LED Lenser (Coast) P7 REVIEW With Beamshots/Lux/Overall Output Readings

[Turbo DV8]

...but I was really impressed with the LL P7, and what it can do with 3AAA's...

Ooops, better make that 4 AAA's!

 

[Turbo DV8]

This is just a musing. I bought an A6 Polestar at Fry's, which has the MCE Cree. I returned it because the non-adjustable beam favored spill over throw, and the over-abundant spill actually interfered with the eye's ability to see farther into the throw by causing the pupils to contract. Basically, the lights spill was blinding me, and this was immediately apparent when going back to the P7 and P14 on spot mode.

The thing is, though, doing a ceiling bounce between the two shows that the MCE clearly had a boat load more overall light output than the LED Lenser. That got me to salivating over what could be, if only LED Lenser put an MCE behind that optic in the P14! OMG! I doubt any other light the size of the P14 would be able to even come close in throw. I doubt the AAA format of the P7 would support the MCE, though. If only...

 

[JaguarDave-in-Oz]

, and the over-abundant spill actually interfered with the eye's ability to see farther into the throw by causing the pupils to contract. Basically, the lights spill was blinding me,...

So true. When I'm scanning my top paddock I have a little grove of trees that I stand in, especially if it's raining, and shine the torch out. I can only do it effectively with the LL P7. When I use my quarks or Eagletacs the spill lights up the hangy downy parts of those trees so well that even if the spot is going a hundred yards outwards I can mostly only see the trees right in front of me.

Can't see the forest for the trees........

 

[Bullzeyebill]

Ooops, better make that 4 AAA's!

Whoops, corrected.

Bill

 

[rlorion]

I love my LL P7...It does throw very well and also flood. I have brighter flashlights but the LL P7 still makes me smile every time.

 

[Egsise]

LL P7 still makes me smile every time.

Yes it sure does. :laughing:

 

[kzb]

Hi, I'm new here. I've just bought a Led Lenser P7. It's going back because it won't switch off !

Assuming I get a functional replacement, why do they warn against rechargeable batteries (NiMH), and seeing as people on here have used them, is there really any problem ?

Thanks

 

[Ice]

"Normal" batteries have an open circuit voltage of 1,5V but drop fast to say about 1V when used.
NiMH batteries stay at about 1,2V most of the time, which is a little higher than the conventional battery obviously.
Many people use NiMH batteries in their LedLensers without problems. You won't get any other anwwer...

 

[kzb]

It annoys me that practically everything you buy says "do not use rechargeable batteries". My other pet hate is things that take THREE batteries, and these products are increasing in number. (In the UK at least, cells are sold in 2- or 4-packs -there are no 3-packs

On the voltage, I find that rechargeables do not have the punch of a new non-rechargeable, and that must be because the voltage is lower, 1.2V versus 1.5V. I really don't understand how you could damage something when V=IR after all. 1.2V is not going to drive the same current through a circuit as 1.5V?

I DID read somewhere that the voltage of a freshly charged NiMH (straight off the charger) can exceed 1.2V by some margin. What you should do is let it cool for a few hours before using it. I wonder if this is the source of the manufacturers' concerns?

 

[Bullzeyebill]

kzb, welcome to CPF. As you spend more time here you will find that a lot of the flashlights on the market have a driver circuit, and that rechargeable cells will provide more current over time to the LED than primary, non chargeable cells. Those lights that run direct drive, most of the 3 battery models, do not have a driver circuit, and will be brighter light initially, but the rechargeable cells will be able to hold the voltage longer and will not dim out as fast. The P7, a four cells light, is direct drive with a resistor, and it too will run longer with good output using rechargeable cells.

Bill

 

[Egsise]

I DID read somewhere that the voltage of a freshly charged NiMH (straight off the charger) can exceed 1.2V by some margin. What you should do is let it cool for a few hours before using it. I wonder if this is the source of the manufacturers' concerns?

Good quality freshly charged NiMH is ~1.45 volts, after a month it's ~1.35 volts.
Actually if a NiMH is only 1.2 volts it is allmost empty...

 

[Ice]

Just a little excursion on batteries: :wave:

Yes, NiMH rechargeable batteries have a better discharge curve meaning that while being discharged they keep the voltage better while the voltage of a normal battery gets lower and lower during its use.

But there's more:
A battery does not have 1.5V under any conditions, independend of its remaining charge.
(If that was true you could draw infinitely much power out of the battery, albeit for a very short time.)
In fact, the higher currents you try to draw from a battery the lower gets its voltage (for both a nearly depleted and a new battery).
So in use a 1.5V battery will not have 1.5V but something lower, maybe even lower than 1.2V.

(You'll find more on this topic under key words like "discharge current" and "internal resistance".)

 

[Turbo DV8]

...why do they warn against rechargeable batteries (NiMH), and seeing as people on here have used them, is there really any problem?

No problems reported using NiMH with the P7, but here's the reasoning behind the admonition against it. The internal resistance of an alkaline is inherently much higher than a NiMH. This means that although the voltage of the NiMH is lower than a fresh alkaline, the NiMH will be able to deliver more current, possibly to levels beyond that which the LED was designed for. Direct drive LED lights are often designed to depend upon an alkaline's inherent internal resistance to be a current-limiter. Using NiMH with it's lower internal resistance/higher current capability could damage or age the LED prematurely. That noted, the LED in the P7 may be overdriven using NiMH, but I haven't heard reports of failure. It would likely manifest itself in reduced LED life. But with LED life in the multiple tens of thousands of hours, a reasonable percentage reduction in lifespan might likely still go undiscovered over the life of the user! An LED will also gradually dim over it's "life" and that could be accelerated using NiMH, but again, we are likely talking many hours beyond normal usage. But then again, we aren't talking about "normal" users on CPF, are we?

 

[kzb]

Thanks for your comments folks. Now you mention it, I do now remember in Physics 101, a cell has an "open circuit" voltage, ie the voltage at zero or neglible current. If you increase the current draw, the voltage will fall. And I can see that the behaviour of different cell types might be different in these circumstances.

However, I still think, in an incandescent flashlight, rechargeables are dimmer than fresh alkalines, and that can only mean the circuit voltage is lower.

As for voltages, I'm surprised that NiMH are 1.35V. They only claim 1.2 or 1.25V maximum. You'd think they would claim 1.35V if that were true, because that would make them closer to standard cells at 1.5V.

 

[Bullzeyebill]

Thanks for your comments folks. Now you mention it, I do now remember in Physics 101, a cell has an "open circuit" voltage, ie the voltage at zero or neglible current. If you increase the current draw, the voltage will fall. And I can see that the behaviour of different cell types might be different in these circumstances.

However, I still think, in an incandescent flashlight, rechargeables are dimmer than fresh alkalines, and that can only mean the circuit voltage is lower.

As for voltages, I'm surprised that NiMH are 1.35V. They only claim 1.2 or 1.25V maximum. You'd think they would claim 1.35V if that were true, because that would make them closer to standard cells at 1.5V.

While on CPF spend some time in the Incandescent Flashlights forum. You will be amazed at what is going on with rechargeable cells in the Hot Wire lights, something that Alkaline primary cells can never do. Actually rechargeable NiMh's can be charged up to 1.45 volts, or sometimes higher. There will be a drop off of voltage while they rest off the charger the first hour or so, but they will still be around 1.4+ volts, open circuit, for awhile, with very high current available. During a runtime in a flashlight, the ideal situation would be the voltage sag to stay at or above 1.2 volts per cell for most of the run, an easy accomplishment for a good NiMh.

Bill

 

[Egsise]

As for voltages, I'm surprised that NiMH are 1.35V. They only claim 1.2 or 1.25V maximum. You'd think they would claim 1.35V if that were true, because that would make them closer to standard cells at 1.5V.

That's why I said good quality NiMH.

 

[kzb]

According to Wiki, the 1.2V for a rechargeable battery is at a discharge rate of "0.2C" per hour. "C" is the capacity, so it means that a 1000mA-h AAA cell supplying 200mA would be at 1.2V. Presumably a bit higher at lower currents and lower at higher currents.

Also I have yet to see a light curve versus time where the voltage from a NiMH at any point on its curve exceeds the initial voltage from a new alkaline (can be 1.6-1.7V). So I'm still a bit puzzled.

I've now got the replacement P7 and the switch seems quite satisfactory. I've another comment though: on the front it has a big red sticker "200 Lumens *". The asterix takes you to some small print on the side, and when you put your glasses on, you can see it says this can vary by +/-15%. Minus 15% from 200 and you get 170 Lumens, precisely the stated output of the previous version ?!!!

 

[Egsise]

And that 200 lumens is the 130% momentarily turbo mode.

 

[Turbo DV8]

...on the front it has a big red sticker "200 Lumens *". The asterix takes you to some small print on the side, and when you put your glasses on, you can see it says this can vary by +/-15%. Minus 15% from 200 and you get 170 Lumens, precisely the stated output of the previous version ?!!!

Unless that version also has the same asterisk! :devil:

 

[Egsise]

It could be +15% too.