LED Power draw

[testraub]

I am getting a set of these http://www.christmas-light-source.com/Blue-Micro-Drop-LED-Battery-Operated-Light-Set-_p_2038.html to test on a 5V DC circuit. The only thing I don't know is the draw of them. Any ideas? Kinda planned to hook them into the 5+ DC on one of my controllers. Know the 9+ is limited to 200Mv. Am ASSUME ing the same on the 5V.

Thanks

Tom Straub

[Max-Paul]

Hi Tom,

Wow, this is my best guess based on the following.

Your power source is 4.5VDC or there abouts. Common LEDs in blue require about 3.3 - 3.6 VDC. So I suppose that there is a current limiting resistor to drop the about 1 VDC. Now also there are 18 LEDs and so I have to presume that all 18 are wired in parallel. And these appear to be smaller LEDs so I am not sure if the 20mA per LED will hold true. But for just a minute lets say each LED will need 20mA. So this is 18 X 20mA = 360mA total. But it could be as low as 10mA each, which would lower the mA draw down to 180mA total.

I highly recommend that you get a cheap but of good quality VOM or DVM as they call them these days (Digital Volt Meter) that also does DC current. Learn how to use it and take readings. All of the above is based on some of my past experiences. But I dont know it all and constantly learning new methods that are being used all of the time.

[Guest guest]

Max-Paul, aren't most batteries 600mA? I just looked at some of my rechargable AAA and AA Batteries, all have 600mA stamped on them. Checked some regular AAA and AA batteries (DuraCell, Sunbeam, Eveready) and none had the mA rating on them anywhere. So since that LED set he's looking at works off 3 AAA batteries (4.5V) and I'm guessing the non-rechargable batteries are possibly the same mA rating, then I'd think 3 AAA @ 600mA = 1800mA would be the minmum required, even, and since these are 4.5v, that extra 1/2 volt (5vdc) I would think would not be a big issue as long as the mA were the same or higher.

But I've been wrong before, just know I've powerd 4.5V LED strings off 5V wal-warts many times with no problems. Most being somwhere around 2800Ma(or higher) @ 5VDC.

[Max-Paul]

Hi Orvile, how is it going down in FL?

Ok, the way I read it Tom wanted to know about the draw of the LEDs. This is what I was answering to. You seem to be addressing the capacity of the batteries. I see just one little error in your math. So let me try to explain the why of it. Ok, you mentioned 4.5 VDC from the 3 batteries. So this means that the batteries are all in series. In series circuits the current does not add up. In your example you took the rating of one battery of 600mA and added the same for the other two batteries to get an answer of 1800mA. This would be true if the batteries were in parallel. But then your output voltage from this pack would only be 1.5 volts. But this is not the case in this situation. So, we have them in series and the output voltage is 4.5 and the output current is only 600mA.
I hope that explains why we do not have 1800mA available.

In a nutshell. In series circuit voltage adds up current remains the same. In parallel circuit current adds up voltage remains the same. Speaking here strictly of power sources such as batteries or could be applied to power supplies too.

Oh, and in the case of rechargeable AA batteries, I think 1200mA is fairly common.

[Guest guest]

Not bad. we never got any of that "southern storm" in my area. Not even a drop of rain from it!



Interesting about the batteries. I guess I'm just getting "oldtimers" as caniac puts in his threads, because you're absolutely right (after reading your response that jogged my memory!).

Like said, I've been wrong before and definitely missed this one.



What the heck was I thinking? Probably shouldn't have been trying to work on a sequence, upload some more files to my site and type all that at the same time. Now I'm going to have to check my sequence I was working and see if I screwed up anything in there too. LOL

Interesting thing about the rechargeable batteries, I have some spotlights that use a higher voltage AA battery (something I've not seen before) with a very high mA rating. These are in some "Solar Spot Lights" that have a head with 3 White LEDs. Tried to charge them in my AA charger, which charges AA batteries (1.5v 600mA/1200mA/3600mA) just fine, but would not charge the solar spot light ones, so I thought the batteries were bad, since I will try and charge the batteries from solar yard lights before installing them. So then I got to looking at the batteries and these are stamped 3.5V, so I got out the trusty DVM and checked the batteries, as I had never seen a battery the exact same size of an AA be more than 1.5v, sure enough, these were just what they said they were 3.5v @ 3800mA. First time for everything.

Now since no one locally sells any such AA rechargable battery at that voltage (and I get strange looks when I ask for them) 3.5v @ 3800mA, I've got to find some for replacment batteries for these solar spots somewhere. So far I have had no luick and I have no idea who made the darn spots, so no help there either.

Let me know if you ever find such an AA battery, like said they are the exact same size of the AA type, just 3.5v/3800mA.

Now just how odd is that?

[Max-Paul]

Multi tasking. Something that I could never do. One thing at a time for me.

As to your batteries. Interesting. Sounds like a set of batteries in the shape of a AA battery. I know that Ni-cad batteries are like 1.25 or so volts, less than a dry cell. Not real sure of Lith-ion or any of the other cells. But I am thinking that your battery consist of 3 cells stacked.
Up here we have a place called Battery Plus. Looks like they can make any battery pack that you can through at them. Dont know if they have such store down your way. Worse case, if you send me one of the batteries I can take it in and ask if they can replicate and make you some.

[Guest guest]

Max-Paul wrote:

Multi tasking. Something that I could never do. One thing at a time for me.

As to your batteries. Interesting. Sounds like a set of batteries in the shape of a AA battery. I know that Ni-cad batteries are like 1.25 or so volts, less than a dry cell. Not real sure of Lith-ion or any of the other cells. But I am thinking that your battery consist of 3 cells stacked.
Up here we have a place called Battery Plus. Looks like they can make any battery pack that you can through at them. Dont know if they have such store down your way. Worse case, if you send me one of the batteries I can take it in and ask if they can replicate and make you some.

Yes, we do and I asked them about them, but they didn't say anything about being able to make one or replicate it. I've been there a couple of times looking for "special" batteries, like for my Digital Camera with no success.

Now I'm thinking all Batteries Plus stores are NOT the same. I believe at one time we had several in my area, but last count I think that had dwindled down to 2.

Maybe they can't find any intelligent people to work them in Florida?,:shock: and why they've closed a few down. I just dunno.:?

Find it interesting your Batteries Plus stores go an extra step and will create/make the battery. Sure doesn't seem to work at the ones in my location here in "dumb" Florida!

I think it's time for me to move into a "more intelligent" state, as Florida sure seems to be getting "dumber and dumber" every day! I'm at the point I'm almost ready to say I wasn't born here! But it's not the native Floridians, it's most of the transplants! Not many of the Natives left here, but know a handful. Aside from that, I think I'm ready to find a new state to move to!

Probably won't, but the way things go down here at times just amazes me, especially when it goes "dumb", no wonder Florida is the brunt of a lot of jokes, they're bringing them on themselves!

I think Florida needs to change their state song, believe it was Swannee River(and had heard it was changed, I don't recall what or when, but the one I'd elect is Carlos Mencia's DEE DEE DEE!:cool: 'cuz I think it is a PERFECT fit for the way Florida has become! ROFLMAO

[Steven]

Orville wrote:

all have 600mA stamped on them.

Are you sure that isn't 600mAh? Rechargeable batteries are measured in milliAmp-hours. If the battery is labeled 600mAh, it means if you draw 600 mA, the battery will be completely drained in 1 hour. It also means that if you draw only 60mA (like a typical LED garden light), then it will be completely drained in 10 hours.

[Guest guest]

Steven wrote:

Orville wrote:

all have 600mA stamped on them.

Are you sure that isn't 600mAh? Rechargeable batteries are measured in milliAmp-hours. If the battery is labeled 600mAh, it means if you draw 600 mA, the battery will be completely drained in 1 hour. It also means that if you draw only 60mA (like a typical LED garden light), then it will be completely drained in 10 hours.

Never really considered the h, as most folks seem to leave it off, but yes, most have the h after the 600mAh, 800mAh, 1200mAh, 1800mAh, 2400mAh, 3600mAh and 3800mAh are what all the batteries I have have stamped on them depending on the battery. All are either AAA or AA types. I do have some from the same manufacturer that don't have the h stamped on them, could have just been someone didn't set the stamper up correctly and it was left off, as these were in the same exact type solar light the others were in, just no h. And that just happens to be the one I picked up the night I was looking at the battery ratings/markings. Go figure.