How much power (kilowatts or horsepower) do you really need?

Gaft

New Member
Feb 22, 2009
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Hobart, Tasmania
I've got to commute a big hill - 450 metres (1500 feet) over 10 kilometres. The 48cc Skyhawk does it nicely with pedal assistance. I've read that its power output is 1200 watts (1.6 HP).

If I regularly did the big hill on an electric bike, I reckon I'd need to carry 0.8 kWH.

Is that right?

How heavy?

How much ($)?

Cheers, Greg
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
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north carolina
I"m not sure how that is figured. But it is more about the draw of the engine and duration of the ride. The question is how big an engine would you need. Then you would need to figure it's amp draw and buy a battery with enough amps to supply it.

For instance I ran an 80cc kit engine for a while. I also ran a lot of DIY friction drive weed eaters. Now I run a 250Watt hub motor and a friction drive 300watt motor.

The 250 watt hub motor is slightly more powerful, not a lot, but slightly. It is 24volt. I am just now testing the range of the batteries on it. The 250 watt has about the same power as a 20cc or so friction drive.

The battery duration on 12ah sealed lead acid batteries was about 4.25miles with me helping by pedaling with the engine most of the time. I tested it today with very little pedal assist and got almost the same results. It went to dying power about a quarter mile sooner but I still got it home.

So what you need is not just a battery pack with the power for that short burst of high amps, but one with enough stored power to get you where you are going as well.

Right now you can buy a 1000watt 48volt system. I would think that would pull that hill with some help. If it works like my system, which I doubt that it would, I would guess maybe five miles on a 12ah battery pack.

They say twenty on their packs. My guess is they are talking 20ah batteries which might get you under ten miles in the real world. On a flat course with no hills or stops you could probably get close to their advertised distances.

I have to finish my tests to be definitive, so I can't really answer your question with any degree of confidence. All this is mostly conjecture.

I also plan to build a chain driven e bike which might be totally different.

Weight depends on the battery type. the SLA is the cheapest and the heaviest. I will be using them because I can't afford the more expensive ones. If money were no object, I would buy the Nichol hydride battery pack.

The sla 20amp hour four pack would probably run you close to $200 as a guess on ebay. I bought a two pack of 12ah and they were around fifty dollars.

There are others who know much more about this than me. So wait for more input before you make any decisions.

ps. A 12ah battery might put out one amp for 12 hours, which is the basis of the rating, but it sure as heck wont put out 24amps for half an hour. You would think that it would, but it won't come close.
 
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Rayzor

New Member
Feb 14, 2009
74
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Bako, Ca
why not make your own kit? off my old electric scooter i got a 650watt electric motor no bigger than my fist (i got a big fist :)) and a controller and twist throttle, i could get new batteries and hook that up to a bike. its got all the charging equipment and everything in need (except batteries) to make a 650 watt bike
 

Cabinfever1977

New Member
Mar 23, 2009
2,290
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Upstate,NY
my 24v electric bike with 300 watt motor and 2 7ah batteries
hill climbing= i dont think so
new = top speed 12-15mph,range 5 miles flat
speed when windy=3mph with peddaling
after 5 months= topspeed 10-12mph,range 1/2 mile
price for charging=free
price for replacement batteries after 5 months = the price of my gas engine kit

i switched to gas engine on bike.
average speed - 20-32mph+ range= 200miles - forever
hill climbing=up the hill like a rocket
speed when winding=20-32mph
price for fuel fill up=$1.00
 
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OzzyU812

Member
May 15, 2008
258
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16
"the bog" NH
Why do want to switch to electric?

E-bike's are expensive. Yes, SLA's are cheap. But they won't pull that hill without significant sag. The voltage and/or Amps (see Disclaimer) drops over long load pulls. It basically feels like you've used up your charge. A home built electric bike using SLA's will cost you at least $200- 250 not counting bike. PLUS the time and effort. Only to be climbing that big hill and somewhere in the middle saying, "What a POS!" Then what do you do? Sell it to hope to get a little money out of it? Or go lithium and spend at minimum $250, $500 is more like it.

You got a good gasser there. My free advice is to use your money to improve upon it.

E-bike's can lead you on a dark path, my friend. Sure they are powerful, smooth & quiet. Then soon enough you'll be learning stuff you never thought about before. Talking about stuff you never talked about before. Spending money on things you didn't know you needed before. Setting charts & graphs as you desktop wallpaper. Oh God, what has become of me?? The next thing ya know I'll be drinking diet green tea!!


I've got a DAX 80 (69.21564611566 whatever) on the way! Then I'll be fine! Right?

:-||
 

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Cabinfever1977

New Member
Mar 23, 2009
2,290
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Upstate,NY
sure i love that electric bikes are quiet and simple for 12-15mph and 30mins of ride time on flat windless ground. that is until the wind blows and youre going nowhere and you try to go up a hill and your battery saids its dead and you walk it home after a long day at work.and that after charging your batteries 50-60 times there dead even thou they say 300 recharge cycles.you know what would be good,a gas 2 stroke engine and 24v alternator to power a electric motor for legality.a real hybrid(peddal/gas/electric)
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
I have owned both kinds of bike. Built several of both kinds. One size does not fit all. That's all I can tell you. What fits me might not come even close to fitting you.
 

Cabinfever1977

New Member
Mar 23, 2009
2,290
1
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Upstate,NY
how much power (kilowatts or horsepower) do you need?
as much hp you can get for as cheap as you can get it.
atleast 1hp or 500-760watts

yes im working on that hybrid bike sometime,but it'll be just peddal/gas for now
i do have electric bike parts to work with but no alternator yet.
 
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cris11368

New Member
Apr 24, 2009
28
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0
NYC
would mounting a gas engine to power an electric motor on a bike be legal in nyc?.. i mean its not really powering the bike, just powering the battery that powers the bike?.. lol
 

Cabinfever1977

New Member
Mar 23, 2009
2,290
1
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Upstate,NY
you could get a trike and put a generator on the back and plug your motor in to that.
or engine plus alternator to power electric motor.
it might help if you put a "powered by electric" sticker on the sides and front and back.
and a sticker that saids "generator is for lights and battery recharging only".
you could put side covers to hide the engine.you still could get pulled over if they here the engine,but it wont be very loud at just idle. Are electric bikes legal in nyc?

i live in upstate ny and i have a gas engine on my bike,no problems yet,but i ride on the side of the road out of the way and only in light or no traffic.
 

cris11368

New Member
Apr 24, 2009
28
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0
NYC
oh electric bikes are legal, they have to be for toys-r-us to sell the ezip bike in there stores here.

thinking of buying just a hub motor from goldenmotors and maybe that Regenerative Braking Controller... has anyone tried this ? that 10-30% more battery would really help me get that little extra mileage on my way back home.