Converting Spotlight Power Supply

[stj]

Re: Converting Spotlight Power Supply

why dont you just draw a diagram of the wiring and board.

btw, your not powering that lamp with the original charger - it will burn up the windings.

[sambul83]

Re: Converting Spotlight Power Supply

A lot of these cheap plug in chargers, in order to prevent damage of the charging circuit of the large lamp load, use a 3-wire switched barrel connector that cuts off the load when it's plugged in.

Yes, that's why the trick with shorting the resistor-diode combo didn't work by itself, so I short 2 power jack mounts too, as it has 3. Will try with the right adapter now. If still not working, will draw the diagram. I don't remember, if the lamp was ever lit when the power adapter was hooked in and the battery charging.

@ Curious.George

Thanks for the explanation and suggested solution. I'm working on it in free time.

[budm]

Re: Converting Spotlight Power Supply

A lot of these cheap plug in chargers, in order to prevent damage of the charging circuit of the large lamp load, use a 3-wire switched barrel connector that cuts off the load when it's plugged in. You'll have to defeat that switch.

Yep, you can see that the DC input jack has two terminals used for switching out the battery negative from feeding the circuit when the charger is plugged into the DC jack. I have similar set up my spot lights.

[sambul83]

Re: Converting Spotlight Power Supply

Just confirmed using an old Buffalo router power adapter 5V 2.5A. Both lamps are lit now with diode-resistor combo short and also the 2 jack terminals short. It draws 3.5A current, but initial voltage 5.9V drops to 5V, so the lamp is not so bright. I guess I need to buy a 6V 4A adapter now. Is there a way to use a 12V adapter by modding the board, since I've a few with 2.5-3A rating, so they will heat up a bit at 3.5-4A but still working?

[eccerr0r]

Re: Converting Spotlight Power Supply

Only if you also add a switching converter.

[Curious.George]

Re: Converting Spotlight Power Supply

Just confirmed using an old Buffalo router power adapter 5V 2.5A. Both lamps are lit now with diode-resistor combo short and also the 2 jack terminals short. It draws 3.5A current, but initial voltage 5.9V drops to 5V, so the lamp is not so bright.

Insert your ammeter into the circuit to see exactly how much power is being drawn by the lamp (power = volts * amps) at that 5V level. This will give you an idea of how much current is likely to be drawn, eventually, at 6V. It rarely hurts to oversize the power supply!

I guess I need to buy a 6V 4A adapter now.

See above.

Is there a way to use a 12V adapter by modding the board, since I've a few with 2.5-3A rating, so they will heat up a bit at 3.5-4A but still working?

Yes, but it would depend on the actual adapter (i.e., it is likely not practical).

A smarter approach might be to see if you can find a (mechanically equivalent) replacement bulb that is rated at 12V (instead of 6V). I have numerous "oversized" lights and use them so rarely that the (rechargeable) batteries are almost always "dead". So, I've taken to just making sturdy (heavy gauge to reduce IR drops over these longer cables) coiled cords with "DC power plugs" (I have no idea what folks now call "lighters" in cars) so that they can be powered from such an "outlet". I've installed additional "outlets" in various places (under hood; rear of vehicle; etc.) to make it convenient to use these lamps. (I also have 12V "power packs" that I can sling over a shoulder for those times when I need to carry such a lamp with me).

What you will then have to worry about is the amount of heat thrown off by any larger lamp that you choose to fit in its place (e.g., you may end up with a 50W lamp instead of 25W -- watts == heat). I have a few "flashlights" that throw enough light (heat) that you can tell if they are on -- with your eyes closed -- just by holding your hand in the beam!

[eccerr0r]

Re: Converting Spotlight Power Supply

... and then the plastic melts (don't go up in watts....)

[stj]

Re: Converting Spotlight Power Supply

plastic melts, wires heat up, tracks burn - and most barrel connectors are only rated for a couple of amps.
the ones on laptops are constructed differently - even the plugs are different and more expensive.

[sambul83]

Re: Converting Spotlight Power Supply

Wouldn't adjusting the resistor value on that board, soldered in sequence now with the diode, and shorting the diode allow to use 12V power adapter instead of 6V? And what can possibly happen with the jack at 12V instead of 6V - melting is not likely I guess? Laptop 12V power adapters are seemingly all switching converters?

I can look at a 12V lamp, but current lamp seems soldered now to the wires in a way hard to get to. I couldn't shake it by hand in its sit after removing the holder, and using pliers on the lamp seems prohibitive. Since you mentioned a "dead" battery, I wonder if I can try recovering the dead lead battery with this smarter Nitecore charger? I know, it doesn't support SLA batteries, but what can happen if I try? Won't provide enough voltage at 7.9V to fully charge, but at least may recover the battery to the initial state, from which it can be charged by the supplied lamp charger? Or the charging cycle for lead batteries is totally different?

[stj]

Re: Converting Spotlight Power Supply

different chemistry.
if you really want to mess with lead-acid batteries then look at a B6 clone like this:
https://www.banggood.com/IMAX-B6-Min...p-1202402.html

[Curious.George]

Re: Converting Spotlight Power Supply

Wouldn't adjusting the resistor value on that board, soldered in sequence now with the diode, and shorting the diode allow to use 12V power adapter instead of 6V?

Think about it... you want to ensure the "bulb" never sees more than 6V (lest you "open" the filament). So, roughly half (6V) of the voltage available (12) would have to disappear across that resistor. In effect, you woul dhave an equivalent light bulb *inside* the lamp operating at the same voltage as the real light bulb (6V) and passing exactly the same amount of current THROUGH it (cuz it is in series with the real bulb). So, you would be dissipating roughly the same amount of power IN that resistor as you are in the real bulb... so far, that seems to be ABOUT 25W.

And what can possibly happen with the jack at 12V instead of 6V - melting is not likely I guess? Laptop 12V power adapters are seemingly all switching converters?

The current through the jack would be the same... instead of ~4A at 6V you would see 4A at 12V (in the case of a 50W replacement bulb).

The bigger issue might be the effects on the "lens" (bulb cover) as the doubling of POWER being dissipated in the lamp increases. Light bulbs are inefficient devices. Most of the power dissipated in them is HEAT, not light. Chances are, the type of plastic chosen wasn't selected for its thermal characteristics BEYOND what the original bulb was intended to produce.

[Curious.George]

Re: Converting Spotlight Power Supply

plastic melts, wires heat up, tracks burn - and most barrel connectors are only rated for a couple of amps.
the ones on laptops are constructed differently - even the plugs are different and more expensive.

Moving to a higher voltage could conceivably only increase the power dissipated in the bulb and not affect the current flowing through conductors (foil and wire). E.g., a 50W 12V bulb would result in the same amount of current flowing as would a 25W 6V bulb.

What's changing is the POWER. And, that translates into heat.

Leave such a lamp on for any length of time and I suspect you'll find the acrylic "lens" turns to mush. Plastic parts in and near the "socket" (I've not examined this particular lamp) could also be compromised.

We ALL know how hot light bulbs get -- having each tried to remove one before letting it cool down, completely!

(Note to OP: don't touch bulb glass -- even while cool -- with your fingertips as the oils from your hand will compromise the bulb. Wear gloves or use a clean tissue/cloth)

[sambul83]

Re: Converting Spotlight Power Supply

I know its long obsolete tech with plenty of heat dissipated. Speaking about efficiencies, can you guys suggest a modern cree led 50W spotlight at low cost? I've small cree or similar flashlights brighter than this spotlight, but larger cree lamps seems to be on a costlier side.

@ stj

Thanks for pointing to this nice recovery charger.

[Curious.George]

Re: Converting Spotlight Power Supply

I know its long obsolete tech with plenty of heat dissipated. Speaking about efficiencies, can you guys suggest a modern cree led 50W spotlight at low cost? I've small cree or similar flashlights brighter than this spotlight, but larger cree lamps seems to be on a costlier side.

You're thinking in the wrong terms (units of measurement).

A "50W cree" will dissipate just as much power (heat) as a 50W incandescent.

What you really want is an LED that throws as much LIGHT as the 50W incandescent/halogen -- but at a much lower power dissipation.

And, this is where things get tricky... are you concerned with "total light output" OR light at a specific point in space? (SPOTlight)

[stj]

Re: Converting Spotlight Power Supply

in plain language, your going to have to deal with the optics to get the beam angle you want.

[petehall347]

Re: Converting Spotlight Power Supply

why not put the old lamp into retirement and buy a nice new modern one ?
i have had lots of them 10 million candle power things . they only last about 20 minutes and take a long time to recharge .
or just get an external battery pack and use that . maybe get 2 packs so you get double time usage .

[Curious.George]

Re: Converting Spotlight Power Supply

why not put the old lamp into retirement and buy a nice new modern one ?
i have had lots of them 10 million candle power things . they only last about 20 minutes and take a long time to recharge .

What's worse is the chargers can't be left unattended; they'll gleefully cook the battery if left on for too long.

or just get an external battery pack and use that . maybe get 2 packs so you get double time usage .

I rescued a couple of 12V packs from bits of portable medical equipment. They have a "lighter" socket wired to the battery (and very little else besides the case and carrying strap). The charger has a lighter plug that you would insert into the socket to recharge the battery.

I've put these in my bug-out-bags as a sort of "universal power pack". In that way, I can have equipment that can be powered from the car's "lighter" socket that will also work with this portable power pack (AM/FM/weather radios, CBs, spotlights, area lighting, etc. -- I even have a 12VDC boost-converter brick to power laptops at 19V)

I know I'll always have a fresh supply of charged batteries -- even if the portable pack is dead (cuz I can steal them from any of the UPSs, here)

[sambul83]

Re: Converting Spotlight Power Supply

@ petehall347
Buying a "new nice modern lamp" would be too trivial thing to do, not exactly what this forum is about. The lamp is far not the only target in the budget hole .

@ Curious.George
With one project I need to evenly lit up a small tunnel compartment 1.5x1.5 ft about 5-10m (200-400 inches) through its length for 5min periodically. In another project, I need a small workspace 4x4m lit up at night for a few hours. One lamp may need to fit both tasks despite differences.

Can you post a weblink to a similar booster to your "12VDC boost-converter brick" for laptop?

[petehall347]

Re: Converting Spotlight Power Supply

time is money . hey i save anything if deemed save able . one mans trash i suppose . sorry my pocket flash light is plenty good enough to light up large areas .. all i need is non fake batteries . fake ones have lasted 2 or 3 years though .

[eccerr0r]

Re: Converting Spotlight Power Supply

On a similar note I have a handheld vacuum cleaner, same problem: batteries are toast. It uses three SubC NiCd batteries. The only PSU I have that will power it as-is without the batteries is my huge SCR bench PSU that can supply the amperes (with current limiting...)

I have an even worse problem in terms of powering it: the motor draws 30W or so steady state, peak instantaneous of 70W. Have yet to find some *inexpensive* Li-ion with a protection circuit that will let me draw 70W without shutting down... ha..