I use LED lighting at a cabin with a 12V battery. I bought a Torchstar MR16 LED (Amazon) that has 4 leds. It just has 2 prongs to plug in and there is no way to tell if one is + and one -. When I hook it up to a small 12V battery (drill driver battery) it works on either polarity. Do I need to worry how I hook it up? I thought LEDs were supposed to only work if hooked up correctly polarity-wise. Thanks

 

The inclusion of a bridge rectifier would prevent damage caused by wrongly inserted batteries?

 

These are "dimmable" bulbs and intended to operate on 12V AC or DC sources. Therefore, you can plug them in either way. They contain internal circuit to sense dimming based on input voltage. This particular model also will not flicker when powered by mains AC because of the internal AC to DC converter and dimmer control.

 

I'm not sure about the "dimmable" part but every 12V LED bulb I've looked at recently has a bridge rectifier so they work equally well for AC or DC. So of course for DC they work with either polarity.

I've seen some with constant current limiters, some with just resistors. Constant current bulbs are not very dimmable.