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Battery powered 230VAC Inverter, safety precautions?

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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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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Folderol » Tue Dec 10, 2019 11:45 am

I think you're missing the point slightly (or maybe I'm not making it clear enough).
There is a reason I asked how old it was - warranty issues!
Looking at a picture I notice that the end cheek where the power entry is has two quite large fixing screws, so it is likely that comes off - with luck bringing the power supply with it.
There was a time when PSUs were part of the main PCB itself, but that is extremely rare these days. It's usually a common module with a plug/socket connection.

If that is the case it would be quite practical to build a low voltage replacement. In fact, some 25-30 years ago I did exactly that for a BBC B computer that was going to be used on a narrowboat :)
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Tue Dec 10, 2019 11:55 am

Hugh Robjohns wrote: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:

:bouncy: :bouncy: :bouncy: :bouncy:

Folderol wrote:I think you're missing the point slightly (or maybe I'm not making it clear enough).
There is a reason I asked how old it was - warranty issues!
Looking at a picture I notice that the end cheek where the power entry is has two quite large fixing screws, so it is likely that comes off - with luck bringing the power supply with it.
There was a time when PSUs were part of the main PCB itself, but that is extremely rare these days. It's usually a common module with a plug/socket connection.

If that is the case it would be quite practical to build a low voltage replacement. In fact, some 25-30 years ago I did exactly that for a BBC B computer that was going to be used on a narrowboat :)

Ah, yes. Makes sense now Will. The XR is still in warrantee hence the current ( :smirk: ) solution.
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Guest » Tue Dec 10, 2019 3:55 pm

Sam Spoons wrote:
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.

So your like me in the sense you need the inverter to run your power transformer, except your mixer is DC and mine is AC

If one where to use the same battery for mixer and speakers then the problem would be the inverter and mixer would switch off before the speaker had run out of power

When you say you mixer uses a +/- 15VDC. Dose that mean it is reverse popularization?
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Sam Spoons » Tue Dec 10, 2019 4:38 pm

No my mixer has an internal SMPSU and needs a 100-230VAC supply. Folderol was referring to the fact that the internal PSU almost certainly converts this 230VAC (in my UK case) into standard dual rail +15/0/-15 VDC supply for the analogue circuits and 5VDC for the data/logic circuits hence the double conversion from my DC battery up to 230VAC and back to +15/0/-15 VDC.

Not sure what you mean about using the same battery for speakers and inverter, are your speakers/power amps 12VDC powered?
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Re: Battery powered 230VAC Inverter, safety precautions?

Postby Folderol » Tue Dec 10, 2019 5:54 pm

There is kit out there that makes no battery checks at all - I know, I made some of it :oops:
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