ebike mileage problem

[rajansaha]

my ebike run 55+ km/h for 80minute without any load. but with load it run only 4/5km with 20+ km/h speed. but again when i unload it run 55+ km/h speed. my battery 36volt 7.5 amp and motor 250watt. i also attached controller specifications.
please can someone tell me what is the problem.

 

[addertooth]

It requires MUCH more power to overcome drag from the air moving past, and rolling resistance when a bike is being ridden. A 36Volt 7.5 Ah battery isn't much go juice (270 Watt Hours of energy). Although, I would expect more. My battery is 48V and 20Ah, (960 Watt hours of energy) and it gets me 30 miles (50Km) travelled at a higher speed of 21 MPH (35Km/h). You have a battery which is literally 1/4th the energy of my battery. But, you get roughly 1/10th the distance 5Km travelled yours, 50Km travelled mine. That number seems very low.

It would appear your run-time is roughly 15 minutes (5Km divided by 20Km/h). With a 270 Watt Hour battery, and a 250 Watt motor, I would expect a longer run time (about 1 hour). This leads me to believe your battery might not be operating at it's rating. It appears to be roughly 25% of its rating. That, or you have some other phenomenal loss/drag in your bike.

 

[pagheca]

my ebike run 55+ km/h for 80minute without any load. but with load it run only 4/5km with 20+ km/h speed. but again when i unload it run 55+ km/h speed. my battery 36volt 7.5 amp and motor 250watt. i also attached controller specifications.
please can someone tell me what is the problem.
View attachment 13523

What exactly do you mean by "without any load"?

 

[DieselTech]

What exactly do you mean by "without any load"?

I think they mean with the wheel off the ground & the bike running with no load.

 

[pagheca]

if this is what he means is pretty reasonable such a difference. What remains to be explained is the very short range with 270 Wh.

 

[addertooth]

The bottom line is, he is only getting about a quarter of the range he should be getting. Wheel "off the ground distance" is not a good metric. But, the milage he should be getting while riding the bike should be more than 4 to 5 Kilometers. It should be a bout 4 times more.

My money is on the battery not meeting its ratings, unless he is an exceptionally heavy rider, pulls a trailer, or lives in a very hilly area.

 

[HumanPerson]

What exactly do you mean by "without any load"?

weight or resistance?

 

[rajansaha]

What exactly do you mean by "without any load

not running on the ground

 

[rajansaha]

The bottom line is, he is only getting about a quarter of the range he should be getting. Wheel "off the ground distance" is not a good metric. But, the milage he should be getting while riding the bike should be more than 4 to 5 Kilometers. It should be a bout 4 times more.

My money is on the battery not meeting its ratings, unless he is an exceptionally heavy rider, pulls a trailer, or lives in a very hilly area.

It requires MUCH more power to overcome drag from the air moving past, and rolling resistance when a bike is being ridden. A 36Volt 7.5 Ah battery isn't much go juice (270 Watt Hours of energy). Although, I would expect more. My battery is 48V and 20Ah, (960 Watt hours of energy) and it gets me 30 miles (50Km) travelled at a higher speed of 21 MPH (35Km/h). You have a battery which is literally 1/4th the energy of my battery. But, you get roughly 1/10th the distance 5Km travelled yours, 50Km travelled mine. That number seems very low.

It would appear your run-time is roughly 15 minutes (5Km divided by 20Km/h). With a 270 Watt Hour battery, and a 250 Watt motor, I would expect a longer run time (about 1 hour). This leads me to believe your battery might not be operating at it's rating. It appears to be roughly 25% of its rating. That, or you have some other phenomenal loss/drag in your bike.

addertooth, do you sure that it is battery problem? when i ridding on the ground its speer gets down to 15km/h after running 4/5 km.but again, when i ride off ground(not running on the ground) it speeds up to 55+km/h.i can't understand whats the problem with.

 

[addertooth]

I am focusing on the bike as a whole. You should get more than 5Km out of a battery that size.
Yes, if your motor is damaged, it can reduce range.
If your tires are badly underinflated, it can reduce range.
If your controller is badly providing power, it can reduce range.
If you climb a lot of steep hills, it can reduce range.
If you are hauling a trailer behind you, it can reduce range.
If you are an exceptionally heavy rider, it can reduce range.
If you are travelling into the direction where you are working against a strong wind, it can reduce range.

But, the simplest answer (if none of the above apply), is that your battery is not performing at the Amp Hour (Ah) rating on it.
Motors do spin slower, as the battery voltage drops; this is quite normal. My bike is slower on the last couple of bars, (which indicate battery voltage), than when the battery is fully charged.
The question is, how far can you go before you are down to the last "bar" of power on your display?
Is it more than 5Km? If so, how far total distance can you ride?
All eBikes will spin the wheel faster, when it is off the ground. This is especially true of bikes with smaller motors (under 500 watts).
This is extremely true if it is a "direct drive hub motor" (no internal gears). These are commonly called "speed motors" for a reason.
They typically can spin fast, but have less torque (acceleration rate) than geared hub motors of the same number of Watts of power.
So, the fact it spins faster when "off the ground" does not give useful clues.

 

[TwoTired]

I think he means he gets 20kph for a short time and top speed drops to 15 kph after that. That is expected behavior.

 

[addertooth]

TwoTired,

Agreed.
He could address that limitation with a larger capacity battery.

 

[rajansaha]

I am focusing on the bike as a whole. You should get more than 5Km out of a battery that size.
Yes, if your motor is damaged, it can reduce range.
If your tires are badly underinflated, it can reduce range.
If your controller is badly providing power, it can reduce range.
If you climb a lot of steep hills, it can reduce range.
If you are hauling a trailer behind you, it can reduce range.
If you are an exceptionally heavy rider, it can reduce range.
If you are travelling into the direction where you are working against a strong wind, it can reduce range.

But, the simplest answer (if none of the above apply), is that your battery is not performing at the Amp Hour (Ah) rating on it.
Motors do spin slower, as the battery voltage drops; this is quite normal. My bike is slower on the last couple of bars, (which indicate battery voltage), than when the battery is fully charged.
The question is, how far can you go before you are down to the last "bar" of power on your display?
Is it more than 5Km? If so, how far total distance can you ride?
All eBikes will spin the wheel faster, when it is off the ground. This is especially true of bikes with smaller motors (under 500 watts).
This is extremely true if it is a "direct drive hub motor" (no internal gears). These are commonly called "speed motors" for a reason.
They typically can spin fast, but have less torque (acceleration rate) than geared hub motors of the same number of Watts of power.
So, the fact it spins faster when "off the ground" does not give useful clues.

literally, i didn't check mileage with last drop of charge, when speeds come down to 15km/h, i feel bored and i start to pedal, beacause it faster than motor. but once i metered voltage of the battery, i showed 40.5 volt.

 

[addertooth]

literally, i didn't check mileage with last drop of charge, when speeds come down to 15km/h, i feel bored and i start to pedal, because it faster than motor. but once i metered voltage of the battery, i showed 40.5 volt.

Yes, when you metered, you weren't riding. This is called a "no load voltage", which is higher than when the motor is running.
A better measure is when the motor is running and you are riding your bike. This is why people like displays that show Volts, instead of bars.
It give you a better feel for your battery voltage sag under load.

 

[rajansaha]

Yes, when you metered, you weren't riding. This is called a "no load voltage", which is higher than when the motor is running.
A better measure is when the motor is running and you are riding your bike. This is why people like displays that show Volts, instead of bars.
It give you a better feel for your battery voltage sag under load.

so, if i make my battery 48v, is it solve this problem?

 

[addertooth]

so, if i make my battery 48v, is it solve this problem?

The solution to avoid the voltage sag after a short distance is to have a battery with a much higher Amp Hour (Ah) rating. It is possible your display was not designed to tolerate 48 volts, or that you have to move jumpers or re-program your motor speed controller/driver to accept operating at 48 volts. Most controllers have a "cut off voltage" where it stops supplying power to the motor (when your battery gets too low). Right now your controller is "set" to work with a 36 Volt battery. This would make the cut-off voltage too low. Keep in mind, MOST battery packs have a power management board which is supposed to disengage the battery when it's voltage sags too low as well. But this may not be true of all battery packs. There are too many unknown factors for me to suggest you go from your 36 Volt battery to a 48 Volt battery.

 

[rajansaha]

when i bought hub motor kit, the seller told me that the display designed for 48v but will run with 36v battery and always will show low volatage in display, but it will work. as controller support both 36v/48v i thought it not major problem. i never think will get too low mileage.

 

[rajansaha]

I got the problem. it was dispaly problem. the dispaly was. 866 model. and configuration was 48v. So, problem arise but now I configured it 36v. thanks everybody.