Most of the consumer chumpstarters (sic) aren't designed to be particularly servicable, from what I've seen. You'd probably have to bust some plastic welds/glue joints, then figure out how to close it up again... I believe these contain fairly standard gel-cell batteries, so if the problem is that the battery has died you can probably find a replacement that will fit. Of course the problem could also be your charger. If it's an external wall-wart, you may want to check that it's supplying the correct voltage, and see whether the jumpstarter is drawing current when you're trying to charge it.