dc/ac inverter

Yes - don't do it. Your battery is too small (see ) for anything but brief use, and the design is not intended for

8kW per the url you posted. The transformer won't handle it, and the pass transistor design is wrong (no emitter resistors) to start with, even for 4.5 kW. If you went with the design, you'd likely have to double the # of transistors and the size of the heatsinks. With no emitter resistors you could easily burn out the transistors. And good luck on designing and winding a suitable transformer based on that url. You'd also need heavy cables - better would be large copper bus bars - between the battery and the input of the inverter. It is just not practical.

What is the application? How long do you need to provide power to it? You might be better off buying a generator, or tripling the number of batteries to get 216 volts DC and running the application from that, provided you need to run the application for only a short time. Then there's the matter of re-charging those batteries ...

Ed

First, I'd worry a LOT about that design. Has a lot of issues that could turn it into a pile of smoldering metal.

Second, You don't day what you're doing with it, but I'd be wary of trying to get 100A reliably out of a 135Ah battery.

You might be happier splitting the load, if you can, and using multiple smaller inverters.

Assuming 100% efficiency, 8000/72 = 111 Amps. Your 135 AH batteries won't like a 111 A draw if it goes no very long. Presumably, the current would actually be a bit higher.

Jon

Not only that but you will not get 72 volts at 111+ amps.

tm

Yes, quite laughable. It is a 50 W inverter design stepped up to something bigger. There is no protection from shorts, overloads, low or high voltage, whatever. As far as I can tell, it is a square wave inverter, no sign of PWM except that the chip is commonly used for PWM control of DC-DC converters, here it is used as an oscillator and push-pull driver at 60 Hz.

The 2N6277 is a 150 V transistor, which would give zero margin at

75 V DC, it would be a lot better to use a 300 V transistor. It would be a lot better to use either a bank of MOSFETs or a couple IGBTs, although you'd need proper emitter ballasting resistors there, too.

The onyl way I could imagine to use something like this would be to use a "step down transformer" as the transformer, these are typically used to convert 240 : 120 V or 480 : 120/240 V in machine tools and other major electrical equipment. These transformers can often be found at scrap yards, but you'd probably need a 30 KVA transformer to do what you want. You lose a power of two with most of them as you end up running them at half voltage. And, then the square-wave operation would make it run hot, so more derating would be needed. But, these transformers can usually be had at scrap prices for the weight.

Jon