How long will my batteries last?

[Hozer]

Trying to calculate how long my batteries will last. I'm running a 48 volt 60 amp battery. I have 2 1000 Watt motors. The rear is always on. I can turn on the front at any time is wish. I only time I turn on the front motor if I am going up a steep hill. So most of the time I run the rear motor only.

So how do I calculate how long my battery will last at lets say 20 to 25mph. Is there any way to calculate a average on how long my battery will last?

Thanks in advance

 

[James340]

Math.Watt hours consumed vs battery watt hours capacity

 

[Hozer]

Math.Watt hours consumed vs battery watt hours capacity

so what I need to do is figure out how many watts I'm pulling at 25 mph correct?

 

[James340]

Yes.I doubt the battery specifications are accurate.I recorded my miles to find out how many I have.My battery will go 40 miles at 25 mph but I pedal enthusiastically

 

[NZSimon]

Not sure what your bike is and if it has a display that tells you what watts you’re using as you travel at different speeds using different PAS levels and different amount of human power. I upgraded to a display that showed watts numerically and it’s been extremely educational.

I have three 48v batteries adding up to 57.5Ah or 2760Wh. I normally only charge to 95% and aim not to go below 20%. That gives me about 2000Wh to play with. Doing 30kmh at PAS 5 and peddling steadily but not breaking a sweat, I’m using about 300w. 2000wh / 300w x 30kmh gives me a range of about 200km.

Hope this sounds logical/useful - but does depend on having a display showing watts as a number such as the 750C display.

 

[pagheca]

Hi @Hozer, sorry for the long answer, but it is like asking how many revolutions a bowl makes.

Correct answer: it depends! *

There is not enough data to define your maximum range (I assume you mean the range, not how long - years - the battery will last). This depends on

- the route you take: changes in altitude are very relevant with bycicles because they are very efficient in terms of friction loss, so what really counts is any kind of climb, unless you are quite fast.
- Your speed - as a rule of thumb, if you double your speed, your range will be divided by four. If you ride at 25 mph, your range is around 70% of that at 20 mph ( (20 / 25)^2 = 0.68), all other conditions equals.
- Your total weight, including the bike, your clothes, and any accessory you may have with you
- Motor and battery efficiency
- The state of the battery
- Acceleration and braking
- The controller setting, if you have "modes".
- ... do you pedal or not? Not clear from your original message...

Even if you take all this into account, the uncertainties in defining the range would be 10-20%.

Regarding the MAXIMUM range, you can extrapolate it by riding on a flat course at a low speed, with the most economical mode set, until you have used, for example, 20% of the battery (starting from 80% and reaching 60%) and then multiply by five. This is the best I can say. Best way is to refer to the instruction manual of your bike, if any.

With a 2880 kWh battery like yours, I guess that 100 miles are reachable on a flat ground, but maybe 150 or 75.

* Actually, in Italian, it's a typical childrens' joke: one kid ask another, the other seem puzzle and says "I don't know?" and the first one replies "it turns, it turns, until it stops", meaning "nobody can tell". I wonder what the analogue is in English!

 

[LightningP38]

Trying to calculate how long my batteries will last. I'm running a 48 volt 60 amp battery. I have 2 1000 Watt motors. The rear is always on. I can turn on the front at any time is wish. I only time I turn on the front motor if I am going up a steep hill. So most of the time I run the rear motor only.

So how do I calculate how long my battery will last at lets say 20 to 25mph. Is there any way to calculate a average on how long my battery will last?

Thanks in advance

The best way to find out how long your battery will last is to ride your bike until the battery meter/light indicates the battery is at 50% charge. Lets say the ride takes 2 hours. But you can’t assume the last 50% of battery charge will last another 2 hours. Also, you need to have a 20% reserve of battery charge, as you don’t want to completely discharge the battery.
But you can assume you would get another 1.5 hours of running time, for a total of 3.5 hours run time.

If your system doesn’t have a battery meter gauge on your display, you can use a digital volt meter to check the charge level after 2 hours of riding. The voltage reading will tell you the level of charge in the battery. You can search up volt readings on the internet to see what voltage reading corresponds to the % level of charge for your battery.

My display shows battery charge level in increments of 20%. I have confirmed the display charge levels with my volt meter, and so I have confidence in the display readings.