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Author Topic: Ebike and voltage monitoring concept – mini article created for young people  (Read 2211 times)

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Offline Kiriakos GR

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By joining the club of ebike owners and by joining in other web forums discovered many young people trying to understand how those Lipo and Lifepo4 cells behave regarding battery capacity measurements.

Therefore I will try by this mini article to give few tips to young people and in light them a bit regarding how voltage fluctuates when the ebike is in use, and how pointless is buying all sort of battery capacity gadgets.

In this test I did use the Agilent U1272A which is not a new meter in the market but even so it is great as self data-logger with a logging sampling interval starting from 1 time per second.

Below is a graphic which is actually one data logging graph of my very own ebike.
Because plain numbers is hard to understand especially to young people, I did add some elements of text and pictures which makes easy to understand of what is happening.

While just the picture speaks by it self that this is the representation of 1.4Km regarding distance and the route includes parameters as traffic conditions and time, what I  found as interesting after analyzing the data, is that my Lifepo4 battery has the habit to raise up it voltage close to it named specifications when there is no load.
At almost two minutes time the battery gradually raise it voltage in to a level that any capacity meter will be fooled and display one totally untrue condition as charge level.

According my diagram the only period of time that I consider the measurement as reliable is when the battery is in use with the motor running at 50-60% of it capacity in Watts.

Not all PASS controllers are build equally, therefore my advice will be in three or four PASS levels controller to select the PASS No 2 level for your experiments and by using your bicycle in a flatland.   

At this point I need to alert especially the young readers, about the placement of a multimeter or of a battery voltage monitoring gadget over the bicycle.
Basically the placement of any such device especially when Lipo is in use it must be considered as temporarily, only for testing and in a place which does not abstract you eyes when driving from the road it self.

According to feedback received by local ebike owners which are using SLA batteries, they enjoying more constant and stable reading compared to Lipo and therefore an permanent placed volt meter or an LED battery status gadget, it does has practical value for them.
To my more knowledgeable  readers, I will say that just the measurement of my ebike voltage fluctuation it did made me realize how difficult it is to predict the consumption of battery powered vehicles, even if you are armed with the finest test and measurement equipment.
Any potholes which you will cross over, every tiny rock in your path, the wind it self, soft breaking so to be in harmony with the rest vehicles traveling speed on the road, all those parameters influences the battery consumption its and every second.
My first conclusion is that every electric vehicle has it very own consumption rating which is in accordance with the terrain that you live in, and therefore flatlanders are the luckiest ones.
According to my measurements which I am not presenting in public view, the use of throttle instead of Pedelec sensor, it causes much less wasted use of energy in a Mid-drive KIT compared to a gear-less hub motor.
In my tests I thought that I would see much of difference when using 15% Throttle and 85% Pedelec with my 10Ah battery in comparison with 5% throttle and 95% Pedelec, but I did not.
The explanation comes from the fact that Mid-Drive is capable to speed-up much faster than a gear-less hub, and also it is very easy for it to maintain the speed level at  20-25Km/h with out consuming much of energy.

I have read one research talking about the actual power which a human needs to waste as to was a motor when driving a bicycle, the lazy slow bicycle driver equals to 100W motor, the regular bicycle driver equals to 150-200W motor, and an athlete bicycle driver will produce an average of 250-300W. 

In conclusion one regular bicycle driver among with one power assisted KIT of just 250W (but with high torque as the Mid-drive) he sends in the back wheel combined wattage of 500W when using Pedelec.
In summary, save your money when using Lipo cells and do not buy battery level gadgets, buy instead a cheap speedometer so to record distance.
If you own gear-less hub motor the use of throttle will drastically waste huge amount of stored battery energy.
If you are using hub motor with gears the energy loss will be less, but heat will be more, and magnets, hall sensors, are getting in higher risk about getting damaged.

The use of any motor with Pedelec as 50/50 cooperation is the best combination of using wisely the stored energy in a battery, additionally the wise use of the motor assistance level will cause less heat in that motor and it will extend it life.

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