Bosch Battery Full?

[Ravi Kempaiah]

It literally doesn’t matter what voltage the charger cuts off at,

It absolutely matters and determines what is being fed into the battery. Controller only reads what the battery has and translates into % or bars on the display.

The reasons behind speed display inconsistencies are already well known

No, people don't know why there is a discrepancy.
Re positioning the magnet onto crank-arm doesn't increase the speed!

That you keep attributing different speed/GPS behavior to different controllers demonstrates you are reasoning about the system from a position of ignorance, which is why your conclusions do not reflect reality.

It is not hard for me to attack you and call you an ignorant snob who doesn't know the basics of physics or EE 101. But, I will let it pass this time.

I have/had 2 Haibikes, 2 Bulls, 1 R&M eBikes with Bosch motors. I know these systems well and Bosch has done some good stuff and some average stuff.

Without knowing the BMS cut-off voltage to which charger stops charging, we can't say what is 85% or 95% or 100%. This is not some rocket science.
If someone wants to feel special because they invested some money into a bike but there are inaccuracies and want to attribute it to some special feature, it is upto to that individual.

 

[lerxst]

Here’s some more detail for you:

Charging Bosch batteries isn’t as simple as applying a constant-current charge voltage and letting the batteries soak up the coulombs. The battery charger first sends a digital signal to the battery to tell it to connect the cells to the external connector (this is why you get a 0 voltage reading if you try to measure your battery with a volt meter. Your meter isn’t sending that magic signal on the battery’s external third pin.) The charger itself actually writes data into the battery’s on board permanent memory regarding the charging parameters. The battery writes its own data to that memory in certain situations too.

That data, in addition to cell voltage, is read by the motor and used in its algorithm for determining what percentage to send to the controller for display. There is likely a lot more going on here than what I’ve described, but that’s the gist of it.

Speed is much trickier and Bosch has done some extra proprietary stuff here to prevent people from exceeding the manufacturer’s speed limit by lying about the size of their wheels in the configuration screen. I do not know the full details here, only that it’s happening, and that it’s a factor in speed display discrepancies.

Furthermore, GPS speed is not always accurate either, especially systems that do not use very high frequency GPS readouts (like Draggy, for cars). It is normal, outside of the field of metrology, for two measuring techniques to report different values for the same measurement.

 

[lerxst]

Ravi, because you have shown us how passionately you believe in the value of knowing the cutoff voltage, despite my attempts to explain why knowing that value will have zero practical impact on charging and operating a Bosch bike, I have set out to determine it for you. I appreciate your passion for understanding these machines, a value I share with you.

I’ve got my 70% full Bosch Powerpack 500 connected to a Bosch 4A charger, while my meter monitors the charge voltage. Once it’s done charging, I’ll note the voltage, and also note my bike’s estimation of its charge percentage. I’ve got to do some other stuff for a few hours, so expect another post later tonight.

 

[Ravi Kempaiah]

The battery charger first sends a digital signal to the battery to tell it to connect the cells to the external connector (this is why you get a 0 voltage reading if you try to measure your battery with a volt meter. Your meter isn’t sending that magic signal on the battery’s external third pin.)

It is not some magic signal. It is well-known that Bosch charger puts out a 5V signal which unlocks th charging procedure and Justin at @Grin Tech has done testing of Bosch batteries.
The Bosch BMS is set to 5A max (different for the 6A fast charger). Similarly, the way BMS is programmed is what dictates the resting voltage of the battery at full charge. if someone is reading this thread, they can benefit watching this video and I have linked the exact point at which they discuss the Bosch batteries.

 

[lerxst]

Came back to my desk to check on the battery and saw your reply- thanks for the video, I didn’t know about the 5v unlock signal! There is still some magic remaining, though (a term I use to mean a phenomenon that is known to exist but for which details are unknown, to me at least), because according to the video you linked, the 5V signal allows for a charge current of up to 5.3A. We know that a 6A Bosch charger exists. So what we don’t know is the unlock signal for that higher rate. Maybe it’s 10v? Glad to see you linking empirical data to back up your claims!

Same video also quotes a Bosch charge cutoff figure of 4.2v per cell, isn’t that value sufficient for your purposes?

 

[lerxst]

Similarly, the way BMS is programmed is what dictates the resting voltage of the battery at full charge.

Do you have reason to believe that different battery packs of the exact same model battery have differing resting voltage programming?

 

[Ravi Kempaiah]

4.2v per cell,

This 4.2V/cell is quite different from the 5V unlock signal.

Charging your Bosch battery to 4.2V/cell is not a good idea. Knowing what voltage/cell the BMS in Bosch batteries charges to, will yield tremendous benefits.

 

[lerxst]

Yes, I quite agree with you, but you missed my point. Earlier you seemed to care quite a lot about what the Bosch charger cutoff voltage was. In the very video you linked, he quoted 4.2v per cell as the Bosch charger cutoff. Isn’t this value sufficient to answer your question? Had you just not watched the video before talking about the unknown cutoff voltage?

 

[Ravi Kempaiah]

Yes, I quite agree with you, but you missed my point. Earlier you seemed to care quite a lot about what the Bosch charger cutoff voltage was. In the very video you linked, he quoted 4.2v per cell as the Bosch charger cutoff. Isn’t this value sufficient to answer your question? Had you just not watched the video before talking about the unknown cutoff voltage?

I hope I don't come across condescending!

In the video, he said....."you know (if you know) Bosch charger charges to 4.2V/cell and you can to limit to 4.05V/cell and get 5 years instead of 2 years"...

4.2V is the upper cut-off for 99.99% of the 18650 cells used in eBikes. Not just the cells used by Bosch.

Smart chargers like Satiator gives you the control to change that voltage/cell but most chargers don't!
On top of that, you could engineer the BMS to limit charging voltage just like the current and at what voltage it initiates the balancing. So, you could make your BMS limit the charging voltage to 4.1V/cell and start the balancing process at 3.8V/cell not at the end of charging cycle.

So, what I have been emphasizing in this thread.." we don't know if Bosch has engineered that limit into the BMS".

This is all that matters. What the display shows has no bearing on cycle life whatsoever.
If the upper voltage cut-off is 4.2V, then Bosch has NOT done anything smart here.

If you need a quick primer on how Li-ion batteries work, we made a video explaining that:

 

[lerxst]

Well, now we do know the cutoff voltage, at least for this set of variables:

1. Powerpack 500
2. Charged off bike, using Bosch 4A charger
3. Bike reported charge as 100% this time, only ever seen that once before, but this is good for our purposes.

As you can see from the image, the highest measured voltage before the charger started backing off was 41.853. Given that these packs are 10 series, 4 parallel, this gives a voltage cutoff of 4.1853v per cell, rounded to 2 decimals is 4.19v, which is pretty damn close to the 4.2v quoted in the video you linked. I do not believe your interpretation of his words as stated here is accurate. I believe he truly was saying the cutoff is 4.2v because he's seen the same measurements I have. But maybe it really is specifically 4.19v and not 4.20v, in an attempt by Bosch to extend usable lifetime of the pack. If they were really striving for that though, I think they'd go lower than 4.1853v.

 

[steve mercier]

Whew....it was looking like pistols at dawn for a while back there.

 

[lerxst]

Without knowing the upper cut-off of Bosch battery BMS attributing some smart battery management to Bosch batteries is just pure confirmation-bias and Pollyanna.

Until the upper cut-off voltage of BMS is known, everything we discuss is pure speculation.

Without knowing a simple parameter like "BMS cut-off voltage limit", you can't somehow attribute some special feature to batteries either

Again, without knowing BMS cut-off limit, we can't say what is 100% and what is 95% and whether it is an inaccuracy or otherwise.

Without knowing the BMS cut-off voltage to which charger stops charging, we can't say what is 85% or 95% or 100%. This is not some rocket science.
If someone wants to feel special because they invested some money into a bike but there are inaccuracies and want to attribute it to some special feature, it is upto to that individual.

We now know the cut-off voltage. Please tell me what's changed because of this new knowledge? Genuinely curious.

 

[tallpaul]

I posted this question a couple of time previously but never got a definite answer.

Interesting thread here. And a lot of response!

I posted these two threads here months ago....

Purchased a new Bosch 500w battery recently and it seems when I charge it I get the same less then 100% charge indication (on my Nyon controller). Usually around 96-97%.
I thought on my old battery that was an indication of usage over the last two years, but this new battery shows the same thing.
Could this be a malfunction of my Bosch charger?
Anyone else experiencing this? Any input appreciated!

I did have the LBS run diagnostics and updates when I got the battery and everything came up ok.

and ...
On my Bosch Performance Class 3 Haibike I notice now that after charging the percentage indicator on the Nyon controller indicate only 95% (occasionally 98% or even 100%). Previously it always charged to 100%. I can plug the charger back in and it will go to 100%.
Perhaps there is a fault with either the charger or the battery? Any ideas appreciated. On my rides I like to have full capacity to go as far as possible.

So it goes still to 95% or so. Charged on or off the bike. Either battery (new 500 and original 400).

Mystery could be put to rest if Bosch was good enough to chime in.

 

[Mr. Coffee]

I'm curious...

Is there any reason to believe that the percentage display itself might be in error?

More precisely, what gives any of us the confidence that the calculated percentage is in fact correct?

I doubt anyone has done a controlled-range test over a known course to know if how many kilometers you can get out of a battery changes in any way with respect to the indicated percentage. And I further suspect that it would be very difficult to find a difference.

 

[Ravi Kempaiah]

Well, now we do know the cutoff voltage, at least for this set of variables:

1. Powerpack 500
2. Charged off bike, using Bosch 4A charger
3. Bike reported charge as 100% this time, only ever seen that once before, but this is good for our purposes.

As you can see from the image, the highest measured voltage before the charger started backing off was 41.853. Given that these packs are 10 series, 4 parallel, this gives a voltage cutoff of 4.1853v per cell, rounded to 2 decimals is 4.19v, which is pretty damn close to the 4.2v quoted in the video you linked. I do not believe your interpretation of his words as stated here is accurate. I believe he truly was saying the cutoff is 4.2v because he's seen the same measurements I have. But maybe it really is specifically 4.19v and not 4.20v, in an attempt by Bosch to extend usable lifetime of the pack. If they were really striving for that though, I think they'd go lower than 4.1853v.

I appreciate that you took effort to measure it.
Most people can't entertain two opposing thoughts in their mind and they can't look at any other viewpoints than their own and you seem to be open to experimenting and I applaud you for that.

Coming back, now we know the Bosch BMS cut-off voltage is almost 4.2V/cell (4.19V), it means that the Nyon display is slightly off because chargers push the cells to 4.19V but the Nyon only shows 94% or 95%.

One can calibrate the display to show 100% irrespective of the voltage in any battery and Bosch chargers are designed to charge the cells to 4.19V. If Bosch had some smart management and Nyon was super precise then at 94-95%, the voltmeter should anywhere between 4.13 to 4.15V.

One needs to keep in mind that Bosch Powerpack was designed in 2014 and has essentially remained the same until now.
Bosch does make high-quality stuff but the display showing few % off is just inaccuracy and not Bosch's engineering.

 

[tallpaul]

I'm curious...

Is there any reason to believe that the percentage display itself might be in error?

More precisely, what gives any of us the confidence that the calculated percentage is in fact correct?

I doubt anyone has done a controlled-range test over a known course to know if how many kilometers you can get out of a battery changes in any way with respect to the indicated percentage. And I further suspect that it would be very difficult to find a difference.

good point!

 

[lerxst]

I appreciate that you took effort to measure it.
Most people can't entertain two opposing thoughts in their mind and they can't look at any other viewpoints than their own and you seem to be open to experimenting and I applaud you for that.

Coming back, now we know the Bosch BMS cut-off voltage is almost 4.2V/cell (4.19V), it means that the Nyon display is slightly off because chargers push the cells to 4.19V but the Nyon only shows 94% or 95%.

One can calibrate the display to show 100% irrespective of the voltage in any battery and Bosch chargers are designed to charge the cells to 4.19V. If Bosch had some smart management and Nyon was super precise then at 94-95%, the voltmeter should anywhere between 4.13 to 4.15V.

One needs to keep in mind that Bosch Powerpack was designed in 2014 and has essentially remained the same until now.
Bosch does make high-quality stuff but the display showing few % off is just inaccuracy and not Bosch's engineering.

I don’t think you read what I wrote carefully enough. I said that the display showed a 100% charge in this instance. Like, this is one of the rare times my battery got charged to 100%. 4.19v charge = 100% on Nyon display.

 

[Bert]

Hi, not much extra info from this side...

...but I also have a Supercharger, not super-charging to 97%.
A first the Kiox-display will tell you it's 100%, but it's 97% after disconnection the adapter.

Riding less than a mile this will quickly be lowered to 94-93%... after that it's fine.

When I charge the battery's outside the bike, it's getting to 100% with a some effort.


I rode a Bosch (single battery Gazelle) never had this problem before.

It looks like the amount of energy it contains is still ok.
Charging with 10km left, it almost took 1kwh.
Measured with a Voltcraft. (This includes the load losses)

 

[tallpaul]

If indeed not charging to 100% adds extended life to the battery I am fine with that.
BTW, my experiences are quite similar to BertV's post above.

In the end it would be nice if Bosch made some effort to explain this.

 

[Mr. Coffee]

...
In the end it would be nice if Bosch made some effort to explain this.

I actually can make a pretty good crack at explaining this and I don't even work for Bosch.

It is really simple. All of the battery level displays, whether with bars or as a percentage, are simply estimates. What is actually being measured is the battery voltage which is at best an estimate of how many electrons are in the battery. Battery voltage can change due to temperature and the load present on the battery, which is why with many less expensive e-bikes you will see the battery appear to drop quite precipitously while climbing a long hill, only to recover some of the battery level after the ride flattens out.

It is also not unheard of for battery voltages to drop very slightly from their peak after charging to full voltage. I suspect that is what is happening in this case.