Electric bike battery

[sspj9]

Using a 48v 1000w motor for my electric bike,  how long will a 48v 11.Ah Lithium-ion battery last on full throttle?
Is it recommended? Thanks

[MosherIV]

Using a 48v 1000w motor for my electric bike,  how long will a 48v 11.Ah Lithium-ion battery last on full throttle?
Is it recommended? Thanks

The current through the motor is
1000W / 48V = 20.833333333333333333333333333333

The battery can supply 48V at 11A for 1 hour,
so roughly speaking this battery can last for around 1/2 hour

Is it recommended ?
Well, are you OK with having to recharge every half hour and you will be going through the life of the battery pretty quickly
(typically they only have 500 to 1000 charge cycles to begin with).
Are you OK with that?

[sspj9]

I suppose that is fine, since I will be using it to go to university which is around 6km, so both ways will be 12km
Now, maximum speed of the bike is 45 km/h so i would be able to cover a distange of (45/2 = 23km). Therefore if I use full throttle I would have to charge every fortnight.
However, I doubt I'll use full throttle, and I sure would be using the paddle occasionally.
I suppose then 11.6Ah will do.

Question?
If the battery life is over would I be able to change the cells individually with a higher power rating?

Thanks

[MosherIV]

I suppose that is fine, since I will be using it to go to university which is around 6km, so both ways will be 12km
Now, maximum speed of the bike is 45 km/h so i would be able to cover a distange of (45/2 = 23km). Therefore if I use full throttle I would have to charge every fortnight.

I do not know how you worked out that you can charge every 2 weeks.

I said the battery will last around 30 minutes at full speed, that is with no load.
So how long is the journey in time - NOT distance.

Question?
If the battery life is over would I be able to change the cells individually with a higher power rating?

When the battery life is used up - they do not retain their charge. It does not matter how you charge, they will not keep their charge or another way of looking at it - they will not charge.
You CANNOT exceed the charging current for ANY Lithium technology battery without running the risk of starting a fire !

[sspj9]

My mistake, i meant I would charge the battery every two days 

I do mean change the individual cells not charge. So i open up the battery and change the 18650 cells which went bad individually but with a higher rating?

[MK14]

Doesn't the bike suppliers information, give you typical ranges for their bikes/batteries ?

Whatever figures they give, I'd suspect they may be over optimistic/ideal and maybe exaggerating. So would expect the real life figures to be two thirds or a half, what they say. Maybe even less than that.

There could be good independent tests/reviews which give the range.

When the battery is down to 5% to 20% of left capacity, it may be too weak to drive the bike and/or a bad idea, as the battery could be damaged (excessively run down).

Also reaching 100% full charge may be problematic as well. Maybe 90% (if done very quickly) is more realistic. (It depends on how fast the charger is, battery temperature and other factors). With enough time, 100% is possible, I guess.

The motor drives and any voltage conversion (if necessary), will waste a percentage of the energy as well.

Accelerating would probably use the most power, I would guess. Heavy battery loads, can reduce the run time, even more, because of inefficiencies in the battery. I.e. Amp/hours ratings, depend on load current over a period of time. Very quick discharges, are usually lower figures.

EDIT:
I'd be scared of getting killed/injured on it and use a safer method of transportation.

[MosherIV]

I do mean change the individual cells not charge. So i open up the battery and change the 18650 cells which went bad individually but with a higher rating?

Sorry my mistake.

It is not advisable to mix new and old batteries of any type. Older batteries would have a much lower capacity than the newer cells.
It is dangerous to over charge Lithium based batteries, again there is a risk of starting a fire.

It is not advised to mix batteries of different capacities for the same reason as above, I presume that is what you mean by "higher rating".

[sspj9]

I see, and makes a lot of sense! Well I hope it would be much more worth it than driving a car...

[sspj9]

I'd be scared of getting killed/injured on it and use a safer method of transportation.

Same goes to motor cyclists!, Well I doubt I would be reaching high speeds with a bike... At least the route from home to uni has cycle paths.

[edpalmer42]

Even though your motor is rated for 1000 watts, that doesn't mean it will always draw that much power.  When you're cruising at a constant speed, your battery drain will be determined by friction, electrical efficiency of the motor and drive system, and wind resistance.  The battery drain under these conditions will be much lower and that will give you more range or more time between charges.  I have no clue what a typical drain would be at constant speed.  The heaviest drain will be when you're accelerating from zero with full throttle.

What is the series/parallel arrangement of your battery?  48V suggests 16 cells in series, but 20A doesn't sound like it would be very good for a single string of 18650 cells.

Ed

[MK14]

I'd be scared of getting killed/injured on it and use a safer method of transportation.

Same goes to motor cyclists!, Well I doubt I would be reaching high speeds with a bike... At least the route from home to uni has cycle paths.

At least if you had an accident in a normal bicycle, hopefully the lower speeds, would tend to minimize/prevent injuries and you would be less likely to be killed. Until you go off the cycle paths, and start meeting cars ...

But if you can do up to 45 KPH, you will be much more likely to injure/kill someone else, or yourself, compared to a peddle powered bicycle, I would expect.

[sspj9]

What is the series/parallel arrangement of your battery?  48V suggests 16 cells in series, but 20A doesn't sound like it would be very good for a single string of 18650 cells.

52 x Samsung INR18650 29E (3.7V 2.9Ah) connected 13 series 4 parallel.. Doubt i could customize it at all

[Fungus]

Is it recommended?

a) 45kmh on a bike? I don't know what brakes/wheels you have but it sounds quite scary to me.

b) How long will the battery last? That depends almost 100% on aerodynamics and how level the ground is (ie. hills). Another big factor will be the weather (temperature).

This graph shows air resistance for a normal bicycle:

https://en.wikipedia.org/wiki/File:CyclingPowerComponents.svg

You want to go at 12.5m/s so you probably need all of the power from your 1kW motor.

Look at the graph though. It's very exponential. At 10m/s you only need 300W. You either need to go a bit slower or add some serious aerodynamics if you want this to be practical.

so roughly speaking this battery can last for around 1/2 hour

They won't last very long if you repeatedly discharge them in 30 minutes (in fact it might not even be possible to discharge them in 30 minutes without overheating).

[Fungus]

52 x Samsung INR18650 29E (3.7V 2.9Ah) connected 13 series 4 parallel.. Doubt i could customize it at all

Here's a datasheet: https://www.nkon.nl/sk/k/29E.pdf

Minimum discharge time is approx one hour. You'll need at least 8 parallel to achieve 1kW. Better double all your numbers. 

You're talking about $1000 of batteries that will probably last about a year (charging every two days).

You'll also need some really fancy charging electronics to avoid having to trash sets of cells because you're not charging them perfectly.

You also risk trashing batteries if cooling is uneven... and maybe a big lithium fire if you mess up.

I dunno. A moped looks cheaper/safer.

[JPortici]

Is it recommended?

a) 45kmh on a bike? I don't know what brakes/wheels you have but it sounds quite scary to me.

same. electric bikes i've used (pedal assistance) could run at most at 26 km/h and sometimes the whole thing wouldn't be stable (you had to keep the handle very tight at higher speeds or it would start oscillating)

OP, is it something you want to build for yourself? the braking system is crucial. you can kill yourself when going much slower than 45 km/h.
an electric bike will also disable the motor whenever you touch the brakes, for obvious safety reasons.

side note: our grandparents use to do this instead

i think i saw one or two when i was a little kid
this evolved into the ciao

[Fungus]

Is it recommended?

a) 45kmh on a bike? I don't know what brakes/wheels you have but it sounds quite scary to me.

same. electric bikes i've used (pedal assistance) could run at most at 26 km/h and sometimes the whole thing wouldn't be stable (you had to keep the handle very tight at higher speeds or it would start oscillating)

I once went downhill on a bike with a speedometer and IIRC I chickened out at about 30 kph. I'm not saying you can't get used to going fast on one but they really don't seem designed for those speeds. I thing you'd need a different frame geometry to keep it stable.

[helius]

For converting a bicycle to electric assist, this startup has a really cool concept. Just change the rear hub!

[Siwastaja]

With 1000W constant power on an Ebike, you'd be going so fast that you'd be scared.

You won't probably draw 1000W except for short peaks, like accelerating, going uphill (which will be saved back during the next downhill by zero consumption), etc.

More realistic average power for you daily commute would most likely be in the 200-500W range depending on how fast you go. 1000W capable motor, inverter and battery pack makes a nice ebike because sometimes you want the extra power to overcome some non-average situations (like uphills).

I welded a pack made of Samsung 29E cells for a friend. It was ca. 50 cells. He's been very happy so far. These cells are nice because they are "old tech" and very cheap in quantities, but still high tech compared to many "hobbyist" solutions like LFP cells. You can see his videos here: . I only did the welding, having built the robot welder that can directly weld copper sheet to the cells. Part3 of the video series shows the welding, while part5 shows the bike up&running.

When using Samsung 29E's, thing of them being capable of 2C peak, 1C continuous power. You want to actually limit the discharge current to about 2C, maybe 2.5C max, by some active design (limit in the inverter) so that you don't blow the protection PTCs open in the cells.

[Mechatrommer]

52 x Samsung INR18650 29E (3.7V 2.9Ah) connected 13 series 4 parallel.. Doubt i could customize it at all

you are nuts... you can use 4 of this... http://www.hobbyking.com/hobbyking/store/__80906__Multistar_High_Capacity_4S_20000mAh_Multi_Rotor_Lipo_Pack_AU_Warehouse_.html
or 4 LA batteries in series. easier to maintain...

[langwadt]

And in EU the limits for an e-bike is 250W and only assist when pedaling and doing less than 25kmh, beyind that it becomes  a motorbike or moped and requires insurance, type approval etc.

[Harvs]

I ride a 750W ebike converted using a BBS02 motor kit and hobbyking packs http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=19499 and their 2S packs, to a total of 14s @ 10Ah.

The thing people miss in all these calcs isn't that it's necessarily dangerous or scary at those higher speeds (a normal road bike going down a hill can easily crack 50km/h), but it's bloody uncomfortable. I typically ride at 25-30km/h and that's ruff enough.

Where you do need the power though (at least in my case) is climbing hills.  The higher powered motor means I can still be doing 20km/h up a hill where I'd normally be down in the lowest couple of gears.  Makes for a great commuting bike.

[ez24]

For converting a bicycle to electric assist, this startup has a really cool concept. Just change the rear hub!

Looks interesting

[zlymex]

I have a electrical uni-cycle with 1000W motor too, battery is 850Wh(5-parallel 16-series of Panasonic NCR18650PF), the typical range is 80km when cruising at 20km/h even road for rider of 65kg. The unicycle is less efficient than a bicycle because it use extra power to balance.

[Fungus]

For converting a bicycle to electric assist, this startup has a really cool concept. Just change the rear hub!

...except they've been on "pre-order" status for as long as I can remember.

[Siwastaja]

52 x Samsung INR18650 29E (3.7V 2.9Ah) connected 13 series 4 parallel.. Doubt i could customize it at all

you are nuts... you can use 4 of this... http://www.hobbyking.com/hobbyking/store/__80906__Multistar_High_Capacity_4S_20000mAh_Multi_Rotor_Lipo_Pack_AU_Warehouse_.html
or 4 LA batteries in series. easier to maintain...