Looking for a 52V Motor Controller (Heilong Mount) – Done with Grin

[Dekay]

Hi everyone,


I’m hoping someone here can recommend a solid motor controller. I’ve been searching around and haven’t had much luck finding what I need.


I’m running a 52V Heilong battery on my e-bike. Until now, I was using one of Grin Technologies’ internal bracket-mount controllers (the kind that mounts inside the downtube where the battery cradle locks in). But after my recent experience, I’m done dealing with Grin and looking to switch to something else.

---

Background (Why I’m replacing it):


I live in Vancouver, so it was easy for me to bring my battery and charger over to Grin in person. Late last year I had major surgery and was off the bike for a while. During that time, my charger died. When I was back on my feet, I took the battery and charger to Grin to have them test it.


They confirmed the charger had failed, so I bought a new Satiator from them. When I got home to hook everything back up, the main power connector on the controller crumbled — it just broke apart into pieces.


So I went back to Grin to buy a replacement connector, but they told me they don’t sell them anymore (too old — the controller and battery are from ~2018–2019). Instead, they gave me a used one they had cut off something else.


I soldered it on, went to plug it in — and got massive sparks. I checked everything: red wire from controller to battery +, black wire to battery –. Still sparked.


Eventually, I opened the battery and discovered that Grin had wired the battery backwards from the factory — the BMS’s black wire was going to the positive terminal, and the red wire was going to negative.


I emailed Grin to let them know, and to ask for proper replacement connectors and maybe testing for the controller since it sparked multiple times. Their response was basically: “That doesn’t sound like something we’d do, and you should have verified polarity with a multimeter before plugging in. Not our fault.”


No offer to help, no acknowledgment that the battery was wired wrong, nothing.


So I reworked the BMS wiring so red went to + and black to –, replaced the connectors with ones from Amazon, and the system came back to life — for a little while.

---

New Problem: Intermittent Cutouts → Final Failure


After the repair, the system ran normally for a few short rides. Then it started cutting out intermittently:

• The display stayed on
• The motor stopped giving power
• The voltage shown on the display would slowly drain down to ~20V
• Then the display would finally shut off

I could turn it back on and it would run again… until the next cutout. This happened maybe 10 times over a few weeks.


Finally, one day it cut out and wouldn’t recover.


Now:

• Display still lights up
• Throttle signal is detected (I can feel the motor bump slightly when twisting the throttle)
• But the motor doesn’t spin

So either the controller is toast or something internal got damaged from the repeated sparking during that initial reversed-polarity situation.

---

What I’m looking for:


So yeah — I’ve spent around $10,000 at Grin over the years, but I’m completely done with them. I just want a new motor controller that:

• Is compatible with a 52V battery
• Can handle 750W or more
• Fits inside a standard Heilong downtube cradle mount
• Preferably something with good reliability and support

So far, all I’ve been able to find are low-power 48V/500W controllers, or weird off-brand units with very little documentation.


Any suggestions, recommendations, or product links would be very appreciated.


Thanks in advance,

 

[Papa]

Hi everyone,


I’m hoping someone here can recommend a solid motor controller. I’ve been searching around and haven’t had much luck finding what I need.


I’m running a 52V Heilong battery on my e-bike. Until now, I was using one of Grin Technologies’ internal bracket-mount controllers (the kind that mounts inside the downtube where the battery cradle locks in). But after my recent experience, I’m done dealing with Grin and looking to switch to something else.

---

Background (Why I’m replacing it):


I live in Vancouver, so it was easy for me to bring my battery and charger over to Grin in person. Late last year I had major surgery and was off the bike for a while. During that time, my charger died. When I was back on my feet, I took the battery and charger to Grin to have them test it.


They confirmed the charger had failed, so I bought a new Satiator from them. When I got home to hook everything back up, the main power connector on the controller crumbled — it just broke apart into pieces.


So I went back to Grin to buy a replacement connector, but they told me they don’t sell them anymore (too old — the controller and battery are from ~2018–2019). Instead, they gave me a used one they had cut off something else.


I soldered it on, went to plug it in — and got massive sparks. I checked everything: red wire from controller to battery +, black wire to battery –. Still sparked.


Eventually, I opened the battery and discovered that Grin had wired the battery backwards from the factory — the BMS’s black wire was going to the positive terminal, and the red wire was going to negative.


I emailed Grin to let them know, and to ask for proper replacement connectors and maybe testing for the controller since it sparked multiple times. Their response was basically: “That doesn’t sound like something we’d do, and you should have verified polarity with a multimeter before plugging in. Not our fault.”


No offer to help, no acknowledgment that the battery was wired wrong, nothing.


So I reworked the BMS wiring so red went to + and black to –, replaced the connectors with ones from Amazon, and the system came back to life — for a little while.

---

New Problem: Intermittent Cutouts → Final Failure


After the repair, the system ran normally for a few short rides. Then it started cutting out intermittently:

• The display stayed on
• The motor stopped giving power
• The voltage shown on the display would slowly drain down to ~20V
• Then the display would finally shut off

I could turn it back on and it would run again… until the next cutout. This happened maybe 10 times over a few weeks.


Finally, one day it cut out and wouldn’t recover.


Now:

• Display still lights up
• Throttle signal is detected (I can feel the motor bump slightly when twisting the throttle)
• But the motor doesn’t spin

So either the controller is toast or something internal got damaged from the repeated sparking during that initial reversed-polarity situation.

---

What I’m looking for:


So yeah — I’ve spent around $10,000 at Grin over the years, but I’m completely done with them. I just want a new motor controller that:

• Is compatible with a 52V battery
• Can handle 750W or more
• Fits inside a standard Heilong downtube cradle mount
• Preferably something with good reliability and support

So far, all I’ve been able to find are low-power 48V/500W controllers, or weird off-brand units with very little documentation.


Any suggestions, recommendations, or product links would be very appreciated.


Thanks in advance,

Reads to me the system was functioning correctly (including the Heilong battery), prior to your surgery. True?

If all Grin was supposed to do, was "check" the battery & charger, why would they allegedly disconnect the power leads on a functioning battery in the first place, just to test it? Then... you claim, they reinstalled the leads "reversed".... ?

So what am I missing here?

Had you not disassembled the battery and re-soldered the connections, but instead, simply returned the battery unmodified, you likely would not have been snuffed by Grin.

 

[Dekay]

You're right that the system was working fine before my surgery. The bike sat untouched during that time, and the problem only started after the charger failed and I brought things in for testing.


But just to clarify — Grin never disassembled the battery or touched the power leads internally. What I said was that when I got everything back home and plugged it in, the connector on the controller crumbled apart (not something Grin did — it fell apart from age or fatigue). I went back to Grin to try to buy a replacement connector, but they don’t sell them anymore. Instead, they gave me a used one they had cut off something else.


I soldered it on, went to plug it in, and got major sparks — even though I wired it correctly: red to +, black to –.


I checked the battery output with a multimeter and noticed the polarity was reversed at the terminals. That’s when I opened up the battery case and found the issue: the BMS was wired backwards — black wire to the positive terminal, red to negative. So the battery had been built wrong from the factory, but I had never seen it before because the original connector had been pre-installed when I bought it (2018/2019) and worked fine until now.


So to be clear:

• Grin didn’t reverse anything recently — the battery was built with reversed polarity from the start.
• I only discovered it when the connector failed and I had to rewire things manually.
• I didn’t modify anything until I verified the reversed polarity with a multimeter, and I only opened the battery because I had no other option.

What bothers me is that when I reported this to Grin, they completely dismissed it — said it didn’t sound like something they would do, and blamed me for not checking polarity before connecting it.


But here’s the thing: if my battery left the factory wired backwards, it’s likely there were others. They could’ve had a bad batch from their supplier or an assembly error that slipped through. So it's not like this is impossible or unimaginable. They may have already seen other cases like this — or just don’t want to admit it.


Anyway, just to be clear — I’m not here to rant about Grin. I only included the backstory to explain why I’m not buying another controller from them and why I want an alternative.


All I’m asking is:
Can anyone recommend a reliable 52V motor controller (750W+ or better) that fits in a Heilong-style battery cradle?


Thanks again.

 

[Papa]

You're right that the system was working fine before my surgery

So, apparently... your system was functioning just "fine" initially, with reversed polarity battery wires???

I took the battery and charger to Grin to have them test it.
....They confirmed the charger had failed,

the battery was built with reversed polarity from the start.

Seems rather odd to me that Grin didn't detect the alleged polarity reversed wires when they 'checked' both the battery and the charger?

 

[lnanek]

It's pretty standard in the ebike world for the wire colors to mean nothing, unfortunately. Kind of sucks your battery had surprising colors inside, but that's par for the course. Expensive lesson, but a good lesson all the same. Too bad you didn't learn it earlier working with safer signals in harnesses.

I doubt Grin assembled it and doubt they cut it open to check when it was delivered from their supplier before they sold it to you. So tough to blame Grin as well. Suppliers don't care about the internal wiring color either, their assembly workers grab whatever is in the bin and go as fast as possible.

For what it's worth, modern XT and Anderson connectors are way better than earlier systems like the RV power connector used by my old Bionx ebike. For that one I still have polarity converters that swap around which side is negative vs. positive that I had to use often. E.g.:

https://a.co/d/3I24rsv

Even in modern times, whenever I order a new Silverfish battery to plug into my ebike, it's completely random which blades on the battery discharge plate are wired to positive vs. negative and I've often had to swap them to match my ebike after checking with a multimeter after purchase.

 

[Dekay]

@Papa


Yeah, I get why that might sound strange at first, but let me clarify a few things.


The reason the system worked fine for years — even though the battery turned out to be wired with reversed polarity internally — is because the controller came with a connector already installed, and it matched the battery’s polarity as it came from the factory. So although the battery had the black wire from the BMS going to the positive terminal and red going to negative, the controller was wired to match it. It was plug-and-play — I never had to open anything or do any wiring back then, and everything just worked.


As for what Grin did when I brought the battery and charger in, I honestly don’t know the exact steps they took. All I know is that they checked them both, told me the battery was fine, and that the charger had failed. I replaced the charger with a Satiator, and that was that.


The problem started when the power connector on the controller crumbled. Not from sitting around, but just from age — the system is from around 2018 or 2019, so it’s got 6–7 years on it. Grin didn’t sell replacement connectors anymore, so they gave me a used one they’d cut off something else.


I soldered that in and wired it up the normal way — red to +, black to – — and immediately got big sparks. That’s when I tested the battery with a multimeter and realized the polarity was reversed at the terminals. I opened it up and found the internal BMS wiring was backwards.


So yeah — the only reason it worked originally was because both ends were “wrong” in the same way. I only discovered the issue when I had to replace the connector myself. If the original connector hadn’t failed, I probably never would’ve known.


Hope that clears it up a bit.

 

[Dekay]

@Inanek


Yeah, I hear you — and you're right that color coding in the ebike world can be all over the place. But here’s the thing: I’ve spent over 30 years as a mechanic, and in that time I’ve dealt with literally tens of thousands of batteries — automotive, motorcycle, industrial, you name it. And in all that time, I’ve never once come across a battery that was physically built with the polarity reversed at the terminals. So yeah, double-checking wiring is second nature to me, but something like this just wasn’t even on the radar.


The only reason I didn’t test the polarity first was because this was a matched system — the battery and controller were both from Grin, pre-wired, plug-and-play. I never touched the wiring until the connector failed after 6–7 years of use. When I replaced the connector and wired it up normally (red to +, black to –), that’s when everything went sideways.


And yeah, you’re probably right — Grin likely didn’t build the battery themselves, and maybe they didn’t even know. But that’s kind of the point: if they’re selling products with no quality control and no accountability, and their response to a safety issue is basically, “that doesn’t sound like something we’d do”, then why would I want to keep buying from them?


Am I supposed to open up and disassemble and inspect every component I buy from Grin before I can safely use it? That doesn’t inspire confidence — especially after spending about $10,000 with them over the years.


As for connectors, I appreciate the tip on XT and Anderson types — I’ve heard good things — but for now I’m sticking with the style that’s already on the battery. I’ll reassess depending on what kind of controller I end up finding.


Which brings me back to why I’m posting here in the first place:
I’m looking for recommendations for a 52V motor controller (750W+) that fits in a Heilong-style cradle mount. I told the story just to explain why I’m not considering another controller from Grin — that’s all.


Appreciate the input either way.

 

[docw009]

You can't wire a BMS backwards like that. It won't work if its black/blue wires are connected to positive end of cells. You can wire a connector backwards or its wires, so I hope that's what you meant. I seem to do that often, but usually catch it, Not always. The claim is that both the controller and battery were wired backwards? Strange stuff happens.

Here's a 48V controller, but it will work on 52V for a Hailong 1 case, They also sell one for a DP-poly case, which looks like a Hailong, but is quite different,

I advise looking hard at pictures, and checking dimensions when you buy something like this, There are three or four different Hailong versions,

10S/13S 36V/48V 15A KT 6Mosfets Sine Wave Controller for Hailong Battery [Hialong 1 Case Controller] - $42.75 : Zen Cart!, The Art of E-commerce

Zen Cart! 10S/13S 36V/48V 15A KT 6Mosfets Sine Wave Controller for Hailong Battery [Hialong 1 Case Controller] - ★★★★★ 36V/48V 15A 6Mosfets Sine Wave Controller for Hailong Battery 1--Rate Voltage:36V or 48V KT sine wave controller 2--Rated Current:7A,for 250W-350W motor 3--Maximum...

topbikekit.com

And here are some complete cradles with controllers, You can study the pic to see if they are what you want.

https://www.aliexpress.com/i/2255800436586242.html?gatewayAdapt=4itemAdapt

 

[Dekay]

@docw009

Yeah, I should’ve been more precise — I didn’t mean the BMS itself was wired backwards internally. What I meant was the battery’s output leads were reversed — red was negative and black was positive. That’s what ended up causing the damage. And no, I didn’t catch it right away because honestly, in all my years working with this stuff, I’ve never run into a pack that was that badly miswired. It was the last thing I expected.


And yeah, apparently both the battery and the controller had the red and black reversed — so they “matched” in a way, but were both backwards. That’s why everything seemed to power up okay at first... until something actually cared about polarity and smoked.


Thanks for the links — the first controller looks decent, but it’s only rated for 7 amps, and I’m going to need more than that. I’m aiming for at least 25 amps. The second link had a few interesting-looking options, but there was zero info — no specs, no dimensions, not even current ratings — so I’ll need to do some more digging before I can figure out if any of those are actually usable.


Appreciate the input — this whole thing has been a hell of a learning curve.