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Challenge of the Day: from halogen transformer to battery charger

Started by Unknown May 3, 2018
It's silly challenge of the day time. I'm wondering if discarded halogen lamp SMPSU transformers could become car battery chargers.

Thoughts so far....
The main question is what can these units be counted on to protect themselves against. Overcurrent & short are the main questions. They will come across these IRL when driving halogens.
How would they respond if the output were bridge rectified and fed straight to a battery?

Slow diodes on a high frequency output, how will that work?

I know it sounds like a daft idea, but not entirely. I might have a use for a lot of them if they survive, stay safe and function somewhat. I'm not considering adding any smarts.


NT
On Thursday, May 3, 2018 at 3:22:31 PM UTC-4, tabb...@gmail.com wrote:
> It's silly challenge of the day time. I'm wondering if discarded halogen lamp SMPSU transformers could become car battery chargers. > > Thoughts so far.... > The main question is what can these units be counted on to protect themselves against. Overcurrent & short are the main questions. They will come across these IRL when driving halogens. > How would they respond if the output were bridge rectified and fed straight to a battery? > > Slow diodes on a high frequency output, how will that work? > > I know it sounds like a daft idea, but not entirely. I might have a use for a lot of them if they survive, stay safe and function somewhat. I'm not considering adding any smarts. > > > NT
It depends. Rick C.
On Friday, 4 May 2018 16:29:14 UTC+1, gnuarm.del...@gmail.com  wrote:
> On Thursday, May 3, 2018 at 3:22:31 PM UTC-4, tabby wrote:
> > It's silly challenge of the day time. I'm wondering if discarded halogen lamp SMPSU transformers could become car battery chargers. > > > > Thoughts so far.... > > The main question is what can these units be counted on to protect themselves against. Overcurrent & short are the main questions. They will come across these IRL when driving halogens. > > How would they respond if the output were bridge rectified and fed straight to a battery? > > > > Slow diodes on a high frequency output, how will that work? > > > > I know it sounds like a daft idea, but not entirely. I might have a use for a lot of them if they survive, stay safe and function somewhat. I'm not considering adding any smarts. > > > > > > NT > > It depends. > > Rick C.
I've concluded that the only way is to try them. They should be protected against overload & short, but making sure would be needed. Also would need to check they can tolerate the unexpected nature of the load. NT
On Friday, May 4, 2018 at 6:52:42 PM UTC-4, tabb...@gmail.com wrote:
> On Friday, 4 May 2018 16:29:14 UTC+1, gnuarm.del...@gmail.com wrote: > > On Thursday, May 3, 2018 at 3:22:31 PM UTC-4, tabby wrote: > > > > It's silly challenge of the day time. I'm wondering if discarded halogen lamp SMPSU transformers could become car battery chargers. > > > > > > Thoughts so far.... > > > The main question is what can these units be counted on to protect themselves against. Overcurrent & short are the main questions. They will come across these IRL when driving halogens. > > > How would they respond if the output were bridge rectified and fed straight to a battery? > > > > > > Slow diodes on a high frequency output, how will that work? > > > > > > I know it sounds like a daft idea, but not entirely. I might have a use for a lot of them if they survive, stay safe and function somewhat. I'm not considering adding any smarts. > > > > > > > > > NT > > > > It depends. > > > > Rick C. > > I've concluded that the only way is to try them. They should be protected against overload & short, but making sure would be needed. Also would need to check they can tolerate the unexpected nature of the load.
How is it that you think they will do a good job of charging the battery? I'd be more worried about that. It is easy enough to add a current limit to the output, but to make a PSU into a battery charger is about the same as starting from scratch. Do you know the voltage output? You said you wanted to charge a car battery. I guess that won't be too hard to do, but it is still a bit of work in terms of added circuitry. Rick C.
On Sunday, 6 May 2018 00:08:00 UTC+1, gnuarm.del...@gmail.com  wrote:
> On Friday, May 4, 2018 at 6:52:42 PM UTC-4, tabby wrote: > > On Friday, 4 May 2018 16:29:14 UTC+1, gnuarm.del...@gmail.com wrote: > > > On Thursday, May 3, 2018 at 3:22:31 PM UTC-4, tabby wrote: > > > > > > It's silly challenge of the day time. I'm wondering if discarded halogen lamp SMPSU transformers could become car battery chargers. > > > > > > > > Thoughts so far.... > > > > The main question is what can these units be counted on to protect themselves against. Overcurrent & short are the main questions. They will come across these IRL when driving halogens. > > > > How would they respond if the output were bridge rectified and fed straight to a battery? > > > > > > > > Slow diodes on a high frequency output, how will that work? > > > > > > > > I know it sounds like a daft idea, but not entirely. I might have a use for a lot of them if they survive, stay safe and function somewhat. I'm not considering adding any smarts. > > > > > > > > > > > > NT > > > > > > It depends. > > > > > > Rick C. > > > > I've concluded that the only way is to try them. They should be protected against overload & short, but making sure would be needed. Also would need to check they can tolerate the unexpected nature of the load. > > How is it that you think they will do a good job of charging the battery? I'd be more worried about that. It is easy enough to add a current limit to the output, but to make a PSU into a battery charger is about the same as starting from scratch. Do you know the voltage output? You said you wanted to charge a car battery. I guess that won't be too hard to do, but it is still a bit of work in terms of added circuitry. > > Rick C.
It's sod all work, add a BR & fuse & it's done. I didn't say it'd be a good charger, it won't, but it will do the job if the psu can cope with the battery's interest in current. That 'if' is the big question, not from a safety pov but continuing to function rather than shutting down. Soon I'll try a couple & see. The output is 11.5v ac, but the waveform is so far unknown. That will have a significant effect on things. Frequency is high, how diodes will react to that is also not yet known. NT
tabb...@gmail.com wrote:

> > It's sod all work, add a BR & fuse & it's done. I didn't say it'd be a good charger, it won't, but it will do the job if the psu can cope with the battery's interest in current. That 'if' is the big question, not from a safety pov but continuing to function rather than shutting down. Soon I'll try a couple & see. > > The output is 11.5v ac, but the waveform is so far unknown. That will have a significant effect on things. Frequency is high, how diodes will react to that is also not yet known. > > >
** Typial output ( burst pattern ) waveform is shown at 1:34 into this U-tube. At 1:40 the HF switching wave is shown. https://www.youtube.com/watch?v=umK1OuRL7n8 Although specified at 11.5V rms output, the max output will be significantly higher - maybe 15 to 18 volts peak, more than compensating the diode drops in an external bridge. You may need to use fast diodes too. .... Phil
On Sunday, 6 May 2018 09:15:10 UTC+1, Phil Allison  wrote:
> tabby wrote: > > > > > It's sod all work, add a BR & fuse & it's done. I didn't say it'd be a good charger, it won't, but it will do the job if the psu can cope with the battery's interest in current. That 'if' is the big question, not from a safety pov but continuing to function rather than shutting down. Soon I'll try a couple & see. > > > > The output is 11.5v ac, but the waveform is so far unknown. That will have a significant effect on things. Frequency is high, how diodes will react to that is also not yet known. > > > > > > > > ** Typial output ( burst pattern ) waveform is shown at 1:34 into this U-tube. > > At 1:40 the HF switching wave is shown. > > > https://www.youtube.com/watch?v=umK1OuRL7n8 > > > Although specified at 11.5V rms output, the max output will be significantly higher - maybe 15 to 18 volts peak, more than compensating the diode drops in an external bridge. > > You may need to use fast diodes too. > > .... Phil
that's quite informative, thanks. With a near square wave output that's only going to be 11.5 or 12v peak though. Not enough. NT
tabb...@gmail.com wrote:
> > >> > > > It's sod all work, add a BR & fuse & it's done. I didn't say it'd be a good charger, it won't, but it will do the job if the psu can cope with the battery's interest in current. That 'if' is the big question, not from a safety pov but continuing to function rather than shutting down. Soon I'll try a couple & see. > > > > > > The output is 11.5v ac, but the waveform is so far unknown. That will have a significant effect on things. Frequency is high, how diodes will react to that is also not yet known. > > > > > > > > > > > > > ** Typial output ( burst pattern ) waveform is shown at 1:34 into this U-tube. > > > > At 1:40 the HF switching wave is shown. > > > > > > https://www.youtube.com/watch?v=umK1OuRL7n8 > > > > > > Although specified at 11.5V rms output, the max output will be significantly higher - maybe 15 to 18 volts peak, more than compensating the diode drops in an external bridge. > > > > You may need to use fast diodes too. > > > > .... Phil > > that's quite informative, thanks. >
** More informative than you think.
> > With a near square wave output that's only going to be 11.5 or 12v > peak though. Not enough. > >
** You have misunderstood the scope traces. The nominal 11.5V output consists of a high frequency, rectangular wave 100% MODULATED at double supply frequency - because the AC supply to the oscillator is rectified but NOT filtered !!. The first scope trace shows just one supply cycle with oscillation stating at about half supply voltage, rising to a maximum at supply peak and then falling until oscillation stops. The amplitude variations are smoothed out by the thermal inertia of the halogen lamp filament. The peak value is much higher than 11.5V and will be enough to charge a 12V car battery - same a using a conventional transformer and bridge rectifier does. .... Phil
On Monday, 7 May 2018 03:06:05 UTC+1, Phil Allison  wrote:
> tabby wrote: > > > > >> > > > > It's sod all work, add a BR & fuse & it's done. I didn't say it'd be a good charger, it won't, but it will do the job if the psu can cope with the battery's interest in current. That 'if' is the big question, not from a safety pov but continuing to function rather than shutting down. Soon I'll try a couple & see. > > > > > > > > The output is 11.5v ac, but the waveform is so far unknown. That will have a significant effect on things. Frequency is high, how diodes will react to that is also not yet known. > > > > > > > > > > > > > > > > > > ** Typial output ( burst pattern ) waveform is shown at 1:34 into this U-tube. > > > > > > At 1:40 the HF switching wave is shown. > > > > > > > > > https://www.youtube.com/watch?v=umK1OuRL7n8 > > > > > > > > > Although specified at 11.5V rms output, the max output will be significantly higher - maybe 15 to 18 volts peak, more than compensating the diode drops in an external bridge. > > > > > > You may need to use fast diodes too. > > > > > > .... Phil > > > > that's quite informative, thanks. > > > > > ** More informative than you think. > > > > > With a near square wave output that's only going to be 11.5 or 12v > > peak though. Not enough. > > > > > > ** You have misunderstood the scope traces. > > The nominal 11.5V output consists of a high frequency, rectangular wave 100% MODULATED at double supply frequency - because the AC supply to the oscillator is rectified but NOT filtered !!. > > The first scope trace shows just one supply cycle with oscillation stating at about half supply voltage, rising to a maximum at supply peak and then falling until oscillation stops. The amplitude variations are smoothed out by the thermal inertia of the halogen lamp filament. > > The peak value is much higher than 11.5V and will be enough to charge a 12V car battery - same a using a conventional transformer and bridge rectifier does. > > > > .... Phil
yes, I hadn't thought that through for some reason. That makes life easier. 11.5x1.414= 16.26v. -2v for diode drops makes about 14.2v peak loaded, not bad for a dumb lead acid charger. NT
On Sunday, May 6, 2018 at 2:03:13 AM UTC-4, tabb...@gmail.com wrote:
> On Sunday, 6 May 2018 00:08:00 UTC+1, gnuarm.del...@gmail.com wrote: > > On Friday, May 4, 2018 at 6:52:42 PM UTC-4, tabby wrote: > > > > > > I've concluded that the only way is to try them. They should be protected against overload & short, but making sure would be needed. Also would need to check they can tolerate the unexpected nature of the load. > > > > How is it that you think they will do a good job of charging the battery? I'd be more worried about that. It is easy enough to add a current limit to the output, but to make a PSU into a battery charger is about the same as starting from scratch. Do you know the voltage output? You said you wanted to charge a car battery. I guess that won't be too hard to do, but it is still a bit of work in terms of added circuitry. > > > > Rick C. > > It's sod all work, add a BR & fuse & it's done. I didn't say it'd be a good charger, it won't, but it will do the job if the psu can cope with the battery's interest in current. That 'if' is the big question, not from a safety pov but continuing to function rather than shutting down. Soon I'll try a couple & see.
Can't say, I have no idea what a BR is. But if your charger doesn't do a proper job of charging a battery it is pretty pointless and can actually damage the battery, so worse than just poor.
> The output is 11.5v ac, but the waveform is so far unknown. That will have a significant effect on things. Frequency is high, how diodes will react to that is also not yet known.
AC??? So when you say transformer, you mean a thing with coils and a metal core? The industry calls all devices for powering lighting transformers or ballasts even if they are constant voltage power supplies or similar. I thought you referred to it as a SMPS but I don't get why it would be AC and a SMPS. Rick C.