Can different battery configurations save you money when using high power LEDs?

[Cavelightchris]

I was wondering what all you need to run a high power LED like the XR-E 7090 Q5?

Does anyone know of any high power LED's(150+ lumens) that can be wired directly to a battery and work reliably?

I wanted to use as few as possible components possible to make my light I am designing, because I want it to be reliable as possible, less working parts usually does this, so I wanted as few as possible.

Can you series / parallel wire up batteries?

I was thinking this, make two sets of: 5 AA batteries in series to get 7.5 volts, then wire both of them in parallel to get 3.75 volts.

If you can wire batteries in parallel, does it cause your setup to drain more power than if you had wired them in series? Cause this article was saying wiring chips up in parallel drains drains power faster:

"wiring in parallel drains your power supply faster than wiring things in series because they end up drawing more current from the power supply. It also only works if all the LEDs you are using have exactly the same power specifications. Do NOT mix and match different types/colors of LEDs when wiring in parallel."
http://www.instructables.com/id/EVSO9B1KO5EV2Z9T0L/

Well if someone can give me a run down of what all the things I must have in order to make a flashlight with a high power LED, that would be great, and if people know of any battery configuration that could save me money on the parts list, that would be great also.


Chris

 

[TigerhawkT3]

I've found that 2AA alks or a CR123A is good for relatively low-output (150mA) DD, and using 3AA NiMH or a Li-Ion is commonly used for high-output DD.

Perhaps you could use some info from the Welcome Mat:

Q: What are series and parallel?
A: Series connections have a device's positive terminal connected to the next device's negative terminal. This is what you get when you line up some ordinary C-cell alkalines (for example) end-to-end, like in a Maglite or other flashlight. This arrangment adds up the voltages of the cells. Such a battery neither handles more current nor contains more mAh capacity than a single cell. This is the opposite of a parallel configuration, which has positive terminals joining together and negative terminals joining together. An example is those 3AA>1D adapters where all three AA cells' positive terminals meet at the top, and all their negative terminals meet at the bottom. Such a configuration has the same voltage as a single cell, but can handle more current draw (or contains more capacity). For example, 1AA alk can push about 500mA at around 1.5V for about four hours. 2AA alks in series can push 500mA at around 3V for about four hours. 2AA alks in parallel can push 1000mA at around 1.5V for about four hours (or 500mA for eight hours, and so on).

Q: What are "direct drive" and "regulated"?
A: A direct drive (DD) light is one that has the battery directly connected to the bulb or LED. A regulated light has some sort of driver circuitry between the two. A DD setup is heavily affected by the battery size and type. In a regulated light, the circuitry will try to minimize the effects of the battery. The huge majority of incandescent lights are DD. They start out bright, then fade over time. The effect is greatest with alkalines, which don't do well in many situations. The effect is least noticable with Lithium-Ions, which maintain a steady voltage under relatively heavy loads. This is why traditional Maglites, which are DD by alkalines, start out bright for about half an hour, then quickly fade out and become dim for the next few hours until the battery gives up. One example of a regulated incan, which provides rock-steady output for the majority of the battery life, is Surefire's A2. In order to drive mostly similar LEDs with wildly different battery solutions, a regulation circuit allows steady output for as long as the battery has power. As an example, the Fenix E0 runs on a single AAA alkaline for eight hours with no decrease in output. If it were DD, it wouldn't light up at all, much less provide constant output. An appropriately DD LED flashlight would be one driven by button or coin cells at somewhere above the LED's Vf. This results in a long runtime with slowly decreasing output, determined by the battery's remaining power.

 

[extas]

If i am reading your post correctly, i think i have an example of what you want to do. I can't answer any of your questions technically though.

http://flashlight-forums.com/index.php/topic,5119.0.html

that post is somewhere on CPF as well, but i can't find it too easily. but i believe that the power issues and the wiring configuration are similar. He did a 4 - LED config rather than 2.

-ex

 

[Gunner12]

Potting a driver would essentially make it immune to any impact(that doesn't break the epoxy, you might kill the LED before this happens)). That might be a better option. Each LED's Vf is a little different, also remember that batteries have a different voltage when they are fresh or off the charger.

3.75v can be 700 mA draw for one LED but 1.2 amp draw for another.

Most people use drivers or even a resistor to keep things in check.

 

[65535]

I would recommend running them in series (cuts the voltage per LED in half but current remains the same) and use an appropriate converter to run them at your desired current. In parallel the voltage used is the same for both LED's but the current is the sum of each LED's draw and may not be the same for both LED's.

 

[Wolf]

Can you series / parallel wire up batteries?

I was thinking this, make two sets of: 5 AA batteries in series to get 7.5 volts, then wire both of them in parallel to get 3.75 volts.

Chris

That part kinda lost me, Are you talking about a flashlight driving 2 leds? or 10 AA batteries total?

 

[Cavelightchris]

I didn't know how batteries work, not like sound systems and ohms, or wiring chips up, but I get it now, but I still don't know, can you series and parallel sets of batteries together.

Can make 3 sets of 2AA alks in parallel pushing 1000mA at 1.5V, and then wire all 3 sets in series to get and output of 4.5 volts at 1000ma?


---

Also I was wondering if you choose to wire up batteries in parallel, does it drain your supply faster than if you had wired them in series?

 

[tanawah]

Generally the more current you draw drom a battery (group of cells), the less energy it will yeild per charge. They are usually rated at C/10 rate, meaning the power it can discharge over a 10 hour period. If you discharge at a higher rate, then the capacity will be less.

Many lights claim a usable time of 1-2 hours to 50% light output. (or something like this. At this discharge rate the power recovery may only be 30-40%.

Therefore if you lessen the load or use more cells, you have the potential to increase the efficiency quite a considerable amount. The easy rule of thumb to give indication of excessive discharge is how hot the batteries get. The higher the temperature, the less efficient they will be.

You can use more cells in parallel to reduce amps per cell or use in series at a higher voltage and hence lower amps per cell. If you are designing a light, the appoach chosen will depend on the emitter configuration and whether you want a boost/buck circuit or simple resistive control.

The bottom line is to design and match batteries to the load required by your emmiters.

 

[yellow]

You will need at least THREE batts AND A RESISTOR to run a high power led.
(even when the value of the resistor is very small, it is a must)
But that will be direct drive and most of us here dont like such a "stone age" quick-from-the-start-extremely-dimming light.

Also I am still not relly sure what You really want to do and suggest to get a Fenix (to start with the best offer by now).
Will be much smaller, better and reliable than anything You will be able to build + even cheaper if You fry the make just one time

Also medium to good quality led-lights will survive more abuse than a mere human will
(so much for rugged)


I have built light for some years now, led lights for at least three years, and dont think one will get better than a Fenix - as long as we talk about AA batts.
PS: when I read the 1st post again and again, I am pretty sure that the led(s) will be fried once at least.
what Do You f.e. mean with THIS here: :thinking:

Can you series / parallel wire up batteries?
I was thinking this, make two sets of: 5 AA batteries in series to get 7.5 volts, then wire both of them in parallel to get 3.75 volts.

Sure one can wire batts in series, but then they are at 7.5 Volts!
Now wiring 2 of such packs in parallel and they naturally stay at 7.5 Volts - what else?

PPS: seems Your last post helps me understand ...
example: 2 AAs, 1000 mAh / 1.5 V each
wired in series --> 3 V / 1000 mAh
2 of these "packs" wired in parallel --> 3 V / 2000 mAh