Low Battery Cutout for Bosch Gen4?

[William - Bosch Team]

Hi All,

Unfortunately, I doubt that Bosch will make the battery reserve configurable, and I personally hope that we do not. I realize that my opinion on this won't be popular, but keep in mind that Bosch designed it the way they did for a reason, and it is in Bosch's best interest to offer as much capacity as they safely can.

[Edited to add this: Bosch is required by at least one regulation to have the 2-hours of light power.]

That being said, the buffer when not using lights or eShift is actually very small. It's just enough to keep you out of trouble if you run the battery till cut-off, and then forget to charge for many months. This happens fairly often, believe it or not.



@Mike Owen Based on the WWW, it looks like your eBike has lights and eShift... Both of these things add to the size of the reserve power. As an eBike sits alone, the low-voltage cut-off is pretty slim. It's the 2-hours of lights + 50-100 eShifts that really add up. Lithium battery cells have a very slow self-discharge rate so it doesn't need to be a lot on it's own. It's the lights and eShift that do it.

I agree, it would be cool if this was possible:

"My ideal Bosch update would be: allow user via Kiox to adjust Powertube reserve right down to Battery protection level. That way I could use more of that currently inaccessible 100Wh range and leave the last battery to cut out at 50Wh in case I screw up again."

The Drive Unit "makes the call" on reserve power based on light settings and eShift, so it has to treat all batteries the same. The only thing you could do to lower the reserve is to have your dealer deactivate your lights, which is not a good idea for safety or visibility. A better option may be to have the dealer lower the reserve watts (as low as 3 watts is possible.) You'd need to be aware of the safety implications of dimmer lights, but it should give you a little of that reserve power back. I'm not sure this would be even savings to be worth it.

 

[Mike Owen]

Hi All,

Unfortunately, I doubt that Bosch will make the battery reserve configurable, and I personally hope that we do not. I realize that my opinion on this won't be popular, but keep in mind that Bosch designed it the way they did for a reason, and it is in Bosch's best interest to offer as much capacity as they safely can.

[Edited to add this: Bosch is required by at least one regulation to have the 2-hours of light power.]

That being said, the buffer when not using lights or eShift is actually very small. It's just enough to keep you out of trouble if you run the battery till cut-off, and then forget to charge for many months. This happens fairly often, believe it or not.



@Mike Owen Based on the WWW, it looks like your eBike has lights and eShift... Both of these things add to the size of the reserve power. As an eBike sits alone, the low-voltage cut-off is pretty slim. It's the 2-hours of lights + 50-100 eShifts that really add up. Lithium battery cells have a very slow self-discharge rate so it doesn't need to be a lot on it's own. It's the lights and eShift that do it.

I agree, it would be cool if this was possible:

"My ideal Bosch update would be: allow user via Kiox to adjust Powertube reserve right down to Battery protection level. That way I could use more of that currently inaccessible 100Wh range and leave the last battery to cut out at 50Wh in case I screw up again."

The Drive Unit "makes the call" on reserve power based on light settings and eShift, so it has to treat all batteries the same. The only thing you could do to lower the reserve is to have your dealer deactivate your lights, which is not a good idea for safety or visibility. A better option may be to have the dealer lower the reserve watts (as low as 3 watts is possible.) You'd need to be aware of the safety implications of dimmer lights, but it should give you a little of that reserve power back. I'm not sure this would be even savings to be worth it.

Hey William.

Thanks for your excellent reply. That’s great that the dealer can reduce the reserve watts down to 3 watts.

My school physics learning was way too many decades ago to remember much about Wh, watts, volts and amps and the younger me was pretty rubbish even then. But in old bloke simple terms: your reply makes it sound like a dealer set “reserve watts” at 3W would mean my 3 x 500Wh powertubes would give me 1491Wh of available assist. Sounds fab!

Hope that’s possible. Can I still keep the lights “auto always on” with that 3W reserve setting?

Really appreciate you sharing your technical knowledge on here. Very generous of you.

Cheers.

 

[William - Bosch Team]

Hey William.

Thanks for your excellent reply. That’s great that the dealer can reduce the reserve watts down to 3 watts.

My school physics learning was way too many decades ago to remember much about Wh, watts, volts and amps and the younger me was pretty rubbish even then. But in old bloke simple terms: your reply makes it sound like a dealer set “reserve watts” at 3W would mean my 3 x 500Wh powertubes would give me 1491Wh of available assist. Sounds fab!

Hope that’s possible. Can I still keep the lights “auto always on” with that 3W reserve setting?

Really appreciate you sharing your technical knowledge on here. Very generous of you.

Cheers.

Hey Mike!
You are very welcome. I'm glad I can be useful sometimes.

The 3w-18w reserve refers to the power that the lights will operate at for approx. 2 hours, so I think the math will differ slightly from what you worked out above. My math skills are awful, but I'm thinking that would be approx. 6 Wh set aside per battery, assuming the setting was at 3w. Whether or not you are actively using the lights for a given ride, the same power amount of power is saved as long as the lights are active in the Diagnostic Software.

I can't recall the amount that is saved for eShift, but it is not affected by the reserve lighting adjustment.

 

[Mike Owen]

Hey Mike!
You are very welcome. I'm glad I can be useful sometimes.

The 3w-18w reserve refers to the power that the lights will operate at for approx. 2 hours, so I think the math will differ slightly from what you worked out above. My math skills are awful, but I'm thinking that would be approx. 6 Wh set aside per battery, assuming the setting was at 3w. Whether or not you are actively using the lights for a given ride, the same power amount of power is saved as long as the lights are active in the Diagnostic Software.

I can't recall the amount that is saved for eShift, but it is not affected by the reserve lighting adjustment.

Oh heck. Whoosh. That just went completely over my head. Got a slight sweat on, a bit like those physics exams all those years ago .

It. Has. To. Be. Really. Simple. For me to compute this.

So here goes:

Simple answer... can I leave the lights alone at full power always on, just as the factory setting? And then get the dealer to only set reserve for eshift to a minimal amount?

 

[dblhelix]

Oh heck. Whoosh. That just went completely over my head. Got a slight sweat on, a bit like those physics exams all those years ago .

It. Has. To. Be. Really. Simple. For me to compute this.

So here goes:

Simple answer... can I leave the lights alone at full power always on, just as the factory setting? And then get the dealer to only set reserve for eshift to a minimal amount?

Hey Mike,

I’d look at it this way.

Each Bosch battery: 13.6Ah x 36V = 482.4 Wh/pack
3Packs: 1447.2 Wh
Less (10%) reserve: 1302.5 Wh.
M99 Mini pro 25 @6V. 5.2W (low beam). 8W (high beam)
2hrs on high beam = 16W

You get 1256.5 Wh. - don’t spend it all in one place. Note that the light (at least this model) uses nominal amounts of energy ...

and the 3w setting means you get roughly 40min of low beam.

 

[Mike Owen]

Hey Mike,

I’d look at it this way.

Each Bosch battery: 13.6Ah x 36V = 482.4 Wh/pack
3Packs: 1447.2 Wh
Less (10%) reserve: 1302.5 Wh.
M99 Mini pro 25 @6V. 5.2W (low beam). 8W (high beam)
2hrs on high beam = 16W

You get 1256.5 Wh. - don’t spend it all in one place. Note that the light (at least this model) uses nominal amounts of energy ...

and the 3w setting means you get roughly 40min of low beam.

Hmmmmm? Huh, thanks Mr Helix. Maybe instead I should focus more on Geography... Physics just ain’t going in.

Impressive maths there. But how do I max out the assist by reducing the 10% reserve?

 

[William - Bosch Team]

My apologies!

First, eShift reserve power cannot be adjusted, it is what it is. I'm not sure the exact amount of energy set aside, just that it's good for (50-100) shifts.


Moving on to lights...

I'm not entirely clear on your question: "Simple answer... can I leave the lights alone at full power always on, just as the factory setting?" I'll throw some more info your way, and if this doesn't not answer it, we'll keep at it!

Unrelated to reserve power: The lights will of course consume energy during normal use. The amount of energy consumed depends on the current draw/ specs from the lights. During normal use, this consumption is not adjustable. You can replace your light with a different light that uses less energy, but that is it. The more energy your lights consume during usage, the faster your battery drains. This has no bearing on the reserve power, but does affect how quickly you get to the reserve power.

For reserve power (after the Drive Unit cuts-off due to low battery): The DU will save enough energy for 2 hours of light operation at the wattage you select (3W to 18W, selected by Dealer.)

I feel like this is still somewhat complicated, so I'll try to give some examples.


For the sake of the example, we'll pretend that your front/rear light combined require 10 watts for normal operation. If you keep them on all the time, they will use 10 Wh every hour. If you ran your lights for 4 hours while riding, you would have theoretically consumed 40 Wh of your battery.

10w * 4hrs = 40 Watt Hours


Regardless of what your reserve power is set at, the above would theoretically be true.

If you did you entire ride without your lights turned on, they would consume:

0w * infinite hrs = 0 Watt hours



Once your battery gets low enough for DU cut-off, we start looking at the "2 hour reserve light power mode." During this mode, your lights will not necessarily have the 10 watts they "want," but will instead have the amount selected between 3w and 18w. If you wanted your lights to have the same brightness during reserve as they do during normal operation, you'd have your dealer set the value to "10w" in the Bosch Software.

The amount of light power reserve would be:

10w * 2hrs = 20 Watt Hours


If you wanted to maximize range, and didn't care about brightness during the reserve period, you might have the dealer select 3 watts.

The amount of light power reserve would be:

3w * 2 hrs = 6 Watt Hours



For the sake of further explanation, if you had your dealer set the reserve power to 18 watts, your lights would still only operate at 10 watts, but we'd "waste" all this extra saved energy.

18w * 2 hrs = 36 Watt Hours



Looking at the total demands on your battery capacity, we can think of it this way:

- Energy consumed by normal riding: DU assistance, lights, eShift, and smaller functions (DU processor, sensors, display charging, etc.)
- Energy saved for 2 hour light power reserve (0 - 36 Wh)
- Energy saved for (50-100) eShifts (unknown)


Does this help, or did I make it worse?

 

[William - Bosch Team]

I'll add this as well... we should consider getting away from using 10% to describe the reserve power. While it seems to be accurate for these specific eBike configurations we are discussing in this thread, I worry that the info will leave here and be misunderstood as the standard amount of reserve power.

Example: An eBike without eShift and lights will likely have a much smaller amount of reserve capacity.

 

[dblhelix]

Hmmmmm? Huh, thanks Mr Helix. Maybe instead I should focus more on Geography... Physics just ain’t going in.

Impressive maths there. But how do I max out the assist by reducing the 10% reserve?

Correct me if I should go back and re-read the thread! I am under the impression from the early posts that the batteries have a non-negotiable 10% reserve. I subtracted 10% of each battery’s capacity To arrive at 1302.5Wh total.

Now there’s the reserve that’s configurable to keep the lights and E-14* going. At this point, if you minimize its setting, you get maximum capacity from your batteries. Please correct me if this is incorrect - I only read the first couple of post on this.

*lights only

 

[dblhelix]

I'll add this as well... we should consider getting away from using 10% to describe the reserve power. While it seems to be accurate for these specific eBike configurations we are discussing in this thread, I worry that the info will leave here and be misunderstood as the standard amount of reserve power.

Example: An eBike without eShift and lights will likely have a much smaller amount of reserve capacity.

Aah, so that 10% is specific to the non-negotiable reserve + E-shift. Good to know that but I’ve been assuming the E-shift consumption < lights and ignoring it anyway, haha.

I’ll add that the light reserve you are setting appears to be set aside exclusively for this purpose. Still, at the lower settings, it appears to be a no-brainer to keep it ”on.”

 

[Mike Owen]

My apologies!

First, eShift reserve power cannot be adjusted, it is what it is. I'm not sure the exact amount of energy set aside, just that it's good for (50-100) shifts.


Moving on to lights...

I'm not entirely clear on your question: "Simple answer... can I leave the lights alone at full power always on, just as the factory setting?" I'll throw some more info your way, and if this doesn't not answer it, we'll keep at it!

Unrelated to reserve power: The lights will of course consume energy during normal use. The amount of energy consumed depends on the current draw/ specs from the lights. During normal use, this consumption is not adjustable. You can replace your light with a different light that uses less energy, but that is it. The more energy your lights consume during usage, the faster your battery drains. This has no bearing on the reserve power, but does affect how quickly you get to the reserve power.

For reserve power (after the Drive Unit cuts-off due to low battery): The DU will save enough energy for 2 hours of light operation at the wattage you select (3W to 18W, selected by Dealer.)

I feel like this is still somewhat complicated, so I'll try to give some examples.


For the sake of the example, we'll pretend that your front/rear light combined require 10 watts for normal operation. If you keep them on all the time, they will use 10 Wh every hour. If you ran your lights for 4 hours while riding, you would have theoretically consumed 40 Wh of your battery.

10w * 4hrs = 40 Watt Hours


Regardless of what your reserve power is set at, the above would theoretically be true.

If you did you entire ride without your lights turned on, they would consume:

0w * infinite hrs = 0 Watt hours



Once your battery gets low enough for DU cut-off, we start looking at the "2 hour reserve light power mode." During this mode, your lights will not necessarily have the 10 watts they "want," but will instead have the amount selected between 3w and 18w. If you wanted your lights to have the same brightness during reserve as they do during normal operation, you'd have your dealer set the value to "10w" in the Bosch Software.

The amount of light power reserve would be:

10w * 2hrs = 20 Watt Hours


If you wanted to maximize range, and didn't care about brightness during the reserve period, you might have the dealer select 3 watts.

The amount of light power reserve would be:

3w * 2 hrs = 6 Watt Hours



For the sake of further explanation, if you had your dealer set the reserve power to 18 watts, your lights would still only operate at 10 watts, but we'd "waste" all this extra saved energy.

18w * 2 hrs = 36 Watt Hours



Looking at the total demands on your battery capacity, we can think of it this way:

- Energy consumed by normal riding: DU assistance, lights, eShift, and smaller functions (DU processor, sensors, display charging, etc.)
- Energy saved for 2 hour light power reserve (0 - 36 Wh)
- Energy saved for (50-100) eShifts (unknown)


Does this help, or did I make it worse?

William, your patience and staying power are admirable.

Thanks for such a thorough explanation. I get it!!!

Reserve setting for eShift is not adjustable.

Reserve setting for lights is adjustable down to 3W. But the Wh released for assist is negligible.

Simples!

Thanks for answering all my questions

 

[William - Bosch Team]

Correct me if I should go back and re-read the thread! I am under the impression from the early posts that the batteries have a non-negotiable 10% reserve. I subtracted 10% of each battery’s capacity To arrive at 1302.5Wh total.

Now there’s the reserve that’s configurable to keep the lights and E-14* going. At this point, if you minimize its setting, you get maximum capacity from your batteries. Please correct me if this is incorrect - I only read the first couple of post on this.

*lights only

I think @E14Delite originally posted about observing a 10% reserve with his configuration, and then I used 90% and 10% in a hypothetical example. That's on me, I'm sorry.

The batteries definitely do have a non-negotiable low-voltage cut-off, but it's not expressed by a percentage that I've ever heard of. Again, my mistake for confusing the issue.

You are correct... you can alter how much is saved for lights, but nothing else.

Hi William. Perhaps you could cast some light on Chris’s comment above that the reserve amount may in future be user configurable.

I may have missed this comment previously. I've not heard anything on this, and I can't imagine how it would be possible. Adjust what's left for eShift... sure, because worst case you can't shift gears. But I don't think they'd ever allow $900 batteries to get dangerously low. Most of what seems like surplus reserve in our discussion here appears to be eShift and light reserve. Unlike sports cars having extra HP made available by a tuning chip, I don't think Bosch is intentionally hiding any extra capacity just so they can release it later.

There is always the possibility that eventually Bosch designs for more battery usage configuration by the user, but I don't see that coming out of the low-voltage cut-off buffer. It would be something different than what we are talking about here. (nobody read into this, just making an example )

Whether you are talking about eBikes, power tools, cell phones, laptops, electric cars, etc., or anything else with a lithium battery, there must be a low-voltage cut-off. When I used to work in power tools, customers would pop the battery out their drill after cut-off, pop it back in, and squeak out a little more battery usage. They'd also kill their batteries prematurely.

 

[William - Bosch Team]

Aah, so that 10% is specific to the non-negotiable reserve + E-shift. Good to know that but I’ve been assuming the E-shift consumption < lights and ignoring it anyway, haha.

I’ll add that the light reserve you are setting appears to be set aside exclusively for this purpose. Still, at the lower settings, it appears to be a no-brainer to keep it ”on.”

I agree with you 100%... definitely worth keeping "on." I'm a big fan of lights, no matter the time of day! Safety is #1. That being said, I can see how it can be frustrating to need more range, but have it tied-up with lights.

When time/ Florida weather allows, or if I can trick a co-worker into helping me, I'll try to get some values for the cut-off point of an eBike with no lights and no eShift. Won't really help you fellas with the e14/ light setups, but might be interesting info.

 

[dblhelix]

I agree with you 100%... definitely worth keeping "on." I'm a big fan of lights, no matter the time of day! Safety is #1. That being said, I can see how it can be frustrating to need more range, but have it tied-up with lights.

When time/ Florida weather allows, or if I can trick a co-worker into helping me, I'll try to get some values for the cut-off point of an eBike with no lights and no eShift. Won't really help you fellas with the e14/ light setups, but might be interesting info.

Geeking out is always interesting!

 

[E14Delite]

Hey Mike!
You are very welcome. I'm glad I can be useful sometimes.

The 3w-18w reserve refers to the power that the lights will operate at for approx. 2 hours, so I think the math will differ slightly from what you worked out above. My math skills are awful, but I'm thinking that would be approx. 6 Wh set aside per battery, assuming the setting was at 3w. Whether or not you are actively using the lights for a given ride, the same power amount of power is saved as long as the lights are active in the Diagnostic Software.

I can't recall the amount that is saved for eShift, but it is not affected by the reserve lighting adjustment.

Hi William,

Thanks for your all your responses on this subject. Much appreciated.

Yes I did indicate that for my R&M model the loss of power from the motor is at 10% on my Kiox display. Other Bosch models may be different.

My R&M configured light power appears to be set at 11w so the potential energy saving if I change setting to 3w is (11-3=8w) x 2 hrs = approx 3% of 500w battery. Not sure how effective the lights might be with 3w of power.

Whether there could be a future software upgrade that provided a user selectable option to recognise that the lights were off when calculating battery minimum might need to be country related depending on local regulations but as the power saving benefit is small perhaps not justified.

It would also be good to have just the brake lights operational when the main lights were off but I think this would need to be an R&M/bike manufacturer option.

If I run with lights off there should still be a power saving of perhaps 11w per hour of riding so in my case the first 90% of power will get me further. For my latest ride I have used 64% of battery power for 54.7 km in Tour Mode with lights on. At average of 20km/hr I calculate I should get an extra 7km with lights off compared to lights on for 90% battery usage. Not a hilly route and some cycling above motor assist speed

The bottom line for us all is if we do not wish to ride a heavy bike without power assist we need to be aware of the cutout value for our particular bikes and manage the available power accordingly. Perhaps a good idea to run your bike to the minimum near to home base so you have some idea of battery value when motor cuts out. Whatever the battery capacity we will always want more.

I am hoping my local dealer will have a battery hire option so for the few occasions I plan to do extended touring I can hire a spare battery for a week.

Regards Stephen.

 

[William - Bosch Team]

Hey Stephen,

Thank you, and everyone else on this thread for your real-world ride stats and observations. Even though I couldn't provide you with a solution for eeking a little more range out of your eBike, your feedback is invaluable. I'll share the thoughts, feelings, etc., from this thread with people more important than myself at Bosch eBike Systems (basically everyone, haha!)

 

[dblhelix]

Hey Stephen,

Thank you, and everyone else on this thread for your real-world ride stats and observations. Even though I couldn't provide you with a solution for eeking a little more range out of your eBike, your feedback is invaluable. I'll share the thoughts, feelings, etc., from this thread with people more important than myself at Bosch eBike Systems (basically everyone, haha!)

William, just want to double-check. If Kiox indicates 64%, this is 64% of total capacity. As a concrete example, for a PowerPack, it would be 0.64*13.6*36 Wh, irrespective of what is withheld for permanent and adjustable reserves?

 

[William - Bosch Team]

William, just want to double-check. If Kiox indicates 64%, this is 64% of total capacity. As a concrete example, for a PowerPack, it would be 0.64*13.6*36 Wh, irrespective of what is withheld for permanent and adjustable reserves?

Great timing!

I just got off the phone verifying this. The battery percentage displayed is the total available capacity. In your example above, 64% is what you have left for assistance, and does not account for any 2-hour light reserve or eShift reserve. Thinking some more on it, it would be really confusing if Bosch displayed total battery capacity, and left us to guess where the reserves and low-voltage cut-out played in. The display shows what you have left to use.*


For example, if we look at (2) identical eBikes, one with lights and one without:

eBike 1: 500 Wh battery, Active Line DU, no lights: 100% battery charge

eBike 2: 500 Wh battery, Active Line DU, lights (10w * 2 hour reserve): 100% battery charge

For #1, that 100% battery charge equals [ X Wh] available
For #2, that 100% battery charge equals [ X - 20 Wh] available


Hopefully this helps?




*In a perfect world, you'd stop seeing assistance right around 0%, but this is not always the case. According to my phone call, we've seen multiple times where eBikes with eShift, high assist levels, etc., get to around 10% and stop assisting. This is because the 10% remaining is not really enough for any assist, given the immense power draw of the system and it's extras (lights, eShift, etc.) Especially true in hilly areas where heavier bikes consume much more energy.

 

[dblhelix]

Great timing!

I just got off the phone verifying this. The battery percentage displayed is the total available capacity. In your example above, 64% is what you have left for assistance, and does not account for any 2-hour light reserve or eShift reserve. Thinking some more on it, it would be really confusing if Bosch displayed total battery capacity, and left us to guess where the reserves and low-voltage cut-out played in. The display shows what you have left to use.*


For example, if we look at (2) identical eBikes, one with lights and one without:

eBike 1: 500 Wh battery, Active Line DU, no lights: 100% battery charge

eBike 2: 500 Wh battery, Active Line DU, lights (10w * 2 hour reserve): 100% battery charge

For #1, that 100% battery charge equals [ X Wh] available
For #2, that 100% battery charge equals [ X - 20 Wh] available


Hopefully this helps?




*In a perfect world, you'd stop seeing assistance right around 0%, but this is not always the case. According to my phone call, we've seen multiple times where eBikes with eShift, high assist levels, etc., get to around 10% and stop assisting. This is because the 10% remaining is not really enough for any assist, given the immense power draw of the system and it's extras (lights, eShift, etc.) Especially true in hilly areas where heavier bikes consume much more energy.

Yes, this helps tremendously, esp since I’ve never dropped below 20% available capacity and have no idea about what might happen below 5%.

 

[E14Delite]

Hi William,

Thanks you for your latest post which I do interpret that 0% would mean all your "available" battery capacity has been used and that anything remaining is that which is required to ensure that the battery is not damaged by excessive discharge. I think all those participating in this thread now have a much better understanding thanks to your input.

I suspect you could get overwhelmed answering posts on a whole range of Bosch related issues if you chose to do so so perhaps one solution would be to start a thread specifically for members to post suggestions for upgrades/improvements to Bosch systems where it is understood that individual posts will not be answered but that any suggestions that make it through to implementation will be acknowledged.

Might need to check with the Administrator whether this would be possible. It could equally apply to other manufacturers.

Cheers Stephen.