It is virtually impossible for a low amperage trickle charger to significantly heat a working Viper-sized battery, so your guess is probably correct. I've seen significant heating from a 25-amp charger, but not from a 1-to-2 amp tender. Something is seriously amiss in that battery (plate-to-plate short) OR there is a short external to the battery that pulled very high current from it. I would do some voltage checks and see what the battery voltage is with no charger and with the charger connected (~12.6V no charger, good battery/ a few tenths higher ~13.2V with a trickle charger connected). Most likely, the old battery has at least one shorted cell and will measure low (each cell contributes about 2.1V to the 12.6 volt total).
If the battery is gone and you install a new one, I would re-do these voltage checks and make sure that something on the car is not pulling a big load on the new battery, though most likely, the problem will be with the old battery itself.
