Has anyone ever used one of the 9 volt memory savers? You just plug it into the cigarette lighter while you change the battery and you don't loose your memory settings. I had one years and years ago and it worked. Not sure if this would work on our cars.

 

Well, the cigar lighter is not active with the engine off so…..

 

When I installed the CTEK pigtail in my 2021 F Type the only settings I lost were the auto up/down window functions and the electric hatch close button. Of course I only had the ground cable for the battery disconnected for less than a minute. The window functions were easy to reset and the hatch only needed to be closed manually to reset the electric button. I didn't lose any radio stations or the trip computer settings.

I suppose if you took more than a few minutes to install the new battery after the old one was disconnected you would lose some memory settings. The best thing to do would be to have the new battery fully charged in advance (check it as chances are that it won't have a full charge right off the shelf) and then make the swap quickly.

 

When I installed my CTEK pigtail I held the ground cable down as I added the CTEK connector so no continuity was lost.

When changing the battery you could connect a charger (proper one, not a CTEK) or spare battery if you have one across the under hood terminals?

 

You do not need much voltage (at least on other brands) to maintain settings. An old mechanic's trick to keep the settings is to connect a 9 volt battery across the battery terminals. I have not personally tried this on a Jag though.

 

Is the idea here that you attach a 9V battery and when you plug in to the cigarette lighter the 9V from the battery flows into the car to keep the memory alive? But, if you did this, or some other similar hack, wouldn't that defeat the purpose of doing a battery disconnect to "reset" the car? I'm not an electronics guy, so please help me out here.

 

Yes it would defeat the purpose of doing a reset. If you wanted to do a reset do not connect anything across the battery terminals or in the cigarette lighter.

 

I posed the same question to my JLR service manager before changing out my battery a few weeks ago and he said I probably would not lose any settings...and he was correct. I was out with the old and in with the new within ten minutes at most, so perhaps that helped.

 

That is what OP is asking for, yes.

 

Really? Seems to me he's asking about changing the battery, not doing a reset.

 

If this matters to you:

We lost our trip odometer readings when resetting the battery, they reset to zero. So write the numbers down if you keep track, for manual calculation of MPG for example.
Yeah you could just subtract total mileage for that calculation, but that requires using too much MATH!