Rear Battery Compartment - Revisited 1

One small advantage of being time limited is that a long time is required to complete the project and each step can receive more effort by "the little grey cells".  Consequently, many mental revisions occur prior to actual implementation.  So it is with the positioning of the batteries in the trunk compartment. 

It was previously shown that 6 Optima deep discharge batteries fit adequately (but not elegantly) in the spare tire wheel well.   Since fully 50% of the cost of an EV conversion resides in the batteries, it was hoped that each battery pack could be lifted out (with an engine hoist or equivalent) and placed into a different EV (or boat) conversion when wanted.

Picture DSC03425 showing the rounded corner (passenger front side) that prevents the placement of a square battery box in the trunk.  The blue lines indicate the metal area that must be removed to allow placement of a square box.

Picture DSC03427 showing an internal obstruction on the passenger side rear wall of the trunk compartment that prevents the placement of a square battery box.

Picture DSC03430 showing the drivers side (front) area of the trunk compartment after a square portion of metal had been removed.   The BMW structural steel on the left has a metal ledge (right side) that will be used to support the final battery box.  The longer cuts were made with a Ryobi P4221 angle grinder fitted with a 1/16" x 4.5" cut off inch disk.  Final cuts were made manually with grunts and a hack saw blade.

Picture DSC03429 showing the drivers side (rear) area of the trunk compartment after a square portion of metal had been removed.  At the bottom of the picture, note a small ledge that was intentionally left to allow additional support of the final battery box.

Picture DSC03428 showing a lateral view of the completed opening that now allows a square "box" structure to be placed.  A tab of metal was left in the floor area (from left to right) that will be used to support the final battery box.

Picture DSC03431 showing a battery box template positioned in the final opening, note the additional area now available to the right and note that no cuts were required on the right side of the compartment.

Picture DSC03433 showing the Optima batteries in place on top of the template.

Picture DSC03434 showing the close approximation of batteries (and future potential battery box) on the drivers side.

Picture DSC03435 showing a top view of the new area now available on the passengers side adjacent to the OEM BMW battery (top).  The contactors and high power fuses will next be rebuilt to allow them to be mounted within this new space and below the plane of a future battery safety cover.


It is intended for the trunk compartment to be water tight.  An effort will next be made to weld sheet metal to completely close off the opening on the drivers side   In principle, if the modified wheel well box area is welded water tight, and if the convenient removal of a battery box is not required, then a battery box would not even be necessary within the compartment as the cells fit nicely by themselves.  A cover would lastly be secured over the batteries, contactors, and fuses, for both cosmetics and viewer safety.