1 kW at 100V or 250V or similar uses a nice, small, flexible wire. It can be quite safe because it can be fused or otherwise protected at low currents, which mitigates the risk of welding things, starting fires, or arcing. Ground fault protection, arc fault protection, and general loss-of-isolation protection are available. It’s easy to rework (lever nuts! screw terminals!).
400A (or even 80A or so like in this article) is a whole different ball game. Sure, you have to work hard to electrocute yourself. But you can easily set things on fire or weld things together without coming close to blowing a fuse. And you need to protect both ends of wires in a parallel arrangement. And the wires are enormous, expensive, and hard to terminate.
I would much prefer one of three alternative designs to become popular:
1A: a series arrangement of batteries at a civilized 48V or so. You can do this with an aftermarket BMS, but they tend to be janky.
1B: same but actually high voltage (a few hundred V, like an EV)
2: batteries with microinverters and a civilized way to share current. A manufacturer could make a single package with a 1kWh battery, a BMS, a low voltage, low current DC auxiliary output, and a ground-fault and overcurrent-protected 110-250V AC input/output. And an RS485 or 10BASE-T1S or CAN connection so that they can coordinate their I-V characteristics to appropriate distribute charge or discharge current.
Now you can connect as many microinverter-batteries as you like in parallel, using #14 wire, to one ordinary circuit breaker per battery plus (depending on the overall arrangement) one big breaker to protect the common bus.
edit: Also, with this design, no one, not even the manufacturer, needs to touch a heavy-gauge wire. Everything in the battery would use cheap, painless busbars or small wires, depending on the internal voltage, and the manufacturer could set the voltage however they like. Although 12V internally might be entirely reasonable if the end user also wants to consume 12V at very low currents through the aux output.
12v is a miserable voltage to work with in general: too high for most logic circuits and for LDOs to work effectively but it’s too low for any large load with high-power applications become cost prohibitive quickly due to the cost of the conductors. Fun fact: Auto makers have gotten away with under sizing starter conductors, despite it drawing 80-100A, because it is only energized briefly and the length of the run is very short.
For GPUs and any USB PD connections ('standard' is up to 20V 5A while 'extended' is 48V 5A) a system power level of ~48v might be very useful. It would also give a chance to replace the recent higher density connectors that aren't designed with a sufficiently robust user experience with improved versions that more clearly lock into solid connection.
Pretty much the only PC part which wants native 12V would be the fans. All the other parts drop it down to 5V / 3V3 for auxiliary components, or 1-2V for the CPU and GPU cores - which use the vast majority of power.
Dropping 12V DC to 1.5V is reasonably doable, but dropping 48V DC to 1.5V is a bit of a pain. In general you do not want to go beyond a 1:10 ratio for efficiency reasons, so 48V doesn't really gain you anything, while at the same time resulting in a massive compatibility break.
The push to 12VO is driven by a desire to get rid of technical debt. The 3V3 / 5V wires can't handle the current you need on those rails, so those are converted from 12V anyways. And literally nobody is using the -12V and -5V wires, so keeping those around is pointless.
Note that simply voltage/frequency alone can communicate everything necessary to evenly distribute load. For example:
Output frequency = 60 + X Hz
Where X varies between -0.1 and 0.1, indicating the percentage of max load the inverter is under(in charge or discharge direction).
Such a scheme will self synchronize any number of inverters, even of varying capacities, into a stable grid, and they will all be the same percentage loaded. The grid can even have a few dumb gas generators on too and remain stable. No fancy comms needed.
Yep, inverters can easily read the frequency change to adapt their output. But a device that reads the network load and translates it into a frequency change is really not trivial. Grids do this because mechanical generators do that translation, but the easiest way to add it to a non-mechanical grid is adding a mechanical device.
Lines exclusively fed by inverters will naturally get undervoltage, instead of frequency shifts.
Also, can a pure frequency-based scheme handle the case where a whole bunch of inverters are in parallel and a load that’s much larger than any one of them can handle individually starts up?
The schematic looks to be pretty adaptable to higher driving voltage, just need separate 12V for control board. There is even one in datasheet for 24-36V operation
>2: batteries with microinverters and a civilized way to share current. A manufacturer could make a single package with a 1kWh battery, a BMS, a low voltage, low current DC auxiliary output, and a ground-fault and overcurrent-protected 110-250V AC input/output. And an RS485 or 10BASE-T1S or CAN connection so that they can coordinate their I-V characteristics to appropriate distribute charge or discharge current.
> Now you can connect as many microinverter-batteries as you like in parallel, using #14 wire, to one ordinary circuit breaker per battery plus (depending on the overall arrangement) one big breaker to protect the common bus.
You can build it right now. AC coupled batteries exist; here is some random one that scales up: https://www.fortresspower.com/ac-coupled/
The problem is that you generally want batteries when you want renewables and in that case just having one big box handling batteries and solar panels is more economical than microinverters everywhere
48V battery pack + BMS is significantly cheaper than same thing with microinverter, and when you scale up one big inverter is cheaper than a bunch of smaller ones.
So yeah, it is "best" but also most expensive way. And frankly, the hardest to develop, which is probably why there is little to no open designs for that.
Old car stereo trick, to power big amplifiers in the trunk: use a second battery and big power lead to it, small power leads from the main battery to the secondary. That secondary can be backed or replaced by big capacitors, too; with commensurate increases in cost and possible risks when things go wrongs. But you can provide rich chunky amps and use skinnier cable than you'd think on the long run to do it.
- you don't want a permanent connection between the main and aux battery to avoid accidentally sucking both batteries dry on the aux-battery side, and to avoid the starter overloading the cable between the two batteries
- you don't want to risk an empty aux battery charging itself on the main battery and engine with more current than the cable supports, hence the fuse
- you do want to be able to connect both batteries in a scenario where you accidentally drained the main battery (e.g. a light left on) to "self-start"
And here I am mad that home-storage server rack batteries are all 48V it seems, but for the same reasons (huge 400+ amp cables required to get decent wattages). When each car charger can do ~14.4kw you need a lot of fat cables running to battery banks
With an inverter, I could then supply (some subset of) my house from the traction battery, giving me a theoretical 18 hours at 1kW in my case (less efficiency losses).
I don't know about leaf's specifics, but most EVs have the heat pump / resistive element wired to the HV battery instead of the 12V one.
An ICE car can have the battery supply ~200A through that cabling, though of course that's burst and not sustained. But it does suggest to me that it's not out of the question - especially as it's normal in the automotive industry for some cabling to carry such high currents for this reason.
It couples the AC side to gnd, and does so through a 100k resistor, which is barely safe (and in my view, any AC that is coupled to gnd isn't sufficiently safe unless it also has leakage detection).
It ought to use an optoisolator or even better have leakage detection, which isnt hard to implement in circuits like this.
But it's still fun to read :)
It is nonetheless interesting if you want to build it as component of something more complex, say DIYing a battery bank out of some recycled cells
I wonder how many changes would be required to run the whole thing on say 24 or 48V. At glance just powering the board with 12V source and just feeding more to MOSFETS seems to be enough
Seriously though, there's enough energy in those numbers to seriously mess you or your electronics up. It's not quite like a bottle of old nitroglycerin, but it's definitely enough energy/power that you must respect it.
That said, most companies don't etch their own boards. That part of the build process could be skipped by sending your schematic out to one of the boutique board fabrication places. They aren't terribly expensive and it avoids having to deal with nasty chemicals. The article even mentions this and I would highly encourage it myself, at least until you have a few boards under your belt and are feeling more comfortable with diving deeper into the process.
The EGS002 looks like a really neat subassembly. It's just that at 1kW the safety issues are significant.
I get the feeling that the frequency wasn't checked for accuracy / stability, because the clock still eventually goes out of time. My KillAWatt shows something like 51 or 49Hz or something like that. Not good enough to run a clock.
Been looking for some other way to get 50Hz AC power... This seems like it could be promising... but I have no idea how stable the frequency will be from a project like this...
Because simplest one would be:
* a cheapo chinese subwoofer amplifier * 12V wall-wart to power it * a quartz-stabilized 50Hz generator (soooo an arduino, with DAC, even simple R2R + some filtering). * transformer fitting subwoofer amp output voltage. Measure amp output voltage at near-max, connect amplifier to secondary and tweak the "volume" till it is right.
Sub amp is like $5, $3 for cheapest arduino clone, probably like $2 for transformer, and few bucks in proto board and other components
If you want to overcomplicate it you could put rPi into it and sync the 50Hz clock to NTP
That’s ridiculous! Buy a little GPS-disciplined oscillator and either scale the PPS output up to 50Hz or use a PLL to derive 50Hz from the oscillator output :)
If I were making something for this problem I would make an AC-DC-AC converter with a PLL to divide the 60Hz input frequency to 50Hz to control the inverter.
This is the best way to do it, especially if the synchronous motor inside the clock is actually fed with a lower voltage from a transformer (which seems to be common in old radio clocks as they needed a transformer anyway to power the radio circuitry). If that is the case, it should be possible to bypass the transformer entirely and build a converter that operates entirely on low voltage; some quick searching suggests that this exact kind of project has already been done before in fact [1].
I'd put a $3 breakout board with any microcontroller and quartz... why would you want to sync to power network in the first place ?
For example if the grid ran at 59.87Hz during the hottest part of the day due to high load then they might run the grid at 60.06Hz all evening offset.
Or, perhaps replace the existing clock with a microcontroller that you can sync with NTP or the 60Hz line.
No, it's 100V, not 110. Japanese mains power is 100VAC, 50Hz in the east and 60Hz in the west. Your clock is from the east, made for Tokyo probably. US 110-120V is a bit high for the clock, but it's close enough that it probably doesn't cause any problems.
It sounds like the inverter you bought isn't terribly accurate, unfortunately.
>Been looking for some other way to get 50Hz AC power...
Actually, it's really simple to get highly-accurate 50Hz power to power your clock. All you need to do is move to Europe. Then you can use a 1:2 step-down transformer to convert the 240V/50Hz power there to 120V/50Hz power, and your clock will be accurate.
All in all, I would estimate that this could be done with a single IC providing a few op-amps, a handful of passive components and a transformer; probably under US$30 or $50 with a nice case and plug.
i don't think those are designed for long-term frequency stability, either. not at the <0.01% level needed for a clock. rest of your comment is on track, but the original low-voltage low-power 50Hz signal needs to come from something that was designed for low long-term drift.
His work is commendable, but I would encourage him to either learn proper soldering techniques or, if he already possesses the skills, to take a moment to use some flux and clean up the joints. It's a simple process that takes just three seconds per joint.
Oh holy, that's not good. If the screw threads manage to touch the inner side of the hole of the metal tab, you have electrical connection.
Besides that, I don't see a short-circuit protection on there - not sure if the "overcurrent" feedback can handle a dead short before the FETs blow up.
Commercial inverters for a LiFePO4, gel and lead acid batteries types usually include a micro-controller to monitor and manage the battery's state of charge. These micro-controllers usually employ a multi-stage charging algorithm to derate and prevent the battery from overcharging (which may lead to its eventual destruction).
I recently installed a cheap Chinese MUST 1000V hybrid sine-wave inverter with a relatively expensive LiFePO4 battery. Has anyone had success communicating with the RS-232 serial port to monitor this brand of inverter?
I am terribly worried that there is a bug in the implementation of the charging algorithm; the officially supported desktop monitoring app is only supported on Windows...
The world would be quite boring without some fearless people like these.
Though it would have been nice to mention not to buy your mosfets from aliexpress/ebay for $0.8/10pcs (some mosfets are quite pregnant [1]). But looks like one commenter already pointed that out on instructables.
That being said, this is not going to be someone’s first project. It probably won’t be their second project. I’m not sure my faith in people’s self preservation is rooted in my confidence that people generally want to be safe or some rather bleak, Darwinistic thinking that eventually only those who do projects recklessly will be “selected out.” In any case, you can work on these systems safely and it’s just mains voltage.
Humans have introduced more complexity to our lives as our technology has progressed, all with thought-to-be grave safety implications. The advent of the motor carriages had one city making a law stating that someone had to be on foot, waving a flag preceding the motorized vehicle at all times. People love to catastrophize, claim the sky is falling, and wax poetically about how far we have strayed from “the lord.”
You all are right, it is unlikely that anyone will actually follow this recipe. I guess I’m taken aback that some pretty serious electrical engineering has been turned into a step by step tutorial with little mention of the potential risks.
If an inexperienced person does decide to save some money on an inverter by following these steps (as is implied), it could very quickly turn into “how to electrocute yourself and burn down your house in 10 easy steps.” I would not want to be liable for promoting or hosting such content. Similar to the issue with the “very cool” electric wood burning fad that killed a few people.
Otherwise: this is a neat little inverter, it's basically a minor variation on the application note for the driver which does all of the heavy (PWM) lifting.
If you can't get transformers that are large enough you can put several in parallel using a small series resistance if the output voltage isn't exactly right (usually a case of one winding too many or too little on the secondary (now primary)).
Be careful too with those HV caps, those can hold charge for much longer than you might think when they are out-of-circuit. If you can use a higher voltage (48V preferred), and go for a transformerless design because that's so much nicer to haul around (besides being much cheaper).
Fire is just as dangerous as electricity, it's just that you can visibly see, feel and smell the danger before being burnt.
Electricity is silently dangerous, but education and maybe a bit more safety via simplicity would be really cool to see (e.g. light weight non-intrusive gloves that glow if near electric fields).
Also, I was not aware that Instructables.com was owned by Autodesk. Guess they must’ve been acquired somewhat recently.
https://investors.autodesk.com/news-releases/news-release-de....
The project page itself states that the inverter will cost at least $20 in total - and that's using essentially the cheapest components you can find. Once you use quality components and include things like proper input/output protection, connectors, and a casing, you're likely looking at a $40-50 BOM.
A $150-$200 retail price is very fair, considering all the other stuff you need to pay for to actually design, certify, make, and sell a product.
Haha, i wonder how the radiated spectrum of this toy looks like.
