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Interest in Charge Doctor-like device?

Interest on a Charge Doctor-like device?  

32 members have voted

  1. 1. Are you interested in getting a Charge Doctor -like device?

    • Yes, if the price is same or lower than current Charge Doctor (around 25-30€/$)
      16
    • Yes, if the price is same or slightly above the current Charge Doctor (say, <35-40€/$)
      10
    • Yes, and willing to pay more if there are more/better features than current Charge Doctor (~50+€/$)
      12
    • Yes, and willing to pay more if there's a mobile app for monitoring charging (>50€/$)
      11
    • I could donate MONEY to the cause if the device was Open Source Hardware / Software
      9
    • I could donate SOFTWARE/HARDWARE DESIGN to the cause if the device was Open Source Hardware / Software
      2
    • No, I don't feel I need to monitor my charging
      6


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10 minutes ago, esaj said:

A few other ideas

Maybe skipping the LCD Display and just using an android app over bluetooth could greatly reduce assembly time and costs? No buttons - just maybe an (multicolor) led for showing some operation modes.

Although its very handy to have immediate readings and operation mode switches, about everyone has a mobile phone around ... And the less work you have the higher the probability of a long term solution? And a small uncomplicated pcb maybe even could be ordered assembled?

Maybe dimensions work out to fit it with the two connectors in some "tube" and "close" it with hot glue?

So they only real "work" needed is a function test, the calibration and repackaging for shipment.

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3 minutes ago, Chriull said:

Maybe skipping the LCD Display and just using an android app over bluetooth could greatly reduce assembly time and costs? No buttons - just maybe an (multicolor) led for showing some operation modes.

Although its very handy to have immediate readings and operation mode switches, about everyone has a mobile phone around ... And the less work you have the higher the probability of a long term solution? And a small uncomplicated pcb maybe even could be ordered assembled?

Maybe dimensions work out to fit it with the two connectors in some "tube" and "close" it with hot glue?

So they only real "work" needed is a function test, the calibration and repackaging for shipment.

Just updated the post with the bullet-point about "Multiple buttons and menus instead of a single button (still, the basic "one-off" charging should be as straightforward as possible, this is just for adjusting things and such)" as you posted this. Making an app for a mobile phone adds considerable time to the development, but I wouldn't be against it really, still, that might be a point which pushes it more towards the open source -approach, as likely I'd need more people working on things. I have made Android apps before, but a single person can only accomplish so much in a limited time, and I wouldn't want to drag this on for a really long time (plus I hate UI-design :P).

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Posted (edited)

Still modified the poll options a bit, added option for willing to pay more if there's an app for mobile phones, and added the the "donation" option to include software & hardware design. On the software/hardware -side, I'd expect the people to be professionals (@Seba comes to mind, both HW and SW :whistling:) or at least advanced hobbyists, not to be blunt, but this isn't exactly the kind of project to learn on the basics of either (chance of actual hardware damage and we've all seen our share of crappy software ;))

 

Edited by esaj
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Abusing my moderator powers, moved this to Mods & repairs -section, maybe it'll gain more visibility that way... :P

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Posted (edited)
14 hours ago, Pete G said:

I’ve been looking into this for a bit, found a few maybe’s but mostly just really expensive off the shelf items.

i did find this ⬇️ Which i thought quite interesting.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F232941753068

Yes, for plain metering (without charge cutoff), there are ready-made solutions available, something like this can be got for less than 10€:

s-l500.jpg

 

A custom-solution will be, unfortunately, more expensive, since there's no "economy of scale" and parts from actual suppliers are more expensive than eBay / Aliexpress / whatever (but at least you know what you get ;)).

It may very well be that so few people have interest in getting one, that it isn't even worth it (at least economically) to start pouring time into this. Even less if hobby16 makes a comeback with the existing Charge Doctor, or I find out that another existing solution is already out there :P 

 

Edited by esaj

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Charger could come with multiple connectors, most of us have multiple wheels. And connectors arent that expensive.

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Posted (edited)
On 6/25/2019 at 8:22 PM, lirva said:

Charger could come with multiple connectors, most of us have multiple wheels. And connectors arent that expensive.

It's not actually a charger, but a device that sits between the charger and the wheel, showing the accumulated charge (in watthours) and the current/voltage/charge time etc... still, the general idea was that there'd be "adapters" instead of fixed wheel-specific connectors, like with the Charge Doctor, so basically what I think you mean.

There seems to be a lot of pretty cheap Chinese "energy meters" around that already handle the measuring-part (voltage, current, power, accumulated charge), but I didn't manage to find any that could also cut the charging at a set current or voltage (there were some that had timing options or such, but needed an external relay to cut the charging). So maybe I was too quick to dismiss this idea (I edited one of the posts above, where I said I don't think it worth it), but we'll see how much time I can put into this.

What I had in mind was more of a "doing it from the scratch" -approach. I've opened up the Charge Doctor V2, and have a pretty good idea how it's done, however, for my "own approach", I'd just like a display without the metering built into it (like the cheap OLED-displays), do a separate charge measuring (basically either "just" a 0.1% precision resistor + differential amp + high accuracy ADC with oversampling or a current-sensing IC, this should already be more accurate than the Chinese meters with proper calibration) and cutoff functionality. At the first look, what the Charge Doctor does is use a pre-made energy meter hardware, likely with custom firmware, and a separate cutoff on the low-side through an N-channel mosfet (that's much cheaper than the dual P-channel high-side "ideal diode" cutoff/reverse polarity protection I had in mind).

I'm not saying Charge Doctor is "bad" (I still use mine every time I charge), on the contrary, it's a very clever design to keep things simple and cheap, and Hobby16 has done a lot of work to reverse-engineer and rewrite the firmware on the meter and add the necessary stuff to handle the cutoff. The adapter-idea is what makes me think I should actually cut the voltage entirely when the charge is to be stopped (it seems with the Charge Doctor, the high-side still carries full voltage, but there's no current flowing because the low-side is cutoff by the N-channel mosfet).

The downside of my idea is that it will be more expensive, because I need to add more and more expensive custom parts. Also the few people who have voted on the poll seem to be siding on the mobile app-approach, meaning a Bluetooth-module is needed (well, at least those are cheap  ;)), and a mobile app (it's been years since I last even touched mobile app-development)... First off, I don't have a Mac or iPhone or experience with Objective-C. so at least on my part, any iOS-support is out the window from get-go. Secondly, my graphics design- and drawing-skills are about the level of your average 5-year old... :D  I was thinking more like simple menus on the display and more buttons than CD (which has exactly one button) to make it easier to use, and more "features", like charge cutoff based on time / voltage / current, saving accumulated charge / cycle counts etc per wheel, warning of over/undervoltage (bad charger) based on selected wheel model and such.

From a hobbyist-perspective, the price and the time devoted is not that much of an issue, but I myself dont really need this... I can get by with the CD v2 just fine. :P From economical-perspective, there's not really much money to be made from this, it's nowhere near enough "mass-scale" product to make much money with (I don't think Hobby16 ever made that much money with the Charge Doctors either), it's a "niche-within-a-niche". There aren't that many EUC-riders, even worldwide, and only a fraction of riders wants a device like CD. If hobby16 comes back, most of that very limited crowd will pick the cheaper device.

So probably, if going forwards with this, the most sensible approach would be to make it open source, so people who have the time and interest can help along, and not think about the money-side of things at all. Maybe sell kits or premade devices to people who don't want to make their own from scratch. However, I only have a limited amount of time and energy, working full-time and doing some other work on the side, so that's why I was (and am) gauging the interest of people on this, doesn't make much sense to design a device and software for something that I don't really need myself and in which a very limited amount of people is interested in in general... 

Edited by esaj
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Could you send me a couple of photos of the internals of the cd? I havent got one to dismantle and, like yourself, i’m pretty sure its simple enough tbh.

The chinese meters though, some are ruff as hell but some are actually quite nice!

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Posted (edited)
15 hours ago, Pete G said:

Could you send me a couple of photos of the internals of the cd? I havent got one to dismantle and, like yourself, i’m pretty sure its simple enough tbh.

The chinese meters though, some are ruff as hell but some are actually quite nice!

Here you go:

9fukUv5.png

The "extra" board has the components and their values marked on silkscreen, so no need to figure them out. Close up:

NwIwplP.png

There are rigid wires running to the board of the meter on the left and right side:

Bmz4Z7J.png

Not seen in the last picture, on the right side, the 3 pins of the J2-"connector" go directly to the board underneath. No idea if there are more components on the other side of the board, I'm not planning to desolder it.

I haven't tried to trace the board to figure out the schematic, but looks like Q2 (BC817, NPN BJT transistor) is used to control the gate of the IRF540 N-channel mosfet. The blue and yellow wire coming from the dual charger connectors are likely the positive side of the charger(s), the black is negative. The other yellow wire coming in from the left side and going to the top right of the board is the low-side of the charger output, going to the mosfet for cutting the current and then likely running through the sense-resistor on the meter board, before returning to the charger inputs through the black wire. J3 is the serial output, S1 is the button.

No certain idea what the diode (1N1418) and the other NPN BJT (BCP56) + some passives are for, I'd need to figure out what connects to where, but don't know if I'll ever do that, as I'm not planning on copying Charge Doctor, and it wouldn't be of much use without the firmware anyway. Could be a stepping-down charge pump for the gate to keep the Vgs-voltage at correct levels when the mosfet is conducting, but that's just a wild guess.

 

Edited by esaj

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Said yes to the first three.

I wanted a charge doctor based on the knowledge here recommending to keep batteries between 20 and 90% for longevity in health.

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I ran some very preliminary calculations based on some very crude basic designs, and the bad news is in:

Quote

 

To sum up the above components price-wise, but these are very preliminary numbers:

  • Crowbar (might be left off):  2€
  • Voltage regulation: 5-10€
  • Charge cut-off:  maybe less than 5€ to more than 10€, depends on the type of mosfets, and if reverse protection is included (or a super barrier diode is used instead)
  • Current measurement (resistor + amplifier + possibly some other passives): Around 5€
  • MCU + crystals + caps: 3-5€
  • 0.96" OLED of Aliexpress: ~1.5-2€
  • Bluetooth module (optional): less than 2€ at cheapest, no idea of quality

This still leaves out:

  • A bunch of passives (mostly relatively cheap capacitors) that likely are needed, a few buttons, say 1€
  • Enclosure (no idea of the price, cheap small plastic boxes are likely <1€, but need to be cut by hand to fit the display and connectors/wiring)
  • All the connectors (if there's adapter both on the input and output-side, that's six connectors in total, if each costs about 1€, that's 6€ already)
  • Wires (doesn't cost much anything).
  • PCB (about 2.5€ per piece, ordered from Chinese fab-house with shipping and import taxes, basic non-ROHS)

It's still possible I've overlooked something here.

Not including the connectors (I'd have to dig closer to the prices) this already gives a price range of (cheapest options, no crowbar, no Bluetooth) 23.50€ to (all the bells and whistles, most expensive options above) about 40€, + how much ever the connectors cost for either option. That's just the parts, no assembly included ;)

Now, the prices do drop when components for more than one device are bought at a time, but the reductions vary between components (looking at the earlier commercial project, the difference per piece if buying for 1 vs. 10 devices at a time was about 20%). To make it much more significant, probably would need to buy the components for at least a hundred or 1000 devices, an amount for which there likely isn't even a market out there.

 

So, looks like this can't really compete with CD on the price... Of course cheaper options and sources could be looked for, Mouser certainly isn't the cheapest distributor.

More details here for those who have interest:

 

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Enclosures are expensive (from my experience). If you go low volume, 3d print them. This allows you to design them exactly to spec and it will make assembly a lot easier.

If you need any help with that I'll be glad to help. I just made a custom enclosure for a 12V DC power supply with integrated replaceable fuses and wires going in and out, for an on board camera in the race car.

 

And about that price: you don't need to compete with CD on price, if CD is no longer in business.

 

I feel like the early 2000's again with my wheels. Each of them has a different connector and a dedicated charger brick. What a mess ....

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Also, concerning the BT module. Why is that needed? I would take time to write custom software on iOS and Android to support that, to do what exactly? Seems to be more expensive to add that than do all the rest of the project.

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Posted (edited)
On 7/3/2019 at 2:11 PM, ir_fuel said:

Enclosures are expensive (from my experience). If you go low volume, 3d print them. This allows you to design them exactly to spec and it will make assembly a lot easier.

If you need any help with that I'll be glad to help. I just made a custom enclosure for a 12V DC power supply with integrated replaceable fuses and wires going in and out, for an on board camera in the race car.

3D-printing is an option, but isn't exactly cheap at least for low volumes if outsourced, a friend's company just had low volume of enclosures made for a custom device, the price was something like 30€ per piece, and the enclosure's not big. But they use "professional" machines, which are a hell of a lot more accurate (and expensive) than the cheaper DIY-stuff. Then again, low volumes could be printed at home, and that's (relatively) cheap, but it takes a lot of time (at least on my crappy printer :D).

 

Quote

And about that price: you don't need to compete with CD on price, if CD is no longer in business.

That's the question, is it (he)? The site is still showing the 'Notice: “buy” links are temporarily disabled. Please get back in about one week to buy again. Thank you.' -message that's been there for at least a couple of months. Judging from the poll results, most people are interested only if the price can be matched (same or lower, round it to 30€ with shipping to customer), or if there's a mobile app (thus also the possible BT module). If hobby16 comes back from the dead (not literally, I hope he's ok :P), there's apparently not much market for the "plain" device without app-support at higher price (even if it's more accurate / with more functions / easier to configure for charge cut-offs etc). Why the app makes all the difference, I can't say, (actually, checking the latest poll results, the "higher-end" model for higher price has as many votes as with app-support, but still the cheapest option takes the lead, of course there's so little votes that nothing certain can be really said) then again my smart phone usage is pretty minimal, I actually used Wheellog for the first time ever yesterday, and haven't used the KS-app with the wheel but maybe less than 5 times in over two years, despite riding at least commutes every weekday 10+km each way (well, not in the winter obviously).

 

Quote

I feel like the early 2000's again with my wheels. Each of them has a different connector and a dedicated charger brick. What a mess ....

Yeah, that'd also be somewhat of a problem, as I don't know all the connectors or their polarities (EDIT: Hobby16's site actually has the connectors and polarities, at least for older wheels, problem at least partially solved). The idea was to put "some" good connector on the device itself (say for example XT60, but that's overkill and a bit "too tight" if/when the cable needs to be changed), and then add adapter-cables between the charger, device and the wheel, like:

Charger: GX16 <-> XT60 : Device : XT60 <-> GX16 : Wheel

Charger: Lemo-plug <-> XT60 : Device : XT60 <-> Lemo-plug: Wheel

This way, the devices wouldn't have to be separately made for every wheel, just the adapters (as long as the circuitry can work with a large enough voltage range, about 40-101V for 15S-24S, including minimum and maximum voltages, which shouldn't really be a problem with correct components).

 

On 7/3/2019 at 2:14 PM, ir_fuel said:

Also, concerning the BT module. Why is that needed? I would take time to write custom software on iOS and Android to support that, to do what exactly? Seems to be more expensive to add that than do all the rest of the project.

Earlier in the thread it was suggested that instead of a display, a BT module could be used to communicate with a smart phone, and the display could be replaced with an app. Still, I'd personally prefer just plain display, so at least display, possibly (optional) BT-module. The BT-module isn't that expensive, as long as it's bought from eBay / Aliexpress, but finding a "good" module with low price and a trustworthy source could become a hassle.

Developing software is "free" unlike hardware, but it takes a lot of time (for which a monetary value could be calculated, but it would be just depressing ;)). I've never touched iOS-development or Objective-C, don't have Mac, iPhone or such, so iOS would be out the window if writing the software comes down to me. Last time I wrote Android-software was with Wheelemetrics, and that was 4 years ago :P If going Android-only, something like Wheellog could be used as a base (or just add support to Wheellog) to get going faster, but I'm not really keen on the app-idea in general.

So... if going forward with this project, I think the most sensible thing to do would be make it open source hardware/software (firmware, maybe the app?) and just sell parts kits and/or prebuilt devices for those who don't want to deal with the hardware-side on their own. I thought of keeping it closed source, but what's the point? Those people who'd build their own from an open source design wouldn't probably buy a pre-made device, and open source does have a lot of good sides (lot more eyes to notice mistakes and problems, and perhaps aid in the sw/hw -development in general).

It's not a gold mine either way, there's not that many riders even worldwide and out of those, only a select few even want to monitor / control their charging, most just plug it in and wait for the green light. ;) While it can be an interesting project on its own right, HW-development can't be done without putting real money up front (parts, boards, shipping) and a lot of time there too (design, build, test). If going towards the more "high-end"/"over-engineered" -solution, the prototype part costs (when buying components in singles / small amounts) can easily mean several hundreds of euros out of my own pocket and 100+ hours of work before the first "proper" prototype is even made (when working on your own time, meaning not a huge amount hours can be spent per week with a day job and other stuff). The question then is, can the sales for a "niche-within-a-niche" -product ever even cover the development costs, if there's something like 10-15€ margin per device... and unlike with software, the sold units still need to be soldered, assembled and calibrated by hand, could be like an hour per device? :D I seriously doubt there'd be anywhere near enough interested people to go for factory assembly (never done it, but I've heard usually it's a total mess at the start and not that cheap again for low volumes).

I'm still on the edge whether I should do this or not, although I do have already started to look out for suitable components, but the price is hard impossible to keep as low as CD without relying on Chinese prebuilt stuff.

 

Edited by esaj

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4 minutes ago, esaj said:

3D-printing is an option, but isn't exactly cheap at least for low volumes if outsourced, a friend's company just had low volume of enclosures made for a custom device, the price was something like 30€ per piece, and the enclosure's not big. But they use "professional" machines, which are a hell of a lot more accurate (and expensive) than the cheaper DIY-stuff. Then again, low volumes could be printed at home, and that's (relatively) cheap, but it takes a lot of time (at least on my crappy printer :D

That's ridiculous. I mean I understand their costs (I printed some parts for a friend of mine that needed them for his business and I also charged something like 50 euro / piece), but there is a difference between doing this in the community and trying not to operate at a loss, or making a viable business out of this. I think it would take about 6 hours to print one enclosure (if I take into account that it's a 2 part enclosure that screws together) and everything will just fit into place, making assembly a lot easier than having to modify a generic plastic box.

What you say about software is correct, but don't underestimate the "time" component. I am a freelance software developer (I know my way around iOS ;) ) and I can tell you that doing Android is maintenance hell. You'll get stalked by people that contact you with phones you've never heard of on which your software bugs. If you don't have a "device farm" to test on it's a real nightmare, compared to iOS. It just never stops. In your case I would do the strict minimum to get a safe product and call it quits. Better have something basic that works instead of something fancy that never gets finisheł. Also it is not your forte, so you should concentrate on doing what you do best, or it will take even more time. I like to tinker with hardware myself but building a product that can be commercialised (even at small scale) would take me so much time I'd never finish it. Software on the other hand I can and do deliver.

And then there is also the legal aspect of selling hardware without any CE certification + the fact that if you sell hardware you need to be registered (in every country separately, I kid you not! Long live the EU...) with their local recycling services (Google "WEEE directive") since sellers of electronic goods are responsible for the recycling process of said goods. This can be done in several countries by registering with a government instance and paying that instance a fixed fee (defined by type of product) for each unit sold in that country, to cover its waste and recycling costs. This is where stuff gets complicated!

 

If you want to go on with this project I would suggest:

- design an enclosure yourself so it can be printed

- open source everything

- ask for donations to recup some of the costs

- build some examples

- don't go launching an official site to sell this stuff

Building hardware and getting paid for it is a nightmare IMO, if you want to do it legally.

 

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Posted (edited)
48 minutes ago, ir_fuel said:

That's ridiculous. I mean I understand their costs (I printed some parts for a friend of mine that needed them for his business and I also charged something like 50 euro / piece), but there is a difference between doing this in the community and trying not to operate at a loss, or making a viable business out of this. I think it would take about 6 hours to print one enclosure (if I take into account that it's a 2 part enclosure that screws together) and everything will just fit into place, making assembly a lot easier than having to modify a generic plastic box.

Yes, I can definitely see the good sides in using a purpose-built enclosure. But if I'd be selling an entirely pre-made device, the cost of making the enclosures could make the price even more off-putting to the few who'd be interested in the first place. :P  I doubt a viable business could ever be built around this product alone, unless a lot more use cases outside wheels can be found, and even then, there are cheaper options (like said before in this thread, without the charge cut-off -feature, basically a 5€ Chinese meter can handle the job if you don't care that it's likely not very accurate, 15€ for the one that already has BT + an app).

 

Quote

What you say about software is correct, but don't underestimate the "time" component. I am a freelance software developer (I know my way around iOS ;) ) and I can tell you that doing Android is maintenance hell. You'll get stalked by people that contact you with phones you've never heard of on which your software bugs. If you don't have a "device farm" to test on it's a real nightmare, compared to iOS. It just never stops.

I worked before for a mobile games company for 7 years as a software developer / architect (mostly designing and coding the plethora of clustered backend-systems, designing the binary protocols, databases, server admin, some Blackberry/HTML5-games etc etc.), so yes, I know software and the maintenance hell of Android and the clusterfuck of devices in the ecosystem. We had between 2 and 6 full-time testers and shelves full of different Android-phones, and there was always some issue with some device... the graphics-department was going nuts with the amount of different resolutions and aspect ratios that needed to be supported, especially on games that had "pixel perfect"-graphics, meaning everything in a single game needed to be scaled correctly to each resolution, and UI-layouts needed to be designed separately for each aspect ratio. It was pretty crazy.

I'm not that interested in dealing with software these days on my own time, I used to code a lot on my own time in the late 90's/early 2000's and when studying to become a software engineer, nowadays, not so much... ;) The reason is that I "get" to do it all day long at my work, although nowadays I've switched from (mostly) backend to embedded to keep things interesting, but once you do something day-in, day-out for living, after a decade or two, it's not that "fun" anymore :D

 

Quote

In your case I would do the strict minimum to get a safe product and call it quits. Better have something basic that works instead of something fancy that never gets finisheł. Also it is not your forte, so you should concentrate on doing what you do best, or it will take even more time. I like to tinker with hardware myself but building a product that can be commercialised (even at small scale) would take me so much time I'd never finish it. Software on the other hand I can and do deliver.

Yeah, but even the strict minimum (at least on the standards I set myself :P) is a somewhat high bar. I guess I put too high expectations on myself, especially since I'm not a professional electronics engineer... ;)

I've sometimes thought of switching to electronics for living, but I've already ruined game programming (and probably soon, embedded programming :D) for myself as a hobby, so probably I shouldn't go down that route... :efef2e0fff: Besides, at least for most positions, software seems to pay much better (of course it's a different thing if you're something like a RF-design guru) and electronics engineer positions seem pretty rare, whereas there's so many open software positions that you get spammed by recruiters.

 

Quote

And then there is also the legal aspect of selling hardware without any CE certification + the fact that if you sell hardware you need to be registered (in every country separately, I kid you not! Long live the EU...) with their local recycling services (Google "WEEE directive") since sellers of electronic goods are responsible for the recycling process of said goods. This can be done in several countries by registering with a government instance and paying that instance a fixed fee (defined by type of product) for each unit sold in that country, to cover its waste and recycling costs. This is where stuff gets complicated!

If you want to go on with this project I would suggest:

- design an enclosure yourself so it can be printed

- open source everything

- ask for donations to recup some of the costs

- build some examples

- don't go launching an official site to sell this stuff

Building hardware and getting paid for it is a nightmare IMO, if you want to do it legally.

Yes, I know, that's why I'd have to sell them, ahem, more "unofficially" (which already is illegal, but do you think hobby16 has a company? AFAIK, the CD's are paid for through private personal Paypal-transfers...). Although, that might also be a reason why he quit (if he quit), if the government started snooping around  :P   If going for the full CE-stuff etc, there's no way this would ever be viable, the EMI/EMC-certification tests alone cost several thousands per product (and need to be done separately for EU, North America, Australia, probably a dozen other countries / geographical areas), and that's IF it's an "unintentionally radiating device", if it has BT or other wireless communication, the number I saw started from $12000 for North America per attempt (if it fails, try & pay again!)... then there's setting up a private LLC, which is something like a minimum of 2500€ + lawyer fees here etc. etc. It would NEVER cover even the set up costs. So no, doing this "legally"/setting up a company for this is pretty much a financial suicide. 

EDIT: There are exemptions to the EMI/EMC-certification for example, if memory serves, things like the "modules" for Arduinos or Raspberries and such (that are not "fully built consumer products" or how should I put it) aren't required to get the certifications and can be sold without.

 

Edited by esaj

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I could make a HW design of such device, using one of Nordic Semi nRF52 SoC and share it under open-source license. I specifically stated nRF52, as this is proven, quite cheap and capable ARM Cortex M4 based SoC with integrated BT. It would act as advanced meter/logger or charger controller, standalone or built into stock charger. It could be equipped with OLED display with some buttons, and at the same time would be controlled or monitored by some Android/iOS app. However I'm too busy to take role of SW developer.

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Depending on the amount of features, developing a basic iOS app that communicates with the device over BLE will not take much time. If our minimum standard is the average Chinese EUC app it will even look better :lol: . I might be able to help there.

Android, can't help with that.

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So yeah, if this goes somewhere ping me. I did a few iOS apps that communicate with BLE devices, so I have some code around for the "hard part". The rest is just slapping a GUI on it.

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Been looking for a random chinese version that might work, and came up with this.

Using a PZEM-017 with a 100A shunt - for monitoring the charge levels, amps drawn etc etc, with an esp8266 this can then be connected to a laptop via a small dongle. A two wire display can give a general readout from the pzem017 and the whole thing can be programmed using their own system, they already have a programming interface to use, i think it was modbus but i may be mistaken.

Last bit to find is the cutout and should work! 

If you have a look at your photos and the rear of a pzem017 it does look very similar to the bottom level board we cant see much of, just with an internal shunt....

Also, the pzem-051 also looks very similar and also has the adjustment button.

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Posted (edited)
19 hours ago, Seba said:

I could make a HW design of such device, using one of Nordic Semi nRF52 SoC and share it under open-source license. I specifically stated nRF52, as this is proven, quite cheap and capable ARM Cortex M4 based SoC with integrated BT. It would act as advanced meter/logger or charger controller, standalone or built into stock charger. It could be equipped with OLED display with some buttons, and at the same time would be controlled or monitored by some Android/iOS app. However I'm too busy to take role of SW developer.

Didn't come to my mind to use a SoC, but why not? Looking at TME, the dev board for NRF52 is a bit expensive (54.93€ + VAT, so almost 70€ for me) (EDIT: there's also a USB "dongle" dev-board that's much cheaper at 16.83€ + VAT, less I/Os?) , but the chips themselves aren't (3€ and change + VAT for NRF52810 or 11, pretty much half the price at TME vs. Mouser EDIT: I was probably looking at wrong model in Mouser, it's about the same there) . At that price, might be better to just build a board for it directly and use SWD for programming (assuming it can be programmed over SWD?).  TME has very poor selection in instrumentation/current sense amplifiers, and pretty much no sensible options in high voltage buck-controllers, so Mouser is probably a better choice (plus you get free shipping from Mouser for orders over 50€).

I was originally thinking of Cortex-M0, since they're dirt cheap, and nothing really complicated or fast should be needed, mostly just for the 12-bit ADC (and more than enough I/O and speed). Otherwise ATMega328P probably would be just fine, about the same price, and it would be more useful for Open Source (lots more people capable of working with Arduino rather than ARMs), but the 10-bit ADC might be a bit too low for accurate measurements, if the measurement range is (say) 0-5A. OTOH, the ATMega has separate VREF for the ADC, so a precision voltage source could be used for that + amplifier to minimize error in the ADC-side and maximise the "use" of the voltage range.

I've used ST's Cortex-M4's before, so I guess it can't be much different, since it's the same architecture. No idea if Atollic Truestudio works with other than ST's (it's outdated anyway, I think ST has already suggested to move to CubeIDE), and I've "cheated" by building the project base and system setup through CubeMX (clocks/pinouts/ADC/CAN/DMA/whatever is needed), so might have to look up the datasheets ;)  Unless there's a nice environment / tools available for the Nordic chips.

The circuitry should otherwise be relatively easy, my biggest "concern" is getting the analog-side "right", so that SMPS ripple or digital noise won't couple in the measurements, and to keep the error as low as possible (I'd bet far less than 1% error can be attained with good instrumentation-, differential- or current sense amplifier + low-ppm sense-resistor + possibly filtering (charger noise?) + manual calibration). What I'm most lost with, is the "correct" (ground) layout and tracing between digital and analog plane, getting low ripple out of an SMPS is mostly a matter of high enough inductance and sticking enough (low ESR) capacitance on the output, plus probably the amplifiers already have high PSRR (+ bypass caps on power rail). If need be, linear regulator or precision voltage source (assuming the amplifier doesn't need much any current, like they usually don't).

Considering it's pretty much established that this has no real commercial potential, the component price shouldn't be that much of an issue. People who want to tinker with stuff like this will build their own, and there the slight difference in price probably won't matter as much.

 

18 hours ago, Pete G said:

Been looking for a random chinese version that might work, and came up with this.

Using a PZEM-017 with a 100A shunt - for monitoring the charge levels, amps drawn etc etc, with an esp8266 this can then be connected to a laptop via a small dongle. A two wire display can give a general readout from the pzem017 and the whole thing can be programmed using their own system, they already have a programming interface to use, i think it was modbus but i may be mistaken.

Last bit to find is the cutout and should work! 

If you have a look at your photos and the rear of a pzem017 it does look very similar to the bottom level board we cant see much of, just with an internal shunt....

Also, the pzem-051 also looks very similar and also has the adjustment button.

100A shunt for charging is a "bit" excessive, there seems to be a 0.01-10A version (PZEM-003). Claims 1% measurement accuracy.

Edited by esaj

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6 hours ago, esaj said:

I was originally thinking of Cortex-M0, since they're dirt cheap, and nothing really complicated or fast should be needed, mostly just for the 12-bit ADC (and more than enough I/O and speed).

I was thinking about nRF52 as this SoC family offers integrated BLE transceiver and BLE stack that is free to use without any licensing fees. I have used this family in several designs and I have good experiences.

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