10 year old lead acid 36V e-bike needing an upgrade!

[monkeychops]

Hello everyone. 1st post from me. Thank you in advance and all that

I have a 10 year old electric bike. It's similar to this one: http://www.ourcar.co.uk/ECOtornado.htm but runs on a 36V lead acid battery. It has a brushed rear hub motor and is limited to 15 mph (due to UK law). I had a go on a friends custom built lithium electric bike and I am feeling the need to attempt to upgrade this old one.

I wondered if anyone could help? I'm not particularly mechanically minded so am looking for relatively easy modifications. Basically I want it to go faster. 20 mph would do. If I could find a way to modify or replace the speed controller to somehow suck more current from the battery then that would be ideal. If I could do that then I'd then want to upgrade the battery for longer range.

I've had a look at the speed controller and it looks like a bit of a black box (the optimist in me was hoping to just be able to swap out a resistor inside it or something). I've uploaded a pic of it, not sure if will help.

 

[Drunkskunk]

Welcome to the forum. We're going to need more info on the bike and controller. Some controllers have an electronic speed govoner, while others relied on only putting out enough power to hit 15mph.
to know for sure, we're going to need to know all the wires that go in and out of the controller. There should be atleast 7: 2 to the battery, 2 to the motor, and 3 to the throttle.

A new controller ment for a scooter motor would be easy enough if nothing else. It appears from the picture to be a pretty straight forward setup. But more information is needed.

 

[monkeychops]

Thank you for the welcome!

Very happy to provide more info if I can. Thanks for your quick response.

On one side of the controller is 2 sets of black red wires. 1 set from the battery, the other to the rear wheel motor.
On the other side is a bit more of a confusion. I have attached a photo. The wires on this side go to the front of the bike. At the front there are:
a throttle, a front light (not working), an electric horn, an ignition key, a voltmeter.
I have had a look inside the throttle it looks pretty simple. Pushing the throttle rotates 2 magnets from one fixed point to another, I'm sorry I can't give the proper technical terms.
The 15 mph speed limit is pretty consistent and so I don't think it's a limit on the power.
I *think* it's a 200W motor. But I only think this from the link I put in the first post. And no idea if this is peak or average.

If there are more photos I that would be helpful or anything else please let me know.

 

[Samd]

Brushed controllers are very easy, so you can take comfort in that. My recommendation is replace everything from the motor on back (controller, throttle, battery), and with the small speed increase you seek you shouldn't be taking a big risk. Or a big jump in watts.

Whilst the motor is a different format, most of what you ask will be a duplicate of the "Aprilia Enjoy" thread on this forum. Might be a good place to read. I should think all the controllers, batteries and throttles mentioned in that thread would be compatible.

Cheers.

 

[dogman dan]

Brushed scooter controllers are cheap, easy to find, and simple to wire. but it might be simplest, to get a matching controller and throttle just to make it that much easier. Then you don't have to figure out throttle wiring, just plug in the new throttle to the new controller. The rest is easy, battery in, + to + . On the motor hook up the two wires. runs forward you got it right, runs backwards, swap the wires. 36v 20 amp controller,( 500w) should get you some more power.

The main problem is that your original motor could be wound real slow. If that is the case,you will still be pretty slow, but much moe powerfull up hills.

Now we are at the part where we suggest you start from scratch, spending the kind of $$$ your buddy did. No way a brushed motor is ever going to perform like your buddies bike. Budget at least $1500 usd. But nothing really wrong with trying a new controller first. You won't be spending that much on that.

 

[Samd]

These controllers are a dime a dozen to find. http://tncscooters.com/index.php?route=product/category&path=41_74 They are often cheaper on ebay - eg search YK40-3 for example.

I would pick one that is rated to 20 amps - this will limit your power to about ~450watts so you don't cook your motor quickly.

As dogman says, two wires feed into the controller from the battery, and two wires supply the motor with increasing pulses of current to increase power (or the converse).
The other connections can usually be left alone. Unless the controller has a key switch facility - if so you can either use your existing one across those two wires, or short them out for testing.

If you get a cheap 3 wire throttle it makes connections easy. If you get a throttle with LED's to indicate power there will be a fourth wire - you can just leave that disconnected too. I don't like LED throttles as they don't tell you much. Use a 5 buck digital voltmeter when you get going.
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*If your Lead acids still work at all, why not just buy a controller and throttle and get the bike working. Then do the batteries.*
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Two bits advice on using lithium batteries. 1) Use a fuse - shorts on Lithium are super scary. 2) Be careful of low voltage cutout on the controller. If you use an 8s lithium pack (33.6v full, 29.7 volts empty) then your controller may cut out at say 31.5 volts. So you can only use half the capacity of the pack. Either use a 9s pack or bigger (may be a more expensive charger), or use a 24volt controller (as the amp rating is what mostly matters) and a voltmeter in line so you know how 'full your petrol tank' is. The latter is what I do.

 

[Sunder]

With something like this:

http://www.ebay.com.au/itm/1000W-48V-ELECTRIC-BICYCLE-e-BIKE-ENGINE-MOTOR-kit-/290443845357?pt=AU_Scooters&hash=item439fcd5eed

Costing less than $350 AUD Delivered, is there any reason why you couldn't just use the frame and replace the electric components?

I know these are very cheap, less than advertised spec kits, but I've got one, and they still are pretty good, especially once you redo the connectors.

 

[Samd]

(if his rear motor is good wouldn't he be better spending the money on batteries instead of a duplicate motor? Does that kit come with a battery?)

 

[amberwolf]

The one thing to keep in mind with your existing motor is that it may not be very efficient at using the power fed to it, so the more power you feed it the hotter it gets, especially at startups and slower speeds, when being run at higher throttle amounts.

So monitor it's temperature somehow, evne if it's just the back of your hand on the casing every few minutes, to see if it's getting overly hot with your new battery/controller.

 

[Sunder]

(if his rear motor is good wouldn't he be better spending the money on batteries instead of a duplicate motor? Does that kit come with a battery?)

The kit doesn't come with a battery, but I'm thinking that the motor will have its limits. I mean, when you compare a 250W motor to a 1000W motor, everything is bigger and the whole assembly is heavier. Sure, you can overdrive a motor by putting in higher than design spec voltage, but as other people have pointed out, there will be limits to that by heat and simply design.

For $350, he could keep his existing batteries for a time, then spend some money upgrading to LiPo when he had more cash available.

It's only one option. The cheaper option might be getting a cheap 48V controller, then overvolting the existing motor?

 

[monkeychops]

Wow, thanks for all the tips and advice.

What I can see happening is that I'll upgrade one thing and then another thing and then another etc. And then likely end up at the end of it thinking that I should have started by upgrading everything at once.

It does sound like I could push the motor a bit harder with a new controller without breaking it.

The bike does currently still work ok and the battery just lasts long enough to get me to work (15 miles) with a certain amount of pedalling but generally the throttle is full on nearly all the time. So if I changed the controller to get more power to the motor I know I would reduce the battery range a bit.

First thing to do then is buy a new 20A controller. Ideally the same size as the one I've got so it fits in the little waterproof-ish housing the current one sits in.

 

[dogman dan]

I'd say do the controller upgrade, just because it will be so cheap. But the motor will heat up faster, and the battery drain faster. Adding just 5 mph can dramaticly change your range. I seriously doubt you'll make more than about 6-8 miles on a 500 watt controller if you get up to 20 mph. The battery upgrade is a given must have to increase your speed and still have range.

A decent plan might be this, buy the controller, get it working. Then get a 36v 15 or 36v 20 ah lifepo4 battery. I'd strongly recomend the 20 ah, from pingbattery.com. Then run the brushed motor till it smokes, planning all along to get a better motor kit by next summer. By next summer, you have a good strong motor, and a battery with 20 mile range at 25 mph. That speed and range has been really usefull to me for 4 years now. You need the range of the larger size battery, because you want to leave some reserve in the battery every ride. That increases the lifespan of an expensive battery. Lastly, deals on lifepo4 too good to be true, are too good to be true.

 

[monkeychops]

Thanks dogman. Good plan.
Next question: how to decide which controller to buy?
The page posted above is useful: http://tncscooters.com/index.php?route=product/category&path=41_74
I'm guessing the ones on this page would all work and it just depends what I else (apart from the battery, throttle and motor) I want/need to connect to the controller?
This one looks the ideal size: http://www.tncscooters.com/JC-116-3.php but it doesn't say anything about a connection to the throttle. Is that the "Derailleur Connector".

 

[dogman dan]

30 amps will drain your battery nice and fast, really, you'd be better off with 20-25 amps. Browsing, I'm not seeing any under 30 amps. Might look at fleabay.

Looks like the plug labeled derialur would be the throttle. Throttle pinout is often match red and black, then the third is signal back to the controller. Sometimes white, or purple. This time green.

 

[monkeychops]

Found this one http://www.ebay.co.uk/itm/36V-25A-Control-Box-Controller-Electric-Scooter-36-Volt-/330616858539 which is 25A maximum.

It's actually on the tncscooters site (http://tncscooters.com/index.php?route=product/product&path=41_74&product_id=172) but the headline max current is 30A but in the detail page confirms it's 25A. It's slightly thicker than my existing one by 0.5cm but I'm sure I could fit it reasonably well in the space available.

Shall I go for it?

 

[amberwolf]

If you can find one with multiple shunts inside, like say, 2 shunts and 40A, cut one shunt and now its' a 20A controller.

 

[monkeychops]

If you can find one with multiple shunts inside, like say, 2 shunts and 40A, cut one shunt and now its' a 20A controller.

There are a couple of 36V 40A controllers on the TNC Scooter site but neither of them say anything about 2 shunts :-(

 

[dogman dan]

Some of those might be potted, and hard to do modifications like that. The ebay one looks as good as any to me.

Also, you don't have to ride full throttle. Well I do, but you don't.

 

[Samd]

If it were me, I wouldn't but a 36v rated controller. That's not to say you shouldn't do it! But I found a problem with this when i did my conversion.

As soon as your lead acid battery sags below 31.5 volts it will cut power to the motor. And on a lead acid battery that is bound to happen very quickly as soon as you try and accelerate hard.
I'd buy a 30 amp 24v controller instead. They will work fine when "overvolted" at 36 volts and you won't know the difference.
I recommend the LBD 14 and have now used two of these daily for about 6 months at up to 1100 watts. Barely gets warm on the casing.
I think I have a third at home - could have a look inside the case in a few hours to see if it is potted or not...

If you don't want a keyswitch just short those two wires out. Or put a small switch across the two wires somewhere out of sight to deter theft.

Then fit a voltmeter in a spot that's easy to see to watch how much your voltage sags - use it to understand range vs speed. When you convert to LiPo you will see a much lower sag, but it will help you avoid going below 3.7v per cell and killing your batts. A much better fuel gauge than those throttles with an LED. And as dogman says it is important to understand the tradeoff between speed and range for your bike.
http://www.ebay.com.au/itm/5PCS-Dig...709?pt=LH_DefaultDomain_0&hash=item3f0f1b380d
i recommend this sort. Don't worry about the stated voltage range of that meter being 30v max, mine is accurate to about 0.25volts at 33.6 volts. Happily works up to 40v and there is only two wires on this one - just pop it across two the power input wires on your controller. You cna put a small switch in series to turn it off, or just leave it on, they use very little power.

And the warm red glow shows your e-grin as you quietly whirr past people at night...

Which country are you in Monkeychops?

 

[monkeychops]

Thanks for that samd.
I am from England.
It does sound then like a 24v controller is the thing to get. So is the low voltage cutoff the only significant difference between the 24V models and the 36V? In my ignorance I assumed that they would output 36V or 24V to the motor and 24V going into a 36V motor wouldn't be enough. I guess it doesn't work like that?
The voltmeter is an excellent tip too. Currently I have an analog voltmeter without any numbes on it. The digital one looks good. Is it reasonably weatherproof?
Like your blog too!

 

[Samd]

Thanks monkeychops - there is a lot of similarity between the aprilia rebuild on my blog and what you want to do - essentially strip everything off prior to the motor and update/simplify it.

My voltmeter is quite waterproof because of the way I reused the Aprilia's plastic overcap, then effectively 'potted it' by shooting up the back full of hotmelt glue to seal it up. It may pay to buy one and pop the bezel off, then glue the bezel back on to the plastic overlay in front of the screen so water can't get under the bezel/surround. I'm sure you can come up with other ideas. Cheap enough to buy two..

Because these voltmeters are an unknown when it comes to accuracy it pays to compare the stated voltage when you plug the battery at various charge states into a LiPo charger - A good liPo charger will tend to be more accurate on stated voltage. Or compare with another quality voltmeter if you can find one handy or borrow.

The good news is that when you are using for example an 8s LiPo pack, even if the voltmeter is ~0.4 volts in error, you are dividing that error across 8 cells in series, which is about 0.05 volts on average. Not a big showstopper when you are trying to avoid your cells going below ~3.70V.

I am sure that a 24v controller just takes any input above 21.5volts and chops it into a signal of varying pulse width output to the motor. The voltage will pass thru pretty much the same. The key is not to exceed the rated voltage of the FET's inside, which sounds like it is often 40V for the cheaper ones. *I think*. If I can find a decent CRO I might test in future.

As an aside my brushes wore out on my DC coffee grinder on the weekend. My dad was in town and showed me how to shape new ones using a file and some spare brushes I got with my last 20 dollar chinese angle grinder. It was so simple I can't believe I was ever worried about my brushes wearing out on the aprilia bike. Don't ever avoid riding hard for the sake of brushes. If you can get to them easily inside the motor , it's a 5 minute job to make more and pop them in.

 

[monkeychops]

I think what I might do is keep using my existing analogue voltmeter (which is in a weather proof case), but calibrate it with a multimeter. I think (but need to find out) that Full = 39V and Empty = 35V. My 15 mile journey to work drains it pretty much all the way from one to the other. The needle obviously drops under load but never significantly below the Empty line. Resting voltage after this journey is just under the mid-line, so around 36.5V I think.

I really want to measure current between the controller and the motor as well, to get a better idea of my current setup. Almost certainly I'm going to be replacing my brushed 200W motor at some point but I'd like to see how much current the existing motor is drawing, especially under load. Can anyone offer advice on doing this? I thought just connecting a multimeter in series would work. But mine says '10A' on it so don't want to overload it. I've also read it's not a good idea to measure current for too long (overheating issue maybe? I can't remember) but I would really like to ride around and see how the current to the motor is changing.

Maybe one of those 'clamp' style current meters would work?

Anyone?

 

[amberwolf]

Measuring current between motor and controller is difficult, because it is not constant nor DC. Depending on controller design, it may even reverse itself during throttle-down or braking, if it regeneratively brakes the motor.

But if yours is a Brushed DC motor, you can measure battery current and call it the same as average motor current at any particular time. (peak motor current may be MUCH higher) THere are some good sites to learn about that, including some threads in the motor section of ES, and http://www.4qd.co.uk/faq/index.html or http://www.4qdtec.com/pwm-01.html


Most multimeters have a rating for how long you can use it for higher amp readings; you'd need to check your manual for htat. If it's a Centech/Harbor Freight/ other cheap meter, it's proably good for 30 seconds at 10A. Higher currents than that, or longer, and it may unsolder the shunt from the PCB inside the meter (ask me how I know ).

removing the back cover to expose the shunt to cooling airflow may make it survive continuous 10A, but going over that may well still cause the shunt to fall out/off.

Better meters may be able to tolerate rated current forever, or might have similar limitations.

Clamp-on meters can do their ratings all day long, or at least till the battery runs out.

 

[dogman dan]

A cheap harbor freight, or equivilant 12v car ampmeter will work for crudely measuring your draw. Might be poorly marked like mine was, in 5 amp increments. But when I got a Cycleanalyst later, I found the readings were not off by enough to care about. Just harder to read on the fly.

I wouldn't sweat the 36v controller thing, if it's lvc is popping, it's because it's trying to save your batteries. Using a lower lvc so you can kill your batterys better is not a solution.

 

[monkeychops]

Thinking about all this measuring a bit more...

How is my bike limited to a powered speed of 15 mph? there is no feedback from the motor to the controller. When I’m going along downhill it still cuts out at 15mph. I’ve got a feeling that no amount of increased current (from a replacement controller and/or battery) will help with this. Top speed must surely be related to voltage in this case?

So to test this I could wire up another 12V source in series with my 3 x 12V SLA batteries (I’m learning the acronyms) to make 48V and see if this spins the wheel round faster. I now wish I hadn't chucked away (recycled) my old 12V SLA batteries. Would it be safe to wire in a 12V mains transformer in series to the batteries? Instinct tells me this wouldn't work or be safe... so I'd need an extra battery from somewhere.