Range calculator

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pengyou
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Range calculator

Post by pengyou » Mar 18, 2018 2:12 am

I found a post that did this - maybe it was a link to another page - but I cannot find it now. I would like to know what size battery I will need to power an escooter with 48V 500 watt motor with 16" wheels to do 50 miles (still leaving a 20% reserve on the battery) at about 20 mph. Land is mostly flat. Does anyone have the link?

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Chalo
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Re: Range calculator

Post by Chalo » Mar 18, 2018 2:26 am

Rough estimate? If you're normal sized, on an e-bike it will take about 500W to the ground, say 600-700W electrical, to maintain 20mph. So 2.5 hours of that will take 1.5 to 1.75 kWh of battery power. Round up for the draggy tires and heavy scooter. Figure 2kWh.

You really want to spend two and a half hours on a scooter between opportunities to recharge?
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pengyou
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Re: Range calculator

Post by pengyou » Mar 18, 2018 2:53 am

Chalo wrote:
Mar 18, 2018 2:26 am

You really want to spend two and a half hours on a scooter between opportunities to recharge?
Thanks! I travel a bit more than an hour to get to a certain place and the same amount of time to return. I am not sure I will be able to recharge in the middle. That is ideal. So, if I assume 2kw, a 50 amp 48v battery would give me a large margin for error.

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Chalo
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Re: Range calculator

Post by Chalo » Mar 18, 2018 3:04 am

pengyou wrote:
Mar 18, 2018 2:53 am
So, if I assume 2kw, a 50 amp 48v battery would give me a large margin for error.
It should be fine. You can fault check with this speed and power calculator:.

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

But it is focused on bicycles so you may have to make some guesses.
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dogman dan
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Re: Range calculator

Post by dogman dan » Mar 18, 2018 11:56 am

I would agree, at 20 mph, about 30-40 ah. My answer based on a crapton of 30-80 mile rides.

20 ah will get you 30 miles at 20mph, To have a huge reserve left at 50 miles, more like 40 ah of 48v.

This type of ride is why one of my custom bikes was designed first and foremost, to carry two 48v 20 ah batteries. To have enough to do 80 miles at 15 mph.

Ride with a watt meter, and know what wh/mile average you need to hit your range. Then adjust your speed as needed out on the road to hit that number, whatever the weather or terrain.

So say you have about 2000 wh, 48v 40 ah. 80% of that would be 1600 wh. You would need to get 32wh /mi average to go 50 miles. 20 mph should be more like 20-25 wh/mi, but depending on the weight of the bike, ( 30 pounds of battery for starters) and the terrain, and the pedaling effort you can do for all 50 miles, 32 wh/mi by the end of the day is very plausible.

This is why I don't give you a promise you can do 50 miles on 30 ah, even if its possible. Unless you ride it slower, which increases the % of the total watts you get from your legs, per mile. Most of us at 20 mph, only produce about 20% of the energy used with our legs. most of us can't put out a 150w effort for 50 miles. Bike racers put out 200- 300w for 150 miles!!!

Anyway, slowing to 18 mph vs 20 mph, will make an astonishing distance possible from 30 ah. When I needed to make it to a town 60 miles away, I'd slow to 15-18 mph. Then maybe, if I did well, I could speed up the last 10 miles.

The tool you need is a cycle analyst, it will read out your average wh/mi. Then if you see 25 wh/mi at mile 40, you can rip it in full speed the last 10 miles.

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Re: Range calculator

Post by markz » Mar 18, 2018 5:35 pm

I am constantly doing range calculations with my total distance known from measurements on Google Maps (plan to buy a cycle comoputer) on a 48V system with a 25wh/km estimate as I'm a smidge heavier ;) :lol: then finding out the battery capacity (Ah). My pack is 13S8P so I can deduce from that. Not like bench top measuring each cell, it seems to be right. Perhaps toothpicks may only use 20wh/km.

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