Whenever I have to unplug my car's battery for various car work or ECU "reset", I lose certain settings on my stereo. I've been trying to think of a way to use a backup batter to keep this from happening. I have some ideas, but I want to know if someone else has succeeded in this or if a retail product extists.


As a side note, what's weird, is that I can set names/all letters for radio stations manually (no RDS ) and they seem to be in non-volatile memory. But all my memory presets and options settings all get lost when I disconnect the battery. You'd think they'd have a place for a watch batter or use non-volatile memory :-/ (JVC KD-SX990)

jason

 

There are "memory saver" devices sold which are basically 9-volt battery clips that plug into the cigarette lighter. The 9-volt battery is enough to hold the ECU and radio memories for a short time while the battery is disconnected, as long as you are careful not to draw any current from it while the battery is off, such as stepping on the brake, or having the interior light or trunk light on.
These things are pretty expensive for what they contain, however, so I made one myself a long time ago and I've used it many times. 9-volt battery clip wired to a cig lighter plug with a series diode to prevent current backfeeding from the car battery into the 9v.
Of course on Subarus and most other Japanese cars, the cigarette lighter is not active with the key off so to use the backup gizmo I had to take some clipleads, hook them to the lighter plug, and connect them directly to one of the full-time power circuits inside the main (underhood) fuse box. Worked great the couple of times I've used it on my car.

 

Unfortunately i want to purge the ECU and save the stereo... guess I'll have to rig something separate up. Thanx for the ideas, though.

jason

 

You can pull the fuse for the ECU rather than disconnect the battery, if you just want to do a reset. Also if you can get a hold of a Delta Dash, it has a function to do a full reset through software.