Battery wiring & capacity Qs

[Agent_Jaws]

I looked through the threads of interest sticky and didn't see anything that answers these questions. I was considering doing some kind of mod on my 2d Mag and was wondering how capacities would be impacted by wiring batteries in different ways. Assuming I want to run the 2d off 6 x AA batts that are 1.5v and 2300 mah. I want to run them in series to bump the voltage up to 9v to the bulb. If I do this, will the runtime increase per battery or will it be limited to around 2300 mah in total? My instinct tells me that running @9v will cause an equal draw on all the batteries at once, and thus assuming a 1A draw I'll only get a little over 2 hours of runtime.

Alternatively, if I were to run them in parallel to 3v, would I get 6900-ish mah?

On the other hand, I see NiMh D cells that show a capacity of 10-12 ah, or over double what I would get with a switch to AA cells. So that begs another question:

My intent was to mod a C/D sized mag to accept P60-sized drop-ins. It doesn't have have to make sense to you, it was just a project for me to play with. That said, I was basing some things around the Malkoff drop-ins, specifically the M60 and M30 modules. The idea would use the 6 x AA cells for the M60 @9v, or 2 x D cells for the M30 @3v. Here's where I come to the battery wiring and capacity issue.

Assuming I only get 2300 mah @ 9v, that would mean the M60 would only run for about 3 hours before quitting, but would put out 230 lumens the whole time.

With the M30 and D cells I'd have closer to 10k mah available, allowing it to run @ 3v for closer to 10+ hours, although only at around 160 lumens.

1) Have I done my math correctly in stating that wiring 6 x AA (2300mah, 1.5v) cells in serial will put out 9v but still only have 2300 mah capacity?

2) Assuming you could run a regulated LED module between 2 and 9 volts, is there any reason to choose 2300 mah @ 9v over 10k mah @ 3v?



I had also considered trying to make something suitable for 2 x AW "C" Li-Ions as well but I'm still debating on that.



And yes I know they make modules for mags, I was thinking of doing this just for fun and to be able to swap out drop-ins depending on what batteries I wanna use. That, and I'm holding out for a good P7 or similar drop-in. I also wanted to machine a different bezel for the mag to make it look more like a big 6P but I want to get the electronics settled first before I get crazy in the garage.

 

[Mr Happy]

This is a really complicated question.

The short answer is that 6 cells of a given kind have the same energy storage however you connect them, in series, parallel, or some other combination.

The short answer is not the whole answer though, because any given bulb or LED module works best when matched with the appropriate supply voltage. Choose a different voltage, such as 3 V instead of 9 V, and you will need a different light source for best efficiency and longest run time.

A rough generalization is that higher voltages when matched with an appropriate light source are more efficient than lower voltages because they run at lower currents. Battery capacities are maximized and resistance losses reduced when the supply current is lower.

So usually I would try to connect cells is series and avoid connecting them in parallel where possible, but this is again a generalization and not a hard and fast rule.

 

[naked2]

When you say 1.5V AA batteries, are you talking about alkaline?

If so, they'd be useless for this project. Don't ask me why technically, others here are MUCH more knowledgeable on the subject, I just know
(by reading what those others have wrote) alkalines would be ueless.

 

[Lynx_Arc]

If you are talking about running 3v (parallel 3x1.2v times 2 series) vs series 9v (6x1.2v series) the power remains the same but capacity as 3v will be 3 times that of 9v as P=IE or Power (in watts) = I (amps) x E (volts). you have approx 2.3Ahr x ~1.2v x 6AAs or about 17 watt hours total assuming you have NO losses. A 3v 0.75A bulb or 2.5watt bulb should run 7.5 hours again assuming no losses while a 9v 0.75v bulb is 6.75watts should run about 2.5 hours. Results will vary though as wiring and the batteries internal resistance will eat up some of your power.
higher amp bulbs will run shorter times.
I used 1.2v as a reference because nimh actually have most of their life from 1.2-1.3v IMO while alkalines have from 1.1-1.5v depending on loading.