Shimano BT-E8035 Integrated Battery Issue: very fast degrading and loss of range

[electricbogaloo]

This is my setup for battery capacity testing:
2 Multimeters with 5/12 digits resolution for voltage and charger current. Shimano charger EC-E6000 modified, removing the output fuse in order to interleave the current measuring multimeter (it´s a very low burden voltage).
AC parameters are logged too
Voltage is measured in the battery terminals, son any voltage drop is neglected, important for a good accuracy of the Wh value
I can measure accurate Wh and voltage values without opening the battery case, as I have calibrated the impedance of all terminals, bms and cables. It´s possible to get the charger efficiency too, so just measuring the AC Energy drawn from the mains outet it´s possible to get the real charged energy with great precissión without using all the test rig (for day to day charging after rides)

All this setup is controlled over the LAN Network with PC and software that logs all the values, calculates parameters and generates graphs.
View attachment 73168
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And here are the results of one test
The battery is a BT-E8010C 504Wh 83% life and 90 cycles
The battery was discharged down to assit cut and then futtly charged at 25ºC
Light is off in firmware (important!!!)
Life in Ah measured, 80.4% is close (whithin 2.6% error) to the life estimator of Shimano (83%)
Seems that Shimano is calculating Ah capacity over the nominal value on the sticker, 14Ah


View attachment 73172
The % values with * are calculated over the Ah and Wh charged in this test (not the nominal Ah and Wh in the sticker)
As the cycles increase, the degradation will increase too, and so these % values will give an idea of the real life decrease and how many cycles it take for certain degradation to be reached from this point

Very interesting! Keep up the good work! Would be nice if you could do this with batteries from other manufacturers aswell also with measurements over time so that we can see how the batteries degrade over time.

 

[surfperch61385]

I have the same issue. Dont have the numbers but im under 100 charges. The technician at REI tested my battery and check the number of cycles and he told me it was degrade far more than it should have been.
I ride the same trail and every ride the battery dies faster than it did the day before. So I'm not going off display readings but how far I can ride up the same trail.
Shimano said it was probably the motor so they sent a replacement but that didn't fix the problem.
Currently Shimano doesn't have replacement batteries. Been waiting over a month now. Probably going to have to wait till early next year.
One thing I noticed early on is that my motor was overheating. The tech at REI says its probably because the battery isn't supplying enough power. Shimano disagreed and said it was probably the motor. New motor does the same thing.

I'd recommend temping your motor. Im not riding my bike anymore because the motor is getting too hot and I dont want to ruin it. Tech said over 125°f is too hot, my motor gets up to 150°f in under 1/4 miles going uphill in boost on a cool day.

 

[lightning]

Wow okay, that sounds bad. My battery "health" is at 80% after about 60 charges, which is pretty poor.

I don't know if the motor is overheating though, how would l know if it was? The casings feel cool and there's no smell from it.

l assume the power backs off if the motor gets too hot, one thing l rarely use "Turbo" and even when l do, it's set at 200% (the max is 300%) so my motor is never being pushed to the limit.

 

[Spiff]

Wow okay, that sounds bad. My battery "health" is at 80% after about 60 charges, which is pretty poor.

I don't know if the motor is overheating though, how would l know if it was? The casings feel cool and there's no smell from it.

l assume the power backs off if the motor gets too hot, one thing l rarely use "Turbo" and even when l do, it's set at 200% (the max is 300%) so my motor is never being pushed to the limit.

If it is still in Warranty, at 80% degradation you can have it repaired/replaced by Shimano

 

[jimbob]

Just to feed more information. Talking to friends who have the same battery with more or less the same number of cycles. I decided to cross information and without any surprise all of them presenting the same pattern, which in my opinion, seems to be a flaw in the firmware of these batteries.

All 3 with 90% health in any application.

and anothe friend ha a battery with 9 cycles with 100% health.

Seeing all these facts, it seems that the drop in the number happens every 10 cycles.
In the past users of the firsts speshhh Turbo Levo reported a similar problem, which was corrected through a firmware update, perhaps this is the case.

I'm taking my bike in on Saturday for a warranty claim. I'll let you all know how I get on!

Its at 76% at 86 cycles.

 

[Spiff]

I'm taking my bike in on Saturday for a warranty claim. I'll let you all know how I get on!

Its at 76% at 86 cycles.

Yes, let us know please. And don't tell Shimano if you use Stunlocker to check the battery, they may void the warranty.

What was the previous Battery Health?

Did it just go down to 76% at 89 Cycles?

Mine is at 87% since 20 cycles, now is at 28 cycles

 

[lightning]

Mine's heading that way.....Shimano BT-8035

60 charge cycles and down to 79%

 

[Spiff]

Mine's heading that way.....Shimano BT-8035

60 charge cycles and down to 79%

Mine is the external BT-E8010

 

[pete-E1]

I just noticed the other day my range was 89km after a full charge and riding 2km, figured I'd pushed hard on the 2km of hills...... Noticed it again tonight after a full charge and putting the battery into my bike.

12 cycles and 90% health. I've contacted the bike shop and Shimano Australia directly to see what answers they both give.

 

[lightning]

They likely won't do anything unless
the battery "health" drops below 80%

 

[pete-E1]

They likely won't do anything unless
the battery "health" drops below 80%

Well, at this rate, it wont be long before it goes below 80%.

 

[lightning]

lt won't, but l am not sure about the accuracy of the battery "health" on the app.

My battery health had dropped to under 80% after 60 charge cycles according to Stunlocker

l bought a new battery and sent the "faulty" one back under warranty.

l've found that the brand new battery has little extra range than the one that had "78% health"

From that battery l was getting 30 miles of range.

And the new battery? On the same kind of riding, and the same routes, under 35 miles.

First charge was 33 miles and it shut off
Second charge was on the reserve at 32.5 miles

So why, if my battery health was supposedly down to 78% am l achieving barely any more range from a brand new replacement battery?

 

[lightning]

Update

lt seems after a couple of charge cycles my new battery has improved

This ride included 2,500 feet of climbing on and off road, mainly in "Trail" and ridden as fast as l can reasonably manage. One KOM and three PR's
So not cruising

(Not sure why the photo appears on its side. lt's not on its side in my photos)

 

[lightning]

28% battery left according to Stunlocker

 

[Deimos]

Update

lt seems after a couple of charge cycles my new battery has improved

This ride included 2,500 feet of climbing on and off road, mainly in "Trail" and ridden as fast as l can reasonably manage. One KOM and three PR's
So not cruising

View attachment 79088

(Not sure why the photo appears on its side. lt's not on its side in my photos)

Shimano changed something with the last update. At least thats what i think, because the battery Life on my 2 BT-E8035 increased by 6%.
1. Battery - before Update 85% to 91%
2. Battery - before Update 87% to 93%

And the strange drops after every 10 cycle are gone.

 

[jimbob]

Shimano changed something with the last update. At least thats what i think, because the battery Life on my 2 BT-E8035 increased by 6%.
1. Battery - before Update 85% to 91%
2. Battery - before Update 87% to 93%

And the strange drops after every 10 cycle are gone.

Was this an update to the bike firmware?

 

[Deimos]

Was this an update to the bike firmware?

Think the Update for the EP8 caused It because in the Patchnotes it states this :

・Improved the display accuracy for the assist traveling range.

 

[Gary]

 

[Spiff]

Which FW was updated ?
Battery or EP8?
Can you please post the new version number

I ask this because if the Battery FW is not updated and the battery is moved to another bike, then the battery health will be the old one.

 

[Deimos]

Which FW was updated ?
Battery or EP8?
Can you please post the new version number

I ask this because if the Battery FW is not updated and the battery is moved to another bike, then the battery health will be the old one.

21. Dez 2021
DU-EP800
4.1.8
・Bug fixes for the error detection function.
・Improved the display accuracy for the assist traveling range.

Thats the Update that triggered the change.
At least thats what i think.
They Updated the Firmware of both ETube Professionell and ETube Cyclist at the same time. But nothing related to the battery as far as i see.


I don't think Shimano releases updates for their batterys? And i don't know wich firmware is or was on my batterys.

Pretty sure that it shows the old values on a Bike with other Firmware Like you said. But i can't test it i'm the only one under my Friends with a Shimano Motor

 

[Bobcat]

Same for me, after the latest update my battery health 'increased' 6%. Now shows 91%, before the update it was 85% after only 30 cycles which is poor - especially as I very rarely use boost and the battery is kept indoors.

Either way the battery life has noticeably reduced, especially the remaining 2 bars - when it gets to two bars now if you aren't near home/the car you better start panicking, it literally dies after 3-4 miles on ECO.

This manipulation of the battery health reading seems suspicious to me, I was expecting mine to drop to 80% in under 40 cycles which would have been a warranty claim, now the 2 years might pass before I get to that point. Seems deliberate on Shimano's behalf to stem the amount of claims.

 

[Milan]

I have promised an update on the new battery that I warrantied when the capacity was around 76%. Shimano asked me to be below 80% first. It took around two months to get the new one. The new battery has now 10 cycles and follows completely the same pattern as was described by many. The capacity has dropped down after only ten cycles to 90%. Since I had it completely new, I treated it entirely like recommended. Charge full only prior to the ride, do not let it discharge below 20%, keep it at room temperature etc. Running the same motor E7000, no overheating. As I mentioned earlier in the first post, you can do anything but this combination of the battery BT-E8035 and Shimano motor degrades very very fast....And now I wonder what I should do in the times when Shimano has no spare parts at all and would only ask me to go below 80% again

 

[Gary]

Sorry to ruin the #drama but your battery health showing a value of 79% doesn't actually stop you riding.

 

[Milan]

Sorry to ruin the #drama but your battery health showing a value of 79% doesn't actually stop you riding.

Hey Gary, long time no see. I’ve been missing your sarcastic remarks No drama here. Will continue riding, only the rides are getting shorter as you would know if you had that combo. IMHO it is pretty unfair/appalling to lose 10% of the battery capacity in just 10 cycles.

 

[lightning]

Would you say that the actual range has dropped 10% when your battery "health"
dropped 10%?

My battery was at 78% "health" after 60 charge cycles.
Although the range was less than new, it certainly wasn't down by 20%.

 

[S13]

Yeah where does it say that battery health is the same as battery range?
Could be that 50% health is still like 90% of its original range. And 0% health is 80% of its original range, or something like that.
Go with actual range numbers, not a "health" number in an app.

 

[jimbob]

Yeah where does it say that battery health is the same as battery range?
Could be that 50% health is still like 90% of its original range. And 0% health is 80% of its original range, or something like that.
Go with actual range numbers, not a "health" number in an app.

True, although very unlikely it is anything but a direct percentage of original capacity.

That doesn't mean that the reported value is correct of course.

 

[Milan]

Would you say that the actual range has dropped 10% when your battery "health"
dropped 10%?

My battery was at 78% "health" after 60 charge cycles.
Although the range was less than new, it certainly wasn't down by 20%.

I have not figured out a way how I could objectively compare a range of a new battery vs. a battery with a 10% drop. You would have to take the same route in the same weather conditions I guess. The battery was new before the summer and now it is 0 or below zero degrees here. All I can say that with the previous battery, which followed the same pattern as this new one, the health status corresponded to the shorter range. When having a new one I could go for a 45-50 km ride not worried if I can make it home. When having 76% and taking a similar ride, I could make 25-30 km and scared about the last two bars as they die faster. So yes, the health status shows a real drop in the range.

 

[Milan]

Yeah where does it say that battery health is the same as battery range?
Could be that 50% health is still like 90% of its original range. And 0% health is 80% of its original range, or something like that.
Go with actual range numbers, not a "health" number in an app.

When you have a new battery the ECO range shows 100 km and the health status 100%. When my ECO range was 76 km, the battery health was 76% plus or minus one percent. We all know that you cannot make 100 km in ECO unless you mostly ride downhill and have it turned off for about 40 kms. My experience is such that when I lost 25% in the health status, I lost around 20 km of the real range. It may not be linear but 10% in health would make 8 km. Most people will not realize any difference, because they do not bike daily and they do not do 45 kms.

 

[robbydobs]

Just had a look at my batteries. They are the older external BT e-8010 style.

Battery #1 - came with a 2018 Meta Power frame purchased Feb 2021 (i.e. a very old battery!)
41 cycles
97% health

Battery #2 - purchased after market, June 2021
26 cycles
88% health!!

Maybe they switched to some cheaper cells after a while and hence removed all the guarantees about capacity??

As for proving the capacity / range drop, I guess the best way would be to attach a mutlimeter to the outputs and sum up the current being delivered over time? Do multimeters do that??
I've got a cheap usb volt/current meter from ebay that does that for usb chargers.