Battery powered 230VAC Inverter, safety precautions?

[ef37a]

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.

Dave.

[Sam Spoons]

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.

[Sam Spoons]

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.

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.

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.

[Hugh Robjohns]

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...

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

[Folderol]

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

[Sam Spoons]

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...

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

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 ( ) solution.

[Guest]

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?

[Sam Spoons]

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?

[Folderol]

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

[merlyn]

I've been through a few batteries.

A car battery can be used but they're heavy and they're not sealed. The chemical reaction produces hydrogen which has to be vented -- for a car battery the solution is to leave it open. Tilt a car battery and it can leak sulphuric acid.

That's why a sealed lead acid battery is preferred.

I took batteries that had been wrecked to a scrapyard and sold them as lead. There was a plastic bin full of them -- all different shapes and sizes. I went back with a multi-meter and bought one that showed ~12V. (I was buying the lead, the plastic was free )

The different types are for different applications. At opposite ends of the spectrum are powered golf bags and backups for alarm systems. (I once got a battery in a golf shop).

For a powered golf bag it is charged up, then discharged, then is charged up .... This type of battery is called 'cyclic application' -- it will survive hundreds of charge / discharge cycles. This is the type most suitable for powering a go-anywhere music system.

A back-up battery is at full charge 99% of the time and is only discharged when there is a power cut. This type don't have to stand hundreds of charge / discharge cycles.

If a lead acid battery gets to 0V it is wrecked -- the sulphuric acid eats the lead away. Keeping the battery charged stops this happening. If you don't use a battery for a while keep topping it up or its life will be shortened. A good charger is important and it's recommended to use a charging current of (capacity/10). For a 7Ah battery that would be a 0.7A charger -- 1A would probably be OK. That means it takes ~10h to charge. If you want to do it faster you can but the life may be shortened. I usually wanted them charged quickly.

The battery I remember lasting the longest was a Yuasa cyclic application like this

[Sam Spoons]

FWIW I intend to try and return the modified sine wave inverter power pack and have bought a similar pack which claims to have a pure sine wave inverter. I've done it partly in the hopes it will solve the noise issue and partly for peace of mind that I'm not damaging expensive electronic equipment*. But, realistically, the modified square wave inverter is touted for running laptop power supplies, assorted device chargers and similar so is it actually going to damage the SMPSUs in my kit or, worse still, fry the CPUs as suggested elsewhere?

* There is a similar thread running on the Bose forum as I type, Bose strongly discourage the use of modified square wave inverters suggesting damage to power supplies and electronics.

[Guest]

Not sure what you mean about using the same battery for speakers and inverter, are your speakers/power amps 12VDC powered?

the charger plug for my mobile speaker tested 15V DC on my multi meter last check
What kind of mobile speaker do you have?

I wonder if there is a way to deactivate the 10V shut off on the inverter with out causing damage to it or the mixer

[Sam Spoons]

Not sure what you mean about using the same battery for speakers and inverter, are your speakers/power amps 12VDC powered?

the charger plug for my mobile speaker tested 15V DC on my multi meter last check
What kind of mobile speaker do you have?

Bose S1 Pro

I wonder if there is a way to deactivate the 10V shut off on the inverter with out causing damage to it or the mixer

I very much doubt it. Most likely the inverter simply needs a minimum of 10VDC to work anyway (and doing so would probably reduce the life of your batteries too).

[ef37a]

As previously stated, we ran car, small lorry really, batteries for PA in the sticks and valve amps caned them good and proper but this was all nearly 50yrs ago and very quickly that clever Carl of CTH electronics came up with some very reliable solid state 100V line amps. I had an early 100 watter many years later, used 8(Ithink, might have been 10) OC26 Germanium OP devices.

Forward a few more years and I was supplying batteries for our air rifle club to shoot targets at night using car spot lamps. I had the good fortune to be given a sweet little ex WD 12V petrol genny. This would sit back of the Nissan hut, purring away putting 12 amps or so back into the batteries which were begged, borrowed and er...SCROUNGED from various sources. One was a monster off my deisel Mitzi Co car. I had it swapped the INSTANT it showed a sign of loss of cranking power but it would run 1/2 doz 55W lamps for hours.

Fact is, like any technology, batteries need knowledge and care in use. I learned this 50 years ago.

Dave.

[merlyn]

I wonder if there is a way to deactivate the 10V shut off on the inverter with out causing damage to it or the mixer

I'm not getting why you want to do this. The inverters I used started beeping when the battery was getting near the minimum voltage. You want to switch everything off when you hear the beep, and not run it until it cuts out.

Switching off when you hear the beep allows you to turn everything off in the recommended order -- inverter last.

[Sam Spoons]

Yup, I think he want's to get more run time out of his battery when what's needed is a bigger battery......

[Folderol]

[
I wonder if there is a way to deactivate the 10V shut off on the inverter with out causing damage to it or the mixer

So, you want to find a way to destroy the battery as quickly as possible. Is that right?
Leaving it idle at 10V is bad. Driving it below that is fatal. Apart from anything else, the individual cells all have slightly different capacities - unnoticeable normally, but under extreme discharge conditions the weakest ones will end up reverse polarised, which will completely bugger up their chemistry.

[Guest]

Bose S1 Pro

That's an expensive speaker you have there. I take it you use it for bigger jobs then just busking on the streets then

I very much doubt it. Most likely the inverter simply needs a minimum of 10VDC to work anyway (and doing so would probably reduce the life of your batteries too).

So, you want to find a way to destroy the battery as quickly as possible. Is that right?
.

As far as I was aware completely draining and recharging (via trickle charge) a battery was good practice for prolonging the life of a battery. Could be wrong hear though, different types of batteries made from different metals but I have had old cold cranking car batteries for cars out of the scrap yard and drained them well flat on the lights of caravans and these batteries have lasted my years past there sell by date and just seamed to keep going. But I would very much doubt they would start a hot engine of a car on a hot summer day. Just don't leave the thing discharged for long periods (months) that I know will destroy it

Yup, I think he want's to get more run time out of his battery when what's needed is a bigger battery......

[ef37a]

AFAIK it was only NiCads that needed a total discharge, 'memory effect' to keep them charging fully for many cycles?

I used to put my battery drills in a vice and cable tie the trigger down (the rest of the factory had already decided I was a bit mad but since I fixed all their Weller irons for them, they humoured me)

I also used to break open multicelled batteries and zap them from a car battery to burn out the 'whiskers' that caused the cells to fail.
I probably should have worn safety classes as the cells could get quite hot with repeated zappings.

Dave.

[cyrano.mac]

Have you tried a car jump starter kit?

Modern ones have lithium ion batteries. Or even LiFe ones. Much lighter than lead=acid for the same capacity.

[Guest]

I also used to break open multicelled batteries and zap them from a car battery to burn out the 'whiskers' that caused the cells to fail.
.

I though it was the acid that dissolved the led inside them that casued the wore down of the cells

[ef37a]

I also used to break open multicelled batteries and zap them from a car battery to burn out the 'whiskers' that caused the cells to fail.
.

I though it was the acid that dissolved the led inside them that casued the wore down of the cells

I am only refering to NiCads? I think the 'whiskers' grew when the cells were left part discharged. I think the electrolyte was an alkali gel?

Wet Lead acids suffer sulphation if left uncharged for a long time. Back in the day, LAs were sent from the factory fully charged but with the acid drained out and the plates dry. They went to a battery agent, my uncle was one for Dagenite, just across the street from me. I have stood in his workshop many a time as a kid and remember the monster meters and rheostats on the wall and carbouys of acid. He would make up fresh dilute acid of the correct SG and refill the batteries. They then had to absorb the acid and have a top up charge. You REALLY had to mollycoddle car batts them days! No alternaters you see and dynamos barely put in a net charge in the winter with wipers, lights, heater fan and that greedy valved radio!

Dave.

[Sam Spoons]

FWIW I intend to try and return the modified sine wave inverter power pack and have bought a similar pack which claims to have a pure sine wave inverter. I've done it partly in the hopes it will solve the noise issue and partly for peace of mind that I'm not damaging expensive electronic equipment*. But, realistically, the modified square wave inverter is touted for running laptop power supplies, assorted device chargers and similar so is it actually going to damage the SMPSUs in my kit or, worse still, fry the CPUs as suggested elsewhere?

* There is a similar thread running on the Bose forum as I type, Bose strongly discourage the use of modified square wave inverters suggesting damage to power supplies and electronics.

Still waiting for the Amazon seller of the original 'modified sine wave' power pack to supply return details (I'm almost hoping they offer me a huge discount to keep it......) but the pure sine wave power pack just arrived, it has the same battery capacity but twice the output of the first one at 200 watts continuous, so should run anything I need it for with ease. It cost £160 instead of £100 but introduces absolutely no noise into the system so excellent all round.

https://www.amazon.co.uk/dp/B072FPVDWN?ref_=pe_3187911_248764861_302_E_DDE_dt_1

[Folderol]

Beers all round then?
Oh.
OK, how about a mince pie

[Sam Spoons]

Next job, maybe, replace the cheap inverter in the VJ for a pure sine wave jobbie, I'll be able to afford one if Foldy's serious abut buying the beers