2 di2 batteries?

Discuss light weight issues concerning road bikes & parts.
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havana
Posts: 353
Joined: Tue Jan 09, 2007 5:04 pm

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?
Most "innovations" in cycling are solutions for non-existing problems.

by Weenie


kulivontot
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Joined: Sun May 16, 2010 7:28 pm

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

glepore
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Location: Pa USA

by glepore

No conflict so long as the battery has same firmware version loaded as the system.
Cysco Ti custom Campy SR mechanical (6.9);Cannondale SS Evo Di2 7970 (5.79); Willier Cento Uno Air Di2 9070 (7.0); C40 Mk2 DA 7800 ; Anvil Custom steel Etap;1996 Colnago Technos Record

Tristan
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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.
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havana
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Joined: Tue Jan 09, 2007 5:04 pm

by havana

Thanks guys. That last solution is the easiest, it's also what Shimano recommends.
Most "innovations" in cycling are solutions for non-existing problems.

froze
Posts: 69
Joined: Thu Aug 05, 2010 3:47 am

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.

egebhardt
Posts: 31
Joined: Wed Mar 19, 2008 8:38 pm

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.
Eric in San Carlos, CA

by Weenie


bulls604
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Joined: Thu May 10, 2018 7:08 am

by bulls604

Did you try it out, how did it go?

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