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Higher capacity than before - but still too low for D cells
on November 14, 2010
The rechargeable D cells in this package (Rayovac Platinum LSD NiMH D, 2-Count) offer two major improvements over previous-generation products from Rayovac:
1. The capacity is now rated at 3000mAh, compared to just 1800-2400mAh for previous-generation products (depending on which version you get)
2. The package claims "Pre-Charged" and "Holds charge up to 2x longer" than standard NiMH cells.
I have tested two of those Rayovac Platinum cells (*), using my rigged-up La Crosse BC-900 charger/analyzer. Right out of the box, they hold an average remaining charge of 2530mAh. That means they arrived with over 80% of rated capacity. After just one more charge/discharge cycle, the average capacity improved to 3100mAh, which is better than rated value. Therefore I have no doubt that those Platinum batteries are indeed low-self-discharge type similar to SANYO eneloop, with 50% higher capacity.
An alkaline D cell is typically rated for about 19000mAh, but only at a very low current of ~30mA. When used at a load of 500mA (such as flashlight), its capacity drops to about half. Those 3100mAh rechargeable D cells offer only about 1/3 the capacity of alkaline cells, which means you'll have to replace/recharge batteries three times more often. But in the long run, using rechargeable will always save you money.
There are other rechargeable D cells with 3x higher capacity (such as the 9500mAh 2-Pack D IMEDION), but they also cost 3-4x more. So this package is a reasonable compromise between price and performance. Another benefit is that each Rayovac Platinum D cells is half the weight of alkaline D cell (70g vs. 140g).
The batteries I purchased are actually the smaller Rayovac Platinum C cells. Both have exactly the same capacity, because internally they all contain a sub-C cell. I prefer the C cells because, if necessary, I can put them in the D-shell adapters that came with my BC-900.
[Update on Nov 24, 2012]
A good alternative to consider is the Tenergy Centura D Size Low-Self-Discharge NiMH Rechargeable Batteries. The Tenergy D cell offers 2.7x greater capacity (8000mAh vs 3000mAh) at less than 2x the price of the Rayovac Platinum D cell.