Fly Electric!

Black Paint and Heat Dissipation

I want to dissipate heat effectively on my lipo balancer so I tested the effect of painting the resistor/heat sink board

The tests confirm that matt/dull finishes improve heat dissipation, by about 5% in the 40' range and a huge 16% at 60'C
Black paint was no better than white in these tests, lending credibility to the view that black aids visual wavelengths only
Tight heat-shrink covering has no adverse effect, but covering that is loose has a big effect and increases temperatures

The test board is 19x31mm 1.6mm double-sided copper board with an 8.2ohm 1W resistor and MCP9701 sensor
The reference and test board temperature sensors were adjusted in software to give the same readings in stable conditions
The first tests were done from a stable base shown for 1min and allowed to ramp up with 300mA (0.7W) for another 9 minutes
The second tests were stabilised for 5 minutes at 300mA, logged for 1min and then increased to 400mA (1.3W) for 9 minutes
The third heat shrink tests were at 350mA (1W) with the black board, one with heat shrink removed and the other with it added

The graphs show temperatures every 10 seconds as logged in my Temp1 device
The environment was an unheated room with the door closed and the sensors hanging in still air
The board is deliberately half the size of my 3 cell PIC balancer to help me assess its performance
The first 300mA tests were therefore also at half the wattage (0.7W) for comparible results
The second 400mA tests were at 1.3W just to see what happened at higher temperatures

The third 350mA 1W test is probably the highest you want to take a board of this size
In the 'Shrink1' test heat shrink sleeving had been properly shrunk onto the board; it was cut off during the test
In the 'Shrink2' test the heat shrink was simply placed over the board during the test but not shrunk so inhibited cooling

TEST 1 - 0-300mA (0.7W)

TEST 2 - 300-400mA (1.3W)

TEST 3 - 350mA (1W)

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