NiMH vs Lithium rechargeables with 2xAA Cree XML-U3 light

Kevlight14

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I bought a Powertac Valor 2xAA light. Using a fresh set of Eneloops (Japan/1900mAh), I can push the light into Max Mode (est. 400 Lumens), but output drops to maybe 150L after 30 minutes then just a dim flicker after 50 minutes. For reference, my Thrunite 2xAA emits a constant 280L for well over an hour with the same batteries. How would the Valor behave if I used rechargeable Lithiums instead?
 

Lynx_Arc

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I bought a Powertac Valor 2xAA light. Using a fresh set of Eneloops (Japan/1900mAh), I can push the light into Max Mode (est. 400 Lumens), but output drops to maybe 150L after 30 minutes then just a dim flicker after 50 minutes. For reference, my Thrunite 2xAA emits a constant 280L for well over an hour with the same batteries. How would the Valor behave if I used rechargeable Lithiums instead?
The rechargeable lithiums if they can put out the power needed to sustain 400 lumens would likely operate at that level and then simply shut off. You may be able to possibly (not likely) get a short flicker of light at a lower level for an insignificant amount of time but having a 3.7v (4v+ off the charger) lithium ion battery inside the 1.5v battery with a probably buck circuit would have it operating well above the battery voltage level till it is depleted to perhaps 3-3.5v depending on the load caving and the shutoff voltage point in the protection circuit. I recall that the 2AA mag LED lights were nice at the time they came out but suffered similarly from the same issue of simply blinking out when the batteries were done for leaving you in the dark without notice which for most of us is unacceptable. Using nimh cells in them made it a lot worse as the output didn't dim noticeably and started at a slighting higher lumen output also. If you do decide to go with this be prepared in advance for the light to go from full blast to nothing just in case have a second light on you.
 

Kevlight14

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Thanks. I'm going to run another test soon. This time keeping the Thrunight in turbo/max, but reducing the Valor from High to Medium. I expect the Valor to at least last longer than 30 minutes this time. I still may end up sending it back.
 

Kevlight14

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The odd thing is when I use eneloop Pros, the light does not show a change in brightness when clicking from Medium to Max mode. However, when using regular Eneloops there is a noticable difference when clicking to Max mode. I ran a discharge/recharge with my Tenergy charger, which made no difference. The Pros aren't that old.
 

Lynx_Arc

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The odd thing is when I use eneloop Pros, the light does not show a change in brightness when clicking from Medium to Max mode. However, when using regular Eneloops there is a noticable difference when clicking to Max mode. I ran a discharge/recharge with my Tenergy charger, which made no difference. The Pros aren't that old.
From what I've heard of the pros (I have only 2 of them with less than half a dozen cycles on them is that they have a lot less cycle life and that cycles are more important than age being around 100-200 cycles or so expected while regular eneloops are (I think) 800-1000 cycles (perhaps 400-600 maybe) and to the regular eneloops age may be more of a consideration in use than cycles as with a few hundred cycles you could find a cell failing after less than a year while heading towards a thousand cycles would have you several years in use with no issues.

I do know differing cells settle to differing voltages after charging and the higher voltages can increase the output in devices that aren't regulated or detect voltage dropping. I'm not totally sure by typically speaking lower capacity rechargeables often can sustain voltage under heavier current demands than higher capacity ones which could mean simply the pros sag more under load than the regular ones do. IMO you would have to research that idea or someone who is an Eneloop extpert can chime in. I've had old crappy 2500mah Energizer cells that would cave a lot under a load due to higher internal resistance that develops more easily in higher cap batteries than lower ones often ruining them form use but in light drain devices.
 

Kevlight14

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From what I've heard of the pros (I have only 2 of them with less than half a dozen cycles on them is that they have a lot less cycle life and that cycles are more important than age being around 100-200 cycles or so expected while regular eneloops are (I think) 800-1000 cycles (perhaps 400-600 maybe) and to the regular eneloops age may be more of a consideration in use than cycles as with a few hundred cycles you could find a cell failing after less than a year while heading towards a thousand cycles would have you several years in use with no issues.

I do know differing cells settle to differing voltages after charging and the higher voltages can increase the output in devices that aren't regulated or detect voltage dropping. I'm not totally sure by typically speaking lower capacity rechargeables often can sustain voltage under heavier current demands than higher capacity ones which could mean simply the pros sag more under load than the regular ones do. IMO you would have to research that idea or someone who is an Eneloop extpert can chime in. I've had old crappy 2500mah Energizer cells that would cave a lot under a load due to higher internal resistance that develops more easily in higher cap batteries than lower ones often ruining them form use but in light drain devices.
I think what you say makes sense. Between your comments and those of others, the best solution for my application is to simply upgrade to a light that uses a better power source.....something other than NiMH AAs. FWIW, Powertac was gracious enough to refund my money and pay for return shipping, so where they may lack in questionable specifications, they make up for offering full refunds.
 

Lynx_Arc

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I think what you say makes sense. Between your comments and those of others, the best solution for my application is to simply upgrade to a light that uses a better power source.....something other than NiMH AAs. FWIW, Powertac was gracious enough to refund my money and pay for return shipping, so where they may lack in questionable specifications, they make up for offering full refund
You could post in the recommend me a light forum and see what people recommend for you there as many folks have a lot of more experience with many more lights than I do.
 
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