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

jimbob

Active member
Aug 3, 2020
520
432
East UK
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.
Unfortunately its not quite as simple as that (wish it was). Really, you want a stable fixed resistive load and then measure voltage and current over time to give you the power output. Unfortunately the battery outputs are electronically switched which makes that very difficult to do. I would give it a go, but the cost of the batteries and risk of damaging them puts me off somewhat!
 

Rich-EMTB-UK

E*POWAH Master
Aug 11, 2019
369
283
UK
As am about to move to a Shimano based bike from my Turbo Levo this seems quite a concern but there again I was reading horror stories before I got my TL in 2019 and have had zero issues with that motor/battery combination which both show 100% health still and have been totally water proof and no drop in range.
So I guess like all electrical products some work better than others and some folks are just plain unlucky.
 

Deimos

Member
Apr 25, 2021
28
10
Germany
As am about to move to a Shimano based bike from my Turbo Levo this seems quite a concern but there again I was reading horror stories before I got my TL in 2019 and have had zero issues with that motor/battery combination which both show 100% health still and have been totally water proof and no drop in range.
So I guess like all electrical products some work better than others and some folks are just plain unlucky.


Best to buy a Shimano bike with a third Party battery then. Then you won't have that Problem.
 

Milan

Member
Sep 9, 2020
91
34
Czech Republic
After having this thread alive for sometime and trying to figure out where the problem with this battery and drive unit could be, would anyone dare making it clear why this is so?
 

Milan

Member
Sep 9, 2020
91
34
Czech Republic
poor quality in = poor quality out :)
Well then, I did understand well. Knowing that Shimano is familiar with that and puts the crap in and gets the crap out (known issue) is a form of lie as they simply cannot meet their advertised cycles and provide appropriate capacity of the battery in the long run.
 

Deimos

Member
Apr 25, 2021
28
10
Germany
You got that wrong. If you want to avoid that Problem and still ride a Bike with Shimano Motor get a bike designed with a battery from a third party like the New Santa Cruz Heckler or Focus Jam they come with a Darfon battery.

But if they are more reliable is another topic
 

Deimos

Member
Apr 25, 2021
28
10
Germany
If there were a third party battery with the form of the Bt-e8035 for example that would be super nice but i don't think we will ever see that
 

joxelitor

Member
May 23, 2020
28
27
Spain
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.
It´s only possible with laboratory mesaruments directly on the battery using a dc load and datalogger.
Fortunately i have both, the lab and a new battery so in the next months i plan to start using it and tracking capacity on the lab vs life indicated on the Shimano Display
 

Milan

Member
Sep 9, 2020
91
34
Czech Republic
If there were a third party battery with the form of the Bt-e8035 for example that would be super nice but i don't think we will ever see that
You got that wrong. If you want to avoid that Problem and still ride a Bike with Shimano Motor get a bike designed with a battery from a third party like the New Santa Cruz Heckler or Focus Jam they come with a Darfon battery.

But if they are more reliable is another topic
OK, did not know that, thx.
 

Milan

Member
Sep 9, 2020
91
34
Czech Republic
If there were a third party battery with the form of the Bt-e8035 for example that would be super nice but i don't think we will ever see that
Spoken to a guy who works for a company that may have some results regarding this in three months. I do not know how likely this is.
 

Pivot

E*POWAH Master
Jun 11, 2020
668
1,088
New Forest, England
I do get the desire to measure degradation of battery, and charging cycles is accepted unit of measure, however…
I am more interested how many km I can travel on the bike and battery charge.

Here are my numbers:
998km, 8 cycles, 100% health
IMG_9774.jpg
 

Spiff

Active member
Feb 27, 2019
448
263
Earth
Tesla Model 3 has 98% Battery Health (2% Degradation) after 160.000Km!!!!

[Sarcasm Mode ON]. What a shitty car, they should learn from Shimano designers Dumb and Dumber!!! [Sarcasm Mode OFF]

 

Milan

Member
Sep 9, 2020
91
34
Czech Republic
I do get the desire to measure degradation of battery, and charging cycles is accepted unit of measure, however…
I am more interested how many km I can travel on the bike and battery charge.

Here are my numbers:
998km, 8 cycles, 100% health
View attachment 81575
Fine and gr8, but your battery is BT-E8036 and this thread is about a different model. BT-E8035 drops down to 90% when you have 10 cycles.
 

Milan

Member
Sep 9, 2020
91
34
Czech Republic
Tesla Model 3 has 98% Battery Health (2% Degradation) after 160.000Km!!!!

[Sarcasm Mode ON]. What a shitty car, they should learn from Shimano designers Dumb and Dumber!!! [Sarcasm Mode OFF]

Yeah, it takes roughly 30 batteries BT-E8035 to make 160 000 km, each with 25% degradation and a bill worth of 18500 eur.
 

mad115

Member
Feb 9, 2022
6
2
Bratislava, Slovakia
is there really no Chinese alternative to the BT-8035?
I have two ebike with BT-8035 ;(( Each with different motor (E8000 and E7000) but degradation issue is same on both ebikes.
 

Milan

Member
Sep 9, 2020
91
34
Czech Republic
is there really no Chinese alternative to the BT-8035?
I have two ebike with BT-8035 ;(( Each with different motor (E8000 and E7000) but degradation issue is same on both ebikes.
Probably not...I was told (it may not be true), however funny or stupid it sounds, the battery and motor communicate too much. As a result, it is not as easy to produce a third party battery. I am not an expert, perhaps somebody else could shed some light on this?
 

mad115

Member
Feb 9, 2022
6
2
Bratislava, Slovakia
Probably not...I was told (it may not be true), however funny or stupid it sounds, the battery and motor communicate too much. As a result, it is not as easy to produce a third party battery. I am not an expert, perhaps somebody else could shed some light on this?

it doesn't sound very satisfactory.
do you think there is a chance to complain?
 

Milan

Member
Sep 9, 2020
91
34
Czech Republic
it doesn't sound very satisfactory.
do you think there is a chance to complain?
If your batteries are still warrantied, you only need to contact your retailer. Depending on the %, you will get a respond what to do. If your are above 80% (means that you have not reached the magical 5K km), most likely you will be asked to go under. If your Shimano dealer is currently with 0 batteries, the scenario may alter. If your warranty is not a rolling one and your bike is "out of service" for a month, your warranty will only extend by one month, i.e. with the next (2nd) battery you have to be fast and make 5K km as quick as possible and use your warranty again because you will have to do the same with the 3rd one too. Then you can claim your bike is not fit for purpose and can claim your cash back. Knowing this and having this discussed with a number of people, I consider this battery a fraud and think all owners globally should jointly make a claim.
 

mad115

Member
Feb 9, 2022
6
2
Bratislava, Slovakia
As i wrote recently, i have two ebike. I give here a summary of how I stand.
Unfortunately both ebikes I have with Shimano BT-E8035 batteries:
MERIDA eBIGnine E7000 1600km 20cycles 87% healty
CTM E8000 4500km 50cycles 80% healty


Although they each have a different engine; as well as a computer; they both behave exactly the same.
The behavior of the battery in Merida is the same as in CTM. After every 10 charges, the battery is degraded (by a few percent).
And of course the range is adequately shorter ..
This is a visible firmware error in the Shimano BT-E8035
Today I do not recommend anyone to buy a bike with BT-E8035 because it is incorrectly designed.
 

lightning

Well-known member
Apr 5, 2021
715
410
UK
My battery was showing 78% after 60 charge cycles, but the range, while less than new, wasn't down 22%
l would still get 30 miles of range where l could manage maybe 33 if l was lucky, when it was new. I sent the battery back and was sent a new one under warranty.

As that took over 2 months, l bought another battery, and despite being a brand new one it just about manages 30 miles on a full charge.

l am wondering if the drop in "battery health" is an issue with the BMS software rather than an issue with the actual cells in the battery.

Has anyone experienced a fall in actual range to coincide with their reduced battery "health" ?

For example if your battery is showing under 80% has your range actually dropped by over 20%?
So if you were getting 40 miles on a full charge you would be closer to 30 miles now.
 

Deimos

Member
Apr 25, 2021
28
10
Germany
Of course its Software related, shimano uses normal cells like every other brand.

Were it cell related not every battery would degrade exact the same amount in the same cycles.

So its out of question that its the Software that absolut shit. I wonder when the first batch with better software comes to the market.
They should handle it like bosch that the batterys are also updateable.

Can't believe it that they can't fix that Problem
 
Last edited:

lightning

Well-known member
Apr 5, 2021
715
410
UK
Okay, so if it's software then maybe forget it, stop checking the battery "health" with aftermarket apps such as Stunlocker and just ride the bike?
 

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