P7 blues

[Roland Gama]

Hello everybody,

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Running the P7 mounted on a copper heatsink with arctic silver at 3 amps. gives a bluish colour sometimes and the output dims as it gets more blue in colour.

Could anyone explain the cause of this. Is the P7 failing or am I pushing it too hard?

 

[spencer]

You did what I did. Your emitter isn't glued down properly. You should be able to pull it off and reglue it.

 

[darkzero]

If you are using Artic Silver thermal grease then there is your cause.

 

[spc]

also make sure your not shorting the neg and pos on the heatsink..

 

[Lumencraft (Matt)]

What you need is the Arctic Alumina thermal adhesive, it comes in two parts and you mix it then apply.

 

[Roland Gama]

I do use arctic silver thermal adhesive and the bond is still good as I rechecked it. Also the battery top has the negative polarity so electrical isolation of the heat sink is not necessary.
I use four eneloops direct drive and at full charge measures 5.4 volts and 3.2 amps.

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[DocD]

hi what bin is the P7 if you j bin 3.5 to 3.75 volts if it's a i bin 3.25 to 3.50 you might have cook it with to much forward voltage as i think 5.4v hot of the charger is might sag down to 4.5 quite quickley but is still to much forward volts even for a j bin i hope i'm wrong cheers DocD

 

[Sabrewolf]

Hello,

Did you also epoxy the heatsink to the barrel of the Mag?
Does the P7 go blue right away? or does it take awhile?
If is right away, then like another member said, you may
have a problem with thermal contact using that particular
epoxy. You may need to get the Arctic Ceramic Epoxy
that has an off-white color, and not brown/black like yours.
If the light takes awhile to go blue, then your heatsink-mag
thermal connection is not workin' to well. If so, then grab
some Artic Silver Thermal Paste, and smear a generous coat
all over the outside of your heatsink where it touches the mag.
Hope that helps!

 

[darkzero]

Since you've cleared up the epoxy & polarity subjects, I agree with DocD. Too much voltage. You should not direct drive with 4 NiMhs. Try throwing a dummy AA cell in your holder, if you have one, & see if you get the same result.

 

[Roland Gama]

Hello all of you,
Thank you all for the quick replies.
On microscopic examination I found a dry solder joint on one of the P7 terminals as seen in the photo. I soldered it back and the problem has been solved.
Quite a good experience though and I guess from now on I will be double checking all solder joints.

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Thank you again.

 

[yellow]

still the wrong placing - with Arctic Silver glue
glue has worse thermal capabilities than heat transfer paste, which is the right way to mount anything going hot.

2nd better point is, that the connection is semi-"glued" when using paste, placing the led and working it around a bit.
That place is not cured within minutes and can be changed (if led was not perfectly centered or so).
Then, when position suits, use normal epoxy around led and sink to glue it in.
Last positive point: less cost

 

[olrac]

I think DocD nailed it, If you have a J bin for instance, the Fv is 3.5 - 3.75 and pushing with 4.8 is too much. (I know this from personal experience,almost lol)

 

[Roland Gama]

That's a good point YELLOW. All the three points in fact.
Thanks for the tips. Sure to go that way from now on.

 

[DocD]

Killed a P7, I bin with 3.9 volts turn blue and then it died so bewear it's easy to kill a P7 with to much forward voltage
But the amps you push in to the P7, ie is still a open question ?
This is my third P7 to past on the body count keeps rising :sigh: cheers DocD

 

[Roland Gama]

DocD,,
Even with 5.2 volts from the four series connected eneloops the max current flowing through the P7 is 3.2 amps which is well within P7 tolerance.
Each eneloop has 2000mA capacity. Thus the current flow is restricted and I feel it cant destroy the P7.
If the eneloops were 5000mA capable then I think your point would hold.

I could be wrong.

 

[LEDninja]

Both SSC-P4 and SSC-P7 turn blue before they die from being overdriven.
Try and stay within specs. 3.5V and 2.8A.
It is better to accept a little less light than to burn out your LED (which would leave you in the dark).

Try using 3 Eneloops with a spacer or use some other less powerful battery.
3 Eneloops should give you 4.05-4.2V and 2.8A at the start dropping to 3.45V and 2A towards the end.

I measured 2.8A with freshly charged 3*2900 mAH RayOvac C cells in my 3C M@g-P7 and also with 1*18650 in my EDC-P7.
Even when the current was below 2A in my EDC-P7, it was still more than 2X brighter than my XRE torches (Dereelight CL1H/18650 and Ultrafire C3 Q5/14500).

I had burned out an Elektrolumens My Little Friend (3xSSC-P4, 4AAA) when I switched from no-name batteries to Duracell 1000 mAH. So 4 cells is a no-no unless you use crappy cells.

Vf of J bin is 3.5V-3.75V
For a 4 battery setup it is 0.875V-0.9375V per battery.
For a 3 battery setup it is 1.166V-1.25V per battery.

Eneloops 2000 mAH are capable of producing up to 10A for a 4 battery setup.
Eneloops 2000 mAH are capable of producing up to 3A for a 3 battery setup.

Energizer 2300 mAH are capable of producing up to 3A for a 4 battery setup.
Energizer 2300 mAH are capable of producing up to 0.5A for a 3 battery setup.

Note 2300 mAH with 300 more mAH produces less amps than the 2000 mAH Eneloop. mAH rating is done at some ridicules low amp draw (like 50 mA) and is no indication of how the battery performs at high amp requirements.
Actually 4 AA Eneloops will outperform 4 D Energizer NiMH in your application.

 

[Roland Gama]

Thanks for the data ledninja.

 

[Essexman]

hi what bin is the P7 if you j bin 3.5 to 3.75 volts if it's a i bin 3.25 to 3.50 you might have cook it with to much forward voltage as i think 5.4v hot of the charger is might sag down to 4.5 quite quickley but is still to much forward volts even for a j bin i hope i'm wrong cheers DocD

Been there done that! The result of low Vf and 3.6V, half dead P7 .

Hay Doc got any spare P7's ??

 

[Roland Gama]

What's the battery voltage got to do with the P7 burning out?
Surely if I use a 12volts battery with a simple resistor to run the P7 at 3 amps its not going to burn out.
The voltage across the P7 remains 12 volts but the current is restricted to 3 amps. IMO its the current that matters.

 

[KowShak]

What's the battery voltage got to do with the P7 burning out?
Surely if I use a 12volts battery with a simple resistor to run the P7 at 3 amps its not going to burn out.
The voltage across the P7 remains 12 volts but the current is restricted to 3 amps. IMO its the current that matters.

You won't have 12 volts over the P7, what you'll have is a lower voltage, e.g. something like 3.6 volts because you've formed a voltage divider.

Ohms law would apply i.e. V=IR, so that if you had 12 volts accross the P7 it would draw a lot of current and become a SED, i.e. smoke emitting diode.