Optima Battery Retrofit to Daimler Ferret Scout Car
Background: 00EA02 is a 1962 Mark 1/2 refitted with a revolving turret. It has been under restoration since 2000. There were no batteries present when acquired. Optima batteries have been retrofitted as part of the final stages of this restoration.
Requirements: Replacement with old stock original ferret batteries was NOT considered due to advances in battery technology in the last 50 years. Optima red tops were chosen because they are sealed-cell batteries of long life that do not require maintenance. A battery cut-off switch would be installed to overcome the ever-present transient phantom current draw that is prone to discharge even modern batteries over time in infrequently used vehicles, resulting in one of life’s most irritating situations – THE DEAD BATTERY. Additionally, an engineering solution was needed to assure the batteries would be firmly attached inside the stock battery box. Without secure mounting there is a likely possibility the terminals or battery cables may contact the metal battery box. This is almost assured were the ferret to roll on its side or become inverted. With a gasoline tank sharing space with the battery boxes, not to mention the crew, this scenario if predictable is also preventable. Lastly, the front battery box hold downs were also missing when this ferret was acquired and another solution was needed to secure the front of the battery boxes to the hull trays………
Some Words of Admonition: Don’t ever be tempted to take the easy path….. The restoration had progressed to a point where interior wise –a lot of the bits and pieces, all properly painted and polished and otherwise detailed had been bolted in place. So much for the whole ‘deferred gratification’ patience thing……When it came time to install the batteries I thought I could do everything with the boxes in place. First task would be to run a tap in the four threaded bosses on the battery box bottoms for the purpose of cleaning out the threads to accept new bolts that would attach the base mounting plate to the battery box proper. The bosses were originally ¼ inch threading. Not much room to spin a tap in those boxes, but, what the hay, a lot easier than removing the boxes…….Four bosses. The first two finished. A lot of metal coming out….On the fourth boss the tap shears in the boss threads. Of course it shears even with the top of the boss so it cannot be removed. What happened next best I can remember was a long string of very bad words, a brief period of disbelief, followed by a briefer period of inattention wherein I banged my head against the Browning gun cradle resulting in an immediate loss of blood and more really bad words. Two lessons here: First forget short cuts, second – pay the price and get good tools, especially dies and taps. Onward and Upward………..The boxes are removed as are the trunnion cover boxes (Explained later) which requires the two floor plates to be removed and did I mention, the pulling of both escape hatches with their attachments (Spare tire, ammo boxes etc).
With the boxes out the actual work begins. First modification is to enlarge the size of the threading in the bottom attachment bosses. I went to a 3/8 thread which required drilling out the ¼ threads and tapping new 3/8 threads. A pilot hole was drilled from inside the box through the bottom of the container. The battery box was then inverted and the boxes were drilled out from the bottom to allow the 3/8 tapping. The bosses were tapped and new 3/8 bolts were fitted.
Note: After the bleeding stopped and during the subsequent headache period it occurred to me that had I simply used my ‘easy button’ I would have been able to take the initial approach. So I located said ‘easy button’ keeping it in plain sight for the remainder of the battery refit. I must admit that after I did this everything else went quite smoothly.
The next task was to fabricate metal bases to which the Optima batteries could be attached. I used the last of my Boeing Surplus Store aircraft aluminum (It was a sad day indeed when that place closed its doors). The bases required some filing and pre-fitting due to the boxes being slightly out of square. Once fitted, the tapped bosses were spotted and the bases were drilled for the 3/8 inch bolts used to attach the bases to the threaded bosses.
This picture shows the base sheet installed in the starboard battery box. Also shown is the installation of a Hella battery cut-off switch with removable red ‘key’. The switch interrupts the ‘earth’ or negative cable coming from the distribution box to the starboard battery.
The next consideration was selecting a method to attach the Optima batteries firmly to the base plate. A number of conventional battery hold-downs were considered and rejected because they all had metal attaching elements either on or adjacent to the top of the batteries and were thus a potential arcing source for both the terminals and the battery cable ends. The cleanest solution was a clamping style billet battery base made specifically for the Optima batteries. The base I chose was manufactured by Wieland Custom Machine, Stanton NE, USA (http://www.wielandcustom.com/). And yes, they are proud of their products. The machining includes their logo, an extra touch that is covered by the battery when installed. IF YOU WANT TO JUDGE GOOD WORK – LOOK FOR IT IN PLACES THAT DON’T NORMALLY SHOW .
This pix displays the two billet hold-downs. One is top view and other is bottom view. You can see the 4 mounting holes with stainless bolts and nuts included. It was necessary to replace the bolts with shorter ones so they do not contact the battery box when installed. The supplied bolts can be cut down but shorter SS bolts were easily obtained. The tray will sit on 4 posts that raise it from the battery box bottom and if the supplied bolts are used the base will not sit firmly on the raised posts.
This pix shows the billet bases attached to the aluminum base trays.
This is starboard battery box with base and tray fitted.
Next the Optima batteries are secured to the billet bases which are secured to the aluminum base plate. The Optima’s have a carrying strap which can then be utilized to lift the whole arrangement into the battery boxes. The blue tape on the plates is simply temporary markings to remind me of positioning within the respective boxes.
Here the port battery has been placed into the port battery box and the cables have been attached. I used marine terminals (which are visible in the first picture) which have the traditional clamp but also a vertical post to accept the original battery cable end eyelet terminals. I then covered the exposed posts with boots made especially for the marine battery terminals. At this stage of the retro you could literally turn the ferret upside down and the batteries will remain as attached. There is little chance or inadvertent arcing. There is no ignition source for a leaking gasoline tank which would undoubtedly be compromised by inverting or rolling a ferret. The cables were remarked prominently to indicate their proper attachment terminal.
Port battery properly secured.
Starboard battery properly secured, showing battery cut-off switch.
View of Hella battery cut-off switch in starboard battery with removable red "key".
Starboard battery box with red ‘key’ removed. Note how unobtrusive this installation is. Once red key removed it is not possible to start the ferret without first removing oil-bath air cleaner, then starboard battery box cover, then bypassing battery cut-off switch. Quite the theft prevention device and will certainly prevent unintentional /accidental starting. Also evident in this picture is the retro battery box hold-down.
The ferret was missing the front battery box hold-down posts. My solution was to create a substitute post arrangement using the trunnion cover box as a natural attachment point. To do this I bolted a strap to the front flange of the trunnion box. To this strap I affixed a brake yoke with a 5/16 threading to accept a 5/16 fine threaded stainless steel rod. To this rod I affixed a stainless steel 5/16 coupling nut. The brake yoke and the coupling nut are secured to the stainless rod by jam nuts. This arrangement allows the rod to lengthen or shorten to exactly fit under the securing attachment point on the battery box.
This view shows the relationship of the retro battery hold-down post and the trunnion cover and battery box. The battery box covers are affixed by bolts that capture wing nuts. This allows removal of the cover bolts without tools.
The finished installation: With the exception of the visible Hella battery cut-off switch, the retrofit appears stock.
MY SINCERE THANKS TO JOE KIRBY FOR PROVIDING THIS TUTORIAL ON THE OPTIMA BATTERY BOX INSTALLATION - WEBMASTER
