12volt to 240volt inverters

Thread Starter

gyro222

Joined May 1, 2018
7
I have a double pronged question relating firstly to a cheap modified sine inverter that I bought and it claims its 8kw peak and 4kw continuous, it won’t even run a 600w drill, it’s now in pieces and question 1 is would it be easier to modify the board to convert it to a pure sine or modify it after output, the filters ect after output from doing some searches appears quite expensive
Part two I know the higher the input voltage drastically lowers the input current needed , I also have a 4kw pure sine inverter plus the useless modified sine inverter both at 12v input.
Is it feasible to attack the input side to change the 12 volt to 24 or 36 as I can easily match the voltage in a few different ways, thanks
 

nsaspook

Joined Aug 27, 2009
7,280
The simple answer: It's not practical to modify an existing DC to AC inverter for a higher DC input voltage or convert a MSW inverter to pure sine.

I only have a 1800W 12 volt inverter but I used 0000 battery cables because of the large DC currents needed at full power continuous operation. For 4000W@12vdc the currents are huge thus requiring huge wiring for full power operation even if the Inverter could actually supply that level of continuous power (unlikely for a cheap inverter).
Many are just power ratings fakes.


My inverter.
Xantrex PROWatt 2000
https://images-na.ssl-images-amazon.com/images/I/A1vznFb+4jL.pdf
 
Last edited:

MrAl

Joined Jun 17, 2014
7,580
I have a double pronged question relating firstly to a cheap modified sine inverter that I bought and it claims its 8kw peak and 4kw continuous, it won’t even run a 600w drill, it’s now in pieces and question 1 is would it be easier to modify the board to convert it to a pure sine or modify it after output, the filters ect after output from doing some searches appears quite expensive
Part two I know the higher the input voltage drastically lowers the input current needed , I also have a 4kw pure sine inverter plus the useless modified sine inverter both at 12v input.
Is it feasible to attack the input side to change the 12 volt to 24 or 36 as I can easily match the voltage in a few different ways, thanks
Hi,

There are a lot of things to consider. If you have a rectangular wave out then the filtering will involve a large inductor and an AC rated capacitor, not too cheap, and that brings up other problems that probably are not addressed in the original design.
As the post right after yours states, it's not easy in fact it is just almost impossible. These designs are carefully planned out from start to finish with every component carefully selected. To match that level of design you'd really have to start from scratch.
You can sometimes change the output a little like from maybe 120vac to 130vac, but big changes require big design changes and big component changes.
 

Thread Starter

gyro222

Joined May 1, 2018
7
The simple answer: It's not practical to modify an existing DC to AC inverter for a higher DC input voltage or convert a MSM inverter to pure sine.

I only have a 1800W 12 volt inverter but I used 0000 battery cables because of the large DC currents needed at full power continuous operation. For 4000W@12vdc the currents are huge thus requiring huge wiring for full power operation even if the Inverter could actually supply that level of continuous power (unlikely for a cheap inverter).
Many are just power ratings fakes.


My inverter.
Xantrex PROWatt 2000
https://images-na.ssl-images-amazon.com/images/I/A1vznFb+4jL.pdf
Thanks and it’s pretty obvious with the internals in mine also that inadequate wiring exists and I can picture it glowing trying to do its job, I did see a smaller conversion on one and he changed a couple of values and it looked like he used a couple of large chokes to achieve the result of a pure sine wave but for me to even attempt it I wouldn’t even know where to get a circuit diagram as I can’t even read the brand on mine it looks like Indian writing, my pure sine works perfectly but as you say at 12 volts the conversion of 1 amp per 10 watts is pretty harsh
 

nsaspook

Joined Aug 27, 2009
7,280
Thanks and it’s pretty obvious with the internals in mine also that inadequate wiring exists and I can picture it glowing trying to do its job, I did see a smaller conversion on one and he changed a couple of values and it looked like he used a couple of large chokes to achieve the result of a pure sine wave but for me to even attempt it I wouldn’t even know where to get a circuit diagram as I can’t even read the brand on mine it looks like Indian writing, my pure sine works perfectly but as you say at 12 volts the conversion of 1 amp per 10 watts is pretty harsh
A passive reactive filter might help deliver a better waveform but the filtered reactive power from the inverter has to go somewhere if the normal inverter waveform is far from a sine wave. This means the harmonic currents are circulating in the circuit wiring and semiconductors causing additional IR losses and heat. This will reduce the delivered load power by a possibility significant factor.
 
Last edited:

Thread Starter

gyro222

Joined May 1, 2018
7
Hi,

There are a lot of things to consider. If you have a rectangular wave out then the filtering will involve a large inductor and an AC rated capacitor, not too cheap, and that brings up other problems that probably are not addressed in the original design.
As the post right after yours states, it's not easy in fact it is just almost impossible. These designs are carefully planned out from start to finish with every component carefully selected. To match that level of design you'd really have to start from scratch.
You can sometimes change the output a little like from maybe 120vac to 130vac, but big changes require big design changes and big component changes.

Thanks it didn’t brake the bank and I’m sure I can find something around that it will run
 

Thread Starter

gyro222

Joined May 1, 2018
7
The simple answer: It's not practical to modify an existing DC to AC inverter for a higher DC input voltage or convert a MSW inverter to pure sine.

I only have a 1800W 12 volt inverter but I used 0000 battery cables because of the large DC currents needed at full power continuous operation. For 4000W@12vdc the currents are huge thus requiring huge wiring for full power operation even if the Inverter could actually supply that level of continuous power (unlikely for a cheap inverter).
Many are just power ratings fakes.


My inverter.
Xantrex PROWatt 2000
https://images-na.ssl-images-amazon.com/images/I/A1vznFb+4jL.pdf
I got most of my money back from them because their picture showed all sorts of things running on it so i sent them a video of my drill pulsing on and off and i told them its lucky to drive a cake mixer but will work running my toothbrush,, 8kw,,,,pigs
 

Thread Starter

gyro222

Joined May 1, 2018
7
The simple answer: It's not practical to modify an existing DC to AC inverter for a higher DC input voltage or convert a MSW inverter to pure sine.

I only have a 1800W 12 volt inverter but I used 0000 battery cables because of the large DC currents needed at full power continuous operation. For 4000W@12vdc the currents are huge thus requiring huge wiring for full power operation even if the Inverter could actually supply that level of continuous power (unlikely for a cheap inverter).
Many are just power ratings fakes.


My inverter.
Xantrex PROWatt 2000
https://images-na.ssl-images-amazon.com/images/I/A1vznFb+4jL.pdf
haha i watched that clip and he sounded like me , he opens everything up,as do i and i noticed inside mine that it would not cope and even the heat transfer paste was virtually non existant , guess i may as well screw it back together one day
 
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