12 volts to 48 volts for an electric bicycle

Huh? If it says 36 Volts then it's 36 Volts.

72V will make it spin a lot faster and heat it up more. Possibly burning it out.

Sellers tend to say things like that, yes. If it was me I'd have confirmed it before handing over the money.

=A0(The guy who sold it to me said they can take 72 volts, but I'm still t= rying to confirm that from their website, which is a bit skimpy. =A0Looks l= ike I'll have to email them.)

for about 3 miles, but left me to pedal the remaining 9 miles home from wor= k. (About fifteen minutes of power? (Assuming ~15 mph) so about 32 amps of current?

out returning them and buying a (heavy!) 12V, 85 A-h deep cycle battery fro= m Costco (only $68). =A0If I go that route, I'll need a DC-DC converter, co= nverting 12V to 48V.

Ahh that looks like it will almost get you home. But if you crash with the deep cycle battery strapped to your bike you may spill acid on yourself.

out =3D 1.25 (1 + R2/R1), from page 9 of the datasheet.http://cds.linear.co=m/docs/Datasheet/1339fas.pdf

There is a current sense resistor. You'll need to pick the right FET's! (But I don't know much about power DC-DC converters.)

Digikey has 12V/ 33 A-h SLA's... not cheap though.

ck.html

le of 75% correct?

t. =A0(The guy who sold it to me said they can take 72 volts, but I'm still= trying to confirm that from their website, which is a bit skimpy. =A0Looks= like I'll have to email them.)

e for about 3 miles, but left me to pedal the remaining 9 miles home from w= ork.

Yes, about 15 minutes, come to think of it. Kind of scary to think I burne= d through 384 watt-hours in just 15 minutes. Stop-and-go traffic (lots of = stop-signs in the neighborhood). The motor was *very* warm to the touch af= terwards, too. Loads of fun to bike home with heavy SLAs (and a heavy hub = motor to boot). =3D)

I bought some more SLAs so I have 6 total (4 new ones, along with 2 old one= s I've been charging every month to keep them alive). Since another poster= mentioned running the motor beyond spec is not advisable, I suppose I coul= d have two banks of batteries in parallel. That's not a bad idea, is it?

about returning them and buying a (heavy!) 12V, 85 A-h deep cycle battery f= rom Costco (only $68). =A0If I go that route, I'll need a DC-DC converter, = converting 12V to 48V.

Yeah, good point... even just tipping the bike over would be pretty nasty. = And that deep-cycle battery is *heavy*.

...

Oh, yay.

Yeah, I'm aiming for cheap. That was the motivation for looking at an off-= the-shelf deep cycle battery.

I would go for a motorcycle, but (1) they're kind of noisy, and I'd rather = save my hearing for enjoying metal music, and (2) in this city of mine the = drivers are half-insane anyway and I'm sure I'll die on a motorcycle. At l= east with a motorized bicycle I can stay in the safer bike lane.

Gotcha, thanks.

From looking it up on the manufacturer's website, the controller looks like= it may take 72V, but you're right, the motor is def. rated at 36V.

Good point. I was watching the prices on Craigslist for some time though, = and this one was offered at somewhat below the average price, enough so tha= t I decided to take a risk and try it out. Sure, the throttle control need= s a new spring, but at least the thing works. Or, well, it is dependent on= battery capacity. =20

...

Hmm, good point! On your advice I found this.

12V, 28 A-h for $79. 24 A-h (3x batteries @$33) from Home Depot would be $99. But, wow, 21 lbs, huh. Would need three of them... (or, again, a DC-DC converter.)

guy who sold it to me said they can take 72 volts, but I'm still trying to confirm that from their website, which is a bit skimpy. Looks like I'll have to email them.)

about 3 miles, but left me to pedal the remaining 9 miles home from work.

returning them and buying a (heavy!) 12V, 85 A-h deep cycle battery from Costco (only $68). If I go that route, I'll need a DC-DC converter, converting 12V to

48V. 1.25 (1 + R2/R1), from page 9 of the datasheet.

--
No.

The output current will be whatever the load wants, with the upper
limit dictated by the voltage dropped across Rsense as described on
page 10 of the data sheet, just above "Output Voltage Programming".



>
>This 555 circuit looks like fun too.
>http://www.dos4ever.com/flyback/flyback.html
>
>Since I want the output voltage to be 4x the input voltage, is a duty cycle of
75% correct?

ist. =A0(The guy who sold it to me said they can take 72 volts, but I'm sti= ll trying to confirm that from their website, which is a bit skimpy. =A0Loo= ks like I'll have to email them.)

ine for about 3 miles, but left me to pedal the remaining 9 miles home from= work.

urned through 384 watt-hours in just 15 minutes. =A0Stop-and-go traffic (lo= ts of stop-signs in the neighborhood). =A0The motor was *very* warm to the = touch afterwards, too. =A0Loads of fun to bike home with heavy SLAs (and a = heavy hub motor to boot). =A0=3D)

nes I've been charging every month to keep them alive). =A0Since another po= ster mentioned running the motor beyond spec is not advisable, I suppose I = could have two banks of batteries in parallel. =A0That's not a bad idea, is= it?

d about returning them and buying a (heavy!) 12V, 85 A-h deep cycle battery= from Costco (only $68). =A0If I go that route, I'll need a DC-DC converter= , converting 12V to 48V.

. =A0And that deep-cycle battery is *heavy*.

off-the-shelf deep cycle battery.

r save my hearing for enjoying metal music, and (2) in this city of mine th= e drivers are half-insane anyway and I'm sure I'll die on a motorcycle. =A0= At least with a motorized bicycle I can stay in the safer bike lane.- Hide = quoted text -

Biking is good for you... exercise and all that. You could always try one of those scooter/ Vespa things. Lots more energy density in gas.

George H.

Looks like even an 85 A-h 12V deep-cycle battery won't be sufficient, huh.

4x12V @ 8 A-h got me 3 miles. That's 128 W-h/mile. Distance to travel (on= e-way, assuming I can charge at work and at home) is 12 miles. So I'll nee= d 1536 W-h. That's 3 12V batteries at 43 A-h, or one 12V battery at 128 A-= h (assuming a DC-DC converter at 100% efficiency).

Then again, since I was running a 36V motor at 48V, I was probably losing m= ore energy to heat than I would otherwise... maybe 128 W-h/mile is a bit hi= gh...=20

More research needed!

Thanks y'all.

...

Yeah, I know! I can pedal the 12 miles in about 58 minutes. Not every day= though. I thought an electric bike would allow me to do it every day, sav= ing me the gasoline. (Round-trip in a Toyota Camry burns through about a g= allon of gas; 24 mpg city is about right.)

No argument there! I was even thinking of those 2-stroke bicycle engine ki= ts for around $300 or so. Then I remembered when I use the weed-whacker on= the lawn I like to wear hearing protection since those engines are kind of= loud...

I would totally go for a Honda Trail 90 (they're about $600 on Craigslist),= but (1) I'd have to contend with the maniac drivers who apparently are una= ware of basic traffic laws, and (2) I'd need to get a motorcycle license.

Thanks!

Michael

 (The guy who sold it to me said they can take 72 volts, but I'm still trying to confirm that from their website, which is a bit skimpy.  Looks like I'll have to email them.)

about 3 miles, but left me to pedal the remaining 9 miles home from work.

returning them and buying a (heavy!) 12V, 85 A-h deep cycle battery from Costco (only $68).  If I go that route, I'll need a DC-DC converter, converting 12V to

48V.

--
Assuming the same speed in both cases, and neglecting the difference
in weight of the batteries,  If 8AH will get him 3 miles, then 85AH
ought to get him about 32 miles.

(The guy who sold it to me said they can take 72 volts, but I'm still trying to confirm that from their website, which is a bit skimpy. Looks like I'll have to email them.)

for about 3 miles, but left me to pedal the remaining 9 miles home from work.

through 384 watt-hours in just 15 minutes. Stop-and-go traffic (lots of stop-signs in the neighborhood). The motor was *very* warm to the touch afterwards, too. Loads of fun to bike home with heavy SLAs (and a heavy hub motor to boot). =)

I've been charging every month to keep them alive). Since another poster mentioned running the motor beyond spec is not advisable, I suppose I could have two banks of batteries in parallel. That's not a bad idea, is it?

about returning them and buying a (heavy!) 12V, 85 A-h deep cycle battery from Costco (only $68). If I go that route, I'll need a DC-DC converter, converting

12V to 48V.

And that deep-cycle battery is *heavy*.

off-the-shelf deep cycle battery.

save my hearing for enjoying metal music, and (2) in this city of mine the drivers are half-insane anyway and I'm sure I'll die on a motorcycle. At least with a motorized bicycle I can stay in the safer bike lane.

You want AGM SLA batteries, like those used in electric wheelchairs.

(one-way, assuming I can charge at work and at home) is 12 miles. So I'll need

1536 W-h. That's 3 12V batteries at 43 A-h, or one 12V battery at 128 A-h (assuming a DC-DC converter at 100% efficiency).

energy to heat than I would otherwise... maybe 128 W-h/mile is a bit high...

You also have to figure in the extra weight of larger batteries.

And that was only 48V...

72V will probably fry it.

But, wow, 21 lbs, huh. Would need three of them... (or, again, a DC-DC converter.)

--- Unfortunately, a DC-DC converter won't help you.

Here's why: Let's say - just to be prudent - that you're running your

36 volt motor with 36 volts across it and that loaded with rider and batteries, at some speed it draws 10 amperes.

That's 360 watts.

Let's also assume that a 12 volt battery is driving a DC-DC converter which is supplying the 36 volts to the motor's controller.

Since nothing's free, and the load is dissipating 360 watts, the 12V battery has to supply 360 watts plus whatever the DC-DC converter needs to do its job.

If the DC-DC converter is 80% efficient, then to get 360 watts out of it the battery has to put 450 watts into it, which is about 38 amperes, arbitrarily rounding up to account for the motor controller's needs.

Now, if you're traveling at 24 miles per hour, your 12 mile journey will take half an hour to complete and the energy the battery will have supplied during the trip will be 19 ampere-hours.

Blowing off the DC-DC converter and supplying 36 volts to the controller directly will result in saving about 90 watts, so the energy saved would be about 20%, allowing you to go one fifth farther than if you used the DC-DC converter.

There's more to it than that, but it looks like three 12 volt, 20AH batteries in series will get you the range you want.

-- JF

(The guy who sold it to me said they can take 72 volts, but I'm still trying to confirm that from their website, which is a bit skimpy. Looks like I'll have to email them.)

for about 3 miles, but left me to pedal the remaining 9 miles home from work.

through 384 watt-hours in just 15 minutes. Stop-and-go traffic (lots of stop-signs in the neighborhood). The motor was *very* warm to the touch afterwards, too. Loads of fun to bike home with heavy SLAs (and a heavy hub motor to boot). =)

I've been charging every month to keep them alive). Since another poster mentioned running the motor beyond spec is not advisable, I suppose I could have two banks of batteries in parallel. That's not a bad idea, is it?

about returning them and buying a (heavy!) 12V, 85 A-h deep cycle battery from Costco (only $68). If I go that route, I'll need a DC-DC converter, converting

12V to 48V.

And that deep-cycle battery is *heavy*.

off-the-shelf deep cycle battery.

save my hearing for enjoying metal music, and (2) in this city of mine the drivers are half-insane anyway and I'm sure I'll die on a motorcycle. At least with a motorized bicycle I can stay in the safer bike lane.

Or go high end, and use light weight LiFePO4 batteries. Sources;

Mikek

st. =A0(The guy who sold it to me said they can take 72 volts, but I'm stil= l trying to confirm that from their website, which is a bit skimpy. =A0Look= s like I'll have to email them.)

ne for about 3 miles, but left me to pedal the remaining 9 miles home from = work.

about returning them and buying a (heavy!) 12V, 85 A-h deep cycle battery = from Costco (only $68). =A0If I go that route, I'll need a DC-DC converter,= converting 12V to 48V.

ay spill acid on >yourself.

y Vout =3D 1.25 (1 + R2/R1), from page 9 of the datasheet.http://cds.linear=.com/docs/Datasheet/1339fas.pdf

yback.html

cycle of 75% correct?

Umm, 8 AH at 48V, vs 85 AH at 12 volts. (assuming no loss in the DC- DC converter) A little less than 3 times the energy.

George H.

Not with the same number of 12V batteries.

huh.

travel

I'll

at

losing

bit=20

For SLAs and any Lead-Acid chemistry you must figure in the Peukert = factor.=20 A battery rated at 8 Ah capacity will provide only about 1/2 that at 8A, = or=20

1C. An electric bicycle should do OK with about 1/2 HP or 400W, and = ordinary=20 4 passenger electric cars average typically 250-350 Wh/mile. Since you = and=20 the bike are probably 1/5 the weight, I would think 50-75 Wh/mile would = be=20 about right. There are several on-line calculators that can help = determine=20 what you need.

My own calculator is:

It has a Peukert calculator as well as estimate of force and power under =

various conditions.

Here are others:

(This is specifically for e-bikes)

You can get SLAs for about $22 for 12V 12Ah at=20

Here are good prices on LiFePO4 batteries:=20

You might check out the DIYelectricCar forum. They have a sub-forum on=20 bikes:=20

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I made a converter from 12 or 24 VDC to 320 VDC to use a three-phase AC=20 motor on a small tractor:

Good luck!

Paul=20

...

r.=20

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My numbers were off; my batteries were 7 A-h, not 8 A-hs as I originally th= ought.

I'm wondering if my controller may be defective...? Well I was riding the = bike pretty hard (stopping at all stop signs, etc. and this was in the city= ). 110 Wh/mile is what I calculated, and then again I stopped using power = when I noticed a drop in power (didn't want to over-drain the batteries). = I'm sure my numbers would look better if I only used power on the long flat= areas near the airport vs. all the stopping and going near the office at w= ork.

=20

Wow, $22 for 12 Ah, huh! Thanks!

tml

=20

Thanks!

Michael