Bad Di2 Battery?

[scoobydrew]

I've been noticing my Di2 battery has been draining fast lately. It's the "BT-DN110A-7" battery for 11 speed Di2 that is inserted into the seatpost.

When I first built up my bike with a brand new battery, it'd last months before I needed to charge. Most recently, it gets completely depleted after a couple of rides (~100 miles total).

I went to charge it again today and noticed the error light on the charger had a constant blinking red light. Per the manual, I tried different power sources aside from the one I typically connect the charger to, but no luck.

It sounds like the battery is done, but wanted to get some input on whether this is the case or if there's anything I can do at home to diagnose. The battery is 3 years old (bought brand new) and only about 5000 miles.

[ap_az]

Your battery is done. This is how Li ion batteries fail. The charge capacity drops and they don't last as long. In some cases a cell will fail completely and then it just stops working.

Number of miles means very little as battery life is primarily a function of number of charge cycles, age, storage conditions, and luck.

[m_sasso]

Originally Posted by scoobydrew

I've been noticing my Di2 battery has been draining fast lately. It's the "BT-DN110A-7" battery for 11 speed Di2 that is inserted into the seatpost.

When I first built up my bike with a brand new battery, it'd last months before I needed to charge. Most recently, it gets completely depleted after a couple of rides (~100 miles total).

I went to charge it again today and noticed the error light on the charger had a constant blinking red light. Per the manual, I tried different power sources aside from the one I typically connect the charger to, but no luck.

It sounds like the battery is done, but wanted to get some input on whether this is the case or if there's anything I can do at home to diagnose. The battery is 3 years old (bought brand new) and only about 5000 miles.

Sounds more like you likely have some type of drain on your battery in your Di2 systems connections, these batteries are quite long lasting. There should be a build date on your battery. Shimano rates these batteries for 300 full charge cycles and could last as much as 10+ years.

Have you tried a different USB adaptor? How many amps is your USB adaptor? Battery testing https://www.youtube.com/watch?v=HjY95-U7_4U https://www.youtube.com/watch?v=3dmWqHR7b9w&t=541s

If you have any RC friends or RC people in your circle they likely have a Lithium battery capacity testing device and they could help you to evaluate your battery.

To purchase a tester: https://atorch.aliexpress.com/store/2949143

If your battery is truly finished I would be happy to purchase your dead battery as I need a battery case and battery brain for a conversion. Please let me know, thanks? I purchased the wrong battery a DN300, made for a 12 speed system and need to convert this battery to the older DN110 battery.

[caneye]

make sure there's nothing draining the battery.

you mentioned a different power source connected to the charge, how about the cables? They make a difference too.

I would check all connections first before changing the battery.


I had a similar experience with a DI2 battery (the old 10s external battery). After 8 years, I thought the battery was on its last legs because it couldn't hold charge. Bought a new battery to replace the old one and still had the same issue
It turned out to be a FD that failed not long after that .. so make sure you check everything before spending the $.

[BdaGhisallo]

If you have a spare front junction box, I would swap that in and see what happens. I have had two of those go bad and cause very rapid draining of the battery.