12V Halogen off batteries

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Pax Writer

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Hey experts

This is probably an easy one. I'm trying to build a simple flashlight from a standard 12V halogen spotlight for household use, and I need it to run on batteries. As far as I know, there are no commonly available (and cheap) 12V batteries available, so I imagined to make a battery pack from common battery types.
I don't want it to be too big, so 8 x 1,5V is not such a good idea - Also because I'd probably have to mount several in parallel in order to properly supply the spotlight.
Now the questions are:
- What voltages can these spotlights accept?
- What combination of batteries would you suggest to power the gadget?
- Are there other and better standard halogen spotlights, I should consider using?

To consider:
- The flashlight is not meant for sustained use - Just bursts of light 30-60 seconds at a time.
- Size does matter. 8x1,5 type D batteries is too large.
- Other suggested types of spotlight should have apprx. 30deg. beam and effect of 20-40W if its indeed possible to construct from batteries.

Thanks in advance for your ideas
 
Presumably you're wanting a very bright torch?, have you considered the million candle power jobs you can buy quite cheaply - these include a sealed lead acid battery, plus chargers etc.

Otherwise, if you're talking a 60W halogen, that's 5A - so you really need a decent battery size, D sized NiCd/NimH or better? (and ten of them for 12V, not 8) - but preferably a sealed lead acid.
 
**broken link removed**
 
Pax Writer said:
As far as I know, there are no commonly available (and cheap) 12V batteries available, so I imagined to make a battery pack from common battery types.
Click to expand...
That's not true, go to your local garage and buy a sealed lead acid motorcycle battery.
 
Hero999 said:
That's not true, go to your local garage and buy a sealed lead acid motorcycle battery.
Click to expand...

Or even cheaper, ask at a local alarm company, they replace the batteries as a matter of course during routine servicing - there's rarely anything wrong with them.
 
But I think the O.P. wants the battery pack to be small and lightweight. The spotlight I gave the link to has an internal 6v pack plus the capability to recharge it from a built-in dynamo, or automobile & 120vAC sources. For $15 that's a very good deal.
 
You coul also consider using an LED light or a fluroscent tube to make your battery last longer.
 
Hello all

First of all I'd like to excuse my absence. I thought the first answer would be the only answer, so I didn't check again later. Sorry for that, because you gave me good answers.
Being done with the excusing of my ignorance, I will go on to comment some of your comments:

1. First of all, as HiTech pointed out, the battery should be small and light while still providing 12V. Of course this is only achievable by reducing the capacity of the battery (is it called capacity when we talk about batteries, or do they have their own word - I'm talking about the Ah-value).

@Nigel: The idea with the 10 D type batteries is good but way too bulky and heavy. I agree with the sealed lead type, and I'm currently trying to located the smallest possible one.
@HiTech:
 
You can get some pretty powerful LEDs, I've seen some upwards of 10W. They're durable and won't be damaged by mechanical vibration. The only thing is they're expensive and probably out of your price range.
 
A quartz/halogen lamp must be operated at its design voltage for the "halogen cycle" to operate properly. If undervoltage, the envelope will begin to darken and the life will shorten.

Dean
 
The bike lights are designed to throw a narrow beam, and probably come with something to clamp on to a tube . There are LED replacements for halogen downlights but the light is still a bit weak, for me.
 
@Hero: Thanks for the comment, although sadly it only served to remind me of my poverty

@Dean: That was a bit surprising. It must be the first time I've heard about undervoltage shortening a component's life. Good to know. Thanks!

@Super: Your comment is noted. Common sense tells me you're right. I'll look into the whole bike-light thing.

Thank you all
 
Some thoughts/comments:

A. If you've identified the spotlight or have actually purchased it, determining the nominal current requirement (at nominal voltage) would go a long way to helping you identify a proper battery. You might see if you can shop on-line to see if any data is available.

B. On occasion I'll see references to various sites that provide a wealth of information on batteries. I wish I had kept the URLs. As I recall there was enough information there to help you determine minimum requirements.

A suggestion would be to just pick a spotlight where you have some information on power requirements then compare it to the various batteries. I suspect that battery life is impacted as short term current demands increase but you can deal with that. You might find on your first pass thru that the minimum battery pack exceeds your size limits - the choice might then be to reduce the electrical requirements or change your requirements.

C. It appears from much of the discussion that the lamps/bulbs being considered are incandescant or LED. High Intensity Discharge, HID, might be an alternative. Some of the high end bike lights are HID. I have HID headlights in my truck. They are very efficient light sources - in other words for the power in they deliver a lot of light output. They are relatively expensive but offer a lot of light per pound. Note that the battery supplies power to a power supply (or ballast, or whatever you want to call it).
 
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