I have a STEPS E8000 bike and wanted to make some improvements, like possibility to charge from any kind of CC/CV charger (even using solar panels when grid is not available) and to charge it to 41v to improve cycle life but things went wrong after first brief charge.

I charged(CC/CV) just a little from 40.3v to 40.6v when i observed that the battery level indicator is not working anymore.

The battery doesn't want to start at all and the Shimano charger is just blinking when connected, meaning some kind of error.

Now i have 2 options: buy a new battery or find some Shimano service but i have no ideea if Shimano fixes a battery without warranty.

The second problem is that im not sure if a new battery will work wihout pairing/programming.

Any thoughts why the battery(or BMS) got bricked when charging the cells directly and will a new battery work (plug'n'play)?


  • 4
    I think this question would be better asked on Electrical Engineering: the only connection with cycling is that the battery you're having problems with happens to be from a bike. The test I'd apply is this: somebody who knows about batteries will be able to answer your question even if they know nothing about bikes, whereas a cyclist will only be able to answer your question if they also know about electronics. Commented Aug 15, 2018 at 14:06
  • It's quite possible its the battery itself that is reporting some sort of error/sabotage state and the management software is taking the appropriate action. It's an expensive mistake, but i'd just contact shimano (or a distributor for them) and find out what needs to be replaced
    – Andy P
    Commented Aug 15, 2018 at 14:11
  • Depending on how urgent the matter is, you could contact Clive: youtube.com/user/bigclivedotcom. He disassembles/reverse engineers/has fun with everything electronic or electrical and would probably be able to tell if what you want to do is possible while making quite entertaining video. People send him broken battery banks on a regular basis.
    – Gabriel
    Commented Aug 15, 2018 at 18:20
  • It really seems that bms bricked the battery when the voltage started to increase unexpectedly. I had another ideea that it sensed a spike in the current when I put the cc CV charger(the charger output caps had to charge themself) and something went wrong. Commented Aug 16, 2018 at 19:17
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    Unfortunately no. I did try asking a Shimano dealer but got no response. I still hope it can be reset somehow, even though Shimano would sell me another one instead of fixing this one. Commented Oct 25, 2019 at 10:13

4 Answers 4


"The second problem is that im not sure if a new battery will work wihout pairing/programming.

... and will a new battery work (plug'n'play)?"

Yes, no problem, I've used three different batteries on my bike so far and no problem switiching between them, nor when the other batteries went back to their original bikes.

  • Yes, thank you. I've bought a new battery and it works without problems. Still not sure what to do with the old one. Commented Sep 25, 2018 at 7:46

It looks like you might have bypassed the charge controller on the pack and charged the cells directly? The smarter pack controllers do a form of coulomb counting and will see anomalous or unexpected pack voltages as a risk and premptively brick.

But before you get to that conclusion, I’d measure the individual cell voltages and make sure they are all within 0.1 volts of each other and that none are anomalously low. Balances often have a limited capacity for rebalancing and will brick a pack that is unbalanced too far.

Finally if you want to repair the pack, you may find a new / used pack controller part on eBay or you might be able to scavenge off an older pack. But be aware some controllers do brick themselves at end of life so you might be SOL anyway.

The worst case scenario is that you bricked the controller on the pack and you can’t recover the controller. It’s not a huge loss. You can still break the pack apart and use the 18650 cells in other projects or sell them on eBay.

  • Well, the battery is brand new and I would exclude from the beginning that the cells are unbalanced. I was thinking too that the cells are closely monitored by the microcontrollers and just bricked itself when the voltage started to increase. I hate this kind of too smart Bms. It will be an expensive lesson. Commented Aug 16, 2018 at 19:12
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    If the controller has shut it down, it can probably be "rebooted" by carefully discharging the battery to about 70% of charge. Commented Aug 17, 2018 at 1:07
  • Do you think so? Have you worked before with shimano batteries? Commented Aug 17, 2018 at 18:36

I looked at the Shimano protocol and they put a challenge response between the bike and the battery in order to prevent replacing the cell.

Looking at your picture, I see a white PCB in order to do not can follow the track of the component on the PCB.

By the way there is some glue on the components and connectors, that means they really don't want you to repair the battery yourself.

It would be helpful to see other pictures of the PCB, If you can show me the component references ?

Maybe if the battery is broken, I'd be interested to see the bottom of the battery PCB

  • I haven't dismantled the battery because I still hope that a Shimano dealer could reset it. I see that the charging port has a few communication pins also, I think a dealer could use some diagnostic equipment to 'reset' it. Now it's like bricked. It doesn't even turn on. Charger blinks like it's faulty. But it's not faulty, just the bms is too smart and shut down everything when I started to charge the cells bypassing the whole bms circuitry. If Shimano can't reset it then it's a very stupid design. I can imagine that they will say "it's not repairable" so to buy another one new for 500eur. Commented Jul 7, 2019 at 20:30

Are you sure all connections are clean between the battery and charger?

I try to keep things clean and have been advised by my dealer ( Cooksons in Prestwitch). Recently neither of us could see a problem so the battery was returned to Madison. They found particles within the charger battery interface. Magnificent service from both!

  • Hi, welcome to bicycles! Since the problem is the controller not responding (the battery management system is described as "bricked") not that it simply won't charge - it won't discharge either, or even report its state - so the problem is unlikely to be the charger contacts.
    – DavidW
    Commented Oct 23, 2019 at 19:25
  • Mine was also causing the charger light to strobe before eventually not allowing the charger to connect. The day before it would only do a part charge. Commented Oct 24, 2019 at 8:31

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