I heard rechargeable batteries (AA alkaline) are bad for the Fenix LD10 and that they can wreck the circuit or something, is this true, and also would this wreck any other lights as well (Fenix LD20?)? thank alot
Typically 'rechargeable' is used to refer to LiFePO4, Li-ion, Ni-Mh and Ni-Cad (lead-acid, not really being relevant to flashlights).
Alkaline, Zinc Chloride, Lithium (covering AA -1.7v, CR -3V and the new 14500-3.6v primary versions) and Silver Oxide are primary types.
Rechargeable Alkaline are neither quite primary nor rechargeable, but are an in-between compromise resulting in similar performance to primary alkaline (with the same voltage characteristics), but have a very limited number of recharge cycles and need special chargers.
The LD10 works best on Ni-Mh due to the cell's low internal resistance and high current output. The initially higher voltage of a standard Alkaline is outweighed by its higher internal resistance under load.
If an Alkaline leaks in your LD10 it might well wreck it, but if you ensure it is not run flat and is well in date, the risks are minimal. Rechargeable Alkaline also have the risk of leaking and this increases with the number of recharge cycles, but will not fry the electronics due to high voltage, so Alkalines are only a risk due to leaking.
With the quality and performance of Low Self Discharge Ni-Mh cells, and the Energiser Lithium AA, I don't see a real place for rechargeable Alkaline.
I would have to check the stats of the lights. The reason why some are not recommended for rechargeables is because the lights are rated for a certain voltage range. Rechargeables tend to have a slightly higher voltage than the typical battery. This voltage can be greater than the limit on the leds causing them to blow out. I have noticed some of the single cell lights with this issue. a lot of the newer lights mainly dual cell have a higher voltage range than batteries supply.
Lets say your light has a led raing of 1.5v; some rechargeables when fully charged will be over 1.6v. I have seen the dual cell lights run in the range of 3-9v so they are safe. I hope this helps and this could be the case with the models you listed.
Not sure I agree....
Only LiFePO4 and li-ion rechargeables will have a higher voltage. Lithium AA primaries have a slightly higher initial voltage up to 1.7V, but this only becomes a problem in multi-cell lights where the cells are in series.
Ni-Mh might have a topped up voltage of around 1.5V, but this quickly drops to the nominal 1.2V, and is the recommended cell for an LD10.
I'm sorry, but I have to correct you a little. Alkalines (reasonnable ones, not dollar store ones) only leak when demanding more power than they can actually give (not the case with current Fenix except perhaps the TK70) or if you forget depleted or depleting alkalines in a flashlight for too long (can be a short time with depleted cells or dollar store crap).
NiMh cells don't stay charged for years... they just very slowly discharge and retain a capacity of ~80% after 6 months and ~60% after a year on the shelf.
Sorry man, just had to get the facts straight.
The latest eneloops retain 75% of their charge after three years.
Good Alkalines are pretty resilient, and don't tend to leak immediately even if over drawn. Once depleted the reactions inside the cell start to build pressure and break down the seals and this can lead to leakage. This will happen quickly if the cell is left closed-circuit (by leaving the power switch on).
