Giant Lafree middrive motor possible replacement

[Zephak]

https://youtu.be/IDOnakBCj5w

On this older Giant Lafree, I'm considering the possibility a new middrive motor.

The bike currently isn't operable as an ebike. My guess is that the brushes in this brushed motor could be the problem.

Replacing the motor and using new electronics might be a way to go.

Looking at the picture of the motor mount shows a unique mount. There's about 4-5/8" c-c of the two farthest mount bolts. The green lines pointing to the motor mounts.

My question: is there a motor that could swap in?

I hope that's enough detail. Please let me know

 

[E-HP]

https://youtu.be/IDOnakBCj5w
IMG_20220214_142449076~2.jpg
On this older Giant Lafree, I'm considering the possibility a new middrive motor.

The bike currently isn't operable as an ebike. My guess is that the brushes in this brushed motor could be the problem.

Replacing the motor and using new electronics might be a way to go.

Looking at the picture of the motor mount shows a unique mount. There's about 4-5/8" c-c of the two farthest mount bolts. The green lines pointing to the motor mounts.

My question: is there a motor that could swap in?

I hope that's enough detail. Please let me know

Can you zoom out a little to get better overall context?

 

[Zephak]

here's the bike...motor and crank is attached with three bolts to the frame; the battery is behind the seatpost, the controller is above the motor.

Thanks for looking. I searched the forum and didn't find a motor mounted like this one.

 

[Hillhater]

If it is just the brushes, that would be a simple quick fix.
A replacement modern brushless replacement will be problematic, not just the mounting etc, but also a new controller, likely a voltage change and hence a new battery installation, with all that is implied in that !
It will not be easy or cheap..!
For “similar motor/ mount” set ups you could consider at the Tonaro bike motors, which can be found on Alibaba etc.
https://endless-sphere.com/forums/viewtopic.php?f=28&t=44867&start=175

 

[Zephak]

Here's the other side of the crank...

 

[Zephak]

I purchased a controller already and then I realized that this is a brushed motor and the controller won't work with this motor. A replacement to the 24v sealed lead acid seems pretty straightforward, maybe higher voltage, or perhaps 8s7p.

The 2p sealed lead acid has the proper voltage but this bike flashes lights when the voltage is low and so there's a problem. My assumption about the brushes was just that, an assumption

 

[Zephak]

If it is just the brushes, that would be a simple quick fix.
A replacement modern brushless replacement will be problematic, not just the mounting etc, but also a new controller, likely a voltage change and hence a new battery installation, with all that is implied in that !
It will not be easy or cheap..!
For “similar motor/ mount” set ups you could consider at the Tonaro bike motors, which can be found on Alibaba etc.
https://endless-sphere.com/forums/viewtopic.php?f=28&t=44867&start=175

@hillhater I checked the thread you linked to but didn't see specifics about the motor... I'll keep looking, thanks!

 

[Hillhater]

You can test the brushes simply by applying 24v direct to the motor terminals . (Chain off or wheel off the ground)
If the motor runs with direct feed, you either have a problem with controller ( cheap) or battery pack/connections.

 

[E-HP]

IMG_20220214_165115923.jpg
Here's the other side of the crank...

It looks like the motor may be providing some of the frame's structural integrity. When you mention replacing it, are you talking about like for like, or something else in a mid drive (Bafang M500, etc.)?

 

[Zephak]

IMG_20220214_165115923.jpg
Here's the other side of the crank...

It looks like the motor may be providing some of the frame's structural integrity. When you mention replacing it, are you talking about like for like, or something else in a mid drive (Bafang M500, etc.)?

The thought was too get a more modern replacement, and it sure is possible for the motor to be part of the frame's structural integrity
But, new twist
Now,
As @Hillhater suggested, I put jumpers from the SLA (25.2v)
Directly to the motor terminals and the motor ran!

So, what to do now? New controller for a brushed motor (wouldn't know what to ask for) and just build a li-ion 7s8p??
Or,
Still search for a motor? A direct fit would be asking a lot, but perhaps with an adapter plate...

 

[E-HP]

Restore it! Clean it up, replace the bodywork, and use modern fuel.

 

[Hillhater]

Good,..at least you know the motor is OK.
Brushed motor controllers are cheap (<$20) and tiny..they fit anywhere. Just search Ebay for “Brushed motor controller 36v”
As mentioned, your most satisfying improvement would be to replace those SLAs with decent lithium, and in the process up the voltage to 36 v !.. 10s. ( buy the controller to suit that voltage.)
PS ..there are bound to be some wiring complications when changing out the controller....so be prepared !

 

[Zephak]

Maybe just install a big, red, easy button... momentary contact for on, normally off.

How much voltage do you reckon that LaFree motor can handle?

 

[Hillhater]

That button ( needs a relay also) will probably cost more than a cheap brushed controller ( the last one i bought cost $13.00 !)
...oh, and that “stop/go” button will mess up the drive gears very quickly ( ask me how i know !)

 

[Zephak]

Would a Electric Bike DC 24V 500W Brush Speed Controller For ATV Scooter Razor E300 E325, like in the attached picture work?

Where would the throttle connect? On the derailleur port??

 

[Hillhater]

Would a Electric Bike DC 24V 500W Brush Speed Controller For ATV Scooter Razor E300 E325, like in the attached picture work?

Where would the throttle connect? On the derailleur port ?

Yes, that is a very poor translation. ( where does a scooter have a derailleur ?)....my guess is it means “speed change “
And using the process of elimination on each of the other connectors, that one is obviously the throttle..

 

[Zephak]

I'm searching for that new controller and I'm wondering if I could get some help on knowing what wattage the current motor is.

I've read that some people think it's a "big honking motor" and one site says it is a 400w
https://www.taipeitimes.com/News/bizfocus/archives/2000/03/06/0000026848

Searching around this forum showed 250w

Would it be possible to jump 25v to the motor and read amps? Without blowing fuses in the amp meter?

Edit: it seems that a clamp meter won't work. There must be a ammeter that could.

Would a 24v 500w controller work or will it fry quickly? Maybe a 24v 750w controller is a safer bet. 7s8p 18650 pack is the working plan.

 

[Zephak]

The problem with the bike appears to be the part of the oem controller that sits in the bottom of the battery box. Picture attached.
I have two questions
Is there a Giant Lafree dealer that someone can recommend for finding a new circuit board? Giant hasn't returned an answer to my inquiry.
What part of this forum the place to ask about battery design? I am looking to build a 7s8p which should fit in the existing battery box, if a bms can fit in there, too.A 7s8p like in the attached

 

[amberwolf]

The problem with the bike appears to be the part of the oem controller that sits in the bottom of the battery box. Picture attached.

Which part of that is doing something it shouldn't, or not doing something it should? (meaning, what do you measure at the various points on it that lead you to suspect it? Or is it just the corrosion?)

Assuming there's no parts on the other side of the PCB, that's a *very* simple circuit, probably just an overcurrent shutoff (voltage across the shunt rises above a certain value triggers the transistor, either turning it on to engage a shutdown circuit, or turning it off to disable a powerup circuit).

The most likely problem given the corrosion is just a connection failure inside one of the wires, at the point they crimp to the terminals, or inside the connector shell between the pins themselves.

It's also possible corrosion ate away at a component pin/leg, leaving part of it disconnected.

Or that a capacitor failed from age, etc.


It's possible (but not all that likely) that the transistor failed from corrosion allowing a voltage it didn't like to connect to the wrong pin enough to damage it. It would be more likely that that voltage, if present, passed to the external electronics the transistor is switching, that might run on a lower voltage and not be protected against the higher voltage.

It may not be a transistor, but rather a tiny regulator, like the 78L05, etc., and again, a failure that passes too high a voltage thru to it's destination connection could blow that destination electronics.

If you take the board off (but don't disconnect the wires) you can trace out all the connections and PCB traces, and draw it out on paper and then post a pic of that, and we can figure out what the circuit does "for sure", and thus how to troubleshoot it.


YOu may even be able to just clean the board of corrosion (after taking detailed pics of both sides, and noting all of the markings on each part, then clean the connector contacts inside and out, and retest, as long as nothing has actually corroded thru anywhere.

 

[Zephak]

Here's a pic of the backside

I haven't traced out a board before.

What is the proper cleaner to use? Perhaps electrical contact cleaner?

The bike exhibits a low voltage condition. With about 25.7 volts, when turning the bike "on", it will beep twice and all five LEDs will flash at about one second intervals. Holding a reset button for about five seconds will turn the lights off, but one, and turning the throttle will incrementally turn all the LEDs on, but no power to the motor.

The contacts on the front are obviously corroded.

I started out to thinking about a new motor, then just the controller and now maybe fixing this controller.

 

[Zephak]

Here are some pics of the board after a light brushing and air:

 

[amberwolf]

Here's a pic of the backside IMG_20220317_144601248.jpg

Yowch. Worse than I expected. I've cleaned and repaired worse, but only once.

If you do fix it, put some nice drainholes at the bottom of that casing so it doesn't accumulate water in it, and what does get in can easily evaporate.

So that's a more complex circuit; I would guess the chip is a dual or quad op-amp or comparator chip; can't read the number on it to find out. I'm also going to guess simple cleaning isn't going to fix it completely; it may at least need touchup on some solder joints at those connectors, possibly elsewhere. If traces corroded thru, you may ahve to install wires to bridge them.

I haven't traced out a board before.

Easy way is to first draw it on paper just like you see it but as big as possible, back first, on one side, then punch holes in it where the holes in teh board are (like where part leads and wires go thru it). Then draw the front side on the opposite side of the paper lined up with those holes. You can put them both on the same side of the paper if you want (but first fold it in half and still do the hole-punching trick to have starting points for the front side after you do the back).

Then write down each component value or marking next to it's location, and then we can figure out an actual schematic for it once we know what all the parts are.

What is the proper cleaner to use? Perhaps electrical contact cleaner?

That may work; qtips and denatured alcohol are what I usually use; it can take quite a bit of scrubbing to get corrosion off. Sometimes it just doens't come off, especially between traces or small components, and then I have to determine if there *should* be a connection between two parts, and then if not just scrape down to the PCB to remove "corrosion bridges" (otherwise just carefully scraping only the corrosion off).

YOu'll need to be careful with the markings on things to try not to remove them, and document as much of what you can see and read before you clean anything off in case the markings come off too.

EDIT: I wrote all this before you posted the next set of pics; hopefully we can figure out what some of those markings used to be if you didn't document them all first, especially on the chip. Without knowing what the chip is, and thus what the pin functions are, it wont' do much good to trace the rest out, as far as determining what the board does and troubleshooting it.

The bike exhibits a low voltage condition. With about 25.7 volts, when turning the bike "on", it will beep twice and all five LEDs will flash at about one second intervals. Holding a reset button for about five seconds will turn the lights off, but one, and turning the throttle will incrementally turn all the LEDs on, but no power to the motor.

Based on the corrosion on the back, where the connector plugs in, I'm guessing the main power connection is actually broken to the motor at that board, or the corrosion elsewhere is simply triggering the shutdown (which probably checks both for low voltage and for overcurrent, since the chip probably has enough op-amps/comparators for both).

 

[amberwolf]

Since the diode is actually broken off, it's possible that it's lead waas already corroded thru and preventing a connection. If so, replacing that might fix the problem, if all other parts are still working and connected.

The PCB silkscreen marking is just D1 (rather than ZD1) and uses the symbol for a regular diode, not a zener, so it is possible a standard 1n4148 or 1n4007 may replace it ok; these are commonly used in many older electronics, if you have any old junk laying around to be sacrificed for salvaging parts from. (no guarantee there's one in any particular item, but the bigger the PCB and more components a device has, the more likely it could have one. Old VCRs and tube TVs often do, sometimes old desktop/tower computer power supplies, etc).

If it's supposed to be a zener, it wont' regulate the voltage like the zener would, so stuff could get damaged...but there's no way to know as I don't see any markings left on the diode.



I also can't tell if any of the traces are completely corroded away; some parts of some of them appear to be at least damaged, if not gone, and may need to have extra conductor added to replace them.

 

[Hillhater]

.
Is there a Giant Lafree dealer that someone can recommend for finding a new circuit board? Giant hasn't returned an answer to my inquiry.

Your chances of finding a new replacement are slim to zero !
Search for used spareparts on Ebay , C list, etc ..you may even find a whole working bike cheaply ?
Unless you are an experienced electronics wizard like Amberwolf etc, i would simply bypass the whole mess, use a remote controller, and rely on manual charge monitoring.

 

[Zephak]

I bought a 24v brushed motor controller, a yk31c 500w, got it hooked up with the included throttle and a watt meter just after the sla battery , 25.6v and wired the "lock" wires together, but no joy.

It took me a while to get back to this project and it would be great if the bike can run again.

The motor turns if I jump from the battery, though the watt meter and then to the motor..

Maybe it's a bad controller or throttle?? Not sure how to proceed.