DIY battery for Shimano Di2 shifting - Page 1
Forum section: electronics / projects

author: artv
author_rank: Contributor
timestamp: May 29, 2022, 06:09:56 pm
content: HiI want to be able to carry an emergency battery for my Di2 on my bike (after a failed battery almost ruined a recent cycling trip!) It runs off a 7.4V Li-ion battery. I tried connecting my power supply in place of battery but get nothing. It looks like you need some electronics to get this working. I'm not sure where to start - but here is the electronics for the battery that I've stripped from a faulty battery. Can anyone in simple terms (!) explain if there's anything I can try to "trick" my power supply into running the Di2?It's only for emergency use so don't need anything for communications or setup.Many thanks!

author: thm_w
author_rank: Super Contributor
timestamp: May 31, 2022, 10:21:31 pm
content: It looks like BT+/Vc/Vss are the three tap points on the two batteries. If it doesn't see the middle voltage maybe its the case it refuses to work.Were the original lithium batteries dead? Do you have some spare cells you can try to connect, so that you have all three of those tap points connected properly?https://ionicindustries.com/battery-info/how-to-replace-battery-shimano-di2-sm-btr2-bt-dn110/

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 03, 2022, 02:50:24 pm
content: Have you realized you can replace the motor, battery, all the electronics etc, with just a simple lever and bowden cable?Nice and reliable, "just works".

author: thm_w
author_rank: Super Contributor
timestamp: June 03, 2022, 10:48:51 pm
content: Quote from: Doctorandus_P on June 03, 2022, 02:50:24 pmI don't use di2 or want to, but, if you don't understand the value it provides or have anything useful to add why are you posting?- lower weight- faster gear shifts- less chance of bad shifts damaging the chain- no adjustments necessary after the initial setup- shift lever buttons can be placed in multiple locationsDo you drive a car with a manual transmission?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 04, 2022, 10:56:49 am
content: A simple search:https://html.duckduckgo.com/html?q=shimano+di2+weightsuggests that di2 stuff is heavier, even though it has "light weight batteries".faster gear shifts..Yeah, I always am fiddling for 10+ minutes whenever I have to do a manual gear shift, that's very annoying.As for the rest, I see you're fully engaged in the marketing blabla from the bike manufacturers.I also do not use those paper thin chains that bend if you just look at them.Batteries go flat, wires get damaged, electronics fail when it gets wet, and if it ever fails halfway a trip it's unlikely you're able to fix it without specialized equipment. (If it's more then a broken wire).I once saw a part of the tour de france. Those guys go cycling for a few thousand kilometers, and then they find it important whether one guy is 0.2seconds faster then another. but during those first 1999.9km they constantly depend on each other. You may find that exiting when you're dragged into that world, but if you look at the overall view, it's nothing but utter madness.And yes, my car does have manual transmission.It does have those synchromesh rings though, does that still count for you?