Abstract: A battery tray assembly is described which has a bottom member and four side walls which are attached to the bottom member thereby forming an enclosure; the enclosure adapted to removably receive a battery therein; one of the walls having integral battery holddown members to retain the battery in position when placed in the enclosure; spaced adjacent to one of the walls a slot for snuggly retaining an electrical control module for modulating the engine performance; a manually operable cover which securely fits over the enclosure and the module when it is placed in the slot, the cover when open facilitates inspection or removal of the battery from the enclosure; integral with the slot for the control module a second enclosure formed of a second bottom member and four sides, the second enclosure adapted to snuggly retain a second module for modulating the performance of the engine; and a second cover being manually removable which fits over the second enclosure.