Series/Parallel Question

[hula]

Lets say I've got a 4d flashlight and a set of four 3 to d holders. The first two holders I load with AA batteries as normal and insert. The next two I adapt the holders so that the three AA batteries that they each hold are in parallel. So now we've effectively got four cells - the first two at 4.5v with 2100mah the next two at 1.5v with 6300mah. All four holders are now in the flashlight in series.
Will I get 9v at 16800mah at the receiving end or is this configuration not possible?

 

[shiftd]

this configuration will kill your battery, one or more.
the capacity of the batteries cannot be determined, at best. Well, the first 2 holder in series would have 2100 mAh in capacity, the second set of 2 holders in series paralel would have 6300 mAh. Sure, you get a nice High Voltage that way, but when the first 2 sets exhausted, the second sets had only drained about 2100 mAH, so you risk one or more of your batteries to be overdischarged. If you want to get 9V at the end, you can use 4 holder all in series configuration. use 2 batteries at each holder or just use 3 holders and one dummy D cell.

 

[Steelwolf]

Let me get this straight. 2 batteries with cells arranged to give 4.5V each, 2 batteries with cells arranged to give 1.5V each. All batteries then connected in series. That would give you 12V in total, not 9V.

Did you want 12V or 9V?

9V is simple enough. You have 4 battery holders, each holding 3 cells in series. You have 4.5V per battery. Connect them in 2 pairs series-parallel. Each pair gives you 9V. Connect each 9V pair in parallel to double your capacity. But the wiring may be fiddly in the tight confines of the Mag body, so you may just decide to use 2 dummy D cells and 2 batteries.

12V is a little more difficult. You need to get 8 cells in series, but you have space for 12 cells. Which means you will have 2 fully loaded battery holders (all cells in series), one holder loaded with 2 cells (also in series) and all other space taken up by dummy cells. The holders and dummy cell are all connected in series.

Are you looking at maximising the efficiency of an EverLED (which has Vin limit of 9V) or are you looking at putting in a PowerPuck (which, IIRC, takes 12V)?

 

[shankus]

This is where Chief_Wiggum's 4 AA-to-D cell adaptors shine. Too bad they are unavailable now.

They were available in series (6V alkaline), series parallel (3V alkaline) or parallel (1.5V alkaline)

Three of the series-parallel config, with one dummy D cell.

 

[Charles Bradshaw]

Series/parallel must be balanced, as shiftd pointed out.

Series: increases Voltage only.

Parallel: increases Current capacity only.