I'm hesitant to cut open my only OEM key again, since I cut loose a wire trace the first time, then had to cut it open again to resolder.

This time, I have a specialty Dremel cut-off wheel (instead of a utility knife), and a "helping hands" device (with magnifying glass) to hold it and help me SEE what I'm doing.
Plus, I got a new pair of trifocal glasses yesterday (my first new ones since 2014), so that'll help, too.

Sent from my moto g power 5G - 2024 using Tapatalk

Brave

The battery will die from non use. It charges from being in the ignition switch. Sadly you likely destroyed the battery in the unused key from not using it.

There was a guy would replace the battery for $65 if you didn't try to open yourself. Might still exist.

My batteries were about 15 yr old when I replaced them. They were still ok at that point; the circuit board had broken solder joints. I reflowed the solder on both boards and they both worked like a champ for a couple years. I lost one key on a road trip so i eventually bought a new key and then was ok with surgery on the old key. That Became the emergency key anyhow and the new key worked as remote from at least 5x as far away so i was thrilled i bought the factory key and recommend to anybody with m an old diamond key !

My new x5 and wife's F10 both use normal coin cells you just replace when dead. Not sure what possessed bmw to use rechargeable batteries making keys "throw away".


–awr–

Using Tapatalk VIP on iPhone

Confirm you do/n't have voltage and buttons work before disassembly. My posts on the topic show exactly where to poke needles to measure voltage and if you press each button you can see the voltage drop if the click switch inside is working. (you can also charge via the pins: i recommend 20mA up to 3.3v).

If the buttons all work but remote function doesn't, use a remote tester found where they sell batteries (my local Home Depot has one) to test if key is sending a signal and if so then re-sync key.

I managed to cut a trace but not with the Dremel: a drill bit. I drilled through to add two cute little M2.5 Allen head screws to hold the keys closed and got too close to the traces on one of the four holes.


–awr–

Using Tapatalk VIP on iPhone

the problem with my OEM diamond key isn't the battery
 

My OEM key fob has no problems with remote functions, but with intermittent EWS faults; I'm wondering if my recent no crank-no start problems might come from the damaged circuit board inside. I cut it open for the first time, to change the (at that time) original 20 year-old battery, and cut too deeply with the utility knife. I glued it back together BEFORE I tested it, regretfully, and had to cut it open again, damaging the circuit board even more.

The OEM case/shell is a mess, and that's why I bought a new aftermarket case w/precut blade awhile back, knowing that it was needed for the next repair. Might as well put in a fresh VL2020 battery, too.This time, i'm only going to lightly glue the case together (if the tabs don't hold it shut, and put a silicon sleeve over it, just in case it opens up by itself.

If & when I get the X back on the road, I'm planning to get a new diamond key...after years of worrying "when will my key fail?"....

Get a new key to give yourself the freedom to fix the old one. Good plan to move the guts over to a clean shell


–awr–

Using Tapatalk VIP on iPhone

That's why I bought the Valet key, first, as a fail-safe measure, while my main expenditures are focused on fixing the fuel delivery system (the fuel pump went out, replaced it, went from lean codes to rich codes, started stumbling on turns).... Buying parts to re-do it all from scratch, including new tools.

It's not the best time of year for diagnostics/repairs, with five vehicles needing inspection from August-January, seasonal spending, property taxes in Jan., new glasses just now, new phone (bought outright from Amazon, for the wife), and me going to an out-of network ortho specialist next week, it all adds up. A new OEM key is way down my must-have list right now. I'm hoping that I can fix whatever might be wrong with the original key.

You already have the "new key" that makes it safe to open up the old remote key.


–awr–

Using Tapatalk VIP on iPhone

I was able to bring 2 key fobs back to life by charging them on a sonicare toothbrush charger as mentioned earlier in this post. An apple watch charger seems to work too.

I brought one back by replacing the battery.