DougM's winter project 2022-23

DIY Builds Battery Builds
#21

Cool build. You’re making me feel better about my very heavy and surprisingly large build!

Couple questions. Is the PCB something a never ordered a PCB type person like me can get? Looks like a better solution than the braided wire I’m using with my Delrin holders. Is the spacing between the packs to allow for flexing while riding?

If you don’t mind sharing - how much do you weigh? I’m surprised the extruded aluminum is strong enough to keep straight over time and not adopt a permanent bend. I like the idea but I’m 230 lbs. I’m using an aluminum plate between the ends to provide support.

Interesting solution to the pulley. I’ve had success using a 0.078 “ bit to mill pulleys from Delrin. I can’t recall off the top of my head who makes the bits but I can look that up if that’s helpful. They are quite long for such a small diameter.

Good luck with the completion of the build!

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#22

It’s not off the shelf, but I can send you the build files (Gerbers) as well as the STEP files for the holders. You can get a couple made via Osh Park or JLCPCB and play around with them. Bear in mind that some assembly (soldering) is required.

Delrin seems a bit expensive for your holders - I use HDPE, TAP Plastics brand name is Starboard. It’s cheap, cuts well and is pretty resilient.

I weigh 200. I’ve been building with 2020 extrusion from day 1 and haven’t bent one yet. But if you’re worried you can go up to bigger extrusion for the stretch under the deck - Misumi has 2525. But remember that you’re flexing both the aluminum and the Baltic ply so it’s pretty resilient.

I honestly don’t know why I started building the packs this way - certainly having flexibility between banks was part of it but I think I never liked the monolithic aspect of the way that regular packs are built. Plus I had all that interesting space between the rails to play with.

Thanks for the offer on finding the cutter but no need for now… I really want to see if these jigsaw pulleys work and if they do I’ll probably just keep making them that way because it uses so much less Delrin.

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#23

C- is a shared/common port for both charge and discharge. I believe the C stands for “Common”

#24

I put a meter across + and C- and got nothing, so I think maybe C stands for Charge, and on some BMS’s P- is the discharge port. But I could well be wrong.

#25

It could very well stand for Charge, but it’s still a common port. Most of the LLT bms use the C- for charge and discharge.

Was the BMS switched on for discharge?

#26

No, it wasn’t. I’ll try that. Currently there’s no connector on the switch PCB connection so I’ll have to add something.

1 Like
#27

You can switch discharge on/off via the app as well, you don’t need a physical switch

#28

I would if I could get the Bluetooth connection to actually work :slight_smile:

#29

I’ve had some before that i needed to flip pins on the wires to make them work. Could be something simple like that

#30

It worked twice, but over probably 100 attempts it failed to connect.

Maybe the better question is what BMS would you recommend? The LLT’s seem to have pretty good hardware but the software is sorely lacking, at least the Android App.

Thanks!

#31

The software does indeed suck, however I pretty much exclusively use LLT, the value for money is decent and i have had minimal issues with them.

One thing i would suggest is to make sure your phone isn’t bluetooth connected to anything else. Sometimes that helps.

#32

Also I don’t know what phone you use, but I think it doesn’t work under android 9 and you need to give the app background autorisation, if I remembre

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#33

FS2 is officially a wrap and ready for her maiden voyage! If I can just get a break in the weather. I did get a short break last week Thursday where in the afternoon it snuck up to a cloudy but dry 56 degrees. I was able to take FS1 (the daily driver upon which that this one is based) out and test with the new tires and the jigsaw pulley and it worked great.

But now, of course, looking at that board and looking at this one I can see where another project might be germinating - if I move the electronics around similar to how I have them on FS2 I can add another battery bank and turn it from a 10S to a 12S, and I can add an onboard BMS. So maybe that will show up on this build thread, though I do have adult spring projects lined up that I really should be responsible about working on rather than playing with my toys all the time.

Anyway, complete . . . with 2 minor exceptions.

I cut, drilled and installed the second blindingly expensive Carbon Fiber cover plate
I CNCed two new end caps
I put grip tape on all wood pieces
I designed, 3D printed, wired and installed the charge port and charged it up amazingly, with a charger I had in stock - a cycle satiator. Even though it’s a smart charger it doesn’t seem to argue with the BMS and I think I get a full charge between the 2.

The exceptions are: I still use Loop Keys - I like the safety aspect of physical electrical disconnection, but the biggest problem I had was continually losing or forgetting to bring the keys. So finally I just zip tied them to the frame. But on this board I can’t do that so I need to design, 3D print and install loop key retainer.

And the second is the volt display. Fortunately there’s a connector right on the Stormcore that gives you a full voltage output, but I don’t happen to have that connector in stock, so another Digi-Key and another week. But that gives me time to decide where to put it and design a slick new housing for it. Or maybe go to a different meter or mechanism. Still noodling.

I’ll report back after her maiden voyage!

As you can see from these photos there is a perfect spot for both headlights and taillights, which may come later. For now I’ll probably print some sort of cover plate.

Here are some glam shots:

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#34

I’m thinking for the next project of getting a BMS that DaveGa supports (DieBieMS, FlexiBMS, ENNOID-BMS) - assuming that avoiding fires is the biggest priority and cost really isn’t (whatever it costs it’s cheaper than a fire :slight_smile: ), which one would be your first choice?

Thanks,

1 Like
#35

:sweat_smile: i have concerns about all of the bms you just listed and unfortunately I wouldn’t recommend any of them

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#36

And just like that you are my BMS guru.

I’ll stick with the LLT and just assume it’s all working.

Thanks,

1 Like
#37

There have been some concerns recently regarding idle drain with the LLTs, but personally I haven’t noticed any significant drain from them on the stock settings.

Always a good idea to routinely check your battery voltage anyway and charge if necessary during storage.

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#38

I took the BT module off and have been watching battery levels - so far not much movement. But I’m running 12S5P of 5K Ah cells, so it would have to drain a lot before I noticed. But recommendation taken.

Thanks,

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#39

With the app you can set a notification should the voltage drop to a level that you want to know about. Also you can turn off the charge/discharge circuits for additional savings when storing.

Also make sure it’s not balancing down below 3.6v as this is going to drain total voltage so if a pack at dangerously low volts is still balancing it will die sooner.

Discharge port can be left off permanently when bypassing anyway.

30Q 18S7P pack survived over a year like this, it hit 3.3v iirc.

2 Likes
#40

The maiden voyage of FS2 was a complete success!

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The Stormcore was wonderfully smooth and predictable, the entire 10 mile run only took about 2V off the batteries and overall the machine felt great - nice and solid and easily as good if not slightly better than the machine off which it was based.

The only issue was that the brakes were way too aggressive, but that’s just a configuration change.

I’ll likely post some followup if I decide to make further changes to the board. At this point the only thing I plan to add is a small display (TFT) that shows me current battery V and current speed.

I’ll also likely both move and switch out the charge port. It’s too big and the space where it currently lives is much better served with a display.

So I’ve been looking at Anderson connectors, the kind they use on big battery banks

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Thanks everyone for following me on this build.

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