Rolls Royce and Bentley seat memory batteries

In my last story I described replacement of the backup batteries in the Rolls-Bentley alarm controller under the dash.  This story sort of builds on that one . . . This time I’d like to look at changing the batteries in the memory seat units.

Each front seat has its own memory unit.  They are located under the seats.  Depending on the age of your car they may take one of several forms.  These pictures show the controllers found in the mid-1990s.

To get at them, you remove the lower cushion, unscrew the memory unit, and withdraw it to the front.  It comes out dragging a large tangle of wire as you can see.  The controller is the box on the floor, just to the right of the Fluke test meter.  I've removed the cover in that photo.

Looking at the cover you see these memory units are something of a homemade affair.  The label is something I could have made up on my own printer!  Looking inside you can see the single battery.  In this car, the battery is not corroded badly but in older cars it will leak and the acid eats away the circuit board, leading to failures.

In the photo above I point out the battery that we are about to change.  The new one will look different, but as long as we match the voltage and technology (don't mix ni-cad and lithium ion) we will be all set.  This particular battery is 3.6 volts.  The original one has a 100MA rating; we will fit a slightly bigger one because that's what they sell today.

These seat memory units cost $2,500 when they were available, and there are none left.  Consequently, we have a lot of incentive to preserve the ones we have.  Changing the batteries before they leak is the best way for you to do that.

We unsolder the battery from the board and remove it.

Then we fit a new battery.  This one is a 3.6 volt battery for a pet collar.  I found it at Radio Shack.  It’s a perfect functional replacement for $20.  It’s a snap to solder in place but you should note that the original battery had two positive wires and I had to add a jumper to replace that missing second positive lead.

The photo below shows the jumper I had to add

If you are like me you test it before assembly.  This one worked.  If it does not work you should look carefully for corrosion damage or installation errors.  Beyond that, you will have to hunt up and electronic technician and further repair is a hit or miss proposition.  That’s why I urge you to change these batteries now – before they fail.  Then it’s back together and off to the other side.