Battery decision

inteli7original

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Dec 16, 2018
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Hello guys,
I don't really know a lot about e-bike, especially about batteries. The bike that I am trying to buy has a 250W electric motor with a battery of 11.6ah.
In my opinion that battery will not be able to give me a good range so I am thinking of purchasing an extra one but I am in doubt. The ones that I am considering buying are the following

36V, 13.8Ah, 500Wh (€449)
36V, 17.3Ah, 620Wh (€546)
36V, 20.7Ah, 745Wh (€597)

48V 662Wh, 13.8Ah (€556)
48V 830Wh, 17.3Аh (€628)

Can someone explain to me which will fit my needs as I want to do at least 100km per charge? Like in order to do a lot of mileage does the battery need to have a high Ah and Wh? Or does the voltage matter in this case? Should I pick 36V or 48?

(I don't mind the price in this case)

I am really sorry if I posted in the wrong section!

Many thanks
 
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Benjahmin

Esteemed Pedelecer
Nov 10, 2014
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The first thing is that the voltage of your second battery must match the voltage of the original battery and the control system of the bike.
The Amp Hour rating of a battery tells you how many amps a battery will (theoretically) deliver and for how long. So a 10Ah battery will deliver 10A for 1 hour. The more useful information is the Wh rating. This is merely the Ah multiplied by the voltage.
Generally speaking a rider will consume 10-20 Wh/mile, depending on terrain, wind, weight, rolling resistance etc etc. A fit rider may get down into the 7-8 Wh/mile. Of course, if you turn the power off the range is infinite.

The most important thing here is that battery quality varies greatly. The ability of a battery to deliver it's power is down to it's spec. There are a great number of 'cheap' batteries on the market made from unamed cells that will have a short life of disappointing perfromance. You will get much better help if you can link to the bike and batteries you are thinking of buying.
 

Nealh

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There are to many variables involved to gauge the range some one may or may not get, suffice to say the greater the ah the greater chance of achieving the required goal. When new I was able to manage 45 miles form an 11ah battery with very mediocre cells for about 6- 8 months after this the miles tailed away as cells lost capacity.

Post a link to the battery or batteries you are looking at.
 

Nealh

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A 48v battery will have 33% more wh then a 36v of the same ah, as stated the bike will need to be able to handle 48v and that means the controller being 48v capable otherwise too high a voltage with smoke the controller and render it useless.
 

Nealh

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Where are you in the UK ?
By the time you have paid for the bike and new battery you will have spent the best part of nearly £2000.
Why not buy a more suitable bike to start with ? One with a larger battery, albeit won't have a Dapu crank drive .
 
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sjpt

Esteemed Pedelecer
Jun 8, 2018
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Or you could buy one with a bigger battery to start with, eg Woosh Keiger with 15aH battery at £1229 http://wooshbikes.co.uk/cart/#/category/uid-0 or http://wooshbikes.co.uk/?krieger

They'd probably be able to supply with 17aH battery. Also, very good customer service.

The Bosch range assistant gives a pretty good idea of what mileage you may expect for what kind of riding. It is designed for Bosch but gives pretty good idea for others too. As said above, the critical things for range in batteries are (1) total capacity in watt hours (volts * aH) and (2) quality (not allowed for in the calculator). So the 11.6*36 is 417, pretty close to the Bosch 400. For bigger batteries multiply up the Bosch figures by relative battery capacity. Most motors behave similarly to the Active Line in the predictor.
 

inteli7original

Just Joined
Dec 16, 2018
3
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Where are you in the UK ?
By the time you have paid for the bike and new battery you will have spent the best part of nearly £2000.
Why not buy a more suitable bike to start with ? One with a larger battery, albeit won't have a Dapu crank drive .
I live in Cosham . Can you provide some links?
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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Hello guys,
I don't really know a lot about e-bike, especially about batteries. The bike that I am trying to buy has a 250W electric motor with a battery of 11.6ah.
In my opinion that battery will not be able to give me a good range so I am thinking of purchasing an extra one but I am in doubt. The ones that I am considering buying are the following

36V, 13.8Ah, 500Wh (€449)
36V, 17.3Ah, 620Wh (€546)
36V, 20.7Ah, 745Wh (€597)

48V 662Wh, 13.8Ah (€556)
48V 830Wh, 17.3Аh (€628)

Can someone explain to me which will fit my needs as I want to do at least 100km per charge? Like in order to do a lot of mileage does the battery need to have a high Ah and Wh? Or does the voltage matter in this case? Should I pick 36V or 48?

(I don't mind the price in this case)

I am really sorry if I posted in the wrong section!

Many thanks
Motor voltage does matter, though some "experts" here appear to ignore it to a degree. So always buy a battery with the same voltage as the motor needs....remember K.I.S.S!
regards
Andy
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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Motor voltage does matter, though some "experts" here appear to ignore it to a degree. So always buy a battery with the same voltage as the motor needs....remember K.I.S.S!
regards
Andy
To a degree 48v will not kill or harm a 36v hub, many on here have tried it still over volt there hubs and have no issues, go over to Endless Sphere and troll your thoughts and they will simply shoot you down in flames after dismissing you out of hand.
Yu cant do it with 36v with inbuilt controllers but can with hubs, as long as you don't go mad with current they are fine to use like that.
 

soundwave

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May 23, 2015
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id not try pulling 100A from it tho pmsl ;)
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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To a degree 48v will not kill or harm a 36v hub, many on here have tried it still over volt there hubs and have no issues, go over to Endless Sphere and troll your thoughts and they will simply shoot you down in flames after dismissing you out of hand.
Yu cant do it with 36v with inbuilt controllers but can with hubs, as long as you don't go mad with current they are fine to use like that.
Do remember that the OP appears to not be an electrically "aware" person, and expecting him to do what others risk doing, is putting him into a possibly bad situation.....
Not forgetting the dangers of a suddenly wrecked motor suddenly braking a wheel, in a delicate traffic situation or even a Li-ion battery fire or explosion!!
But there is a very simple solution to this, you yourself could openly here guarantee the OP personally online here that he can use a 48 volt battery with a 36 volt motor and if he ever gets into any sort of problems, you will pay for all the repairs needed.
We used to call it "putting your money where your mouth is!"
If you fully agree, I see that as a problem solved!
Giving what I personally would call "poor quality" advice is something nobody on a open forum should ever do without taking full responsibility as well.
For my own statements about staying with the correct voltage, that is the only safe and honest advice anyone of us here should ever give. As an electrical engineer of many years standing, that is how we handle such situations.
What you or your friends experiment and carry out on your own equipment/Bike is an entirely different matter, as you take the responsibility fully on yourself of course...
I am sure that my reply will cause much "gnashing of teeth" for you, therefore in the future please take more care of what you say......then I or someone else here has no need to point out your errors and a "fix" that will possibly not appeal to you!.....OK?
Have a great day
Andy
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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Sorry, I must have missed the post where anyone has advised OP to fit a 48v battery to his bike.
See post #11.
In answer to the OP who appears not to be educated (no criticism!) electrically, nor does he need to be if the asked for advice is safe and accurate.....

regards

Andy
 

Nealh

Esteemed Pedelecer
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Scare mongering we don't do, but in practice there is no harm in over volting as power is often only used intemittenly, running 48v or 36v runs no extra risk.
Go else where and scare other forumites with your continued bleating.

Replies are in answer to Op's #1 as he has listed 36 & 48v batteries, al that has been done is to make him aware of issues with wrongly spec'd controllers.
If some smokes their hub then they simply replace it they are cheap enough and as for a wheel braking, if it is built correctly there is no issue.
 

Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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Scare mongering we don't do, but in practice there is no harm in over volting as power is often only used intemittenly, running 48v or 36v runs no extra risk.
Go else where and scare other forumites with your continued bleating.

Replies are in answer to Op's #1 as he has listed 36 & 48v batteries, al that has been done is to make him aware of issues with wrongly spec'd controllers.
If some smokes their hub then they simply replace it they are cheap enough and as for a wheel braking, if it is built correctly there is no issue.
I notice that nobody, including yourself, has offered to "guarantee functionality" (correct me if I have missed such a post!) with regard to the comments of putting a 48 volt on a 36 volt motor, but labels mine as scare mongering.
Now that was very insightful for all here!!!
If you are someone who has a lot of electrical experience in setting up a controller to reduce current and therefore power to the motors, when using a higher voltage than recommended, can achieve what you say, but its really not a good idea to pass it off as simple to do for a beginner....
For safe usage, the motor internal temperature should also be monitored, just in case!
We can either agree to disagree on this subject or not, but the point would have never arisen if you had made it fully clear in the beginning of the possible risks, as this educates, and the person interested can make a good informed decision, before starting, or not starting.
I have nothing against doing that myself, as long as the risks are fully detailed.
And he full method is also carefully explained point by point.
Have a great day.
Andy
 

anotherkiwi

Esteemed Pedelecer
Jan 26, 2015
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1. You can use a 48 v battery with a 36 v motor, it will spin 33% faster
2. You can't use a 48 v battery with a 36 v controller (unless you are very clever/have experience)
3. When you upgrade a 36 v motor to 48 v it is recommended to keep the controller limited to 17-18 Amps (about the same number of Amps you would use at 36 v)

There, I think all points have been covered?

A 250 W nominative motor will run all day at 500 W without even getting warm. They are designed to do that - read EN15194 to understand why.

Doing the math on the modifications listed above, the controller Watts (not the Watts at the wheel) will peak at 936 W with the battery hot off the charger. Let's say you are being silly and use your motor badly - you might have a hill steep enough that you take in the wrong gear and so 50% of that power is lost as waste heat into the motor.

468 W of heat* is not enough to warm any of the brand name geared hub motors most people have to above 80°C. That is the lowest internal temperature that can cause (temporary) damage. Permanent damage to a motor starts at about 120°C, the nylon gears on the clutch wil strip their teeth. At 180°C the insulation on the wires will melt.

*I have an induction hob - 600 W level takes forever to bring a pot of water to a simmer, about 80°C.
 
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Andy-Mat

Esteemed Pedelecer
Oct 26, 2018
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1. You can use a 48 v battery with a 36 v motor, it will spin 33% faster
2. You can't use a 48 v battery with a 36 v controller (unless you are very clever/have experience)
3. When you upgrade a 36 v motor to 48 v it is recommended to keep the controller limited to 17-18 Amps (about the same number of Amps you would use at 36 v)

There, I think all points have been covered?

A 250 W nominative motor will run all day at 500 W without even getting warm. They are designed to do that - read EN15194 to understand why.

Doing the math on the modifications listed above, the controller Watts (not the Watts at the wheel) will peak at 936 W with the battery hot off the charger. Let's say you are being silly and use your motor badly - you might have a hill steep enough that you take in the wrong gear and so 50% of that power is lost as waste heat into the motor.

468 W of heat* is not enough to warm any of the brand name geared hub motors most people have to above 80°C. That is the lowest internal temperature that can cause (temporary) damage. Permanent damage to a motor starts at about 120°C, the nylon gears on the clutch wil strip their teeth. At 180°C the insulation on the wires will melt.

*I have an induction hob - 600 W level takes forever to bring a pot of water to a simmer, about 80°C.
If there are any other electrical engineers reading this post of yours, I am sure that they are all having a good laugh at your misunderstanding(s) about electricity.
By the way, I "did the math" probably many years before you were born!!!
I started my studies almost 60 years ago!!!
I really am very surprised that anyone would open up their lack of fairly basic electrical knowledge to possible ridicule!!
For your information:-
Some e-bike motors are simply built for a higher voltage/wattage, just to save money in having different models available, IMPORTANT please note that the speed is not "affected" by the voltage!! But the power is partly, so speed control is therefore achieved.
The good e-bike motors on most bikes nowadays are basically a miniature 3 phase motor, often with hall effect sensors built in, to give feedback to the electronics of "where" the motor rotor "is" in its revolution.
The speed itself is therefore governed by the controller, by it setting a "frequency of switching" on and off, of large MOSFET transistors, allowing variable speed control. The quicker they switch, the faster you go!
The voltage therefore has therefore no net effect on speed.
Once the current set is achieved, the field(s) is switched off early, if need be.
As no overheating can be allowed.
The time between pulses to each field coil (there are at least three or sets of threes, depending upon design!) sets the speed of the motor therefore the e-bike.
Plus other settings with wheel size of course.
A cheap speed upgrade that many do not understand for some reason, is to set a smaller wheel size than the bike actually has, as the controller has no way of measuring wheel size! Though I have never heard of anyone actually doing that!!! But its very simple to do if the controller can be used on smaller diameter wheels!
VFD motors work in a very similar manner. Look here for further infos:-https://en.wikipedia.org/wiki/Variable-frequency_drive
There are still some e-bike motors with "brushes" around on the bike market, these are partly affected by voltage. BUT the controller then uses PWM to reduce the POWER to control the speed of rotation!!
A short tutorial for PWM can be found here:-
https://www.electronics-tutorials.ws/blog/pulse-width-modulation.html
Then there is the problem of brush wear and the mess the carbon makes inside the motor for such motors!
If simply by changing the voltage, the motor speed was also changed as you apparently believe, I can see some huge possibilities for even more danger to the rider than he already has.....
Remember, we are not talking about simple DC motors as <ou seem to imagine.....
A place to start reading, which covers the theory even better might be here:-
https://en.wikipedia.org/wiki/Pedelec#Motor_control
Where you can read the following with regard to e-bikes:-
When the motors are regularly used heavily, especially when going uphill they may heat up significantly, some have a temperature sensor in the motor winding, where if a certain temperature is reached the electronics may reduce power to the motor.
Just for your information only, I spent a great many years learning my job and studying as well, to know how electrics (and electronics by the way!) REALLY work.
But for example, in all my years, I have never ever in my life ever found an electrician that really knew his job, in all the countries I have worked in, mainly the USA, the UK and Germany!
But I have identified and repaired their "handiwork" in those countries plus all the Scandinavian, EU,Middle East and African ones, for over 50 years now.....
They apparently knew,only little bits of knowledge, cobbled together into what they thought was electrical knowledge......it wasn't! It cause expensive damage to expensive machines!
Why did you mention this:- "*I have an induction hob - 600 W level takes forever to bring a pot of water to a simmer, about 80°C."
Let me address that for you too so you may understand better just how an Induction Hob REALLY works:-
The hob runs at a set frequency, (but variable amplitude for power/heat control), which has been selected to work best with most cookware.
Therefore the basic functionality, when comparing between an e-bike and an induction hob is quite different, but still power control!!
Different frequencies are needed for different cookware metals.....which is why only certain ones will work! Aluminium, copper and some stainless steels will not work!!
Often, in my experience, cast iron cookware works best, though I have only tested using such cookware that I have possessed of course!!
Aluminium or most types of stainless steel, will either not work, or will only work badly.
A simple test is a magnet.
When it sticks to the base, that usually implies that the pot will work on induction hobs. Using the same magnet on the sides will often not stick there if aluminium or certain types of stainless.
This is why a good stainless steel or aluminium pot, one that works on an induction hob, has a steel disk moulded into the base.
It is only that disk which actually gets hot!!!
Many do not know this!!
Not the rest of the pan, except by conduction, not induction!!
A cast iron pot is basically similar to that disk of course, but "all over"! Which is why it works so well generally!
So you either have a pot(s) not designed fully for induction, or of the wrong material, but remember 800 Watt is very low for Hob cooking anyway.
I would suggest a minimum of 1800 Watt per hob, or better.
Also, its possible that the hob has the wrong frequency as well of course due to a failure in design or manufacture.....so try it with cast iron to see if that helps in any way....If not, it is simply too weak to be useful for some reason.....
Comparing the two as you wish to do is a really bad idea, comparing apples and pears.....as they regulate power in different ways to each other.....that only an engineer would fully understand.....
Finally, there is no way to inform you accurately, without you possibly getting upset, about what you do not understand, but that is your problem not mine.....
Furthermore, I have no interest in trying to train you (or anyone else for that matter) to being fully electrically literate on an online bike forum, as that sounds like rather hard going for us both.
Maybe the Open University runs such courses nowadays in the UK on electricity and motor control.
So today, I have only raised a few points to hopefully spike your interest in learning properly what you think you already know, but don't!!
As the more you write here, the more obvious you make it as to just how little you really know/understand.....Sadly! As I am sorry to be the bearer of such news.....
Have a great day anyway.
Andy
 

anotherkiwi

Esteemed Pedelecer
Jan 26, 2015
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motor.png

Same motor, same controller, different battery.

Oh dear the motor with the 48v battery goes faster :eek: ... Something must be wrong with the years and years of hands on experience of the people at ebikes.ca not to mention all those crazy hot-rodders over at endless-sphere.com.

Because we both know I am halucinating and don't know SFA about electric motors and pedelec controllers don't we? Hey did you know I haven't managed to fry a controller or a motor yet? Only 7,000 km under my belt so I probably still have time.

I think you need to read up on how a common KT controller actually works.
 
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