L100 Smoke Around Battery???

I got an older L100 and had took the trickle charger off the battery and then tried to start it. There was a loud pop....not a backfire...and then some smoke coming out from around the battery. Any idea what that was about?

For Safety sake, i would remove battery & take to local auto parts store & have them load test battery & check it out, this should be of no cost to you. Is battery maintenance free or otherwise? If you need to ever replace battery try to remember CCA's cold cranking amps., your new battery should have same if not a little more CCA's.

Check to see with the leads are lose, maybe just a lose cable.