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Mine Exploration Forum

Author KDLitker pocket supertorch

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Joined: 13/06/2007
Location: Great Wyrley near Walsall

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KDLitker pocket supertorch
Posted: 05/04/2018 13:19:41
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This is a detailed review of a new pocket size torch from Kaidomain which has the appearance of being one of the most powerful small pocket torches available yet. Most of us have a collection of torches, and I would bet that most people use the typical single 18650 cell pocket size more than any others, the way that I do. So the appearance of one of this size with a claimed 2200 lumens appears a desirable purchase.

Link: http://www.kaidomain.com/p/S027413.KDLITKER-C8_2-Cree-XHP35-HD-White-6500K-2200-Lumens-5-Mode-LED-Flashlight-Black-(-1x18650-)

The torch is based in Crees latest design of emitters, the XHP series. I have looked at the XHP 70 and and dismissed them as being of any use in a headtorch. This is well born out by the Imolent DX 80 I recently purchased wich uses an array of 8 XHP 70 emitters to give a maximum output of 32,000 lumens. However, this is in the form of more of a controlled flood than anything resembling a beam.

The XHP 35 and 50 are smaller footprint being 3.5mm X 3.5mm and 5mm X 5mm respectively, therefore more suitable for focusing into a defined beam such as required in a headtorch or caplamp. However the voltage requirements presents some difficulties.

I will be testing these in the future and reporting my findings. I will also look at some driver solutions available.

The KD pocket torch uses an XHP 35 which is readily focusable into a good controlled beam. The caplamp possibilities of the XHP35 were part of my incentive for buying the torch. Testing the torch proves this to be correct, actually it’s a bit too controlled and the lack of peripheral light could present an issue, especially underground. Testing the torch underground I did observe sufficient peripheral light, but would prefer more.

Kaidomain do offer alternative models with either High Density or High Intensity emitters in different colour temperatures. Mine was the High Density as having highest output. High Intensity appears even more focused according to the data sheet.

Their description reads: Very Lo(0.01%) > Lo (5%) > Med(40%) > Hi(150% reduce to Hi(100%) after 60 secs)
Hidden Strobe: Double click
Circuitry: Digital Regulated 1500mA max. Current Output
Brightness: Hi Mode: 2200 Lumens (manufacturer rated)
Hi Mode: 50 to 60 mins (manufacturer rated)
Med Mode: 3 to 5 Hours
Lo Mode: +10 Hours

Powerful, it certainly is but the claimed 2200 lumens exceeds the Cree data sheet, to its time to take it to the lab.
First a bit of explanation. The XHP 35 runs on a high voltage of just over 12 volts, but a relatively low current of 1050 mA, just over 1 amp, in order to give maximum output. It therefore obviously requires a boost driver. So just how good is it?
That is what we intend to find out.

I partially dismantled the torch in order to fit a meter between driver and LED, then tested it on a variety of 18650 Li Ion batteries. I had a years old Trustfire which would still charge up and give good service, plus a Sanyo 3500 mAh as used in my own power banks, and a Sanyo 2600 mAh High Discharge (20 amps rated). All fresh off charge.
I also tested it off the lab power supply in order to compare power in with power out.

The old Trustfire would only deliver 700 mA which is of no surprise. Both the Sanyo delivered 1.43 amps, ouch! So this is where the claimed output comes from. Its overdriving the emitter!
Lab power supply gave same results set to 4.2 volts. Lowering it to 4 volts it suddenly dropped to 1 amp. But I am pleased to be able to say that the output was fairly consistent down to nominal voltage and below, good.

I also worked out some efficiency readings, in the three intermediate modes it was running about 80 to 85% efficient, but in the maximum turbo mode a miserable 63% efficiency at 4V+ but improving to 69% at 3.7V as the battery voltage dropped.

Dismantling the torch I was impressed by the O ring setup which by method of fitting should give a high level of waterproof integrity.

So exactly what is the driver.

Well, I was somewhat puzzled at first until the penny dropped to what I was seeing. They have a voltage booster supplying a liner driver setup. Thinking about it, most liner drivers are designed for LED strings running off a mains transformer and as such are suitable for up to 40 volts. The 350 mA 7135 chip is different in that it is a torch driver but only rated at up to 6 volts.

Reading further the description it appears that the driver is suitable for both the XHP 50 at a max of 1.5 amps running off 2 serial Li Ion cells, and an XHP 35 at 1.05 amps off a single. Obviously we are looking at different voltage ranges with the cell arrays and the driver is typical Chinese generic being designed to be suitable for different torches, except that somehow they have got their sums slightly wrong, possibly with respect to a resistor value somewhere.
If identified it could be changed so as to maker it more suitable for purpose.

It is logical to assume that over a period this overdriving on fresh charged batteries will cause deterioration of the emitter.
Looking at the driver it is difficult to analyse a schematic due to most components being covered by the large inductor.

The bottom line on the torch is that it is extremely powerful and for £22 one cannot grumble.
Regardless of the overdrive, one is only going to be using the Turbo mode on occasion, it switches down automatically after so long anyway, and once the battery voltage has dropped a bit you will get normal drive current.

The HXP 35 does have some strong possibilities for a head torch, but if I do ever use them I will probably be looking at making my own drivers up. 3 series would need a boost to over 36 volts for full performance. I will also be looking at the XHP 50. The efficiency of the Chinese driver on the turbo mode is appalling, but I still consider it a good torch.

Some pictures

Below, neat size

(click image to open full size image in new window)

Beam pattern in my hall at 5 metres.

(click image to open full size image in new window)

Beam underground, Devonshire Cavern.

(click image to open full size image in new window)


..................a proper engineer not a marketing man.
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