Getting good insulated wrenches is the first thing I'd suggest if you're ever going to disengage a car battery. These will save you from sparks or shorts by mistake, especially if you are in the midst of working with metal. You'll need to start by unplugging the negative terminal (which is very important), so you're less likely to spark or land. Also, cover the terminal connectors with a cloth or electrical tape while they are disconnected so you don't accidentally reconnect them. Check the battery's voltage first. Take a digital multimeter, set it to measure DC voltage and hook it up to the battery terminals. If it reads 12.6 volts or more, it's still good. Anything less than 12 volts could indicate it's discharged or, if it's not getting better after charging, you need a replacement. Batteries typically get old, so if you're finding problems after you've charged it, don't go all the way-just swap it out, and you might never need a dead battery again. For insulation, yes, a battery blanket is fine but I would recommend using a thermal wrap for car batteries. It is meant to keep the battery at the right temperature in both extreme temperatures and conditions, thus prolonging the battery's life. Normal blankets trap moisture and are not designed to work there. Thermal wraps, however, provide good insulation without the threat of condensation or overheating. It's one of those things you don't think of until you're out in the wild, but it's a big factor when it comes to ensuring your battery stays healthy.