I have to admit that I really dislike using ~12V batteries for high power applications like this. I say this having built a ~400A ~14V system. It’s miserable.

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.

While people are talking about use cases, I've been shopping for exactly this. My Nissan Leaf's DC-DC converter that drops the HV traction battery down to 12V (well, 14.6V-ish) to supply the regular vehicle electrics is apparently 1kW capable, as the heat pump needs a lot of power. If you turn the climate control off but leave the car on, then you can apparently pull 80A or so from the 12V "battery" perfectly fine as the DC-DC converter will keep it supplied. This is a relatively safer way of tapping into the traction battery without having to deal with the HVDC.

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 like the design of the voltage feedback circuit here.

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.

This is one of those "if you don't understand all the words in the article then you should not be attempting it" articles.

But it's still fun to read :)

I have an old wall clock from Japan that runs on 110v/50Hz. It keeps time like all old clocks, using the frequency of power. I can plug it into a US outlet and it runs, but it runs fast, since we're 60Hz here in the US. To remedy this, I bought a 12v power supply, and an inverter from Japan that had the 50/60Hz selectable on it. I couldn't find any other inverters that had an option to run at 50Hz.

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...

Clearly, he possesses considerable expertise, but it's puzzling why such a skilled individual would falter towards the end, resulting in poor solder joints on the 2.54mm pin headers. This isn't merely a question of aesthetics; these joints are susceptible to failure.

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.

> The MOSFETs I'm using comes in a TO-220 package. The metal tab of the MOSFET is technically tied to its drain pin. Electrical isolation must be applied to avoid conduction between the other sets of MOSFETs. I usually leave the upper MOSFETs from the H-Bridge unisolated as they share a common drain pin (Vcc).

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.

That's a neat little project, but as almost always nowadays, don't even expect to save any money by building an inverter yourself, unless you have the expensive parts (transformer, mosfets, driver board) lying around anyway. Otherwise, the 30$ mentioned in the article wouldn't even come close to cover all the parts in the list.

I am not an electrical engineer and stand to be corrected:

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...

This seems like an irresponsible thing to make into an instructable

Circuit breakers or fuses on both the input and output sides would be a good idea.

The duct tape insulation at the bottom of the heat sink is a pretty bad idea, better use some mica and/or some stand-offs for this. Duct tape has some insulating properties but simply isn't made for this application and given the voltages in play I would definitely not use it.

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).

I think the most important thing to realise is that electricity is becoming a bit like a common tool that _anyone_ should be able to wield to do amazing things.

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).

That’s pretty neat!

Also, I was not aware that Instructables.com was owned by Autodesk. Guess they must’ve been acquired somewhat recently.

I think the receptacle looks so scared, because it's about to deliver 220V when it's only rated for 110V?

I'm really surprised that board is only $3 given how expensive off the shelf inverters are. I would think there would be enough competition in the pure sine inverter market to drive prices down, but I guess it's just small enough to not function optimally.

> 1000W 12V –> 220V Inverter

Haha, i wonder how the radiated spectrum of this toy looks like.

After looking at the instructions, most would rather buy

I have a 2kw(?) 12v inverter that I use to power a small welder from my vehicle, it's really useful on the go for repairs.

Why doesn't the title include the efficiency?

Sooooo how much power does that clock use ?

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

The (presumably) low power demand means you could do pretty much anything... you could digitally control the frequency of the power to this clock if you ran your own inverter. Like in software you would know exactly how many cycles had elapsed since previous time and how many need to elapse before the next to achieve synchronization with some NTP source. There are all sorts of ways you could sort it out, assuming the clock is not mechanically slipping relative to AC cycles.

It seems quite strange that the clock isn't compatible with both 50 and 60 Hz. Japan uses both frequencies in different regions.

Fun thing is that inverter is the clock in this case. The time keeping device. The wall clock is just a display.

You could use a mechanical 60 to 50Hz converter. Basically a motor connected to a generator. They tend to be very expensive but maybe there are options.

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.

It won't keep time because on an actual mains grid the operator tracks frequency variations over time and makes corrections in the opposite direction to keep the average very close to the stated Hz - one reason for that being mechanical clock sync.

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.

You could probably hack your inverter with a simple DPLL, to keep it in sync with the wall. I'm assuming you could interface with the clock generator (cap or resistor), if you wanted to keep it "analog" :).

Or, perhaps replace the existing clock with a microcontroller that you can sync with NTP or the 60Hz line.

>I have an old wall clock from Japan that runs on 110v/50Hz.

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.

What's the power draw of your clock? 50Hz is within the range of most LFO circuits (Low Frequency Oscillators) of the kind used for modular synthesisers and guitar effect pedals. You could combine one of those circuits with a simple voltage follower (consisting of a power op-amp or BJT transistor plus a couple of resisters) to keep the frequency at a stable 50Hz under load, and finally a transformer to convert the signal up to 110V.

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.

Are you positive it’s not meant for 100V? That’s the standard in all of Japan from what I know.