Jamie,

I have a feeling that a battery going pop means that it over heated. Probably due to too much current being drawn.

You have 4 drill motors being overvolted plus a linear actuator running along side. That is a huge amount of current for a pack that should only be able to discharge 35amps max.

If you can afford them I would go for the A123s. Been playing with mine and they are $exy!!!! Huge current discharges and light as hell. Throw them in drumroll and you will notice a huge difference!