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Battery powered 230VAC Inverter, safety precautions?

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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Hugh Robjohns » Mon Dec 09, 2019 4:02 pm

Sam Spoons wrote:I might stick the 'scope on the output from my new power pack later and see what the 'modified sine wave' looks like.

Image

This website will give you some more info (although the way that 'scope is set up doesn't make it very clear what's going on!)

https://www.altestore.com/blog/2015/10/pure-sine-wave-vs-modified-sine-wave-whats-the-difference/#.Xe5hq5P7TRY
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Folderol » Mon Dec 09, 2019 5:26 pm

Exactly!
I really don't know how they can get away with calling it 'modified sine'. It bears no resemblance at all to a sine wave, and is a positively evil thing to do to an innocent transformer - I rather suspect that the one in the inverter has a bit of an air gap to reduce the chance of core saturation, although that will reduce the efficiency even further :protest:

P.S.
Actually the drawing is wrong. That is the voltage waveform, the current one would be exponential curves.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby ef37a » Mon Dec 09, 2019 5:34 pm

Folderol wrote:Exactly!
I really don't know how they can get away with calling it 'modified sine'. It bears no resemblance at all to a sine wave, and is a positively evil thing to do to an innocent transformer - I rather suspect that the one in the inverter has a bit of an air gap to reduce the chance of core saturation, although that will reduce the efficiency even further :protest:

B.b.b.b.but! In another thread we were talking about car radios of old and vibrators (shut up that boy at the back!) They must have produced a very similar waveform? Never had a traff go.

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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Folderol » Mon Dec 09, 2019 5:48 pm

ef37a wrote:
Folderol wrote:Exactly!
I really don't know how they can get away with calling it 'modified sine'. It bears no resemblance at all to a sine wave, and is a positively evil thing to do to an innocent transformer - I rather suspect that the one in the inverter has a bit of an air gap to reduce the chance of core saturation, although that will reduce the efficiency even further :protest:

B.b.b.b.but! In another thread we were talking about car radios of old and vibrators (shut up that boy at the back!) They must have produced a very similar waveform? Never had a traff go.

Dave.
They were square wave, and definitely were air gapped. I know, cos I took one apart in my yoof. They were also distinctly low efficiency. The radio I had drew 5-6A from a 12V battery :o
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Mon Dec 09, 2019 5:50 pm

Of course I wouldn't be having this trouble if Berry had built the XR12 with a 12V line rat PSU like my Mackie DL1608 instead of a built in jobbie :headbang:
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Folderol » Mon Dec 09, 2019 5:58 pm

Hmmm. What's the rated power consumption, and how old is it?
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Mon Dec 09, 2019 6:23 pm

Didja mean the DL or Dave car radio?

The DL is rated 12VDC and 48 watts so by my reckoning a 7AH SLA battery would only run it for an hour or so, possibly less, before the voltage dropped too far. Maybe my Anker Li-Ion battery pack would fare better as it has a regulated 12VDC output. I'd give it a try but the power connector in the DL is unconventional and I don't have a spare handy.....
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Folderol » Mon Dec 09, 2019 7:10 pm

Nooo. I meant the Berry :roll:
The thing is you're currently doing two conversions, neither of them particularly well.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby wireman » Mon Dec 09, 2019 9:26 pm

Hugh Robjohns wrote:
Sam Spoons wrote:I might stick the 'scope on the output from my new power pack later and see what the 'modified sine wave' looks like.

Image

This website will give you some more info (although the way that 'scope is set up doesn't make it very clear what's going on!)

https://www.altestore.com/blog/2015/10/pure-sine-wave-vs-modified-sine-wave-whats-the-difference/#.Xe5hq5P7TRY

I should look at the output of my UPS to see what the waveform looks like, not sure if I can post the result however and it will be a couple of weeks before I can try.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby blinddrew » Mon Dec 09, 2019 9:27 pm

Folderol wrote:The thing is you're currently doing two conversions, neither of them particularly well.
That eloquently sums up my day.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Guest » Mon Dec 09, 2019 10:02 pm

Sam Spoons wrote:A typical inverter will shut down when the battery voltage reaches 10V which is a safe level for the battery to help prevent damage. This will probably represent 50-60% total battery capacity.

Sam Spoons wrote:Deep cycle batteries are designed to cope with being discharged to lower voltages than cranking type batteries, I don't think it makes much difference to the effective capacity but they last many more charge/discharge cycles used correctly. Car starter batteries can supply much higher amperages, typically several hundred amps, which would damage a deep cycle battery.

So what are you saying? an inverter running off of a deep cycle battery will cut off of 10 volts or not?
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Tue Dec 10, 2019 1:03 am

The inverter will cut of at 10V, as I understand it the deep cycle battery is designed to cope better with slow, deep, discharge. A starter battery is built to provide high currents for brief periods of time with immediate recharging. I don't know the details of how that works (other than it is to do with plate thickness and gaps) but they are built differently.

In practice it is the inverter that decides what voltage to shut down at and I don't know if a DC battery would supply more energy before reaching that voltage than a starter battery but I doubt it.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Tue Dec 10, 2019 1:10 am

Folderol wrote:Nooo. I meant the Berry :roll:
The thing is you're currently doing two conversions, neither of them particularly well.

:crazy: Can't remember what the Berry draws now (didn't write it down) will check tomorrow but it wasn't much (less than 0.2A at 220VAC I think).

Anyway remind me which two convertions and I'l swat up in the morning ;)
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Folderol » Tue Dec 10, 2019 2:06 am

By that I meant you have a conversion from 12V DC to 240 AC, followed by the conversion back down from 240 AC to (probably) +-15V DC +5V DC

You can get converters that will go straight from the battery to those voltages.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Guest » Tue Dec 10, 2019 9:10 am

Sam Spoons wrote:A typical inverter will shut down when the battery voltage reaches 10V which is a safe level for the battery to help prevent damage. This will probably represent 50-60% total battery capacity.

Sam Spoons wrote:The inverter will cut of at 10V, as I understand it the deep cycle battery is designed to cope better with slow, deep, discharge. A starter battery is built to provide high currents for brief periods of time with immediate recharging
.
So are you saying a cold cranking batter would only have about 50%-60% of it total capacity when it has been drained down to 10V. And a deep cycle battery will have much more capacity then the cold cranking battery when drained to 10V?
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Guest » Tue Dec 10, 2019 9:14 am

Folderol wrote:By that I meant you have a conversion from 12V DC to 240 AC, followed by the conversion back down from 240 AC to (probably) +-15V DC +5V DC
DC-AC-DC Why do that?
That is like going round the sun to get to the moon
That is like buying an inverter to charge your mobile phone up from the pin plug it came with in the box when instead you may as well get a car charger that will drop it from 12V DC to 5V DC
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby ef37a » Tue Dec 10, 2019 9:57 am

tonyztigger wrote:
Folderol wrote:By that I meant you have a conversion from 12V DC to 240 AC, followed by the conversion back down from 240 AC to (probably) +-15V DC +5V DC
DC-AC-DC Why do that?
That is like going round the sun to get to the moon
That is like buying an inverter to charge your mobile phone up from the pin plug it came with in the box when instead you may as well get a car charger that will drop it from 12V DC to 5V DC

Heh! My best mate had an inverter so he could use a decent hi fi amp in his van with a mains MDisc player (ripped CDs) Also had a 200W 12" sub in a partition twixted cab and load space. REALLY hissed off Sudaru men!

And er, batteries. Seems to me the type matters little if the inverter drops out at 10 V? Might as well go for the biggest Ah you can and car batteries are cheaper.

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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Tue Dec 10, 2019 11:03 am

tonyztigger wrote:
Folderol wrote:By that I meant you have a conversion from 12V DC to 240 AC, followed by the conversion back down from 240 AC to (probably) +-15V DC +5V DC
DC-AC-DC Why do that?
That is like going round the sun to get to the moon
That is like buying an inverter to charge your mobile phone up from the pin plug it came with in the box when instead you may as well get a car charger that will drop it from 12V DC to 5V DC

Because the device I want to power (Behringer XR12 mixer) does not have a low voltage dc input. Internally it runs on low voltage DC but that is not accessible.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Tue Dec 10, 2019 11:31 am

tonyztigger wrote:
Sam Spoons wrote:A typical inverter will shut down when the battery voltage reaches 10V which is a safe level for the battery to help prevent damage. This will probably represent 50-60% total battery capacity.

Sam Spoons wrote:The inverter will cut of at 10V, as I understand it the deep cycle battery is designed to cope better with slow, deep, discharge. A starter battery is built to provide high currents for brief periods of time with immediate recharging
.
So are you saying a cold cranking batter would only have about 50%-60% of it total capacity when it has been drained down to 10V. And a deep cycle battery will have much more capacity then the cold cranking battery when drained to 10V?

No, not really 'cos I don't know, what I an saying is that lead acid batteries don't like being discharged below about 40% capacity and deep cycle batteries are better able to cope with frequent discharge to that capacity than starter batteries. A car battery, as Dave says, will be cheaper and will work fine, long term use it will probably fail sooner.

Folderol wrote:By that I meant you have a conversion from 12V DC to 240 AC, followed by the conversion back down from 240 AC to (probably) +-15V DC +5V DC

You can get converters that will go straight from the battery to those voltages.

True but you can't get at the +/- 15VDC and 5 VDC supplies in the XR12 without serious modification so the only practical method is to supply the XR with 230VAC.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Hugh Robjohns » Tue Dec 10, 2019 11:37 am

Isn't it annoying when manufacturers insist on building the power supply into the unit itself, rather than supply an external wall-wart or line lump supply?

.... oh... wait... :lol:

Why is that angry looking mob of hedgehogs coming at me.... :bouncy:
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