Hey, if it works and you can get the data you need, it’s a perfectly good setup/test! Aesthetics can come later (function over form). KISS for now 
Btw, depending on where you are, I love to help print and ship you an enclosure!
I like the idea of multiple configurations/models but I don’t think modularity is a good idea if it will come at any cost of efficiency, and I mean this in the broad way. Space, price, quality, etc… Which I think it will, no?
The main groundbreaker for me is a good & smart (and leaning toward cheaper) discharge only BMS. There isn’t a good option until now.
I can’t give enough likes… 
Do you have a thingiverse account? I’d love to print some of your creations
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Sorry, don’t have a thingiverse account 
I’m also doing some class D audio amp designs alongside audio op-amp filtering for those speakers of mine. Below is an amp board meant for that two-way speaker, board also has op-amp crossover to separate the highs and lows, bass boost and dedicated class D amps for both speaker drivers. The board is meant to be powered from a single cell lithium battery and has a boost circuit to raise the voltage to ~12V for higher power/volume.
The yellow mono speaker actually has the same amp board inside, but only uses one of the amp ICs and I did some jumper tricks in the op-amp section to use the bass boost, but skip the cross-overs. Sounds pretty decent, but is still a bit lacking in the lower bass.
I want to make super meaty ghettoblaster/boomboxes now and I’m looking into higher power amps, more complex audio EQ/filtering/DSP setups and higher voltage battery packs to integrate into the enclosures. This is also one place where I would see a lot of use for the USB PD implementation charging wise.
But I’m gonna head to bed. Need to wake up earlier than today and finish assembling those 7 boards and start doing the rest as a batch after that.
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Update on the tester boards.
7 are done and I have started on 8 more, but I unfortunately ran out of 100nF ceramic caps and 4R7 resistors, so I can’t assemble them completely at the moment. I’ll prep them partially meanwhile waiting for the missing components, so I’m not completely wasting time.
I’m gonna order more of them and couple other components, but this is the first I’m gonna order a full reel of any component. Always ordered cut tapes before, but this is a pretty common capacitor value, so it just makes sense to order it in larger quantity to save some money.
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Yeeeww! Ramping up!
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Can I call first for when these actually come out?
Diebiems wont fit my build, so this is my best option 
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Im also in for one!
If the beta test goes to plan, when can we expect them to be out for the public? And will the price point still be around 40-60€ as mentioned over on .builders?
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I would guestimate a realistic schedule to be that I’m going to be working on the FW and testing the HW of the Lite with the testers for the rest of the year and maybe at the beginning of next year will step-up to first production batch, given that FW is in good state and HW has been found to be good.
If one or more of the testers back out of tester role, then I’ll inform about it in this thread and open the tester application form again to find new testers for the spare boards.
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I hope I don’t come off as greedy or anything but do you happen to have any extra boards? I’m wondering for testers such as myself with a single board, if I/we make a mistake, I/we can no longer contribute. I guess that’s why you have so many testers though but I’m wondering if there’s a contingency plan?
edit: As I write this, I feel kind of silly to worry because we’re all suppose to be knowledgable around electronics here haha
Sounds good to me, my board for this BMS wont be done for a whiiiiile
Update. It’s been an annoying week. I’m gonna vent, this post might be a bit lengthy.
Had a bit of a headache with Digi-Key, which hasn’t happened in a long time.
So, I submitted the order for the lacking components at the end of last week on Sunday. Received an email from Digi-Key on Monday asking on the line of: “Is this order an individual or company order? Order will be on hold until we receive all this information.”
This confused me a little bit as they have never asked that before via email, as your Digi-key account tells them which one you are. In hindsight I think they may have asked that, because I was ordering stuff by the full reel and shipping it to my workplace’s office where I can be present to receive the shipments during the day. So they may have wanted to confirm that it was to me, an individual and not to a company.
I think I didn’t reply that day, but I received a Digi-Key invoice email later that evening with an UPS tracking number, so I thought they had figured out the problem out by themselves and shipped the order. Next day I got an email from UPS for a permission to sort the order through customs. At this point I thought for sure that it was the component order and everything was fine.
Received the packet on Thursday. Opened the packet aaaaaand… It was only the solder paste that was sent for the mistakenly sent solder flux a week before. Ok… So they actually had put the component order on hold, just like they had said. Very quickly I then responded to the question email that the components were for an individual order and for a hobby project.
Then, when I was on a walk Friday evening, I received another email from Digi-Key with topic line of “Your credit card has been declined”. What the f***. I guess they couldn’t charge my debit card anymore as I had originally placed the order on Sunday, it was now Friday and I had cleared the question for which they had placed the order on hold. I just needed to select my payment method again.
But yea, I got the solder paste that I wanted, but I didn’t get the components that I needed this week…
Welp, checked the UPS tracking for the components order and it now had the estimated delivery time on Monday of next week.
Digi-Key wasn’t the only one who I had problems with shipping things this week though.
I had ordered my new smartphone on last week’s Tuesday with an estimated shipping time of a week. Cool, everything kosher. It didn’t come this week’s Tuesday though, not on Wednesday either, but at least they had the courtesy to send me an email on Thursday to inform that they don’t have the phone in stock and it will be another 2 weeks before it will be here… Motherf… Son of a … a week my ass then. I wouldn’t have ordered it from them it they would have indicated that they don’t have it in stock…
Shot the customer support and email back asking if they have the same model in stock in a different color, but seems they reserved the courtesy to not respond to my query… I sent the question to them on Thursday before noon as I had received the non-stock status couple hours earlier in the morning… So now I’m a bit of a limbo, because they haven’t responded. I would have been cool to receive another color of phone and if they said they don’t have any colors in stock I would have cancelled the order and went to a local store to buy the same phone model immediately for 40 euros higher price (phone was 230€ at the online store, 270 at the local one).
I’m just fed up and I guess I’m taking the endurance defeat and I’ll just wait for the online store to get the phones in stock and ship them… What a frickin’ annoying deal…
Could you ship my boot to your bottom, thank you
Talking about shipping stuff, I sent the US guy who I’m working with on the FlexiBMS HV some boards also on Thursday. Pic below. I sent 2x bare HV boards, 2x bare 0.4 Lite boards, 2x fixed proto batch assembly 0.2 Lite boards and the debugging/flashing jig. I added stuffing to the box, so they didn’t fly around in shipping.
I had followed the post offices guidelines to the best of my ability to send a letter to the US, which means you have to put a customs declarations on the letter informing what’s in it. They had the CN22 custom’s declaration available on their site as a .pdf download, so I downloaded it, filled it, printed it and taped it to the letter. So far so good.
Walked to the post office Thursday morning (notice how everything clustered on Thursday ). “I got a letter to the states”. Well the cardboard packet that I’m using is literally right on edge between being a letter or a packet with it’s thickness, the letter size is much cheaper to send. The post lady pulls out the “letterbox/slot simulator”, which is a hole in a plastic frame. If the shipping container goes through it, it’s classified as a letter, if not, it’s either a packet or a Max-letter. Well it didn’t fit, but the interesting thing is that I had sent another letter last week using an identical cardboard box and the post lady that time had managed to get it through the “simulator” with a small amount of force, but alas this time it was a different lady and it didn’t “fit”.
Okay, not gonna make a scene (I will ask in the future, if they could try with a little bit more force). I asked what my options were and she recommended to send it as a max-letter. Asked what the pricing difference was, if I had been able to send it as a letter, it would have been 7€ in economy and 12€ in priority, as a max-letter it was 12,50€ and it’s automatically a priority letter, so I was fine with this.
Shipping stuff: The electric boogaloo
Now, at this point I thought I was done and I just needed to pay for the shipping. Lady: “Okay, gimme a second. I’ll print you a new customs declaration on the letter”. Wait, what? What’s wrong with the one I have taped to the letter?
“Oh, this is the old one. It doesn’t have a barcode on it like the current ones.” *shows me otherwise identical customs declaration form apart from a barcode being on the top of the form.
Okay, she starts filling the form on her terminal in Finnish and values in euros. The post’s website said the customs declaration needs to be filled in the receiving country’s language and currency, why is she filling the form in Finnish?! I hope that she is not gonna stick on top of my current one, I don’t want my letter to bounce back in the US customs. I ask her about this and she assures me it’s how it’s done… k
At this point it has been, I would guess 4-5 minutes, normal I would assume for this kind of interaction. Note that most of the post “offices” in Finland have been integrated in to local convenience stores and dedicated postal offices have been retired, with sorting center’s acting as their main hubs these days. Now in couple places this means that the store register and the post office front are a “one unit” in the smaller stores, with the attendee jumping between the store register and post office duty. This meant because my customership had reserved the only attendee there, the line was backing up on the register on the store side and I’m getting a line behind me on the post side because I’m trying to get my letter shipped and I feel a bit conspicuous, being the only one served at that moment. I just take a glance at everyone around me in the lines and just visibly shrug.
Okay, so surely this is it. I can get my letter sent? The lady can’t complete the filling process for the new customs declaration… She tries multiple times, but for some reason can’t advance in the process to be able to print the new declaration. Meanwhile lines are getting longer… At this point she at least asked for some help at the register via her radio. She starts pulling out instruction manuals and papers and looking at them on how to complete the process (to be fair, this seemed like something was fockin’ over on the software side on her terminal, so it really wasn’t her fault). At this point it has been I guess 10 minutes and I throw the possibility of coming over tomorrow again and they check what was wrong in the process, because I need to get going to make it to the bus.
“No need, I’ll mark the contents of the letter as “empty” so I can get the post’s tag on it and get it going. You do have a customs declaration on the letter (the one I printed), so it should be okay”. Okay, then what the f*** was the point in even making a new customs declaration for it from the beginning then?! Well whatever at this point, as long as this letter leaves now I’ll be happy. She asked me to take a picture of the letter just in case, as this did seem a little bit out of protocol.
I then had to run to make it to the bus…
Assembled the first HV board yesterday and I think it looks pretty dang neat. Have not started writing code for it.
Got started on the Kicad project for the USB-PD and QC compatible powerbank. I’ve been studying the USB-PD and QC protocols during the past week and looking at the physical layer control and implementations and feel like I have a good enough grasp on them to start moving onto design implementation.
Gonna assemble the Lite boards forward today.
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I have a question.
Most ESC will cut-off when the battery voltage goes under the set threshold.
What’s the line of defense of FlexiBMS Lite if only one of the series of cells goes very low but doesn’t trigger the ESC as the main voltage is still high enough?
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Ïf you’re using VESC and have hooked up it up to the FlexiBMS Lite via CAN-bus, then the BMS can inform the VESC that a cell or cell X has gone under minimum allowed voltage. The VESC can then start lowering the available power or cut-off acceleration completely and allow only braking. It’s all about how the software will be implemented.
If you’re not using a VESC variant with CAN. Then if there is a logic input for low battery voltage or something to allow to signal the ESC that battery is low, there are 3V3 logic outputs available from the BMS or a Opto-isolated output.
The Lite-version itself doesn’t have discharge path control, so it can’t cut-off the battery from the ESC, but it can used to signal the ESC about low battery, given that the ESC has some sort of input to read external signals.
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That would require changes to VESC FW. @rpasichnyk, are you going to do the FlexiBMS integration to Metr? If yes, would it be possible for Metr to detect the cell undervoltage and update the VESC settings such that it shuts down in a controlled way?
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Yes exactly that’s what I asked you to do on the thread from the dead forum.
I’m planning on using Unity, is that supported?
Have you actually put some code to handle this function?
And that’s a very good thing.
Many full blown BMS suffer from oversizing due to need to switch the main power, but still end up with max 150A which for some builds is a limit.
And why would you need to do that if ESC is a switch itself already…
If you’ll get your Lite BMS polished it will be how all future BMS will look/function like.
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I think this is too complicated. Either add a discharge functionality to BMS or don’t touch discharge at all.
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Obviously, youre the pro on the subject, but ignoring the sheer amount of code that would need to be added, could it be done? If implemented it could be a huge step up in the useability of the VESC and VESC based ESC’s in terms of esk8 reliability and useability
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Just a note.
I’m talking with a forum user via PMs at the moment about the possibility of adding more temperature sensors to the Lite. I don’t think analog sensors are really gonna be viable due to the difficulty of interfacing them, but I looked around and there are available options with UART- or I2C-interfaces and these could pretty easily be used with the 4-pin PH-connector, as it has I2C or UART connected to it.
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