MiniMed Guardian Transmitter vs Charger Problem?

I’ve been having issues with my MiniMed Guardian sensor system. I want to know if it is the charger versus the transmitter that is faulty here. I plug the transmitter in to the charger and immediately the light is green as though it is fully charged, however even after a full night of charging the battery is only 13%. I tried to clean the pins on the charger and one looks kinda darker than the others- maybe dull or dirty? But I don’t want to drop $700 on a new transmitter and $150 on a new charger if I can figure out that it is one or the other having issues.
Of note, the transmitter does get found by my pump even though the battery is low and appears to be working to get my BGs to my pump.
Thanks in advance!

Is it still under warranty? Have you called Medtronics tech support?

I haven’t tried the mini med guardian, but I did have an Eversense system, and remembered that it would only charge on a 5w usb charger…USB c is now 18watts, and most chargers are now at least 2.4amps, or 10watts, so the actual charger might be the problem…most USB hubs are 2.4 amps…could also try to replace the charger

The charger is a product specific device and not a USB anything sadly. It is out of warranty which is why I am trying to be wise with how much $$$ I spend. Looking for any advice from Guardian users still and thank you all!

Amy G. Johnson MD

Is it this transmitter charger, with battery that can be replaced?
If so, did you try new battery ?

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I recall it lets you know the battery is low by blinking red

Hello Tony,

I did try installing a new battery. What happens is as soon as I connect the transmitter to the charger, the green light immediately flashes a few times, becomes solid green for a few seconds, then turns off. It is like it is telling me it is all charged when it is not charged much at all.

Amy G. Johnson MD


I am a Tandem and Dexcom kind of a guy … so have no relevant expertise … but hate to see folks struggle with technical stuff.

For starters, I agree with @MM1: the first thing to try is to get a nice, fresh AAA alkaline battery and replace it. While you are replacing the battery, look carefully at the battery you remove and the metal electrodes on either end of the battery case for any corrosion or white, crusty stuff (that is a technical term that only specialists use …).

If that looks OK, try again to charge your transmitter … looking, in particular, for any red and green flashing LED signals.

If I am not mistaken, this should be a link for the manual for both your transmitter and charger and includes details on changing the battery in the charger and using the LEDs on the charger to help troubleshoot the problem:

As I say, I know nothing about your Medtronic device, but as a retired, hands-on engineer I have fixed many thousand broken things in my career. Even on complex things, you’d be surprised to learn how many times a simple battery … or, in some cases … plugging something in … fixed things. I will hope that your repair cost is no more than the price of on AAA battery, but keep us posted if you learn more.

Best of luck … and stay safe!



While I was posting, I see that you have already replaced the battery. Everything nice, clean, and shiny in the battery compartment?

When I look at the troubleshooting on pages 21 and 22, I don’t see the flashing pattern that you are seeing described. Do you agree?

When you cleaned the charging pins, did you follow the instructions in the manual? Certainly discoloration CAN be an insulating layer that can prevent full charging. Can you try to post an image of those pins?

Good luck.