Converting incandescent flashlight to LED but for NiMH (i.e. 1.8-2.4 V)

seanspotatobusiness

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Jul 12, 2010
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I have an old incandescent flashlight which uses two AA cells. I prefer to use NiMH rechargeables. I would like to replace the incandescent bulb with an LED. It does not need to be bright at all; there is no heatsinking and the flashlight is rubberised so it mustn't be so bright that heat is a concern. My problem is that all the drop-in incandesent-to-LED upgrades I've found assume alkaline batteries and don't even seem to function below 2.8 V which isn't even good for alkalines IMO. They're basically just an LED and no circuitry to regulate the current or increase the voltage. Does anyone know what I can do or get to replace the incandescent with an LED? I don't mind making it myself but it needs to stop at 1.8 V so I don't risk reversing the voltage on one of my rechargeables which a joule-thiefy thing won't do. Again, I don't want anything flashy - I just need it to not walk into things. Thanks!
 

HKJ

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You could use 1.5V LiIon AA batteries, they maintain 1.5V until they are empty. I have reviewed a few lately.
 

Lynx_Arc

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I have an old waterproof incan flashlight that I put a dropin from an older Energizer 1D LED flashlight that the only problem is these dropins sometimes burn out running off 2AAs with nimh being lower voltage that helps. Most boosting dropins that work well with nimh will probably drain them down lower than you desire. I've converted most of my "liked" incans to LED but over time I've invested in 18650 LED lights and multi mode lights with newer more powerful and efficient LEDs with better tints and output and all my converted incans sit gathering dust. I don't use any of them even once a month as with 18650 I have no issues with reversing batteries and they run tons longer and brighter.
One other candidate for a dropin if you haven't tried it... the Rayovac 2AA plastic light that comes with 2 heavy duty cells for around $2 in stores. The dropin may work better for you and is dirt cheap.
 

xxo

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A lot of the cheap 2 cell LED drop-ins are direct drive and won't run unless the Voltage is close to 1.5V, which sucks for NiMH's and alkalines that have been drained a bit or pretty much anything. Better drop ins will run on a wide range of Voltages, some of them as low as 1 Volt - superbritleds sells some of these. The Nite Ize 55 or 74 lumen drop ins work down to about 2 Volts which is fine for a pair of NiMH's.
 

bykfixer

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Presuming you have a PR base bulb. The PR base Nite Ize reportedly works up to 6 volts.

A typical alkaline is about 1.5 volts idle but 1.2 when under load. 2x wouldbe 2.4 or there abouts. Mine work just fine even on low fuel 2cell lights.
 

pc_light

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Feb 10, 2004
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Old Dominion, USA
I used a "AA 800mA Linear Boost Driver from FastTech" in my incan Mini-mag mod, described here.

It runs on single or double AA NiMH batteries just fine. I haven't actually timed but Low mode lasts hours.
 
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