Will the AMC7135 1000ma driver overheat?

[andersonEE]

I have a XR-E Q5 from DX and I want to drive it with the 1050mA driver from DX: http://www.dealextreme.com/details.dx/sku.1885

My plan is to use 4 Energizer rechargeable Nimh batteries (2700mah, 1.2V) for a total of 4.8Volts. I know that people were saying the 7135 will overheat at more than 4.5 volts and since the fresh batteries will probably be at 5.2 for a little while when they're fresh will this cause problems? If so could I heat sink it using Arctic Alumina to resolve the problem?

If not, please recommend a different rechargeable battery solution that I could use with the 7135 (since I already have them).

Thanks!

 

[Lighthouse one]

Not a problem- these are very robust drivers. I run mine ( the 2 and 3 chip versions) off 2 123 primaries often. At 6 volts it's wasting the power a bit, but never had any trouble. If you glue the driver with the thermal glue that DX sells or Arctic Alumina- fine. It will help, Unless you're going to run the light for a long time - say over 30 minutes at a shot- don't worry about it if you don't have perfect heat sinking for the driver.

I sometime just pot my drivers with permatex high temp gasket maker.

 

[andersonEE]

Thanks!

 

[Benson]

I have a XR-E Q5 from DX and I want to drive it with the 1050mA driver from DX: http://www.dealextreme.com/details.dx/sku.1885

My plan is to use 4 Energizer rechargeable Nimh batteries (2700mah, 1.2V) for a total of 4.8Volts. I know that people were saying the 7135 will overheat at more than 4.5 volts and since the fresh batteries will probably be at 5.2 for a little while when they're fresh will this cause problems? If so could I heat sink it using Arctic Alumina to resolve the problem?

You ought to heatsink it as well as you can -- probably be OK without, but better safe than sorry.

The 4.5V some people talk about is obviously not a hard limit, and in fact is looking at completely the wrong number. What matters is the difference between Vbat and Vf, as this determines the power lost in the AMC7135, so if you have a particularly low-Vf LED, your driver will need more heatsinking (but your LED will need less).

 

[carling]

The datasheet of the AMC7135 says that it has a built-in thermal protection that will automatically shutdown the regulator when it overheats.

I'd still recommend heatsinking the drivers though...