Guardian 3: Charged or Not Charged?

I currently use the Guardian 3 for CGM. When charging the transmitter, I place it on the charger like I am supposed to, and the green light on the charger starts blinking, showing that it is charging. Then I let it charge while I take my shower (it is in a different room, so humidity, temperature, etc. are not involved in this conversation). Afterwards, the green light is off, which (and correct me if I am wrong) means it is charged. But then if I remove it from the charger and immediately put it back on, the green light (on the charger) starts blinking again for 15 minutes or so. Did it charge the first time? How can I determine if it is charged before I connect it to my sensor? I think the charger should have a separate light indicating that it is charged. Even though I have never had any transmitter battery problems, it seems strange that it claims to be charged and then starts charging again before I use it. Has anybody else experienced this?


I don’t have the Medtronic cgm so ignore if this seems non-relevant.

My experience with other technology which uses current rechargeable batteries with auto-off in terms of charging is similar to what you mention.

A device left on the charger for a sufficiently long time and indicating fully charged will seem to indicate charging yet again if removed then placed back on the charger.

Potentially this is part of the underlying battery charge technology that senses a fully charged battery. My best guess is that the charger is not able to immediately detect a fully charged battery but rather requires a period of time after being placed on the charger in order to detect if the battery is in fact fully charged and no longer requiring a charge.

But without knowing how Medtronic has constructed their cgm and the charger this is only a guess.

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Mine works essentially the same way. After 7 days of use, the full charge usually takes about 30 minutes. Mine will also blink if I reinsert it into the charger, but in my case, only for about 5 minutes.

I cannot explain it, but what you describe is normal operation. It is not necessary to place it on the charger a second time.

Note: I am a Medtronic ambassador. My opinions are my own. They did not pay me to say nice things about Medtronic devices or the company. OK, they sent me a shirt and a cup but even I am more expensive than that.

Why put it back on

If it is a decent charger it will charge until it senses a voltage drop - this will take some time -

I am fairly new to the Guardian. Started November. I am unhappy so far because the claim was that it lasted 7 days. That refers to the sensor. However, I am not getting 7 days out of the charge in my transmitter. I start up Sunday morning and expect to change again next Sunday. I am experiencing transmitter battery expired long before that 7th day. I especially love the 2am wake ups. I try to work around my work schedule and life schedule so I can count on the CGM readings. It is not working out so well!

If you are not getting 7 days out of the transmitter charge, you might have a defective transmitter. You should call Medtronic and demand a new transmitter. My G3 is over a year old and and it has never failed to last 7 days until the change sensor alarm is triggered.

I am usually quite successful in removing the transmitter for recharging without removing the sensor, then reattaching the transmitter for another 7 days.

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I do not usually recommend using it for 7 days, because I have been told (and experienced in most cases) that even though that is the claim. My supplies are covered by insurance (if your supplies are not, then this schedule may not work as well for you), so what I usually do is change my infusion set & sensor at the same time (or if I need to change my infusion set often enough, every other change) even if the sensor is only at about 2 days remaining. I believe the accuracy decreases as the life approaches it’s end, and if your numbers have larger jumps (although hopefully they don’t, since that’s what we try to avoid) it can shorten the sensor lifetime.

I would exchange my transmitter. Having said that, the transmitter will be taxed if your blood sugar is going up and down a lot, or if there is excessive calibration.

Now in 19 months of wear I have never run out a battery, so that makes me think you may have a faulty transmitter. Call the help line and ask for an exchange. This may be as simple as getting the new version upgraded transmitter.

Note: I am a Medtronic ambassador. My opinions are my own. They did not pay me to say nice things about Medtronic devices or the company. OK, they sent me a shirt and a cup but even I am more expensive than that.

Thanks for the info. I will try Medtronic again. I went through a lengthy call with trouble shooting in January.

Thanks for the info. Your experience as described is what I was expecting. I will be in touch with Medtronic again.

My insurance does not cover these sensors so each one is $70 out of pocket or $10 a day.

So the only reason the sensor “expires” is the transmitter is dying? You are extending your sensor life by recharging? I realize you are not a doctor, but I have been searching for a way to make my supplies last as I am unemployed and without insurance.

I can usually get a second 7 days out of my G3; however, it sometimes gets wacky prior to the 14th day. Apparently, the chemicals on the sensor deteriorate after a while, usually after 14 days, but sometimes sooner