An embodiment of the technology described herein is an auxiliary power unit assembly. The driver circuit is configured to change at least one of the value of the first voltage and the value of the second voltage so that a voltage difference between the first and second voltages becomes large when the power loss of the switching elements is estimated to exceed a certain value. A base includes variable footplates to stabilize the hydraulic grapple by remotely adjustable telescoping legs. The containment body may be configured to receive therein a pipe leading from a cement pump truck.