Car battery too powerful for LED MR16's



This claim was made by a popular ebay seller (female) today.

My original (filament lamp) boat lighting (boats use a 12V car battery supply) pulled 28 Amps when all the lights were switched on. Just fitted a mixture of white 4500K (heads-bathroom), and warm white (3200K) MR16's and total current all switched on 3 Amps. Stonking - no more flat batteries.:clap:

I know that these 12V LED lamps can be destroyed if an electronic transformer suitable for halogen lighting (white box few inches long) is used because these power supplies only chuck out 12V if the load is between min & max stated on the transformer (usually wattage). Because LED's draw so little, the transformer will go over-voltage and puff!!! no more LED's.

So with a nice rock steady feed from a 12V car battery, one would think that this was the perfect means of supplying the LED MR16's. Allegedly not. The lady assistant claimed that she has had many returns from a big warehouse customer who did not use the recommended LED psu's. Claimed that the supplies they used were too powerful. And I will have the same problem.

Surely, the LED circuitry only pulls what it needs, but I think what she was getting at is that the large surge currents destroy the LED's. I'm dubious but only time will tell.

Have any forum members heard of this claim?

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Active Member
I'm with you, the LED's will only pull what they need and as long as it's 12V what's the problem?

How is the battery charged? When the engine is running? Any surges then maybe?


Just like a car - alternator + voltage regulator = around 14V max on batteries.

I think she was more hinting at the large current capability of a car battery (300+ Amps).

Surely the LED's (60 off per MR16 equiv to 50W but consumes 3W) have a current limited supply. And I'm guessing that there's a full-wave rectifier directly on the MR16 pins since these bulbs work either way round so this would drop 2 lots of diode = 0.7V x 2 = 1.4V.

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