Is LED driver regulator circuit necessary for NiMH batttery use?

[Jack Blake]

Saw some forum posts alleging that NiMH batteries produce "too much
current" when used with LEDs and suggesting that a resistor or
regulator circuit is necessary. Is this true? I use NiMH with
un-regulated 5mm LED and 1-watt (said to be unregulated) Luxeon Planet
Bike headlights. So far, I've burnt out the cheepie LED headlights and
1 (of 3) Princeton Tec Yukon headlight, but all the others are running
fine. Please educate [me] this layperson about they "why" of LED
regulators for NiMH. Thanks.

 

[Ian Stirling]

Saw some forum posts alleging that NiMH batteries produce "too much
current" when used with LEDs and suggesting that a resistor or
regulator circuit is necessary. Is this true? I use NiMH with
un-regulated 5mm LED and 1-watt (said to be unregulated) Luxeon Planet
Bike headlights. So far, I've burnt out the cheepie LED headlights and
1 (of 3) Princeton Tec Yukon headlight, but all the others are running
fine. Please educate [me] this layperson about they "why" of LED
regulators for NiMH. Thanks.

Yes, you need a resistor.
LEDs burn out very easily with overvoltage.
If you increase the voltage, the current increases much faster than
the voltage.
If the current exceeds the stated rating of the LED by much it will
likely fail, either immediately, or over time.
A resistor is generally a good idea, unless you've performed the
calculations to find that it's not needed.