New E-Biker needs help! *Confused*

[Quillist]

Okay, just to say first of all; I'm completely new to all of this, and am based in London, England....

I recently bought one of these 1000Watt Brushless built-in hub motors from my beloved eBay; installed it fine, and it comfortably takes me to and from Uni everyday [an 12 mile return trip] at a top speed of around 20Mph...

Having had it about 3 weeks; it's still taking me a good 25 mins either way; so I was looking to increase the speed; I've read about over-volting [to a limited comprehension extent] the controller in order to do this; however from my basic knowledge of physics Watts = Volts x Current....

Now using the batteries supplied with the kit - 48V at 14Amphours what on earth is the wattage. I only ask, because the motor is rated to 1Kw, and I don't want to damage it...

I was thinking of getting six of these 12v 7.5Ah Batteries to make a 72V combo.

Is it really that simple? Would the controller then 'see' the new increased voltage, and whisk me along faster? [Albeit at the expense of battery life]

Basically, I'd love to be able to do a constant 30ish if it all possible; more if achieveable! To reduce my travelling time, there aren't many hills, and terrain is relatively flat, so 'strain' on the motor shouldn't be a problem? Also, it's about 5 Degrees Celcius here, so heat shouldn't be a problem either?

I should probably point out, I ride along bridleways, which are legally 'off-road' and have no speed restrictions.

Any help with speeding this little beauty up would be much appreciated!

Regards,

Quillist.

 

[deardancer3]

First you would need to ask the seller if the controller is rated at 72V. Doubtful, but maybe. I did not see on your sellers listing anything about the controller ratings.

It would be useful to know the maximum current draw and power actually used. this would tell you if your present batteries are actually deliverying the required 20 amps to make 100 watts, more like 30 amps adding in losses to get to the peak power. May have to add an amp/watt meter to tell this

Next it would be nice to know more details about your bike and the terrain; it could be tires inappropriate to the speeds.

Your post indicated a 14.4 average speed with a top speed of 20mph. Do you have some significant traffic or some stop and go lowering your average speed? paved?

So ask your seller about the controller, and post some more details here, and we will see how to assist.

d

 

[dogman dan]

It appears to me that one thing confusing you is the difference between amps, a measure of current flow, and amp hours, which is a way to rate a battery for how long a standard current can flow. I like to think of a bucket of water, and a hole in the bucket. The sise of the hole, is amps, how fast the water flows out. This is the main function of your controller, to act like a valve and regulate amps. The sise of the bucket is amp hours.

Some controllers can take one more 12v battery and some can't. You may be able to get a 48v controller from your motor vendor, or if not, others such as ecrasyman can. If you open your controller up, and see some little soupcan things inside that say 60v on them, you may have a controller that can take 48v.

Another way to get more power is to increase amps, by buying a more powerfull controller. This may not increase speed, generally more amps give higher tourque rather than higher top speed. But if the new controller is made to take 72v, then zooom! :lol:

 

[dogman dan]

I should read better, you are allready at 48v. Weird, you should be seeing 25mph for sure. Sometimes a motor can be slowed down by too small wiring, Maybe you could do some rewiring in the leads to decrease the voltage losses from skinny wires. Link has really good threads on that stuff on this forum.

Another thought, If the batteries are not too great, that can really lower your voltage. Get a voltmeter, Just a cheap one, and see if they are above 13v when fully charged. If not, there is part of the problem. And, er, are you hefty? The power of small motors like ebikes is kinda weight sensitive.

 

[swbluto]

I should read better, you are allready at 48v. Weird, you should be seeing 25mph for sure.

The OP did say that (s)he rides "Off road". I'm not sure what a bridleway is, though but if it's dirt, it has more rolling friction.

Also, I think we can infer the OP is using lead which has more voltage sag than some chemistries we reference. If this were a 408-like hub motor, 20 mph would not be surprising at all. I think Lead's internal resistance increases dramatically once you start to approach freezing temperatures, but I might be wrong, so you might also be seeing more of a voltage sag because of that.

Using the calculator at http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=6892 on a 408 with a rolling resistance coefficient of .03, 48v with .5 ohm battery resistance(total combo = ~19.8 mph), it looks like 72 volts should get you upto 29ish mph(30-32 w/ pedaling). But upgrading means checking your controller and it's more likely than not your controller is limited to ~55-60 volts.

Hm. Does the British still use the Imperial system? I thought it was just us Americans. :lol:

 

[Link]

Very weird that you're only getting 20mph out of it. I'm getting close to 30 from that same motor (I'm pretty sure it's a Golden). The phase wires are undersized, but they were only robbing me of 1-2mph. I'm only 165lbs, but still. More weight shouldn't make THAT much of a difference. I'd say the batteries were junk, but they seem to be taking you about as far as they should.

And FWIW, I run the motor at peaks of nearly 2kW (48V 40A), and it's only hot-ish. I could hold my hand on it all day. 72V would be crazy for my setup, as that would get me close to 45mph. If yours is really just wound lower than mine for some reason, then, yes, 72V would get you to 30mph.

 

[dogman dan]

Maybe the 1000 watt controller is only putting out say 600 watts? That would explain the low speed wouldn't it? No telling what people put it these kits these days.

 

[Link]

Don't think so. Unless you're on a hill or dragging a parachute behind you, 600W is much more than you need to hold 20mph. :?

 

[swbluto]

If the bicycle is "geared" inappropriately(i.e., non-optimal wheel size and/or non-optimal winding count. ), then the speed, and corresponding power, at which it stabilizes could be much less. Anyways, you should notice the seller mentions a really low number of "22+ mph", so add in some extra friction(like from dirt/stone roads that "bridleways" seem to be) and some increased internal resistance from the lead acid batteries for being ~41 degrees Fahrenheit, and 20 mph is not unexpected at all.

 

[Link]

Hmm...I suppose. Just seems weird that he's only seeing 20 when he should be seeing around 23-24. Then again, my numbers are based on lithium's slightly higher voltage, so I dunno. :?