D Cell Battery Capacity

[Photonz]

I'm going to be doing a build with Mrcrouse's 2D Maglite and i'll be using an x-boost set at 1.8A with either a m140 or a 9mm 445nm diode. Will two 1.5V D Cells be enough to boost off of? I researched the capacity and a few websites said each cell has 14000mah which is beyond what I need, but as far as the potential difference, will 3V be enough? Thanks:beer:

 

[ChaosLord]

You mean standard alkaline D batts? They might work, but I doubt you'll get full power with those. Standard alkaline aren't the best at high current drain.

Lithium D cells would work much better, but finding a li-ion equivalent would be the best option.

 

[Photonz]

Yes, they are alkaline (not li-ion) batteries. I'll try the alkaline ones and see how much power they put out when the build is finished

 

[Benm]

One very important thing to notice with alkaline batteries is that their voltage drops quickly with discharge, especially under heavy load.

They could well be rated 14 Ah, but that figure is normally achieved under low load conditions (discharge current of 1.4 A or even less), and with a cut-off point of 1 or even 0.7 volt per cell.

The latter could be a big problem if you need the voltage: If your driver has, for example, a minimum required input voltage of 2.5 volts, you'll only get a fraction of that 14 Ah out off the cells before the voltage drops too low. You can still use the cells after for something less demanding*, but you will have much shorter runtimes that you'd expect when calculating with the 14 Ah figure.

* say, to power an ordinary maglite with incandescent bulb which will light for a long time, albeit ever more dimly.

 

[Photonz]

Okay, so It sounds like I should just switch to Li-ion cells. Is there a way of managing that with a voltage between 3V to 5V? I may just have to resort to a battery spacer.

 

[Benm]

Its probably best to use a spacer if your driver cannot handle over 5 volts.

 

[Photonz]

Okay I'll just go with that