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Finding the correct power adapter for a no-name brand music stand light.

The stand light looks like this:

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but the light I have has only 9 LED's.

The only information on the battery is 3.7 volts and it looks like this:

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however my battery does not have any amp-hr rating written on it.

My question is, how can I figure out what voltage and current rating the power adapter needs to be in order to power the light and charge the battery efficiently? If I put 4.0V on the input jack without the battery installed, the lamps seem to light up fine. If you look closely inside the battery wrapper, you can see an attached pc board. The wiring from the DC jack goes to a series diode, then a transistor, then to the red wire extending out of the neck of the lamp where the LED's are attached. There is also a blob of round black stuff on the main pc board that looks like it could be covering a uP.

Thanks for your replies.

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David Farber 
Los Osos, CA
Reply to
David Farber
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OK, that's a Li-ion rechargeable cell.

It's not so much 'efficiency', but safety that you should be concerned with; presumably there's voltage and current charging limitations (I'd guess

0.1 to 1 ampere of charging current), plus whatever your LEDs require (could be up to one half ampere). The voltage must not get more than 4.3V, typically, on such a battery (but that could be regulated in the power adapter, OR inside the lamp circuitry).

The circuitry and envelope around the battery are intended to prevent fire.

The prudent course is to find another identical unit, and get an exact match to its wall tumor charger. Otherwise, you need to reverse-engineer the charging scheme of a poorly documented battery that has the potential to burst into flame if mistreated.

This kind of problem is why cellphone chargers are USB micro-B with 5V output: no one could get the right charger when they needed it, and nations passed laws...

Reply to
whit3rd

Thank you for the detailed explanation. I will try and get some information about the chargers that come with similar stand lights containing Li-ion batteries.

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David Farber 
Los Osos, CA
Reply to
David Farber

Am 12.01.2017 um 22:24 schrieb David Farber:

can you show us the power-connector of the lamp?

peter

Reply to
Peter Gierschner

The battery cell is a rechargeable one.

This explains the diode and transistor.

So a standard 5V 3A power supply is enough.

But according to what you say, the battery is empty ; needs a 24-hour recharge.

Reply to
Look165

Peter Gierschner wrote:

Here is the connector:

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I have a 5V 1.5A power supply from an old Epson Zip drive but the connector is too big. The connector on the lamp seems to be on the smaller end of the spectrum.

Here is the pc board:

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Thanks for your reply.

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David Farber 
Los Osos, CA
Reply to
David Farber

David-

I recently purchased a similar stand light, so your article caught my eye. Mine is more like the 10 LED version with replaceable batteries.

Searching Amazon, I found at least four 9-LED lights that are close to what you have. I think they all can be powered (or charged) from either an AC adapter or a from a USB outlet.

The four are: Kootek Sipik Ohuhu Lumiens L9B.

It is possible that two or more of these are actually the same light imported by different companies. Is there anything about yours that might suggest one of these names?

Fred

Reply to
Fred McKenzie

Hi Fred,

I personally have the 9 LED Mighty Bright that I purchased a couple of years ago which uses 3 AA batteries. It also can be powered with an AC adapter which is 4V 400ma. There isn't any kind of identifying writing anywhere on this other light. I haven't opened up the lamp compartment but I may do that just because I've looked everywhere else.

Thanks for your reply.

--
David Farber 
Los Osos, CA
Reply to
David Farber

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