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Open Roads Forum  >  Tech Issues

 > Square wave inverter to LFP battery?

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Almot

out there

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Posted: 04/21/23 11:36am Link  |  Quote  |  Print  |  Notify Moderator

I've been charging small electronics with a small $20 SQ for years. Laptop, phone, toothbrush. Don't have much use for a bigger/better one. Other than slower charging due to intermittent DC, is there a reason why this might be a bad idea?

Small motors like electric shaver or water flosser do work on SQ wave, but quieter and "rougher" - it's like I can almost hear intermittent work at 30 HZ pulses.

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The Western States

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Posted: 04/21/23 11:58am Link  |  Quote  |  Print  |  Notify Moderator

Square wave produces a number of higher frequency transient voltages which can cause the type of issues you're seeing. With your years of use I don't see a problem.

Sine wave inverters are cheaper these days and you may get longer life with some equipment.


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pianotuna

Regina, SK, Canada

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Posted: 04/21/23 02:07pm Link  |  Quote  |  Print  |  Notify Moderator

Almot,

I did run my roof air and microwave with a modified sine wave inverter from Cobra. It was designed to work with motors.

I got a true sine wave as soon as I could afford it.

One reason I did so was the kill-a-watt would read the ac output voltage as 176.

In short, I think modified is a bad idea.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

KD4UPL

Swoope, VA

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Posted: 04/21/23 07:33pm Link  |  Quote  |  Print  |  Notify Moderator

MSW inverters are known to damage some electronics. Apple devices, electric blankets, and gas ranges to name a few. If you haven't burned up anything yet yoh're lucky.
MSW inverters are like black amd white TV's. Yeah, they work, but is anybody really that cheap?

wa8yxm

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Posted: 04/22/23 05:13am Link  |  Quote  |  Print  |  Notify Moderator

There are other issues with MSW inverters as well.. The biggest is that the "Sqauarish" waves have harmonics that can go all the way up into "Frequencies of interest) (TV/Radio) and cause interference with same.... PSW/TSW are far less likely to do that.

My psw inverters ... Well some very sensitive radios I have could not hear them at all MSW.... The Radio sounds rather nasty. (Radio is running on battery power)


Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
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StirCrazy

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Posted: 04/22/23 08:52am Link  |  Quote  |  Print  |  Notify Moderator

Get rid of that and get a pure sign wave before you wreck things haha. seriously though a MSW can use up to 30% more power to run the same equipment due to inefficiency and noisy wave form. They produce more electrical interference and can damage sensitive electronics (read BMS) and anything with AC motors.

for the price difference nowadays there is no real reason to have a modified sign way anymore.


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MEXICOWANDERER

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Posted: 04/22/23 11:49am Link  |  Quote  |  Print  |  Notify Moderator

I can only comment about things I have seen.

I have not played around with pure sine wave.

But seven different modified sine wave inverters reverted to square wave after battery voltage sags to a critically low level. Trace, Xantrex, and others did it. Forty years ago the instantaneous burn out of an electric blanket control taught me to be careful with asymmetrical wave form power.

Inductors heated up and caused FET transistors to draw additional amperage. Electrical motors ran hotter. Batteries discharged significantly faster.

[emoticon] your mileage may vary

jaycocreek

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Posted: 04/22/23 05:01pm Link  |  Quote  |  Print  |  Notify Moderator

Some high end RV's come with a modified sine wave inverter installed....


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Almot

out there

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Posted: 04/22/23 06:22pm Link  |  Quote  |  Print  |  Notify Moderator

I was mostly concerned about battery charging with MSW. LFP battery in laptop and phone, NiMH in cordless drill. I am not running any electronics on MSW. The only piece of electronics that I've been running on it was a corded electric shaver, it has an AC-DC converter hidden in massive 110V plug.

pianotuna

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Posted: 04/22/23 08:00pm Link  |  Quote  |  Print  |  Notify Moderator

Almot wrote:

I was mostly concerned about battery charging with MSW. LFP battery in laptop and phone, NiMH in cordless drill. I am not running any electronics on MSW. The only piece of electronics that I've been running on it was a corded electric shaver, it has an AC-DC converter hidden in massive 110V plug.


Most batteries hate heat. MSW inverters do cause batteries to get hotter when charging at least on my laptops.

What sort of wattage do you want to run? I got a very nice 700 watt psw inverter from Victron for $109.00 about 5 years ago. They may be cheaper than that now.

Here is a 375 watt:

https://www.amazon.com/Victron-Energy-Si........ZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU&th=1

* This post was edited 04/22/23 08:08pm by pianotuna *

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