Q: I recently upgraded my bike with electronic shifting and—wow!—what a change. The shifting is perfect, but I worry that I will run out of battery. I have been charging it every ride. Is this bad to do, and what are your recommendations?
A: Glad to hear you love your new purchase and upgrade. Electronic shifting is excellent, but as you pointed out, there is a possibility of having a flat battery and being stranded in one gear. Just ask assistant editor David, who made this mistake at the 2018 DK200.
In reality, David suffered his battery fate because of a few mistakes. The most obvious is trust without verification. The process is pretty simple for the everyday rider who isn’t swapping parts around and making last-minute changes. Charge them when they tell you to or when there is about 25 percent left.
The batteries used in our cycling components suffer from the same limitations as most other rechargeable batteries. They have a total number of charge cycles before they lose total-use duration. The number of charge cycles doesn’t matter how full or empty the battery is. In short, If you charge them after every ride, the battery will not last as long as if you use the majority of the stored energy, then charge them.
Most modern cycling computers will wirelessly connect to your electronic shifting system and tell you the state of the battery. This is convenient because it offers a visual verification that you are okay, or an easy way to determine if another lap over the hill is possible.
If you don’t have a head unit with this feature, both Shimano and SRAM have a convenient LED system that gives you a more general idea of how much charge is left. Since they both rely on color changes and flashing LEDs for status checks, it’s less accurate, but if you see red, charge them ASAP.
In general, Shimano uses a single battery and, from our testing, it does last longer than SRAM. We generally get between four to six months out of a charge, but the whole system goes down when it goes flat.
SRAM utilizes a battery attached to each component, and while smaller in size they are interchangeable. We usually get 1 to 3 months of riding out of these batteries. However, if your rear derailleur battery dies, you can swap it out with your front one and finish a ride. You would have a limited gear range because your front would now not shift.
I would also note that the new Shimano semi-wireless shifters and all-SRAM wireless shifters use a coin-cell battery. These batteries are not rechargeable, but they are easy to replace, inexpensive and last nearly two years from our testing. If you are getting ready for a ride and see that your battery is low, charge it. Batteries charge very quickly to 75–85 percent, then trickle charge up to 100 percent. Putting the charger on for 15–20 minutes will give you more than enough charge to get through most rides. At the end of the day, if you charge too often, you will need to replace the battery sooner, but that’s probably three to five years down
In conclusion, charge your batteries when they need it, not all the time. The exception is if you are doing a huge adventure or long ride, then give them a charge before the big day, just don’t forget to start the ride with those SRAM batteries still on the charger!