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  #11  
Old 05-13-2020, 12:55 PM
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Originally Posted by andrewwynn View Post
I believe he said he tried to charge in the ignition key. If they could get charged via aa (that's a very good trick) I have a bench power supply so I can limit the current but since 2 AA close to 3v just a little higher when new it prob is very close to recommend amount.

Before glueing or screwing back together I would make sure they take a charge in the car. Tape it together where you still have access to the bat (maybe solder some pigtails on the battery leads so you can plug in the ignition and observe the voltage rise.
Nice idea. I'll see if I can do that. When doing my tests yesterday, I soldered some stubs of solid copper wire to the key battery solder joints to allow easy alligator clipping, etc. Will try the same with the new batteries.

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Originally Posted by andrewwynn View Post
Before I reflowed my solder joints the symptom I had was the remote function would only worth within a minute or two of being on charge. Either from on my bench supply or in the ignition.

It was so confusing. I could lock the car leaving and could immediately unlock and re-lock but if I left and came back no go.
Since I'm "in there" I'll reflow the easier joints too. Any suggestions on what to hit that may not be obvious? And BTW, I must say that after cutting open the key, I am very impressed with how it all looks. Sure looks like it was built to last.

Over the years, I have tried my electric toothbrush charger, which did not seem to work.

But my method (detailed above) where I put the key fobs in the ignition area, with the car powered on for many hours has proven to be a very reliable way of making sure I get the EM field present for charging. Maybe once a year in the past it has worked great on all 4. Lately, 2 of the 4 have become unreliable in charging and holding that charge. I.e., not programmable or programmable but failing soon after.
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  #12  
Old 05-13-2020, 01:45 PM
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You'll know in minutes if the key is taking a charge.

The important joints seemed to be on the IC and the antenna coil. But the switches tend to be suspect as well.

On the bench the best way to test the switches is to measure bat voltage when you press them. The radio takes enough power to drop the voltage. If you don't get a drop the switch or contact to it is bad.

If either of the the main two switches won't click reliably of course you can't program.
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  #13  
Old 05-13-2020, 04:02 PM
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I also came up with this "workaround" when I was in a pinch about 2 years ago.
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Alternatively, i have an original key, and a chinese diamond as my spare on one key ring at home, and my main keys consist of the plastic key, with a chinese diamond which i cut the blade off of. The chinese diamonds can be programmed to open and close the car, while the plastic key lets me start the car. Same idea with the spare at home, the original key lets me start the car and the chinese copy allows me to open/close doors. Since the battery issue is strictly a lock/unlock issue, my workaround does the job fine, especially @ $5 per diamond on ebay...
Eventually, I replaced the battery in the standard key. I didn't want to worry about snapping the plastic key, every time I started the car. Opening the key is really not that bad if you are careful. You need to watch out for the small SMD components around the diamond, so open from the keyring. Luckily, I didn't need to reflow solder or anything of the sort, so connecting the battery was pretty straight forward. Solder it up & your good to go. Unfortunately, odds are the rechargeable battery (Panasonic), probably isn't going to charge with the "workaround" anyway.
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Old 05-13-2020, 10:20 PM
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I found out some cool things today, while I had the voltmeter hooked up to the battery in one of the key fobs (that came from a diamond key). EDIT - I turned on the voltmeter, measuring battery voltage on the fob, without doing anything at all, no buttons pressed, etc., so the battery was at a very steady state. It was holding steady to the mV. So I could then just move it to different locations, such as on the charging pad, etc. and watch the mV click up for example at about 1 mV per minute while on the charging pad.

I confirmed 100% that my Braun / Oral-B electric toothbrush charger does nothing to charge the battery.

My son's iPhone charging pad thing DOES work to charge the key. Will keep that in mind for the future.

When holding the key right where it would be if it were still part of a diamond key in the ignition, it charged pretty well, a little faster than the charging pad. Then I tested by holding it a couple of inches lower, exactly where it would be if it were on a key ring connected to a valet key, and there was hardly any charging. Surprising to me. So the charging region is very localized, aligned with the key cylinder.

I think I found that the one fob I tested extensively was a little flaky still, even with 3+V applied from the 2x AA batteries. And it seemed that when I'd pull up on the right corner of the circuit board while pressing on the button it would work consistently. Then I reflowed the solder joints on the buttons and coil, which seemed to make it work consistently all the time.

I keep reminding myself that I bought these keys off eBay for $15 each, but it's a fun project to figure things out. And the knowledge on keeping them charged going forward will help, as will the new batteries when they arrive.
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Last edited by oldskewel; 05-13-2020 at 11:31 PM.
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Old 05-13-2020, 10:53 PM
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Interesting and helpful info about the qi charging pad. Only certain toothbrush or shaver chargers will work but if qi charger works that's great. keep that in mind for the future.



The megentic core of the antenna is very directional. In fact if you drilled a hole in the right place to use a qi charger with the key poked through would make it work much better.

The symptom you describe of working when bending the circuit board is exactly what a broken solder joint acts like.

Great feedback for the forum
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Old 05-14-2020, 01:00 AM
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Originally Posted by andrewwynn View Post
Interesting and helpful info about the qi charging pad. Only certain toothbrush or shaver chargers will work but if qi charger works that's great. keep that in mind for the future.
I've tried several different Qi chargers, but never really been convinced they worked - although I wasn't monitoring the battery in the FOB.

I think some of the "smarter" Qi chargers have some form of load sensing and don't output anything useful unless they detect a compatible device is in the RF field.

I know my Samsung Qi (WPC) charger lights up blue to indicate its charging the phone and changes colour to green once the phone is at 100% charge - inferring some form of feedback from the device being charged.
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Old 05-14-2020, 02:09 AM
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My iPhone charger will light blue when charging 10w but since iPhone will only charge at 5 or 7.5w the charger changes to green but stays green the whole time charging. I suspect yours does the same and just goes to green when the current drops.
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Old 05-14-2020, 09:58 AM
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Originally Posted by andrewwynn View Post
The megentic core of the antenna is very directional. In fact if you drilled a hole in the right place to use a qi charger with the key poked through would make it work much better.

...

Great feedback for the forum

I came here to say this -- there is no way that the diamond fob is being charged when it is hanging from the key that's in the ignition. Wireless charging becomes completely ineffective when things are misaligned like that, or when they are a couple of inches away. I am guessing this fob has just been draining its battery, and the battery has lasted for however many years oldskewel has been doing this. After all, other manufacturers don't have wirelessly charged keys, and their fobs last many years without charging. (We had two Scion fobs which never needed battery replacements for the nine years we had the car.)
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  #19  
Old 05-14-2020, 01:53 PM
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I came here to say this -- there is no way that the diamond fob is being charged when it is hanging from the key that's in the ignition. Wireless charging becomes completely ineffective when things are misaligned like that, or when they are a couple of inches away. I am guessing this fob has just been draining its battery, and the battery has lasted for however many years oldskewel has been doing this. After all, other manufacturers don't have wirelessly charged keys, and their fobs last many years without charging. (We had two Scion fobs which never needed battery replacements for the nine years we had the car.)
Good info. When I'm back in there once the spare batteries arrive, I'll do some more careful testing, varying proximity and direction of the key coil, within the charging coil's field - both for the car ignition and the iPhone charging pad.

EDIT - the iPhone charger is a Belkin F7U027
https://www.amazon.com/Belkin-Boost-...075M59ZB7?th=1
https://www.belkin.com/us/support-ar...icleNum=274455

Based on my son's feedback, I really can't recommend it as an iPhone charger (too slow), but it most definitely charges my BMW keys.

Watching how it works, it does have a single green LED, that comes on briefly when the thing is plugged in. Then it comes on and stays on when an iPhone is placed on the surface.

BUT, when a key is put on the surface, the green LED will stay off, even though the key battery is being charged - confirmed with a voltmeter on the battery.

So I'm thinking this unit works by having a constant field out there, ready and scanning for any iPhones. Then when an iPhone is present and starts drawing power, it steps up to a fuller iPhone charging mode. True or not, the important thing for these BMW keys is that the charger's LED-off state is still charging the key.

My test setup is pretty convincing. I measure the battery voltage directly on the key, after it has reached steady state, and observe how it will click up or not based on moving it around. For the charging pad, it was clearly going up at about 1 mV per minute, with a very steady mV reading.

EDIT - some quick followup testing with the iPhone pad confirmed about 2x-3x faster charging based on the orientation of the key - specifically, with the key pointing basically down toward the flat charger, so the key's coil axis was within about 15 degrees of vertical, it was 2x-3x as fast increasing in battery voltage, vs. the key laying flat on the charging pad.

And more careful testing in the vicinity of the ignition key coil: Right at the location where a diamond key would be maybe 5x what the charging pad did. Field strength drops off pretty quickly with proximity in all directions, either axially or radially from that point. And slightly affected by direction (whether the key's charging coil is pointed at the ignition key coil) as well.

So the basic conclusion is that the key fob arrangement is definitely worse than the diamond key location, but still enough to probably keep things alive, perhaps needing an annual boost, just as I have found over the years. Now knowing the charging pad works will make that a non-issue.

Swapping in the new batteries went pretty easily. I did tune up the prongs slightly with my Dremel tool to let it fit at the right height, but I probably did not need to do that. Splitting the case was very easy using a sharp bladed utility knife. Reassembling with super glue gel worked great. I had also previously reflowed the critical solder joints at the buttons, and of course the battery connections were re-soldered in.

I think one of the batteries I replaced was definitely on its way out. It maxed out at about 2.82V after solid charging. The other one maxed out around 3.00V, and was probably good - and in that one, the real problem was probably only a failed solder joint. But I replaced both batteries with the new ones I ordered, keeping the old ones for the retired parts museum.

I also definitively tested when charging occurs at the ignition key coil. I had read conflicting info on here whether it is activated when the key is OFF, ACC or ON.

With a voltmeter on the battery, I confirmed convincingly for my 2001 E53:

Charging is on when the key is in ON and also in ACC. No surprise in the ON, the ACC has been reported differently.

Charging also works when the key is in OFF (and still inserted in the ignition key cylinder) and the car has not yet gone into sleep mode. So it charges for about 16 minutes after the key is turned off. I had seen conflicting reports of this out there.

BTW, I know exactly when my car goes into sleep mode because I have a dash cam that runs off a power source that is similarly on when the car is in ON, ACC, or OFF-but-not-yet-sleeping. So I could see when the dashcam's green LED went out it marked the beginning of sleep mode, which also was the end of key charging.
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Last edited by oldskewel; 05-19-2020 at 12:05 PM.
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  #20  
Old 05-19-2020, 12:07 PM
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All done now. I updated post #19 with my findings. Hopefully helpful.
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