Coast P14 rechargeables

Coast says not to use rechargeable on the p14 although someone wrote that Nimph rechargeables would work fine with the right rechargeables. What exactly am I looking for as in rechargeable that will work well in the p14? Thanks.

1.2V nimh batteries will work fine in it in all their lights...not sure why they said not to use rechargables...maybe they meant not to use 3.7v li-ion rechargables or maybe they think the runtime will be shorter on nimh batteries because of the lower voltage.

Runtime at near full light output is actually improved with NiMH batteries though the total usable runtime may be reduced as NiMH batteries fall on thier face pretty badly as they near the end of thier time at high output. They are similar to both NiCad & Lithium-Ion in that regard. They all maintain very low output resistance until the capacity is used up.

Alkaline batteries on the other hand have near linear increase in output resistance as the batteries capacty is used up, consequently the alkaline battery voltage drops to a voltage under load that is below the rated FV of the LED far more quickly, long before thier real capacity is used up. After going below the rated VF of the LED the current draw is dramatically reduced. This allows the alkaline battery to continue to deliver close to its rated capacity but at reduced light output. By the time the current drops to 1/4 the normal current rating of the LED the efficiency of the LED has dramatically improved & is delivering 1/3 to 1/2 the rated lumens. At this level of current draw the alkaline battery can last a quite a while. Even so the actual lumens for the alkaline batteried torch will drop a fair amount further before the NiMH battery starts losing noticable brightness. By the time the lumen output reaches 1/8 the original intensity with the alkaline battery the alkaline battery will likely be brighter than the NiMH battery as the NiMH battery will be falling on it's face by now & continue for many more hours that way as they will still have some capacity wheras the NiMH battery would be pretty much dead.

I think they say that to cover their asses across the whole line of torches they make... That and their outlandish run times makes them sound incompetent as a torch manufacturer, however as germanium says, re-chargables seem to work well in the P14.

One more thing. LedLEnser (Coast) makes their own alkaline batteries...

https://www.candlepowerforums.com/threads/213513

LL recommends not using NiMH because their lights are designed to use the higher internal resistance of alkaline cells. The lower internal resistance of NiMH allows the light to run brighter, which generates more heat, which is detrimental to the light because LL uses a very limited heatsink.


Using some sort of regulator circuitry would eliminate this issue, but LL only uses simple drop resistors in direct drive.


Many do run NiMH in their LL lights without issue, but it is against LL's recommendation due to the design.

germanium said:

Alkaline batteries on the other hand have near linear increase in output resistance as the batteries capacty is used up, consequently the alkaline battery voltage drops to a voltage under load that is below the rated FV of the LED far more quickly, long before thier real capacity is used up. After going below the rated VF of the LED the current draw is dramatically reduced. This allows the alkaline battery to continue to deliver close to its rated capacity but at reduced light output. By the time the current drops to 1/4 the normal current rating of the LED the efficiency of the LED has dramatically improved & is delivering 1/3 to 1/2 the rated lumens. At this level of current draw the alkaline battery can last a quite a while. Even so the actual lumens for the alkaline batteried torch will drop a fair amount further before the NiMH battery starts losing noticable brightness. By the time the lumen output reaches 1/8 the original intensity with the alkaline battery the alkaline battery will likely be brighter than the NiMH battery as the NiMH battery will be falling on it's face by now & continue for many more hours that way as they will still have some capacity wheras the NiMH battery would be pretty much dead.

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That is not exactly how it works. Under load, alkaline cells cannot deliver anywhere near their rated capacity. Under the approximate load they are under in a multicell light, they can only deliver about 1/3 to 1/2 of their rated capacity.

Marduke said:

https://www.candlepowerforums.com/threads/213513LL recommends not using NiMH because their lights are designed to use the higher internal resistance of alkaline cells. The lower internal resistance of NiMH allows the light to run brighter, which generates more heat, which is detrimental to the light because LL uses a very limited heatsink.

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Yes, that's true. But that's theory. In practice P7 and P14 are slightly less bright with Ni-MH than using alkalines.

phantom23 said:

Yes, that's true. But that's theory. In practice P7 and P14 are slightly less bright with Ni-MH than using alkalines.

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Only for the first 5-15 minutes, then NiMH is SIGNIFICANTLY brighter for the majority of the time.

No because P14 (and P7) holds quite constant brightness. It's significantly brighter with e91 lithium though. I can assume Ni-MH's are ok for LedLensers, in contrary to lithiums.