ejkeuck2

Background: Bike unused fro awhile. Charged battery but ended up with only a solid red light on the SM-EW90 B unit but no shifting capability. Decided to replace batteries in battery pack. No response needed about this.

When I disassembled the battery pack the battery output was checked with the two batteries connected together and measured 8V +. Individually each were 4V +. Therefore there didn't seem to be a need to replace the original batteries. When connected to the bike's battery cable there were no lights on the SM-EW90 B unit. Did a recharge for good measure with no change. I then removed the SM-BTR2 battery pack and rechecked the voltages. Again 8V + and 4V +. The voltages measured the same when checked at the soldered joints at the control circuitry. The readings were the same. Then the voltage at the end of the cable at the end of the pack was tested. The voltage seemed to repeatedly cycle from 4V, 0V, and millivolts. It did this either way the probes were connected. Is this normal? Barring a clear explanation I'll just replace the entire battery pack with the newer BT-DN110. However is there any difference between the BTDN110 and the BTDN110-A? (I understand that the newer battery packs will provide adjustment of features via E-tube.)

Many thanks

Barry2 

Often the cause of a Di2 battery that won't charge is the USB power supply.
Shimano spec is for input 5V 1A, but a lot of the 1A adaptors that come with phones can't actually manage 1A.

I'd suggest finding a 5V 2A adaptor and charging them again.

Barry

BTW Welcome to Bike Forums

mpetry912 

get a 12 v bulb like a tail light bulb at the auto supply store

solder 2 wires onto it, and attach alligator clips

use some wire to connect to the battery poles and drain the battery using the bulb as a resistor

then (re) charge the battery

/markp

Barry2 

Why?

Barry

mpetry912 

that's a very good question.

/markp

Barry2 

Only reason to discharge and recharge (Cycle) a rechargeable battery was due to the memory effect when using NiCad batteries.
NiMH and Lithium don't suffer from memory, so no reason to cycle.

Barry

jgwilliams

In fact it was my understanding that it isn't a good idea to fully discharge Lithium batteries. You get the best life from them if you recharge when they're down to 40% and only charge up to 80%, although I've never bothered myself.

TerryDi2C

There is no functional difference between BT-DN110 and BT-DN110-A.
(the -A is slightly better built though)

Barry2 

ejkeuck2 ,
Did you ever get the pack to charge ?

Barry