max safe limit when overvolting/amping a 48v 1000w brushless gearless hub?

[jimmyhackers]

hello

The name says it all.
ive purchased a 48v 1000w brushless gearless hub motor kit from ebay. it works perfectly.

http://www.ebay.co.uk/itm/181237508447

as a heads up, im running a pedal bike with no pedals/pedaling so essentially a cheap electric motorbike.

.only had it today and im very much impressed. Even running on 4x 20ah SLA batteries i was getting speeds of just over 30mph and getting a good hours runtime up and downhill.

however, knowing my nature sooner or later i will want more speed/torque from it. so im going to throw a few questions out there regarding performance increases.

1. i know the weight loss of exchanging a 20ah sla batteries for 20ah lifepo4 would save me close to 20kg. However this battery costs a lot (more than the whole bike+motor kit) so im reluctant to do so when my sla's cope so well so far. Will i see an increase in torque, acceleration or top speed if i went to lifepo4?

2. my current controller is rated at 1000w, ive seen other 48v controllers advertised at 1500w and 2000w.
2.1 will my motor take 1500w or 2000w?
2.2 if the motor can take higher wattage (essentially more amps) will i see and increase in torque or top speed? 2.3 how noticeable will the difference be?

3. instead of increasing watts and keeping the voltage the same. would a 60v 1000w controller (and an extra battery) be a better/safer idea?

thats it for now, sorry if these question seem a bit noobish, as you can see im leaning towards the controller swap option instead of batteries for now as its cheaper. I dont want it to turn out ive bought a 48v lifepo4 battery when i really wanted the speed of a 60v or 72v (if my bike can take it )

 

[oldtom]

hello
The name says it all.

as a heads up, im running a pedal bike with no pedals/pedaling so essentially a cheap electric motorbike.

Are there no forums then for cheap, electric motorbikes?

Tom

 

[Alan Quay]

Are there no forums then for cheap, electric motorbikes?

Tom

There is one that I know of Tom. Its here in the UK off road, S Pedelecs and Overseas part of the Pedelecs forum.

If you look closely, the time of posting suggests that our new found friend may live abroad. Either that or he has trouble sleeping.

Anyway it falls to me to say Hi Jimmyhackers, welcome to the forum.

 

[Alan Quay]

hello

The name says it all.
ive purchased a 48v 1000w brushless gearless hub motor kit from ebay. it works perfectly.

http://www.ebay.co.uk/itm/181237508447

as a heads up, im running a pedal bike with no pedals/pedaling so essentially a cheap electric motorbike.

.only had it today and im very much impressed. Even running on 4x 20ah SLA batteries i was getting speeds of just over 30mph and getting a good hours runtime up and downhill.

however, knowing my nature sooner or later i will want more speed/torque from it. so im going to throw a few questions out there regarding performance increases.

1. i know the weight loss of exchanging a 20ah sla batteries for 20ah lifepo4 would save me close to 20kg. However this battery costs a lot (more than the whole bike+motor kit) so im reluctant to do so when my sla's cope so well so far. Will i see an increase in torque, acceleration or top speed if i went to lifepo4?

2. my current controller is rated at 1000w, ive seen other 48v controllers advertised at 1500w and 2000w.
2.1 will my motor take 1500w or 2000w?
2.2 if the motor can take higher wattage (essentially more amps) will i see and increase in torque or top speed? 2.3 how noticeable will the difference be?

3. instead of increasing watts and keeping the voltage the same. would a 60v 1000w controller (and an extra battery) be a better/safer idea?

thats it for now, sorry if these question seem a bit noobish, as you can see im leaning towards the controller swap option instead of batteries for now as its cheaper. I dont want it to turn out ive bought a 48v lifepo4 battery when i really wanted the speed of a 60v or 72v (if my bike can take it )

1. When I went from SLA to Lithium (also 20ah) it made a significant difference in performance.
2.1 Sorry, don't know
2.2 Roughly speaking amps = torque, volts = speed.
3. For extra speed, yes Its not any safer though!

"..if my bike can take it..." - I think this is a very real concern if you are intending to go over 30mph.

 

[Deleted member 4366]

The controller's rating in watts doesn't really mean anything. What you need to know is the maximum amps it will allow from the battery, which should be written on it. Most 1000w ones are 25A at 48v, which is about 1300w. The big 1000w DD motors can easily go to 35A, or more if you don't make the motor run slow up hills. Some go to 4kw or more.

 

[Stalkingcat]

The motor link is for a front wheel. Edit, no its not you can choose. hope you got the rear!

 

[Stalkingcat]

For the fun stuff. The watt ratings of these motors don't really mean much, they may have different windings for better/worse economy depending upon how you do most of your riding. Essentially they are all the same 9c clone motor.

For the purposes of marketing to the masses, they are usually built into 26" rims, which isn't really a good choice for hot rodding. Your biggest problem is heat.
If you can lace wheels or know anyone who can, you would be better off re-lacing it onto either a 22" or 24" rim.
Or sell the wheel and buy one of these basically the same motor but you will need a disc adaptor if using disc brakes.

 

[Stalkingcat]

Learn how to take a hub motor apart from
Here

 

[Stalkingcat]

Then start researching the best way to cool a motor. All sorts of fun can be had. You can put around 6000w through them but they do max out and start to moan, It gets to a point that its not worth putting any more through them as the power returns aren't worth it, most of the power is eaten up by heat. This is my most successful try, after 3 previously destroyed motors.

A usable level is 3000w.

 

[Stalkingcat]

Battery wise, do you need to have 20ah, ie do you need to go a certain distance, or are you just playing around with this?

if just seeing what's possible, then def get rid of the weight and learn about lipo. The big C rating of lipo means that you don't need to parallel batteries up in the same way for high Ah, this is great for experimenting and can be set up pretty cheap.

The 48v controller you have will likely run 60V anyhow, the internals are prob rated for 63v so its on the limit. I ran a 48v kit controller with a 60v (more fully charged) pack for 2 years with no problem. I think I've still got that controller somewhere. Going to frame it one day and hang it on the wall

If you want to try hot rodding controllers, research mods Here, amazing what can be done but expect a box full of burnt out electrical stuff and some frustrating evenings.

 

[jimmyhackers]

thanks for all the replies. its really helped.
i am from brum so yes a bad sleeper.

i did think about an electric motorbike forum but seeing as im using a bike as a base frame and a bike hub motor i thought itd be better on here, and it is

sorry mike my mistake, i meant hub instead of bike. the bike itself is a very lucky charity shop find. strong thick steel and oversized everything. ill also note i wear full bike armour/leather on it, safety is pretty high on the order of things.

thanks for the info cat. theres some impressive stuff there. i did get the rear kit. i dont think i want to go quite to 6kw more 2kw. 20ah slas were cheaper and available to me (charity shop) 20ah seems a nice number that churns out about an hours runtime "in theory". which is about as much as my backside can bear

at the moment as i weigh 10 and a half stone its kindof compensating for the battery banks weight. so i wont be changing that till last. hopefully they'll be cheaper by then

on the controller side. im pretty handy with a soldering iron. ive seen a pretty good article online about replacing the mosfets etc. could that be a cheaper alternative to upping the wattage of my controller instead of a brand new one?

on the hub side, i think my expertise could stretch to air cooling it. drilled holes seem easy and within my grasp. anyone ever done angled ducted holes to scoop the air in? ive never seen it, i wonder if the extra wind resistance will be a noticeable power drain

how slow is too slow? at the moment im managing 25mph uphill and 30 to 33 on flats and downhill respectively. is that fast enough? nothing seems to get even warm at the moment, even after an hours ride.

sorry for all the question there a probably a lot more to come. let me know if i should be posting them individually or like this?

thanks again jim

 

[Stalkingcat]

i dont think i want to go quite to 6kw more 2kw.

Hi Jim,
Yep go for it, be warned though, once you go 2kw you may want 3, or even 4 and so on! Well that's how it worked with me anyhow

There is always a trade off somewhere if wanting large power levels.

The reason that I did this experiment was because I couldn't bring myself to put a 13kg motor on my back wheel. There are motors than can run this sort of power without any mods but they are twice the weight and 5 times the price.
That much weight clamped to a 'normal' bike frame, then means beefing up your bike to carry it, before you know it, your into 40kg+ territory..

I suggested 3kw as a good level but 2 would be fine without having to break the bank.

There are big debates about the best way to cool a motor. Angled air holes have been used many times to create an intake and exhaust, along with radiators, electric fans, all sorts!

Imo, Oil cooling is the way to go and can actually be done very easily, quickly and cheaply. You dont need to go the whole way as above.

Take the motor cover off the drive side
Tap a small hole for a breather/filling bolt
Seal up the axle inside where the wires go, with high temp silicone
Put the cover back on and seal those up
Fill with 200ml of castor oil and you're off!

nothing seems to get even warm at the moment, even after an hours ride.

You usually cant tell without using an internal thermometer.and there lays the problem.

The air between the motor windings and cover, prevents the heat from getting to, and escaping through the cover. You need to try to overcome this problem somehow, hence the copper internal disc fitted in my experiment.

Oil helps by taking the heat and putting it in direct contact with the cover so that it has some chance of escaping.

Go for air holes if you feel more comfortable with that. You'l be able to run 2-3k no problem. well maybe a few

As D8veh pointed out, your controller is prob around 25amps. you could run 60v through it with no mods,
Then maybe try a simple shunt mod, which effectively tricks the controller into reading false current numbers, so that it start to output more amps.

Say you got it up to 60v x 35amps, then this is the easiest way to be getting up to your 2kw . However there is a difference between 2kw input and what is actually being output. Maybe monitor with something like This

If you want more voltage than 60, then you will need to start replacing other things.
As Mike said
Roughly speaking amps = torque, volts = speed.

 

[Alan Quay]

i did think about an electric motorbike forum but seeing as im using a bike as a base frame and a bike hub motor i thought itd be better on here, and it is

Sometimes FPCSO (Fun-Police Community Support Officer) OldTom gets lost and strays over the border into places where he has no jurisdiction. Don't worry, he can't even tell you off for using the wrong re-cycling bin here.

Those SLA's might be OK (ish) for testing and messing about with, but if you decide to use this machine in the real world I fear they may be very limiting. At the kind of current you are talking, your SLA's wont give you even half of the rated AH. I reckon you should count them as 5AH, giving you a range of about 7 miles.

They will also have a very limited lifespan if you thrash them like that - perhaps 100 re-charges, perhaps less.

Compare that with the equivalent in Lithium, and you will find them a false economy.

 

[Stalkingcat]

Four of These would give you your 60V (higher when charged) 16s is about your limit with your current controller as it is (don't quot me if it goes bang though!)
Personally, i'd get your head around balance charging and fork out around £150 including a charger, more if you want a faster charger.
If you want more Ah's then just build another pack for £100 and carry it with you. Each pack weighs about 2kg.

You would need some sort of protection against cell failure when riding but this can be done on the cheap.

 

[Stalkingcat]

i dont think i want to go quite to 6kw more 2kw

Here's some interesting figures to try to understand real life power levels
. I'm new to this forum so not sure what been covered before, sorry for any repeat info.

1Hp is approx 750w which is approx 30cc
The learner limit... (what you can ride with just a CBT) is 125cc
So 3000w is somewhere in the power range of a learner legal scooter/motorbike.

 

[flecc]

So 3000w is somewhere in the power range of a learner legal scooter/motorbike.

With far more permitted:

3. What can I ride if I have a provisional motorcycle entitlement?
A motorcycle up to and including 125cc with a power output of 11kW (14.6bhp).
.

 

[Stalkingcat]

Ok so technically an 11kw electric motorbike can be ridden by a person with provisional entitlement? Is that correct flecc?

 

[flecc]

Yes, according to the licence advice sites. I copied and pasted from one.
.

 

[Stalkingcat]

Even I have have to say that, that's a bit scary.

 

[flecc]

Even I have have to say that, that's a bit scary.

I suppose, but coming from a time when I was riding at 14 (and in the trade at the time!) and legally at 16 on as much as 1000cc bikes, it doesn't seem too bad. I passed my full motorcycle test at two weeks after my 16th birthday, so I do feel a bit sorry for today's beginners with the hoops they have to jump though.
.