At the last aviation job I had, another shop down the road had an old golf cart for running around, and they used some old "unserviceable" aircraft Ni-Cad batteries to replace the stock lead-acid deep-cycles. Made it a real hot-rod. One day a guy was riding in the rear and the driver floored it and it threw the rear rider off the cart, hit his head on the concrete, fractured his skull, severe brain damage, damned near died. He never recovered fully.