Ok I need more help with inverters...

Do I understand correctly, that to use this device, I need to connect the output to an inductor and a transformer (in series), before a load? If so, why? Just to clean up the power?

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HR19 said:

Do I understand correctly, that to use this device, I need to connect the output to an inductor and a transformer (in series), before a load? If so, why? Just to clean up the power?

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The transformer is needed to step the voltage up. The inductor is needed to reduce the high frequency components.

The inverter circuit is only capable of switching the input voltage on and off (including reversing polarity) very quickly. It will not increase the voltage. The transformer needs to run at 50 or 60 Hz. You can use a transformer that is designed to step the voltage down, so it will be mass-produced and cheap. It will be connected in reverse, so the "primary" is actually used as the secondary, but that's fine.

Cheap transformers are designed for 50/60 Hz will not have the correct laminations for higher frequency, so it will get hot if it's connected to powerful high frequency signals. That is why the inductor is needed. It will also reduce the high frequency signal that appears on the output.

Using an inverter like that may end up with a large and heavy transformer because the transformer has to run at 50/60 Hz. Many modern inverters run the transformers at much higher frequencies, then rectify and smooth to give a DC link at high voltage, and then use another set of switching transistors to change the DC to AC, and then maybe an inductor to reduce any of the high frequency switching noise. It is much more complicated, but the high frequency that the transformer is run at means that the transformer is much smaller.

Ah, ok. So basically this probably isn't a very good option?

I don't know if it's a good solution for you.

A large and heavy transformer is a robust item, and not too expensive. You might even be able to re-purpose a transformer from something else to save cost. Weight may not be important to you.

What is it that you are trying to run from your inverter?

I'm trying to make something reasonably portable for our relatively frequent power outages where I live that can run off of Milwaukee M18 batteries. I don't have anything specific in mind, but maybe up to 1500W or so for a freezer and/or fridge.

HR19 said:

I'm trying to make something reasonably portable for our relatively frequent power outages where I live that can run off of Milwaukee M18 batteries. I don't have anything specific in mind, but maybe up to 1500W or so for a freezer and/or fridge.

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That sounds like a VERY expensive way to do it?. Car batteries are usually the most cost effective type of battery storage for a fixed installation.

How long do your power outages last? - I presume you are aware that fridges and freezers will last for a fairly long time without power?.

Nigel Goodwin said:

That sounds like a VERY expensive way to do it?. Car batteries are usually the most cost effective type of battery storage for a fixed installation.

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Portable, not fixed. Also I *have* lots of Milwaukee M18 batteries as I'm using them for a number of projects and for personal and my work tools.

Nigel Goodwin said:

How long do your power outages last? - I presume you are aware that fridges and freezers will last for a fairly long time without power?.

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It really varies, sometimes minutes, sometimes hours, sometimes a day or more.

HR19 said:

Portable, not fixed. Also I *have* lots of Milwaukee M18 batteries as I'm using them for a number of projects and for personal and my work tools.


It really varies, sometimes minutes, sometimes hours, sometimes a day or more.

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A day is fine, as long as you don't open the fridge or freezer.

If you're using LOT'S of batteries you've got the problem of balancing them and keeping them safe.

Nigel Goodwin said:

A day is fine, as long as you don't open the fridge or freezer.

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7 people in this house, we gotta eat, they're gonna get opened a lot.

Nigel Goodwin said:

If you're using LOT'S of batteries you've got the problem of balancing them and keeping them safe.

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Why is that a "problem?" The batteries are extremely well designed with their own BMS's. They should balance themselves and keep themselves safe.

Don't know the batteries talked about but just buy an inverter that will power your fridge. To produce 1500W for a full day will take ~36 average car batteries.

Mike.

Pommie said:

Don't know the batteries talked about but just buy an inverter that will power your fridge. To produce 1500W for a full day will take ~36 average car batteries.

Mike.

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I know, but I won't need 1500W all day, may not need it ever, but I'd rather have it and not need it than need it and not have it, especially when the cost difference vs 1000W was only like $30 for me

So just buy an inverter that meets your needs.

Mike.

Pommie said:

So just buy an inverter that meets your needs.

Mike.

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HR19 said:

7 people in this house, we gotta eat, they're gonna get opened a lot.


Why is that a "problem?" The batteries are extremely well designed with their own BMS's. They should balance themselves and keep themselves safe.

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As long as you only use ONE of them - that's fine - using multiple ones will completely mess up their BMS's. I presume you're aware that the BMS isn't a charge controller?, so you need to build a suitable charge controller as well.

Nigel Goodwin said:

As long as you only use ONE of them - that's fine - using multiple ones will completely mess up their BMS's. I presume you're aware that the BMS isn't a charge controller?, so you need to build a suitable charge controller as well.

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The batteries have direct leads that bypass the controllers. I am using them in parallel or series (depending on the application) for discharge only, then charging them via Milwaukee brand chargers.

Edit: so far, no issues.

HR19 said:

The batteries have direct leads that bypass the controllers. I am using them in parallel or series (depending on the application) for discharge only, then charging them via Milwaukee brand chargers.

Edit: so far, no issues.

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That sounds remarkably complicated

Nigel Goodwin said:

That sounds remarkably complicated

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I have little adapters that I bought off Amazon. I slide the batteries in when I want to use them and when I'm done I pull them out and I slip them on a charger.

Edit: there's a few distinct advantages to this. one is that this allows me to have relatively few batteries but switch them between multiple projects so I can spend money on having higher quality battery packs instead of having more, and a dramatically increases the net portability quick is what I'm really looking for. I don't have to run extension cords all over the house from a noisy generator, instead I can take the power right where I need it. Also I can have power extremely quickly with much less setup than a generator.