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Preserving Motronic ECU OBDII Settings Upon Battery Disconnection
I hate doing the OBDII Drive Cycle. Doubly so, because I have a 1996 car, and the Drive Cycle requires at least two cold starts.
Anyways, at some point in the future, I will have the change the battery, and I would like to avoid having to do the drive cycle all over again. Has anyone successfully temporarily hooked up the car to 12v through the cigarette lighter while changing batteries such that the OBDII settings were not lost?
I use a 1.25amp Deltran Battery tender to maintain my battery, but I do not know if this would work upon battery disconnection to maintain the OBDII settings. Thanks.
I hate doing the OBDII Drive Cycle. Doubly so, because I have a 1996 car, and the Drive Cycle requires at least two cold starts.
Anyways, at some point in the future, I will have the change the battery, and I would like to avoid having to do the drive cycle all over again. Has anyone successfully temporarily hooked up the car to 12v through the cigarette lighter while changing batteries such that the OBDII settings were not lost?
I use a 1.25amp Deltran Battery tender to maintain my battery, but I do not know if this would work upon battery disconnection to maintain the OBDII settings. Thanks.
A more reliable approach (the tender may switch off when it doesn't see 12V) is to just connect a jumper battery, e.g. common 12V battery,
across the vehicle's battery cables and then replace the original battery.
A more reliable approach (the tender may switch off when it doesn't see 12V) is to just connect a jumper battery, e.g. common 12V battery,
across the vehicle's battery cables and then replace the original battery.
Thanks! I didn’t think of the possibility that the tender would switch off. I will try your approach with a low-current 12v source.... like a bench-top 2amp 12 volt power supply
Not sure a tender will work as it is not a highly regulated power supply or noise filtered and attached to an electrical system w/o a battery may damage things. I seem to recall folks would attach a 9-volt transistor battery into the cigarette lighter to hold settings for a very short while however, I question its fractional amp-hour rating is up to the job. One of our electrical engineers here can probably do the calculation for us. Never tried it myself.
Attaching a 12-volt battery or a series of batteries that add up to 12 volts with a little more amp-hour capacity will probably work.
Could be one of those lithium-Ion Jump-Start units or simply a series of eight 1.5 volt AA, C or D cells would do the trick. Line 'em up in a paper tube and attach wires on the ends and you're probably good to go! You could get fancy and purchase some PVC conduit at The Home Depot and make a proper battery holder the length of 8 cells or buy some battery holders on eBay.
My battery maintainer has been used to keep the bus hot many times with the battery out. It’ll work fine for you. Will trip on internal overload if you start putting load on the bus like a trunk light. Resets when the overload link cools.
Male sure all your courtesy lights are off that’s all you have to do. And of course don’t turn the radio on or open glovebox, that sort of thing. It doesn’t take much to trip the maintainer and then you’re back to your original problem.
Not sure a tender will work as it is not a highly regulated power supply or noise filtered and attached to an electrical system w/o a battery may damage things. I seem to recall folks would attach a 9-volt transistor battery into the cigarette lighter to hold settings for a very short while however, I question its fractional amp-hour rating is up to the job. One of our electrical engineers here can probably do the calculation for us. Never tried it myself.
Attaching a 12-volt battery or a series of batteries that add up to 12 volts with a little more amp-hour capacity will probably work.
Could be one of those lithium-Ion Jump-Start units or simply a series of eight 1.5 volt AA, C or D cells would do the trick. Line 'em up in a paper tube and attach wires on the ends and you're probably good to go! You could get fancy and purchase some PVC conduit at The Home Depot and make a proper battery holder the length of 8 cells or buy some battery holders on eBay.
A bunch of connectors that you probably have lying around in your garage.....
Solder it up, and now you have tons and tons of 12V power for saving your car's ECU / memory settings! You could make whatever cable harness you want to interface with your car --- OBD2, cigarette lighter, etc.
09-02-2020, 01:46 PM
Preserving Motronic ECU OBDII Settings Upon Battery Disconnection
