New Grin G310 Rear Hub Kit Keeps Dying

KitsBeach

10 mW
Joined
Sep 21, 2022
Messages
30
Hi All, I've just installed a brand new Minimal G310 Rear Hub Kit from Grin and it has died twice. Both times within 5 kilometres from my house (3 miles). This is all the mileage the kit and this build have on it.


Kit:
G310 hub
Baserunner Z9 controller
B3624LiM battery in DP9 Reention case
Throttle only


Symptoms:

- Clunk-clunk-clunk feeling before it dies (like a dead battery)
- The clunk-clunk-clunk is intermittent and happens at random times (easy flat sections or uphills).
- Rear wheel does not want to spin backwards (such as when pushing bike around)
- If I do spin wheel backward by hand it also makes a jerky clunk-clunk-clunk motion/feeling.
- Battery lights show 3 green and 1 red (like a full charge). But after first break-down the battery took a full multi-hour charge, so I assume it was dead.
- Battery lights showed 1 red after it was fully charged.
- Bike ran great after battery recharge but broke down second time a similar distance away (4.3 kilometres this time).
- After second break down I tried to charge it again. Charger switched to green after a few minutes and battery lights now show 3 green and 1 red after charge.
-There is a bit of silicone/goop leaking from where the motor wire exits the hub. this was not there when I assembled bike.

I also tried loosening the axle nuts to see if that would help the wheel spin backwards and it did not help. I also removed the disc caliper completely, and checked for any other rubbing.

Symptoms seem to me to be similar to a dead battery, or an overheated motor. But it couldn't be overheated after such a light ride (all the bargain bikes zip by me).

Any ideas?

Here's a picture of the bike and the goop coming out of hub.

Progress shots Oct 2 2022-1.JPG

weird bafang hub goop.JPG



I've ridden the bike very easy and the first ride (last night) was mainly downhill or flat (but not as nice coming home with no motor).

Today's ride had some uphill but I was easy on the throttle and the problem began almost right away. Motor has stopped completely now. It may turn on and offer a weak micro-horsepower attempt but that is it. It stopped completely on the ride as if it was turned off.
 
KitsBeach said:
- Clunk-clunk-clunk feeling before it dies (like a dead battery)
I'm not sure what you mean by it being like a dead battery. Could you explain the relationship you feel between them?


- The clunk-clunk-clunk is intermittent and happens at random times (easy flat sections or uphills).

Are there any other symptoms or conditions at the same time, or just before / after that, that are the same each time it happens?

- Rear wheel does not want to spin backwards (such as when pushing bike around)
Is this with power on, or off?

A geared hubmotor has a LOT more resistance backwards than forwards, because it usually has a freewheeling "clutch" inside that lets it freely roll forwards without power, but the gearing inside is engaged when rolling it backwards (just like it is when the motor drives if forwards), and that along with the motor itself creates a lot of drag.

If it is more drag than normal, then it can mean a blown FET in the controller causing phases to be shorted together in the motor. Unplugging the motor from the controller will reduce the drag if that's the case. Or a direct short within the motor's internal wiring causing this, which won't change when unplugging the motor.



- If I do spin wheel backward by hand it also makes a jerky clunk-clunk-clunk motion/feeling.
With power on, or off?

- Battery lights show 3 green and 1 red (like a full charge). But after first break-down the battery took a full multi-hour charge, so I assume it was dead.
Sounds like the meter isn't accurate, possibly for the wrong battery voltage. Not much way to test that without a variable voltage source and disconnecting the meter from the battery inside it's case to use the variable source to see what lights up vs what voltage.



- Battery lights showed 1 red after it was fully charged.
Just one red? Or other lights as well?



- Bike ran great after battery recharge but broke down second time a similar distance away (4.3 kilometres this time).
- After second break down I tried to charge it again. Charger switched to green after a few minutes and battery lights now show 3 green and 1 red after charge.
The same trip should take the same amount of capacity, assuming the same conditions and riding style. If the first trip was done after fully charging the battery, and so was the second, then the battery should be in the same state after each trip. If it was not, then either the battery wasn't fully charged (or anyway not nearly the same amount of charge) on the first trip, or the second one's conditions used much less assist.

Without something (like the cycle analyst or other wattmeter) to show how much charge went into and came out of the battery on each charging cycle and trip, it's difficult to know which, if any, of those is the case.

Another possibility for the second-breakdown-charge results is that there is something wrong with the battery, such that one or more cell groups doesn't have the same capacity as the others, so reaches full state sooner than the others, which triggers the BMS to stop allowing charge to protect the full groups from overcharging. If this is the case, then leaving the battery on the charger will let the BMS drain the high group(s) enough to restart charging for a short time, and then shut off, and cycle thru these repeatedly until it balances the pack. But a pack that requires this will always require this, and the problem will grow worse over time, because the problem is (usually) caused by cell group(s) that aren't as capable as others and that never gets better without replacing them. (it can also be caused by a defective BMS that's draining a cell group(s) constantly but this is rarer than cell problems).

-There is a bit of silicone/goop leaking from where the motor wire exits the hub. this was not there when I assembled bike.
If it's really silicone, that should be long-cured and solidified, and it won't change shape without such extreme temperatures that you'd notice the heat from the motor casing, axle, etc.

If it's something else that is more malleable, then more gentle motor heating could allow it to change shape.



Today's ride had some uphill but I was easy on the throttle and the problem began almost right away. Motor has stopped completely now. It may turn on and offer a weak micro-horsepower attempt but that is it. It stopped completely on the ride as if it was turned off.
Does the system have any display or LED indicator on the controller (outside of the battery itself) to show whether power is still on or not? If so, was power actually cut off? If so, it's probably a battery issue. If not, it's probably a controller/motor issue.


If the battery is really fully charged and workign correctly, that usually indicates a failure within the controller (blown FETs) or motor (damaged hall sensors or windings), both of whcih are typically caused by excessive heat from excessive load, which sounds unlikley. Can also be a poor connection from motor to controller, like plug that is not fully seated.
 
Wheel doesn’t really want to roll backwards with power off. It’s like brakes are on.

Anyone with a rear hub have trouble rolling backwards (such as removing bike from a bike rack).?
 
I’m curious what is the normal difficulty rolling a rear hub bike backwards.?

Mine is totally locked up. The back wheel would need to be lifted up to roll the bike backwards.
 
KitsBeach said:
Symptoms:

- Clunk-clunk-clunk feeling before it dies (like a dead battery)
- The clunk-clunk-clunk is intermittent and happens at random times (easy flat sections or uphills).
- Rear wheel does not want to spin backwards (such as when pushing bike around)
- If I do spin wheel backward by hand it also makes a jerky clunk-clunk-clunk motion/feeling.
- Battery lights show 3 green and 1 red (like a full charge). But after first break-down the battery took a full multi-hour charge, so I assume it was dead.
- Battery lights showed 1 red after it was fully charged.
- Bike ran great after battery recharge but broke down second time a similar distance away (4.3 kilometres this time).
- After second break down I tried to charge it again. Charger switched to green after a few minutes and battery lights now show 3 green and 1 red after charge.
-There is a bit of silicone/goop leaking from where the motor wire exits the hub. this was not there when I assembled bike.

I also tried loosening the axle nuts to see if that would help the wheel spin backwards and it did not help. I also removed the disc caliper completely, and checked for any other rubbing.

Symptoms seem to me to be similar to a dead battery, or an overheated motor.

Are there other symptoms, or which ones listed indicate an overheated motor?
 
KitsBeach said:
I’m curious what is the normal difficulty rolling a rear hub bike backwards.?

Depends on the gearing ratio in the geared hub, and sometimes even the motor windings.

If the gear ratio is very high, like for a hub with double gear reduction, it could be very hard to manually rotate backwards.

If the motor windings are such that the generated voltage from spinning the motor externally at the speed the gear reduction causes is higher than battery voltage, the controller will "automatically" even if powered off feed back current into the battery, causing even higher drag on the motor and making it even harder to turn.

May also depend on whether the system is powered on or not at the time, such as if it has an antitheft function that tries to fight wheel rotation (it can't do anything about forward rotation in a geared hub, but backward would feel like a locked up wheel).



A direct drive hub rolls the same forwards or backwards, with no power.

With power, depends on controller features (my SB Cruiser trike has a controller that actively fights reverse rotation of any motor wheel, for no externally-controllable reason. Just having power on and phase wires attached to the controller, no other wires connected to anything, does this. Forward rolling is completely normal...it also has an antitheft function, but when engaged that works in both directions equally).
 
KitsBeach said:
Wheel doesn’t really want to roll backwards with power off. It’s like brakes are on.
If you can answer some of the questions posed previously, it may help solve (or at least explain) this as well.

For instance, did it have this kind of problem originally, or only after the failure(s) occured?
 
amberwolf said:
If you can answer some of the questions posed previously, it may help solve (or at least explain) this as well.

I was going to mention that, but decided to just wait for the responses. Based on the Q to A ratio, no need to invest time in asking more questions.
 
Update: I dropped the hub off at Grin to check out. Really nice people.

I probably could have dropped off controller and battery too, but I think the hub was able to spin backwards initially, so hub seemed a good place to start.
 
Update: I picked up my warrantied hub today from Grin. Put the bike back together and it died in the first minute on flat road (190 metres to be exact).

Green tape on it said "fixed new core" which I assume means they replaced the hub internals with new stuff (since my hub is laced to my rim etc).

Bike feels really good up to about half throttle (I have throttle only). Then as soon as I add throttle it cuts out. Powering the battery off and back on resets it, then it dies again anywhere past half throttle.

I'm assuming the controller needs some programming, even though the kit is called "Ready-to-Roll". Maybe I'm reaching some kind of maximum with my throttle.?

Could this be something in the programming.? Like is there a setting that could limit the throttle to what the G310 would be happy with.? Maybe I got an off-the-shelf controller programmed for something else, or set with default generic settings.?

IMG_6649.JPG
 
Problem solved..!!!

I went back to Grin and received first-class friendly service.

They took me right in to their workshop and plugged the controller in to a computer and adjusted some things and it ran. Just a short ride home (3.3 kms) but everything feels good..!! I will give it a longer test ride later in the week.

I was curious what burnt up the original hub motor, but they didn’t have time to look into the original RMA (warranty return). I suspect it was something in the controller settings.

They did tell me that my controller had been set with default settings, that is to say they had not tuned it for the ready-to-roll kit I had purchased from them. I think they usually set-up the controller to match the kit, but that this one had slipped through the cracks.

Anyway I’m happy to have a running bike and looking forward to cleaning up the wire routing and generally finishing the build.
 
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