SRAM AXS rear derailleur low battery warning in spite of the battery being charged, could it be the weather?

I am getting a low battery warning on my SRAM AXS rear derailleur g in spite of the battery being charged. I put in a freshly charged spare, same problem, swapped the battery with the front where it works but get another low battery warning for the rear. Anyone know what this could be? It is sort of chilly here (around 0 centigrade so not really cold)

(edit:i just brought my bike inside and no more battery warning)

I have a similar issue but believe the problem may be my bike computer and not the rear derailleur. I have an older Wahoo Element and it gives me multiple low battery warnings (the SRAM AXS rear derailleur being one of them).

Not sure if you’ve considered your bike computer is the issue?

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The led on my rear derailleur flashes red and the axs app also reports low battery

Interesting.

I went out last week on the gravel bike. Temp 2-3 deg C.

Checked the battery before leaving - green.

90 minutes into the ride - 20% warning.
2.5 hours into the ride - 10% warning.

Took the fast way home (on road), for just over 3 hours ride time.

Are you suggesting that a) the low battery report is inaccurate in the cold or b) the battery life is significantly reduced in that temperature?

To over simplify, the colder the temperature, the slower the chemical reactions (i.e. the battery drains faster). For example, Telsa only gets about 70% range below freezing compared to 70-75 degrees.

PS. You all are beasts for riding in those temps!

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If it only happens when it’s in the RD and shows green in the FD, it sounds like an issue with the RD. Either not making good contact (try cleaning the contacts?) or just not properly reading the voltage. I’ve had pretty good luck calling SRAM support direct on these kind of issues. They may tell you you need to take it to your LBS if they deem in a possible warranty issue, but they can be helpful with troubleshooting.

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Ahh ok. I was going to suggest that it might be the shifter, not the derailleur, as I was experiencing that a few weeks ago.

My computer (Wahoo BOLT v2) alerted me that the rear AXS battery was low at the end of 2 different rides, but it turned out it was the shifter battery, not the derailleur battery.

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I had similar issues with my RD recently and had to get a warranty replacement as I wasn’t even getting a 2 hour ride out of a fully charged battery. LBS reckoned it was a water damaged RD

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I have crud battery life in the cold on axs. I just started bringing a backup just in case. Picked up some off brand axs batteries that as far as I can tell are identical, without the “SRAM” logo on them. was like $75 for a 3 pack with a charger

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I have noticed similar thing a couple of times with my Edge 530. The computer has given a warning of low battery, but when checked with Sram AXS app, the battery is just fine.

In general the AXS batteries do not suffer very much in cold weather. I ride my AXS equipped mtb during the winter months in temperatures ranging from just a couple of degrees below zero to 15 degrees below zero and the batteries work just fine. My rides are short, usually less than two hours, however.

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Both are true. In cold weather the battery’s internal resistance will increase resulting in false low battery readings, but also a reduced capacity. However at 0C the actual reduced capacity should not be all that big a deal, whereas internal resistance will be considerably greater.

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I think the plan will be to go out in the cold with a spare battery, and a) check the app (didn’t think of that for some reason) and b) see if the original actually stops working after carrying on riding through the 10% warning on the Garmin