I tested the XHP70 again last night, now mounted on a XHP70 Sinkpad, with the romantically wandering traces avoided by scratching some masking away, does not look pretty but it works alright. What is most important is that the thermal path of the middle pad has improved compared to my makeshift board using a XM-L Sinkpad and copper bits.
It is the exact same led as the first test and I plot the results together the makeshift board results because that is pretty interesting: at high currents this led really wants a good thermal path:
As you can see, the led has suffered somewhat from the 15A treatment of the first test: the output is a tad lower and the voltage a bit higher. But over 6.6A that effect is taken over by the better thermal path of the XHP70 board. It maxes out now at 11-12A.
Still my numbers are very low compared to Dale's numbers, so after cooling down I did some quick tests that were done more like how Dale measures with his flashlights: still the board was on the copper mount but there was no active cooling (fan out), and I went straight to the target current (I tested 8A and 12A), then looked for 1 minute every 10 seconds at the light output:
8A 0 seconds |
5340 |
8A 10 seconds |
5280 |
8A 20 seconds |
5230 |
8A 30 seconds |
5190 |
8A 40 seconds |
5140 |
8A 50 seconds |
5100 |
8A 60 seconds |
5050 |
12A 0 seconds |
6631 |
12A 10 seconds |
6258 |
12A 20 seconds |
6164 |
12A 30 seconds |
6024 |
12A 40 seconds |
5838 |
12A 50 seconds |
5744 |
12A 60 seconds |
5557 |
That helps! apparently at very high currents there is a noticable difference between measuring at 30 seconds and measuring at 'steady state' like I do in my tests. These numbers look a bit more like Dale's, and any difference leftover I am willing to explain by different calibrations or differences within a led bin , or he used a different bin. And my led was already tortured, as can be seen in the graph above.
To get the maximum out of the led I turned the current from zero to 15A in a moment and for a nanosecond I measured over 7000 lumen.