High Current/Low Voltage vs Low Curr./High V.

[kuksul08]

I am trying to figure out some new design for my light, and can't decide if I'm digging myself into a hole and going in the wrong direction here.

Currently, I have a 4.8V battery that splits into two and runs individually switched XR-E's. My power source is 4s2p AA batteries, and current draw is up to 2 amps when both are on. I think that's kind of a lot, and it requires me to have thicker wires.

The other option is to get a higher voltage pack, and wire them in series resulting in less current draw. Technically with similar setups, the run times should be close. The difference being 9.6V and 1A versus 4.8V and 2A.


Is it better to use the higher voltage for some reason? I know nothing about this... please inform me.


(The reason I ask, is because my next rendition of the light I am thinking will have an MC-E and an XR-E... this means potentially 3.8A of current from a 4.8V pack. I haven't heard of anyone doing this, so it must be bad in some way.)

Thanks

 

[Mr Happy]

With the way you describe it, it may not make any difference.

For instance, if each XR-E has its own wires going all the way back to the battery pack then the wires will only be carrying 1 amp, which is no different from the series configuration.

Secondly if the 4.8 V battery pack is wired two parallel, then each individual cell will only be seeing a 1 amp draw, which is the same as the series configuration as well.

The main advantage of higher voltages and lower currents is if a single wire is carrying power over a long distance, in which case the resistance losses are lower.

 

[kuksul08]

Thanks. The wires from each LED go to a global power jack, then an 18Ga cable to the battery pack.

Like that^ so, the power cable carries 2 amps.

edit: yeah, my friend was referring to the high voltage long distance power lines when I asked him. So I guess it doesn't make much difference here? I'm just worried about losing efficiency.

 

[Mr Happy]

Here's a handy cable size and voltage drop calculator for you:

http://www.powerstream.com/Wire_Size.htm

But I don't think you have much to worry about with 18 AWG copper flex as long as you keep the run lengths reasonably short (say 3 ft or so).

 

[kuksul08]

Here's a handy cable size and voltage drop calculator for you:

http://www.powerstream.com/Wire_Size.htm

But I don't think you have much to worry about with 18 AWG copper flex as long as you keep the run lengths reasonably short (say 3 ft or so).

Oh I have definitely been using that I don't understand the difference between the chassis wiring and power transfer recommendations, though. I have seen people here use both. I have always been using the power transfer just to be safe, maybe it's overkill.

The wire is 6 feet long from the light to the battery pack. I could easily cut 2 feet off and still have plenty of slack, but I don't think its causing issues with the current setup.

Thanks again for the help.

 

[Mr Happy]

You don't need to worry about chassis wiring and power transfer considerations for your application. All that really matters to you is the resistance of the wire and the voltage drop encountered.

In higher power applications there might be a concern about how hot the wires can get, but that is not going to matter for small battery powered applications.