The more D cells you have the longer run time you will get in LED maglites.
That's just adding up the mAh of the cells being used. I wish the 123s had the runtime of larger cell batteries. Something the industry needs to improve IMO. Until then I will continue using rechargeable
I always get caught up in these flashlight threads!
Typical D Cell mAh:
<table class="wikitable"><tbody><tr><th>
</th> <th>
Zinc–carbon</th> <th>
Alkaline</th> <th>
Li-FeS<sub>2</sub></th> <th>
NiCd</th> <th>
NiMH</th> </tr> <tr> <td>IEC name</td> <td>R20</td> <td>LR20</td> <td>FR20</td> <td>KR20</td> <td>HR20</td> </tr> <tr> <td>ANSI/NEDA name</td> <td>13D</td> <td>13A</td> <td>13LF</td> <td>
</td> <td>
</td> </tr> <tr> <td>Typical capacity</td> <td>
8000 mAh</td> <td>
12000 mAh</td> <td>
</td> <td>
</td> <td>
2200–12000 mAh</td> </tr> <tr> <td>Nominal
voltage</td> <td>1.50 V</td> <td>1.50 V</td> <td>1.50 V</td> <td>1.25 V</td> <td>1.25 V</td></tr></tbody></table>
Typical 123 mAh:
<table class="wikitable" width="100%"><tbody><tr><th width="20%">Most common name</th> <td>CR123A</td> </tr> <tr> <th>Other Common Names</th> <td>Camera Battery, 123, CR123, R123 (Li-Ion), RCR123A, RCR123 (Li-Ion), 17345, 16340 (Li-Ion rechargeable)</td> </tr> <tr> <th>IEC Name</th> <td>CR17345 (lithium)</td> </tr> <tr> <th>ANSI/NEDA Name</th> <td>5018LC (lithium)</td> </tr> <tr> <th>Typical Capacity (mA·h)</th> <td>
1500 (lithium),
700 (Li–ion)</td> </tr> <tr> <th>Nominal Voltage (V)</th> <td>3 (lithium), 3.6 (Li-ion)</td> </tr> <tr> <th>Shape</th> <td>Cylinder</td> </tr> <tr> <th>Terminal layout</th> <td>+ Nub cylinder end, − Flat opposite end</td> </tr> <tr> <th>Dimensions</th> <td>L 34.5 mm, D 17 mm</td> </tr> <tr> <th>Comments</th> <td>CR (cylindrical lithium) 1 X 2/3A which breaks down further as 2/3 the size of an 'A' cell (an 'A' size cell is an industrial size)</td></tr></tbody></table>