eTap battery leaking

brownian

My SRAM Red eTap rear derailleur battery seems to be leaking. After charge, it is fine for two days of weekend, then I hang the bike in the garage. Next Saturday, the rear battery is flat.

The bike doesn't move and the pedals and wheels don't turn, so eTap should be 'asleep'. Indeed, after I swap for a fresh battery, the shifters have no effect until I've spun the pedals.

Seems like the battery+derailleur is leaking power. It happens with all three of my batteries (so it's not just a dodgy battery).

This happen to anyone else?

crosstownk

Have you tried the same batteries on the FD? If they behave normally on the FD then I'd say the RD is the culprit. It's also worth remembering that the RD is master unit for the system.

ED E

Leaking + lithium had me confused from the title - Liion cells don't typically leak. But you don't mean it in the normal way.

If you have access to a multi meter or simple voltmeter:
1. Charge the cell fully
2. Leave stand for 6hrs
3. Measure voltage
4. Wait 3 days
5. Measure again

If significantly different then its an internal short in the pack and thus is for the bin/RMA to retailer. If its good then you need to check the rest of the system for a short.

brownian

@crosstownk - yes. Only the RD causes the battery to run down.

@ED E - sorry for terminological inaccuracy. I know it's not the battery ('pack'?), as all three of my batteries (which are interchangeable) run down in the same way. How does one check a RD for a 'short'?

I don't have a multimeter, but I could lay hands on one, I'm sure.

Thank you both.

lismuse

By any chance was the shifter making contact with a wall or something else while idle ?
Was the rear derailleur left in either the highest or lowest gear and making contact with a limit screw ?
Was there a Garmin or other device that had not been disconnected ?
Firmware update ?
Other than that its the unit itself.

ED E

Fool on me, ETap packs mount on the F/RD directly so there's no cable to even investigate a short. Internal failures would be beyond user servicing. As long as you're sure theres nothing waking it then I'd be looking at warranty.

smacl

brownian wrote: »

I don't have a multimeter, but I could lay hands on one, I'm sure.

I'd guess a multimeter would possibly just confirm what you already suspect. If you get one, put it on an impedance (resistance) setting, disconnect the battery. and measure the impedance by touching the probes to the battery inputs. The impedance should be very high (or infinite indicating an open circuit) and be similar for front and rear. I'd suspect it is much lower at the rear indicating some kind of partial short. Try cleaning around the connectors using an alcohol swap or similar on the off-chance it is external gunk of some kind causing the issue, but I'd guess it is more likely internal caused in manufacturing, water ingress or picking up a knock. If its in warranty at this point, I'd return it. Otherwise I'd take it to someone good at servicing delicate electronics.

Crocked

If the garage is unheated could the cold weather be affecting the battery?

Idleater

Crocked wrote: »

If the garage is unheated could the cold weather be affecting the battery?

That's a good point, I remove the batteries and keep them inside in winter as the bike isn't used.

crosstownk

brownian wrote: »

I don't have a multimeter

Obviously warranty would be the preferred option if it's available to you.

However, if you're stuck for a lend of a multimeter, send me a PM and we can sort something.

TychoCaine

crosstownk wrote: »

Obviously warranty would be the preferred option it's available to you.

However, if you're stuck for a lend of a multimeter, send me a PM and we can sort something.

yeah, this is an open and shut warranty case. All 3 batteries get drained only when connected to the RD. Contact Sram. In fact I'd go further and say not to go poking around yourself, as they could use it as grounds to void your warranty.

brownian

So...I talked to SRAM, and they said bring it back to the shop. The shop's in Italy. But they said that maybe (?) a local sram shop would look at it...the Bike Rack is one such. So I'll go down and have a chat with John or Al....

Thanks all for the feedback. And to crosstownk for the offer.