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2 di2 batteries?

Posted: Thu May 18, 2017 7:13 am
by havana
Silly question...

I own a second internal battery as a backup. My primary broke down one day so I want to have a backup in my cycling bag.

Can I charge the battery by unplugging the RD and hooking up the secondary battery?

Re: 2 di2 batteries?

Posted: Thu May 18, 2017 10:33 am
by kulivontot
Don't think so. The batteries have a chip that communicates with the system, so I imagine they would conflict. In addition, the batteries would be at different potentials, so you'd effectively be shorting out the fresh one with the dead one. This is one place where the external battery mount has an advantage

Re: 2 di2 batteries?

Posted: Thu May 18, 2017 10:33 am
by Weenie

Re: 2 di2 batteries?

Posted: Thu May 18, 2017 11:44 am
by glepore
No conflict so long as the battery has same firmware version loaded as the system.

Re: 2 di2 batteries?

Posted: Fri May 19, 2017 9:04 pm
by Tristan
havana wrote:Can I charge the battery by unplugging the RD and hooking up the secondary battery?


I assume you want to use the RD wire as it's easily accessible and your primary battery is internal and thus hard to get to? Assuming you have an external junction A box you could unplug the etube wire leading to the junction B / RD / FD / primary battery and plug the secondary directly to the junction A.

I haven't tried plugging in or charging two batteries at once but this is how I charge a secondary battery.

2 di2 batteries?

Posted: Sat May 20, 2017 11:06 am
by havana
Thanks guys. That last solution is the easiest, it's also what Shimano recommends.

Re: 2 di2 batteries?

Posted: Sun Jun 25, 2017 6:51 pm
by froze
As an added note about these LiIon batteries, you should be charging the battery when it's no more than 25% used, if you charge when it's only about 25% discharged you could double your battery life in years, otherwise these batteries are only lasting 2 to 3 years on average because people are discharging them too far.

Re: 2 di2 batteries?

Posted: Sun Nov 12, 2017 4:19 am
by egebhardt
It depends if you have the external or internal battery.
Every 'Etube' system (6770 ultegra and on) requires a special 'chip' on the battery.
The external batteries have the chip in the mount. The internal batteries have the chip in the battery.

Re: 2 di2 batteries?

Posted: Thu May 10, 2018 2:28 pm
by bulls604
Did you try it out, how did it go?

Re: 2 di2 batteries?

Posted: Thu May 10, 2018 2:28 pm
by Weenie