get the most out of your battery after awhile of use, make sure that the connector end is clean. For my batteries I clean them at least one every to weeks. Look at the connector end and if you can see any black grim that has built up, its time to clean.
1. Take a push pin and scrape out the 3 air holes that are at the bottom for the connector. That will allow more air to pass through so it won't burn out your carts as fast.
(Warning- doing this will make it seem like you aren't getting as much of a throat it right away because you are use to how it was working so hard before. *Simply place your two finger around the base of the cart when it is connected to the battery until you find good pressure in you hit.* *Doing that trick will reduce the cartridge life faster but it might be something to give up for solid hits.*)
2. The connector is two parts. Part one is the piece that connects to the charger and the carts to give them power. Part two is the surrounding part with the 3 holes in it that the cart screws into.
Now in between those parts are an open space that a lot junk can build up. To fix this and to prevent future issue- Take a push pin with a long pin part, make sure its not to thick and place it between the two parts. You will have to find the right angle to move smoothly and not move parts to much around. Usually if you lean it back away from the direction that your pushing works best.
(Warning- Only do this if there is a lot of build up because sticking anything into the battery and scraping around can always mess it up. Just use common sense and be careful. If its not going smoothly just stop.)
3. If you have had your battery for a long time- chances are the the connector top is getting a little worn down. A simple fix for this is to take really fine grain sand paper and scape off the grim and expose the metal again. Make sure when you do this not to scrape it to much and to hold the battery so the LED end is pointing straight up, not to get sandpaper bits in the battery.
Then just blow on the connector end to get any sandpaper or grimy bits out. A can of compress air used for keyboard cleaning works really well.
*These are just homebrew quick fixes and I am not responsible for anything you do. Just be safe (don't use knives), smart, and use common sense and it will work great.