Are Bosch Purion Controller speed calculations accurate?

[Sparky731]

Numerous times I encounter police street radar monitors whereon the speed of oncoming traffic is displayed.
EVERY encounter shows my transport speed as consistently 2 mph SLOWER than what is displayed on my Purion controller.
EX: The radar shows 13mph and the Controller displays 15mph.
Per my simple calculations, this results in an overall reduction in obtainable motor assist speed.
It is consistent between my Trek Verve+3 and my Trek Allant+7s.
Which is most accurate: The police radar, or the Purion controller?
Is this common across all Bosch controllers?
Are we missing out on better performance if the controller is inaccurate?

 

[AlanDB]

Inflated speed display with several controllers has been discussed in several threads regarding different brands and models. Many people have observed this when they use a GPS receiver beside their ebike display. The GPS speed will consistently show 1 to 2 MPH slower than the ebike display. I have posted about this with both my Bosch Intuvia display and also after I switched to the generation 1 Nyon display. This upsets some people especially with Class 1 ebikes because in their view, the assist cutoff is really occurring at an actual 18 MPH rather than the advertised 20 MPH as shown on the display.

 

[Dallant]

Well not sure about speed but odometer readings between my Purion and my Apple Watch are certainly not the same.

 

[fooferdoggie]

yes about 1.5mph. the wheel size can be adjusted to fix this but you cant do it yourself with the two low end purion and intuvia

 

[William - Bosch Team]

The Purion is very accurate, assuming a very accurate circumference value programmed in the DU, but there are so many factors that will cause small discrepancies. The DU controls max speed, not the display. The display just shows what the DU is "thinking." In reality, everyone's effective circumference will be a little different due to tire type, tire pressure, rider weight, etc. OEMs have to choose a single value to program for each model of eBike, so there will always be differences in each individual's ride experience.

If you are curious, you can compare the circumference value (not the correction value) on a Diagnostic Report from your dealer with the circumference value obtained from a weighted roll-out on your bike. The difference in these (2) values should directly correlate to the observed speed read-out differences, give or take some small margin of error.

Keep in mind, GPS is good for navigation, but explicitly not to be used for precise speed measurement.
https://support.garmin.com/en-US/?faq=rXBlOOUg4c47KShikBeEX5

 

[steve mercier]

The Purion is very accurate, assuming a very accurate circumference value programmed in the DU, but there are so many factors that will cause small discrepancies. The DU controls max speed, not the display. The display just shows what the DU is "thinking." In reality, everyone's effective circumference will be a little different due to tire type, tire pressure, rider weight, etc. OEMs have to choose a single value to program for each model of eBike, so there will always be differences in each individual's ride experience.

If you are curious, you can compare the circumference value (not the correction value) on a Diagnostic Report from your dealer with the circumference value obtained from a weighted roll-out on your bike. The difference in these (2) values should directly correlate to the observed speed read-out differences, give or take some small margin of error.

Keep in mind, GPS is good for navigation, but explicitly not to be used for precise speed measurement.
https://support.garmin.com/en-US/?faq=rXBlOOUg4c47KShikBeEX5

My wife and I have Purions. Hers will say around 99-100 km when mine says around 94-5 and my other bike ( Intuvia ) will say about 96-7 so you can see there is a small (<5 %) margin of error. The GPS will also say around 96-98.

 

[Deacon Blues]

My purion display reads approximately 1.5kph fast at 30kph, so my motor cuts off at just over 30kph, instead of 32kph.
It sure would be nice if the motor cut off speed was the other way- 34kph.
2kph doesn't sound like much, but fI often ride at that speed-very frustrating.

 

[William - Bosch Team]

On all Bosch systems, your dealer can adjust the cosmetic speed readout by +/- 5% in the Diagnostic Tool. Some displays (Nyon, Kiox, SPH) allow the user to adjust the cosmetic speed readout using the display itself.

If you think your speed is significantly off, you can ask your dealer to check with the OEM on what the programmed value should be, which can then be compared to the result of a physical roll-out on your bike, performed by your dealer. There are several in-depth posts on this topic. I will try to look for them later.

 

[webcurl]

yes about 1.5mph. the wheel size can be adjusted to fix this but you cant do it yourself with the two low end purion and intuvia

Can be done on the Intuvia.

 

[Sparky731]

On all Bosch systems, your dealer can adjust the cosmetic speed readout by +/- 5% in the Diagnostic Tool. Some displays (Nyon, Kiox, SPH) allow the user to adjust the cosmetic speed readout using the display itself.

If you think your speed is significantly off, you can ask your dealer to check with the OEM on what the programmed value should be, which can then be compared to the result of a physical roll-out on your bike, performed by your dealer. There are several in-depth posts on this topic. I will try to look for them later.

William, a different Purion question:
Can you share the formula Bosch uses to calculate Range?
In particular, the number of previously ridden miles and assist levels?
I start with a full charge each morning. The Ranges vary up to double day-to-day.
The Range will often increase or decrease while riding, depending upon at what speed I am riding at the time.
I have a PowerTube 500 + 500W Range Booster.
Most days the starting Range on Eco is ~190 miles and Turbo ~45 miles
Today I had Eco 260 miles and Turbo 90 miles -- see pix.
Can you share the formula Bosch uses to calculate Range?

 

[fooferdoggie]

it is based on a lot of things speed how much power you put out how much power you use like hills. I have found the range pretty accurate as long as you don't change what you doing often. its usually underestimates a mile or two.

 

[William - Bosch Team]

@Sparky731
A few notes on range, some of which you may already be aware of:

- Range is calculated using approximately the last 1.5 miles of riding.
- Range calculation will vary based on what assistance mode you currently have selected.
- Range calculation may be heavily influenced by multiple factors and conditions, ie: temperature, ascent/descent, total weight of eBike+rider, speed, wind, cadence, tire pressure, position on bike (upright vs. aero), condition of bicycle (efficiency), starting/stopping vs. steady speed, etc.

You can reset the range before every ride, but keep in mind it will then have less to base it's estimate on.

If you hang your bike on a rack, turn it "on," and pedal it in the stand very fast... the DU will count that distance traveled and factor in the near zero amount of energy required to cover that distance. You may end up with a unrealistically large residual range.

If you turn your bike on, and pedal slowly up a hill in a low cadence/turbo, the residual range calculation will drop.

Cold batteries will have less range than room temp. or warm batteries.

It is not uncommon to turn the eBike "on" and find a slightly abnormal range calculation, due to any of the factors listed above. That being said, things should begin to normalize with some riding.

The "high" range numbers you listed seem to be at the upper end of what is realistic, though not impossible. Could be caused by finishing your last ride with a long downhill. Could be caused by the rear wheel spinning freely while transporting the bike on a car rack.

Bosch designed the range calculation to be as accurate as possible, and to constantly update, therefore you will likely see the occasional abnormal value displayed. You will also likely continue to see fluctuations. It's definitely different than the "miles to empty" shown in most automobiles that is fairly steady in comparison. There is a much greater ability to influence range and efficiency with an eBike compared to an automobile.

I hope this helps!

 

[Dallant]

I doubt there is a reasonably priced device that can accurately determine (at the beginning of your ride) the ultimate exact range you will have at the end of your ride unless you’re on a totally level ride with the same wind resistance at the same temperature.

 

[fooferdoggie]

I doubt there is a reasonably priced device that can accurately determine (at the beginning of your ride) the ultimate exact range you will have at the end of your ride unless you’re on a totally level ride with the same wind resistance at the same temperature.

true but bosch does pretty well you can use the nyon gps and it will show you the range on the map you can get including hills in the rage you have

 

[Sparky731]

@Sparky731
A few notes on range, some of which you may already be aware of:

- Range is calculated using approximately the last 1.5 miles of riding.
- Range calculation will vary based on what assistance mode you currently have selected.
- Range calculation may be heavily influenced by multiple factors and conditions, ie: temperature, ascent/descent, total weight of eBike+rider, speed, wind, cadence, tire pressure, position on bike (upright vs. aero), condition of bicycle (efficiency), starting/stopping vs. steady speed, etc.

You can reset the range before every ride, but keep in mind it will then have less to base it's estimate on.

If you hang your bike on a rack, turn it "on," and pedal it in the stand very fast... the DU will count that distance traveled and factor in the near zero amount of energy required to cover that distance. You may end up with a unrealistically large residual range.

If you turn your bike on, and pedal slowly up a hill in a low cadence/turbo, the residual range calculation will drop.

Cold batteries will have less range than room temp. or warm batteries.

It is not uncommon to turn the eBike "on" and find a slightly abnormal range calculation, due to any of the factors listed above. That being said, things should begin to normalize with some riding.

The "high" range numbers you listed seem to be at the upper end of what is realistic, though not impossible. Could be caused by finishing your last ride with a long downhill. Could be caused by the rear wheel spinning freely while transporting the bike on a car rack.

Bosch designed the range calculation to be as accurate as possible, and to constantly update, therefore you will likely see the occasional abnormal value displayed. You will also likely continue to see fluctuations. It's definitely different than the "miles to empty" shown in most automobiles that is fairly steady in comparison. There is a much greater ability to influence range and efficiency with an eBike compared to an automobile.

I hope this helps!

William, This makes perfect sense, i.e., the highly variable Range given the 1.5 mi factor.
My ride home is uphill several blocks and I generally ride in high speed. Next charge yields ~45 mi on Turbo.
If I car-carrier home after a group ride where the last miles are relatively slow and mild, the next charge yields 80-90 mi in Turbo.
I had expected the mileage input factor to be several multiples of 1.5 to mitigate and flatten the impact of short duration, highly variable terrain.
Got it now. Makes sense. Thanks.

 

[webcurl]

I had expected the mileage input factor to be several multiples of 1.5 to mitigate and flatten the impact of short duration, highly variable terrain.

There is no user adjust on the averaging used in the formula. Some people prefer a quicker response to the estimate than others.
Can't please everyone unless you provide an adjustment
If they did provide that then maybe steps of 2.5km, 5 & 10km?