Wiring 4.5 volt battery pack

@bluedragon posted:

I have several of the 4.5 volt battery packs that i use to display christmas lights.   I tried to connect and wire a 4.5 volt adapter to it but i cannot get it to light up. Does anyone out there know the method for connecting these battery packs to a plug in adapter??

Thanks,

Dunno anything about those particular Christmas lights, but they appear to be LEDs, so the polarity of the source would be crucial, and the first thing I would check.

Coincidentally, I just put together a roughly 4.5 volt home brew DC power supply for a couple of new Menards purchases (using a 5 VDC supply wired through a 2.5 ohm voltage dropping resistor array), and when I first plugged in one of the devices (a lighted 48 Ford police wagon) it didn't work at all. A quick check revealed that I had reversed the wires, and switching the polarity brought instant gratification!

The Battery positive and negative terminals which normally has 3 - 1.5 volt batteries installed... .I removed the batteries and connected the positive and negative adapter wires to the + and - connections inside the battery pack, but i could not get it to light... I did use a muliti meter to check that the adapter was putting out 4.5 volts....!

@bluedragon posted:

The Battery positive and negative terminals which normally has 3 - 1.5 volt batteries installed... .I removed the batteries and connected the positive and negative adapter wires to the + and - connections inside the battery pack, but i could not get it to light... I did use a muliti meter to check that the adapter was putting out 4.5 volts....!

Have you tried reversing them, or checked the polarity?

I would put the batteries back in and make sure that the string of lights is still working.   The circuit may not have any current limiting resistor which may be acceptable when using AAA batteries (which are rated up to 50mA), but the much higher current capacity of the 4.5v power supply may burn out the LEDs.  

Without knowing the wiring scheme (likely a series/parallel arrangement) and presence of any resistors, it is difficult to know how to proceed.  

Bob

I reinstalled the batteries and the Lights are still working..   One thing i did not mention was that the battery pack has a small circuit board with an ON OFF switch..  I dont know what mA limit the lights may have but the adapter i used has a 2 Amp output... Having said that since the lights did not light without the batteries, I may not have been getting any power to the lights... as i was not sure how to connect the adapter... surely someone out there has thought of using the lights like i want to do and has a solution??   

Thanks,

@bluedragon posted:

I reinstalled the batteries and the Lights are still working..   One thing i did not mention was that the battery pack has a small circuit board with an ON OFF switch..  I dont know what mA limit the lights may have but the adapter i used has a 2 Amp output... Having said that since the lights did not light without the batteries, I may not have been getting any power to the lights... as i was not sure how to connect the adapter... surely someone out there has thought of using the lights like i want to do and has a solution??   

Thanks,

Where have you been trying to attach the replacement power supply? I had assumed you'd just cut the wires leading out of the battery pack and spliced the replacement power onto the light side. OTOH, if the light string uses a circuit board to do fancy patterns of flashes or color changes, you'll need to preserve the internal wiring.

The photo is pretty blurry as to the contents, but assuming the battery pack is conventionally configured, it might be possible to fabricate a dummy battery array, something to fit where the batteries have been, with contacts on diametrically opposite corners (top on one side, bottom on the other) to feed power into the switch and circuit board (a small hole in the cover will allow the PS wire access). Done this way, you can always go back to batteries.

In the alternative, you could solder the wires to the contacts for a more permanent installation. Temporarily holding the PS wires against contacts on opposite corners, matching polarity, should let you know whether it will work before you commit! Good luck! 🤞

It's possible you may not be connecting the negative lead from the power supply to the correct negative battery terminal.

The batteries would normally be connected in series (electrically daisy chained positive end to negative end from one battery to the next) when installed in the holder.  If connections are made in the middle of a broken chain, the electricity won't flow to the LEDs.

I would suggest checking connections as follows:

The terminal marked positive should be correct.  Only one of the two marked negative will work.

@SteveH posted:

It's possible you may not be connecting the negative lead from the power supply to the correct negative battery terminal.

The batteries would normally be connected in series (electrically daisy chained positive end to negative end from one battery to the next) when installed in the holder.  If connections are made in the middle of a broken chain, the electricity won't flow to the LEDs.

I would suggest checking connections as follows:

The terminal marked positive should be correct.  Only one of the two marked negative will work.

I believe you're pointing to the wrong place; with batteries installed, I suspect you'd read only *3 volts* across two of the batteries between the "plus" and either of the "minuses", and with the batteries removed, you'd read an open circuit across both.

Typically IME, one of the wires to the lights (through the switch, etc.) would be connected to, say, the contact at the bottom of the left-most battery where you've marked "-" in your annotation, while the other wire would be connected to the contact at the end *opposite* your "-" mark, at the top of the right-most battery. I'm assuming there's a metal bridge at the top between the left-most and the center batteries, and a similar bridge between the bottom of the center and right-most batteries -- other configurations are of course possible, but not common IME. Again, the frosted case makes it hard to make out the wiring, but closer inspection (or some experimentation) should provide clarification.

@Steve Tyler posted:

I believe you're pointing to the wrong place; with batteries installed, I suspect you'd read only *3 volts* across two of the batteries between the "plus" and either of the "minuses", and with the batteries removed, you'd read an open circuit across both.

Typically IME, one of the wires to the lights (through the switch, etc.) would be connected to, say, the contact at the bottom of the left-most battery where you've marked "-" in your annotation, while the other wire would be connected to the contact at the end *opposite* your "-" mark, at the top of the right-most battery. I'm assuming there's a metal bridge at the top between the left-most and the center batteries, and a similar bridge between the bottom of the center and right-most batteries -- other configurations are of course possible, but not common IME. Again, the frosted case makes it hard to make out the wiring, but closer inspection (or some experimentation) should provide clarification.

Steve, after thinking about what you're saying, I think you're probably correct in thinking that the end (of the chain) contacts are on opposite diagonals inside the battery case.  AKA, where the power supply would need to be connected.  So, one of these 2 options should be correct:

If I'm seeing what I think I am, there appears to be a wire or something running around the inside, right side of the case from the uppermost right battery contact to the PCB, which would make Option 1 most likely.

Steve, thanks for setting me straight on this

@SteveH posted:

Steve, thanks for setting me straight on this

No problem, and remind me to hire you to illustrate all my replies -- I could save a lot of words! 😉

@Steve Tyler posted:

No problem, and remind me to hire you to illustrate all my replies -- I could save a lot of words! 😉

Thanks.  If you're interested, I used Windows Snip & Sketch.  It's built-in to Windows 10 and makes screen grabs and annotation with the mouse very easy.  Not much of a learning curve either.

Gentlemen, both Steve's thanks for your input...  i will try these options this weekend and let all know...FYI i bought about 10 of these light kits for about $3 each and they have both colored christimas lights and white lights.  The intent is to use them on my Christmas layout, they look good around towers, houses, and across bridges... I just got tired for running around the layout to turn them on and then replace the batteries..  Thanks.

Update.... I used option 2 from Steve H, and it worked.. Appreciate everyone's input. 

@bluedragon posted:

Update.... I used option 2 from Steve H, and it worked.. Appreciate everyone's input.

Glad you got it all sorted. Yep, the "D" in "LED" is for "diode", which will allow the current to flow (and thus light the lights!) in only one direction, so it sorta-kinda had to be one or the other of those options!