Battery range estimation

[BenjAZ]

Hi guys,

First of all, apologies if there is any other post with this topic.
I used the search engine and couldn't find any useful info.

I'm working on my next project bike. It's going to be a fast bike
I want to take it to a circuit, at least 70km/h and the battery should ride about 70km.
I've selected a 5kW system, 72V/80A controller.
I'm wondering whether there is any battery calculator/simulador.
Thinking to build a 20s9p battery with 30Q cells (27Ah, upto 135A) or 35E cells (31Ah upto 90A).
It would be sooooo frustrating to get to the circuit and not finishing the race because of the battery pack wrongly defined.

How many Ah would it require to make the 70km at circuit pace (continuously changing from full throttle to full braking and back again)?
Do you guys use any software/website to calculate the range of your battery/system?

I found out the motor simulator website but I'm going the buy the motor/controller from Aliexpress and it's not in the motor list. I don't know the motor values either.

I'd really appreciate any info or experience with 5kW systems.

Thanks!!

 

[flippy]

First: are you planning to use a direct drive/hub motor and use a controller capable of doing regeneration? That makes a huge impact in power needs as you can recoup a LOT of energy that way.

I will not expect a controller or motor from aliexpress to survive circuit racing for long.

Also: that battery will not survive many trips on the track. Asking 10+ amps per cell is way too much, especially of you are going to use regen.

I would crank up the volts as far as you can that a controller (with analog regen) can handle and build a battery that can survive this level of abuse. You need more cells at a lower capacity in order to get a more durable battery.

 

[Hillhater]

.... at least 70km/h and the battery should ride about 70km.
I've selected a 5kW system, 72V/80A controller.

Too many variables, and not enough data to accurately calculate pack capacity..
But an estimate might be to say this.....
..a 70 km race distance, with a max of 70 km/hr, suggests a run time of 1.5 hrs approx (average 50km/h ?)
..If "racing" , then assume a duty cycle of approx 75% motor power..(say 4kW average) ?
..therefore the pack would need to have a useable capacity of 6kWh roughly
Which on your 72v pack would suggest a 84Ah capacity ( 24P of those 35E cells !)
That is a large (25+ kg ) pack of 500cells !
Notice many "approx" , and "estimates" in there..?... Because without knowing the bike design, motor type, weights, track type, etc etc, it impossible to do much more than "estimate".

PS.. A 70km Ebike track race is very extreme ?... Are you sure that is the distance ?

 

[markz]

http://www.ebikes.ca/tools.html

 

[BenjAZ]

First: are you planning to use a direct drive/hub motor and use a controller capable of doing regeneration? That makes a huge impact in power needs as you can recoup a LOT of energy that way.

I will not expect a controller or motor from aliexpress to survive circuit racing for long.

Also: that battery will not survive many trips on the track. Asking 10+ amps per cell is way too much, especially of you are going to use regen.

I would crank up the volts as far as you can that a controller (with analog regen) can handle and build a battery that can survive this level of abuse. You need more cells at a lower capacity in order to get a more durable battery.

Hi,

Yes, both. Direct drive hub and the controller has the option of 10A regeneration.

The battery pack and controller will generate plenty of heat so I want to make some kind of air cooling system.

Do you suggest using other cells like the HG2 or 25R?

 

[flippy]

10A is way not enough. you need a much more capable controller. otherwise you are doing all your braking on the disks and not on the motor.
try looking into a 72V kelly KLS controller.
i would start by looking into the 2900mah range. panasonic PF or samsung 29E for example. both are much cheaper.
more cells means more power. and more capacity means you get less heating of the battery so you dont need much active cooling.
also: you need a 4kW motor in order to not overheat. 70kph with constant acceleration means huge loads on the motor.
just sustaining 70kph requires 3kW easy.

i would love to see what aliexpress thing you expect to do races with.

 

[BenjAZ]

.... at least 70km/h and the battery should ride about 70km.
I've selected a 5kW system, 72V/80A controller.

Too many variables, and not enough data to accurately calculate pack capacity..
But an estimate might be to say this.....
..a 70 km race distance, with a max of 70 km/hr, suggests a run time of 1.5 hrs approx (average 50km/h ?)
..If "racing" , then assume a duty cycle of approx 75% motor power..(say 4kW average) ?
..therefore the pack would need to have a useable capacity of 6kWh roughly
Which on your 72v pack would suggest a 84Ah capacity ( 24P of those 35E cells !)
That is a large (25+ kg ) pack of 500cells !
Notice many "approx" , and "estimates" in there..?... Because without knowing the bike design, motor type, weights, track type, etc etc, it impossible to do much more than "estimate".

PS.. A 70km Ebike track race is very extreme ?... Are you sure that is the distance ?

I want to take this bike to several circuits, but the most demanding one will be the Isle of Man (UK). It's about 60km long, way longer than any other circuit race.

6kWh!!?? My god, that's seriously large...

 

[BenjAZ]

This is the one I'm considering:
https://www.aliexpress.com/item/High-Speed-Electric-DIY-Motorcycle-DIY-72v-84v-5000w-Electric-bike-Kit-Electric-Bike-Conversion-Kit/32804931352.html?spm=a2g0s.8937460.0.0.19572e0eO3uSPD

I'm quite new to bikes and just experienced with systems between 500W and 2kW. For urban riding, absolutely no extended abuse like racing.

Absolutely open to suggestions

 

[BenjAZ]

10A is way not enough. you need a much more capable controller. otherwise you are doing all your braking on the disks and not on the motor.
try looking into a 72V kelly KLS controller.
i would start by looking into the 2900mah range. panasonic PF or samsung 29E for example. both are much cheaper.
more cells means more power. and more capacity means you get less heating of the battery so you dont need much active cooling.
also: you need a 4kW motor in order to not overheat. 70kph with constant acceleration means huge loads on the motor.
just sustaining 70kph requires 3kW easy.

i would love to see what aliexpress thing you expect to do races with.

I'll check the Kelly KLS controllers, thanks!

 

[flippy]

no way that dinky little motor can handle your load without burning out. the price makes it impossible. it might handle 5kW but it sure aint rated 5kW. that is a 1.5kW motor at best. those can do 5kW peaks for a few seconds.
there is zero way that setup will survive a track at the advertised power rating.


this is the motor you need:
http://www.cnqsmotor.com/en/article_read/QS%20Motor%204000W%20273%2040H%20V3%20E-bike%20Spoke%20Hub%20Motor/260.html
you can dump 8kW peaks into this hub. if you ask QS they will also rim it for you.
this motor is actually rated for 4kW continous. something you need at those speeds.
if you grab a 72V 250~300A KLS controller with that you can hook up the temp sensors so you dont blow up the motor and those can do 150A regen if you want to. you would lock the tire if you did but you can.
that will be a WAY more durable solution then the aliexpress one.

battery is still a discussion. you need a much bigger battery then you first pitched. you need a 4~5kWh battery in order to keep everything in one piece and have some durabillty. bigger battery also means you can absorb more regen and have less heat soak. if built correctly you only need minimal cooling.

 

[rachdatu]

Check http://www.kreuzotter.de/english/espeed.htm

That's for a normal bike (no bat!). This will give you a rough idea how much power you need for your battery.
And keep in mind, if you double your speed, you need 8 times more power...(valid above ~25 km/h)
There are some nice formulas at the bottom of that page that explains it.

Walter

 

[Hillhater]

I want to take this bike to several circuits, but the most demanding one will be the Isle of Man (UK). It's about 60km long, way longer than any other circuit race.

6kWh!!?? My god, that's seriously large...

IOM TT circuit on an Ebike
That is a fast open mountain circuit.. The Zero TT bikes average near to 200km/hr around there.!
There are very few corners that are below 50km/hr, so your bike will be at max speed 90% of the time, with very little oportunity for regen.
Assuming you gear it for max speed, that means max power for 90% of the time also.
That will require a very tough motor, controller, and battery, to prevent melt down for over an hour at max output.
You should plan to run short races (<10-20km ) first to gather data on speed, power, battery consumption, temperatures, reliability, etc etc,..and work your way up on distance fixing and changing things as you go.
Many of the pro TT Zero teams have turned up to race , only to fail miserably part way round the course.

 

[amberwolf]

Regarding heat and cooling systems:

Don't build something that will *need* a cooling system.

If it needs one, and it fails, you're screwed. Unless you have some kind of thermal sensing and protection, you could end up with a bike on fire between your legs, if the battery overheats enough, or wiring gets hot enough for insulation to fail, etc.

Build a bike that has good enough parts on it to not generate much heat, and to handle the heat they do generate by themselves in a safe way.

It isn't cheap, but it can be done.

This means buying parts from known good vendors, that sell the real thing, and not the cheapest stuff you can find that happens to be labelled with the right name--they're probably either rejects or fakes.

This means making or buying a battery that has low internal resistance over the whole range you're going to use it in. Also probably means having one with significantly more capacity than you actually need, just to have more parallel cells to drop the resistance. The battery is the heart of the whole system, and if it isn't able to deliver the power you need without stressing it out, the rest of the system suffers, and the battery itself could fail. It has to handle high discharge currents without much voltage sag or heat, and it has to handle high charge currents without damaging the cells or heating up. (partly for useful braking regen, and partly just to quickly top it off).

This means getting a motor that is designed to continuosly handle the power you need, and has the right winding to run at the speed you want it to in the wheel and tire size you're going to use, at the pack voltage you're going to use.

This means getting a controller that can handle that motor, and any regen braking needs, that has the features you want and is reliable. The cheaper it is the less likely it'll be reliable. (though cost is no guarantee of quality).


I recommend reading up on some of the electric racing motorcycle builds here on ES and elsewhere, to get an idea of the power and battery and motor needs, even if your planned bike is smaller than that (it might end up having to be bigger to do what you want).


FWIW, I also think you're probably going to end up with at least a small motorcycle frame, not something bicycle-class, with the weight of all the stuff you'll need to do the speeds and range you're after. Otherwise the frame may twist and flex too much as you ride, especially if there's a lot of turns, braking, maneuvering, etc.

 

[Hillhater]

on the subject of cooling batteries and electric bikes at the IOM Zero TT race..
Whilst the race teams are very secretive about their set up, ...one throw away comment by the winning Mugen Honda team was that their battery pack was not actively cooled to save weight, and keep it compact, ( approx 20kWh on a bike !) and only just lasted one lap before being swapped out for the next run.
BUT, the used batteries have to stand in a cooler box for 2 days to allow the core cells to return to ambient temperature !

 

[jonescg]

on the subject of cooling batteries and electric bikes at the IOM Zero TT race..
Whilst the race teams are very secretive about their set up, ...one throw away comment by the winning Mugen Honda team was that their battery pack was not actively cooled to save weight, and keep it compact, ( approx 20kWh on a bike !) and only just lasted one lap before being swapped out for the next run.
BUT, the used batteries have to stand in a cooler box for 2 days to allow the core cells to return to ambient temperature !

I'm pretty sure that's an exaggeration - the specific heat capacity of a battery cell is about 2000 J/kg.K Unless they kept it in a styrofoam box I think it would lose that heat faster than that.

 

[BenjAZ]

Hi,

My ebike won't be built on a regular mtb frame. The frame will be specially designed for my requirements, because of that I'm trying to figure out the battery pack I'll need to make a safe (heatwise) and full lap to the IOM circuit. It won't be with the crazy insane-pace racers. I love my live and don't want to lose it :lol:
So, I don't need a speed monster. Just want a relatively fast ebike to be able to get in the race tracks with decent performance. I don't mean beating the speed world record.

Maybe the kit I was thinking is not good enough to withstand a 60km lap at full throttle most of the time. haha

Any suggestion for the motor and controller?

Thanks

 

[flippy]

Already gave you a link to the right motor above.

 

[Hillhater]

on the subject of cooling batteries and electric bikes at the IOM Zero TT race..
Whilst the race teams are very secretive about their set up, ...one throw away comment by the winning Mugen Honda team was that their battery pack was not actively cooled to save weight, and keep it compact, ( approx 20kWh on a bike !) and only just lasted one lap before being swapped out for the next run.
BUT, the used batteries have to stand in a cooler box for 2 days to allow the core cells to return to ambient temperature !

I'm pretty sure that's an exaggeration - the specific heat capacity of a battery cell is about 2000 J/kg.K Unless they kept it in a styrofoam box I think it would lose that heat faster than that.

I would not think the Mugen guys need to exaggerate much to make a point, but anything is possible..
https://www.bennetts.co.uk/bikesocial/news-and-views/racing/isle-of-man-tt/news/tt-2018-why-are-mugen-racing-electric-bikes-at-the-tt-and-what-does-the-future-hold

....Mugen Euro boss Colin Whittamore
“To keep the battery cool, we duct air through it from side vents and through the central fairing duct. Keeping the outside cells cool isn’t a problem because they’re on the outside; it’s the ones in the core that get hot – in the past we’ve had to leave the battery to cool down for two days, when we overheated it. We could open it up and put more airways in, but then we’re wasting space that could’ve had a battery in it. The water-cooling is for the inverter, and the motor is oil-cooled.”

 

[jonescg]

Unless it went thermal

 

[BenjAZ]

Already gave you a link to the right motor above.

Sorry, had missed it!

Thanks