Speedict Neptune BMS - anybody used one ever?

Hi, has anybody used a speedict Neptune BMS before? This one connects to the VESC over UART. It’s a Bluetooth controlled BMS in a small package, but I’m under the impression I might be one of the first people to buy a couple.

I’m working on the first build - a modified evolve gtx with 12s12p 18650, flipsky v6.6-dk and vx2 remote, with 6374 motors. It’s a pretty tight fit but I’ve bought two of everything so plan on doing another board shortly too.

I’m finding over cell voltage protection, as well as the 39 amps limit to charge current to be problems from braking.

So yea, anyone seen one of these or used one before? Tim.


Havent tried it before but there is a new opened box one for sale over on Endless-Sphere.com for about 1/2 what they’re going for new.

Thanks, I have two already so don’t want a third, I wonder why they’re selling it. Maybe I should ask them. Cheers, Tim.


I don’t fully understand your issue, however, have a simple solution for you. Bypass the VESC from the BMS. This is fairly standard that we only connect the BMS charge/discharge cables to the Charging port.

The VESC can be directly connected to your battery (through a 200A fuse in case of cable chaffing). Now The BMS cannot stop the VESC, even if the batteries exceed safe limits. A small BMS like this cannot handle the full force of a VESC.

You should program the Battery min/Max current limits inside the VESC (FSESC 6.6DK) if you have not done this! As this will prevent the VESC from causing over-current on the batteries

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Thanks, Yea I’m looking at trying to bypass now. I keep having overvoltage errors when braking (On or off the board). The 12S battery is at 49V, and its spiking up to 60VDC in the fault log just using the vesc tool to spin one wheel. I think you could be right, perhaps I need to have a look with the osciloscope across the BMS and see if theres a spike of 11V.

Also, the 39 Amps I mentioned is highest settable limit of the BMS for charging. After that, it disconnects the load. It’s supposed to handle 175 Amps of discharge but the software only allows 135 A, I’m still waiting on Speedict to answer this one. They originally designed the BMS for a 10S Vesc arrangement and ported it to a 15s model with UART to collect duty cycle and temperature data.

Off topic, I have way less off the line torque than my elvolve GT and GTR, and only get error 255 for Hall effect sensor trying to setup BLDC operations.

Starting to consider just ordering the new evolve hadeon and possibly a lacroix for long trips. This whole DIY stuff is getting real time consuming! Cheers, Tim.

Fault : FAULT_CODE_OVER_VOLTAGE Motor : 1 Current : -11.5 Current filtered : -15.9 Voltage : 60.41 Duty : 0.063 RPM : 7992.0 Tacho : -4385 Cycles running : 168 TIM duty : 421 TIM val samp : 3360 TIM current samp : 3360 TIM top : 6720 Comm step : 0 Temperature : 33.29

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This isn’t right. Is that fault code is actually from the VESC or the BMS (I think it is a VESC fault)

What gauge cable do you have from the battery to the VESC?

If this is too thin and long, then you can get voltage drop issues like what you are describing

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Basically, you want your VESC to BATT wire as thick cable and as short as possible (with minimal joins/connections). This will give you better performance.

If you have the BMS between Battery and VESC, and long/thin cables. Then you will have a voltage difference(drop) between the VESC and the Lithium (this will get bigger the more current you draw).

Then as the motor slows down (-11.5 Amps in your fault) the VESC is making electricity. It cannot get back into the Lithium (cable size and/or BMS), so the volts build up in the VESC until it hits the safety limit of 60V (to avoid component failure).

It’s very likely your actual battery voltage does not increase much during this fault.

Re-do that bit of wiring, as best you can, bypassing the BMS, and your fault should be gone. Here’s a drawing that may help.

Lots of people don’t use the big Fuse, and I do understand the idea. In your case I really think you really should.

Since your main battery cables are outside of the enclosure, it’s totally possible for something to rub through them, so you want your battery to be safe (and not a fireball) if the Red and Black wires are ever to meet. Then I highly recommend to put a 150A+ fuse inside your battery enclosure, and preferably on the red wire.

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well I’m not up with the AWG standards (I’m an electrician and we don’t use that here), but it has the standard cable on the flipsky vesc, and I extended it with about 150mm of 10mm, and then it has the extremely compact speedict bms on an XT90 connector. I soldered the bms straight to the battery. The battery is made with 0.2mm nickel. 4 groups of two and then a strip over the 4 pairs, and groups are soldered together with short cable to handle the small amount of flex the board still has since thickening up with oak.

I could reduce some of the cable, but I doubt there would be much resistance from it unless it was hot.

Should I worry about BLDC detection not working? Or just stick with FOC?

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10mm2 is okay, that’s just a bit bigger than 8AWG. (which is what I’m using). And that length seems okay too.

I suggest you bypass the BMS, and repeat the test.

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As I understand it… A BMS does several tasks to maintain the battery health.

  1. Balancing Cells
  2. Over-charge protection
  3. Over-discharge protection
  4. Current protection
  5. Cell Fault monitoring

By connecting the VESC directly to the battery. We lose items 3&4. However the VESC software can do both of those.

Items 2 & 5 will also no longer happen during a ride. Which is fine, as we wouldn’t want to lose the ability to stop at 20 mph because of either of them, however when we get home, and it won’t charge, then we know we have an issue to investigate.

Everything in your setup sounds just fine, I’m keeping my fingers crossed for a little re-wire getting you out skating.

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Hi Louis.

Thanks for the help.

I’ve just measured 10 volts dropped across the bms during braking. Given that it’s designed for an eBoard and was reasonably expensive it’s a little disappointing. The vesc interface in this BMS was supposed to be so it knew that it knew the board was moving as opposed to being on the charger.

I think I’ll try get some shots with the scope and provide that feedback to speedict.

Hopefully the balance function still serves it’s purpose, and I will still get phone notifications it I get cell over voltage etc.

As for gettimg out skating, I’ve got two standard evolves anyway but since I bought about 2500 18650 cells cheap I figured I ought to start using them. (About 100 lime scooter batteries).

Cheers, Tim

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Yeah that is a shame.

It has a bluetooth interface and can talk to your VESC, so it is pretty well featured for a BMS.

It looks too small for discharge BMS on a dual motor 6374, that carries a lot of current and needs lots of heatsinking.

This to me looks like a charge only BMS, as this is how most of the DIY esk8 world run their boards.

I did start with a 120A Daly BMS, but it got ditched in the first rebuild, as it was way too chunky and heavy.

The BMS will still balance and alert you of problems. So this sounds like a winner, although maybe not quite what you expected.

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Yea I’ll go fuse shopping tomorrow if I find the time. I just looked up that BMS of yours, its huge! I don’t think I could fit that anywhere.

Speedict did intend the BMS for discharge, but perhaps their OEM project was for a hubmotor board or the likes.

I’m also wondering if I should have got 140 kv motors. I was expecting 12s and 63mm motors would have rocked the socks off my evolve boards 5063 motors but the starting torque hasnt been great yet. I don’t know how much can be gained with VESC tool yet, but maybe best to get that BMS out of the circuit first anyway.

Cheers, TIm.

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12s and 6374s are powerful enough.

It’s true they can feel a bit weak on pull-away. But as soon as they are spinning, they will rock your world. They will leave your evolve in the dust.

If your Torque is too low, see if you can reduce your motor gear by a tooth, that will help you get the wheel torque you are looking for, but probably isn’t necessary once you get used to the feel of your new ride.

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Yeah, I think some has to do with the VX2 controller as well. There is a time based ramp up on the throttle I cannot remove. Perhaps a PPM alternative such as the Hoyt might allow more tuning in VESC tool.

I’m only using stock evolve 32 tooth gears, so can get some steel 5m gear bar machined or any tooth count if it comes to it, and they’ll last forever then too. From what I can tell 6374 motors top speed is crazy fast more than I need anyway.

Actually, its evolves Hadean release that got me finally pulling finger and jamming a modded board together. Evolve’s the only board available here in NZ from what I can tell.

Been trying to read up on BLDC control since VESC fails hall effect detection in BLDC. I’ve noticed the flipsky motor hall effect sensors are not at equal phase angles from each other. I tried two Flipsky 6374’s, and 6384’s so far.

Speedict opinion is still that the BMS should work too. I considered building a C-L-C line filter to lessen current spikes but came home with a couple 200 Amp fuses instead. That time is better spent skating or beer drinking. I’ve got about 2500 cells and my own life is worth more than the batteries! As you say, still a small form factor cell balance and charge controller. It reports VESC temperare and duty over bluetooth as well, but having it and the vx2 remote doesnt leave a spare UART for a VESCtool bluetooth adaptor. There’s a communal UART on the same pin header as the PPM interface but I couldnt get that to work for the BMS so don’t know if it’s useful for bluetooth dongle - probably not.

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Hi Timmy,

If you are only using 32’s, you may be able to go up in the wheel pulley, that would be better than smaller on the motor. If you can get up to the 44’s, it’ll get more torquey, maybe have a look next time you’re wheel shopping.

You can plug your BMS UART into the second controller port. That still has to a VESC UART, so will read you out most useful information, although sometimes you need to program the settings to that one over USB (to make sure wheel speed is correctly scaled for example).

In the main power cables? Please don’t, I think it’ll only make things worse.

Increasing the capacitance as close to the VESC as possible, and reducing the resistance to your battery will give you a better improvement.

You battery is like a big reservoir, you want the VESC to be able to access and offload the power as quickly as possible (to avoid voltage changes), adding an inductance here will only impede the ability for electricity to flow.

Yea my plans basically now just to get some more screenshots on the scope over the bms, to send feedback to speedict then that thing gets bypassed. I expect all will end well.

I’ll look into bigger gears and belts. Evolve do 36 tooth plastic gears and belts if I can’t find anything else.


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Your’re right about leaving the evolve runnin gear for dust! This thing is mental! I’m about 6ft, and can’t help but get the impression after riding it, that above 50kmh the GT bamboo deck with my vesc in the box on top might be a little too short.


Above 50kmh, everything is a little sketchy. :rofl:

I was amazed by how narrow the trucks are on the Evolves, the wheels are so damn close together, especially compared to my ATB trucks with similar wheels.(Trampa / MBS / L-Faster)

I went asking around or good decks for esk8s, and everyone kept suggesting 42" beasts, I ended up going for a 39" It’s still a massive deck, I think I can still get roughly your setup all mounted in a box underneath.


Mr Louis_bro,

That board and enclosure looks bang on. Are those cloud wheels any good? I’ve only ridden 97 urethane up til now. (Evolve on AT wheels felt too narrow, gutless, and boring - I actually don’t see how a street board and an AT board can be the same board).

I’ve emailed a guy, https://www.eboardsperu.com/product-category/enclosures/. I’d reather just pay for an enclosure than take the time to make it at the moement. I was just looking at those landyuchtz decks too, they look alright - and they plant a tree for every board sold which I think is good.

BMS did good today, it’s just not so good when the battery is fully charged. I’m hoping Danny can get some firmware ammendments made and I think it could actually be an excellent product. It’s still V1.0, and a new model.

After taking the VESC for a ride I think I no longer want the new evolve either. Vesc felt like it was at only half power doing 54kmh, even on 107’s and with 32t belts it got up and went. I’m actually a little scared of it - probably better to keep the evolve for going out drinking! The VX2 remote I’m sure dulls the throttle response from off the line. The evolve which is what I’m used to smacks out full current as soon as the triggers pulled.

I don’t see many other eskaters here. I think I could count a maximum of four other people ever, and all on evolves, never met anybody else yet who knows what a VESC is even.

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