Why does there seem to be no such thing as a handlebar mounted indicator of battery capacity (Ah) remaining. Some displays seem to show volts, or even worse 4 or maybe 6 bars indicating charge remaining whereas a simple indication of Ah would give an accurate indication of capacity available. Such meters are common enough in the boating industry, so why not for ebikes I wonder ???. There are meters that will do this, but they are not waterproof and not handlebar-mount friendly. Am I missing something ?
Battery capacity indication ............ am I missing something ?
- Thread starter CPD
- Start date
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I don't know anything about such meters in the boating industry (electric boats?)
The displays show volts (or bars based on volts) because the only thing that can be measured accurately is battery output voltage. No controller can actually measure amp-hours remaining, it is calculated/estimated/guessed by the software. For example when voltage falls below a certain threshold it's deemed empty as it doesn't really have enough juice to provide power without damaging the battery. It can record how many miles were done in that trip and how much the voltage dropped over that distance.
I know I'm oversimplifying this and there will be folks with a deeper understanding of ebike electronics, but phones and laptops can measure more accurately the amount of charge put in, and some proprietary ebikes or chargers can do the same because the on-bike controller is managing charging, or there's circuitry in the battery pack to do that, which is then fed to the bike controller when the battery is plugged back in. A non-proprietary one might be charged with a simple jack plug and not have any way of recording the amount of charge in the cells. For example my Orbea Gain has a built in battery, charges on the bike. Its display shows a percentage battery remaining which seems fairly accurate. My home converted hybrid bike battery charges (on or off the bike) via a jack plug. Its display just has bars and seems to be purely voltage based.
The displays show volts (or bars based on volts) because the only thing that can be measured accurately is battery output voltage. No controller can actually measure amp-hours remaining, it is calculated/estimated/guessed by the software. For example when voltage falls below a certain threshold it's deemed empty as it doesn't really have enough juice to provide power without damaging the battery. It can record how many miles were done in that trip and how much the voltage dropped over that distance.
I know I'm oversimplifying this and there will be folks with a deeper understanding of ebike electronics, but phones and laptops can measure more accurately the amount of charge put in, and some proprietary ebikes or chargers can do the same because the on-bike controller is managing charging, or there's circuitry in the battery pack to do that, which is then fed to the bike controller when the battery is plugged back in. A non-proprietary one might be charged with a simple jack plug and not have any way of recording the amount of charge in the cells. For example my Orbea Gain has a built in battery, charges on the bike. Its display shows a percentage battery remaining which seems fairly accurate. My home converted hybrid bike battery charges (on or off the bike) via a jack plug. Its display just has bars and seems to be purely voltage based.
fossyant
Ride It Like You Stole It!
- Location
- South Manchester
Things need to be simple for consumers, so either fuel bars, like cars have, or percentage like your phone, is fairly simple for all to understand.
Don't forget it's estimated on your recent energy use, so whack it in turbo, you'll soon burn through the juice.
Don't forget it's estimated on your recent energy use, so whack it in turbo, you'll soon burn through the juice.
a.twiddler
Veteran
Yes, it's interesting that even your phone or laptop can tell you how much time tou've got left before you need to recharge even though if you do intensive downloading it could be less.
If an e bike could tell you "you've got n minutes left at this setting" converted to time rather than voltage etc then it could give a better idea as the assistance wouldn't be used all the time anyway, and you could pace yourself better on a longer ride without worrying so much about running out of battery capacity. Naturally that depends on the programming being accurate and able to compensate for declining battery capacity with age, or low temperature. It would appeal to those who enjoy pitting themselves against the displayed mpg in your car (ie, me) and hypermiling.
I could imagine setting off with some kind of read out. "3 hours of low assistance, 1.5 hours of medium assistance, 45 minutes of high assistance available", which would naturally decline during the course of your ride, unless you turned the assist off. You could visualise and manage your resources much better this way.
Perhaps these figures are unrealistic as I have no e bike experience but the idea appeals.
If an e bike could tell you "you've got n minutes left at this setting" converted to time rather than voltage etc then it could give a better idea as the assistance wouldn't be used all the time anyway, and you could pace yourself better on a longer ride without worrying so much about running out of battery capacity. Naturally that depends on the programming being accurate and able to compensate for declining battery capacity with age, or low temperature. It would appeal to those who enjoy pitting themselves against the displayed mpg in your car (ie, me) and hypermiling.
I could imagine setting off with some kind of read out. "3 hours of low assistance, 1.5 hours of medium assistance, 45 minutes of high assistance available", which would naturally decline during the course of your ride, unless you turned the assist off. You could visualise and manage your resources much better this way.
Perhaps these figures are unrealistic as I have no e bike experience but the idea appeals.
Slick
Guru
That's exactly how my bike works. Its obviously based on what you have used so far, but will alter as you go through the assist settings.
ebikeerwidnes
Guru
- Location
- Z’ha’dum
We have 2 ebikes
The Carrera folder has a 4 led system on the controller on the handlebars
it is very very basic and if you go up a hill and use up a lot of charge then it often drops from 4 leds right down to two or one in a very short period fo time
Then goes back to 4 or 3 as soon as you get to the top of the hill
so overall it is just an instantaneous measure of voltage
On my main bike it has a Bosch system
the main display shows a system of bars - it does delay a bit until the first one goes - but generally it just gradually looses a bar in a sensible manner as you go along - if you go up a long hill then it may drop down - but never goes back.
I assume it bases its measure on a more complete measure ment of the battery condition and probably has a delay built in so it can average it over a short period of time
It also has an estimate of how many miles are left before the charge is fully depleted
this is also an estimate and does change if you go to a more economic form of riding but not quickly unless you change the power assistance level
so - my point at long last - it depends on the system - basic ebike systems will give very basic information which you really have to know the bike to really know what it is on about
more expensive systems are more complate and give you more useful information
The Carrera folder has a 4 led system on the controller on the handlebars
it is very very basic and if you go up a hill and use up a lot of charge then it often drops from 4 leds right down to two or one in a very short period fo time
Then goes back to 4 or 3 as soon as you get to the top of the hill
so overall it is just an instantaneous measure of voltage
On my main bike it has a Bosch system
the main display shows a system of bars - it does delay a bit until the first one goes - but generally it just gradually looses a bar in a sensible manner as you go along - if you go up a long hill then it may drop down - but never goes back.
I assume it bases its measure on a more complete measure ment of the battery condition and probably has a delay built in so it can average it over a short period of time
It also has an estimate of how many miles are left before the charge is fully depleted
this is also an estimate and does change if you go to a more economic form of riding but not quickly unless you change the power assistance level
so - my point at long last - it depends on the system - basic ebike systems will give very basic information which you really have to know the bike to really know what it is on about
more expensive systems are more complate and give you more useful information
presta
Guru
It's not the only way, it's just the cheap and simple way, and it doesn't work reliably because the relationship between voltage and charge state depends on battery wear. The accurate way is by measuring the charge directly, then you have a continuous tally of the charge going in and out, and can recalibrate the capacity of the battery at each discharge cycle.
ebikeerwidnes
Guru
- Location
- Z’ha’dum
Ah - is that why my Bosch on my Raleigh is better than the Carrera???
bonzobanana
Guru
It is the BMS in the battery pack that really can give an accurate view of remaining charge, external readings are not as accurate typically as the display on the battery pack itself. Bosch is a proprietary system with all components purposely designed to work together which allows more data to be used on other components like the display. Many cheaper ebikes use generic ebike components that are more of an open standard.
There used to be battery packs that had bluetooth I think which was always on and broadcasting data to an app with accurate charge level readings but the bluetooth circuit was always consuming current so if you didn't charge regularly the battery pack would be bricked as too far discharged.
There used to be battery packs that had bluetooth I think which was always on and broadcasting data to an app with accurate charge level readings but the bluetooth circuit was always consuming current so if you didn't charge regularly the battery pack would be bricked as too far discharged.
ebikeerwidnes
Guru
- Location
- Z’ha’dum
That makes sense
My Carrera is a Bafang system and seems to be separate battery and motor and display - maybe not all totally seperate but certainly not a fully integrated system like the Bosch on my Raleigh which - according to "the Internet" will brick itself if you paint it the wrong colour!
but the integrated system does seem to do a far better job overall!
presta
Guru
Possibly.
What this market needs is standards. The commodity systems lack the integration and function of the big manufacturers, but offer interchangeability, repairability and lack of "lock in". Imagine if you could buy a battery from whoever and just drop it into your Bosch engined bike and it would just work with all the features. Or your Mahle motor dies so you could wire in an Aikema unit and it would work with a simple pairing via open source software to enable the comms.
The key to this is open standards but standards development is long, complex and costly. I do a lot of work with interoperability standards for IT systems and building non-trivial interop standards takes years.
Companies that develop standards off their own back tend not to want to give all that work away for free so they make them proprietary and make other companies pay to join the "club" before they can get the specs. It often takes governments to force big companies to play ball with each other without forming cartels to exclude the small guys. But if they do there are big benefits to everybody, even the big companies, although it takes vision for them to see it and the payoff for the big boys may be years down the track.
The key to this is open standards but standards development is long, complex and costly. I do a lot of work with interoperability standards for IT systems and building non-trivial interop standards takes years.
Companies that develop standards off their own back tend not to want to give all that work away for free so they make them proprietary and make other companies pay to join the "club" before they can get the specs. It often takes governments to force big companies to play ball with each other without forming cartels to exclude the small guys. But if they do there are big benefits to everybody, even the big companies, although it takes vision for them to see it and the payoff for the big boys may be years down the track.
Ming the Merciless
There is no mercy
- Location
- Inside my skull
That’s very much going to depend on upcoming terrain, road surface, and weather. An impossible task.
