SRAM eTap battery options?

[LittleWheelsandBig]

HK has had SRAM Red eTap on her Moulton since early 2019 and my Moulton similarly but more recently. Our Moultons are mostly used for 1000+km overseas brevets and we have ridden none of those in the past couple of years.

HK had a spare eTap battery from the beginning as eTap doesn’t make it all the way through a 1200 without a top-up on the rear at least. We do carry a charger and recharge during a rest stop but swapping a derailleur battery roadside is, at most, 30 seconds and some redundancy is a good thing.

One of her three batteries seems to be discharging prematurely after a long storage period (maybe half capacity?) and I probably  need to get another spare battery for myself. I see that there seem to be (slightly) cheaper aftermarket batteries available now, alongside the real deal. Does anybody have any relevant experience with replacement eTap batteries?

[LittleWheelsandBig]

The problem isn’t the battery not holding charge but the rear mech not going into sleep mode when not being ridden. Any tips on how to reset the rear Red eTap mech or otherwise solve the issue?

[Karla]

No idea, but please let me know if you find an answer.

[BFC]

It may not be the same, but I eventually figured out why my Di2 battery was sometimes flattened after parking the bike for a while.
I started checking that the thing still worked by shifting rear mech whilst stored, and shifting back to original position. This made the problem far worse - pretty much assured the battery would be flat when I wanted to use the bike - or at least a lot less charged than I expected.
The solution - the cranks must be turned a few turns after any intentional or accidental shifting to let the rear mech complete its idle adjustment after any shift. I now trust the bike for longer rides again!

Biggest risk is mass parking on big events and levers getting knocked by a third party. Pulling the plug somewhere between switches and battery may help but could cause other connector durability or water ingress issues on Di2.

For the SRAM issue keeping track of things tried and trying to identify cause and effect is the best way to narrow down a problem - it may turn out to be unfixable without a software or firmware fix though. Have you checked SRAM support for updates - or is the units software fixed at point of manufacture (not point of sale) without an update option?

[LittleWheelsandBig]

AXS 12sp has firmware updates but SRAM 11sp is frozen in time from release.

[Horizon]

I've had the original eTap on my Mason for just over 4 years now - no issues with it at all and very happy. That said, the rear battery cracked the tab in the warranty period, which was replaced under warranty, and it's been fine ever since. I read this was a common issue at one time, presumably they have fixed it by now, as the current series uses the same on. It is odd that the supplied dongle for servicing has never been implemented by SRAM and they effectively abandoned the series as soon as the 12 speed came along. I assume the sleep mode is triggered by a giro, which is why you're advised to remove batteries when transporting the bike. I wasn't aware that third party batteries were now available.

[Horizon]

As an aside, I've yet to hear of anyone who's changed the button batteries in the eTap shifters - SRAM I think said a 1 year life SRAM say a 2 year life - mine are still the original 4+years old and showing 'good' on the battery check after 7000 miles.

[jiberjaber]

As an aside, I've yet to hear of anyone who's changed the button batteries in the eTap shifters - SRAM I think said a 1 year life - mine are still the original 4+years old and showing 'good' on the battery check after 7000 miles.

Sounds like they are well shielded from the cold when in use, which is the opposite of power meters (garmin V2 & 4viiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii) which as soon as they temp drops the batteries start to have a shorter operational life as their volt sag under demand increases with lower temperatures, CR2032 - not sure whats in the SRAM shifters though?

[Horizon]

They're CR2032's. They are well embedded in the shifters, under the hood and a plastic cover, protected from windchill. I checked with SRAM and its up to 2 years, not 1 as I say above, but still impressive at 4+!

[grams]

Objects that aren’t above ambient don’t experience windchill.

IME power meters burn the majority of their power while indoors with no one riding them. The SRAM shifters only need to be woken up when you press a button, which is the ideal scenario for minimising standby current.

[BFC]

If you have been carrying spare batteries around that are as old as the ones in the shifters don't expect much out of them before they also fail when used. On these ultra long life applications battery life is more down to self discharge within the battery, it is also an issue with spare batteries for car remote keys - another on demand application.

Whilst there are guaranteed ways to kill batteries in some applications (like parking original garmin speed/cadence sensor with the crank aligned to the sensor), battery life cannot be extended past the real world shelf life. Some batteries suffer corrosion of their casings and discharge highly corrosive chemicals before their voltage drops.