Review: Ultrafire WF-501B with 5-mode MC-E drop-in

Could it be something else limiting the current? The switch maybe? Or may be your MC-E is a bit shit with a very high Vf? Perhaps try 2xCR123 if you dare?

It can't be the switch because I'm measuring the current at the tail without the switch being in place. It could be the LED, but I don't think more voltage would help the SB driver because it is a linear regulator and is going to provide some set amount of voltage regardless of the input voltage (I think).

Let's not talk about the LEDs that have died in contact with my 7.2V 85A capable battery pack. It is claimed to hold its voltage at 80A though I've never attempted to discharge it at that rate. It is rather too far past the Vf of most LEDs to be a sensible test pack. It will run a 500W device briefly. 500W through any LED is definitely cruelty.

It’s my understanding a linear regulator like the 7135 works a bit like a resistor but provides a constant current (which also means it’s inefficient with high voltages since it just burns off the extra voltage as heat). This also means it’s also a bit like a buck regulator, although doesn’t have much of a voltage drop but perhaps most importantly, it doesn’t perform like a boost driver and can’t provide a voltage higher then what you start with (basically it becomes direct drive if the voltage is too low). So if the Vf in your LED is high enough, the driver can’t do anything. http://www.candlepowerforums.com/vb/showthread.php?t=247543 Aqualab: LED Driver List - LED Drivers and Regulator Boards (database driven) provide some details. That’s the why in most lights the brightness drops off as the battery voltage runs down (preferably your light will start off at maximum brightness and only reduce near the end but depending on the Vf it can easily never reach there).

You could try bridging the reverse polarity protection diode, as the 7135s get their reference voltage via the MCU. I tried this on a NANJG 101-AK, modded with a fourth 7135 to drive an XP-G R5, because it would only draw about 1.2A. Worked great, now it draws the expected 1.4A.
Tido

Did this help with fresh 18650 batteries? Or some other kind of batteries or unfresh ones? Reason being from what I understand it’s unlikely to help with fresh 18650 batteries and in fact will generally only help if the Vf of the battery is really low (between 2.7-3.3V) and the voltage is within that range. See the posts by Torchboy http://www.candlepowerforums.com/vb/showthread.php?t=192677&page=2 (several of them) which offer some explaination.
Although this is a bit late, it occurs to me that it’s probably best to test your LED under direct drive. With a P7 or MC-E this is usually safe I think, just be a bit careful. If the current is above 3A then using a linear regulator may work well (and you should also not test for too long). If the current is below 2.8A then you are already driving the LED at the maximum recommend current under DD so adding a linear regulator or a buck driver won’t help unless you want it at that constant low level or for different cells. Of course your best bet is probably to test the Vf under different currents with a reliable constant current source if you have that.
BTW some more thoughts to try to improve output. I thought SB would provide a driver with good soldering, wires etc for the output current but may be not. See http://www.candlepowerforums.com/vb/showthread.php?p=3279436#post3279436 http://www.candlepowerforums.com/vb/showthread.php?p=3299582#post3299582 So yeah replacing the lead wires as you mentioned in your earlier post is likely to be a very good idea.

Hmmm . . . . I tried direct driving the LED from an 18650 at 4.15V and the current draw was only 1.56A. I was using some heavier leads from some solid wire phone cord I had. So it isn't the driver. Now it's down to either the meter or the batteries just can't produce that kind of amperage.

Disconnect the meter and see if it gets any brighter with a wall bounce or something? You could use your camera to help presuming you can set everything manually.

BTW is that voltage when being driven?

Awesome review brted! Very professional and great pics and usual. Thanks! Sticky'd and Frontpage'd. Sorry I missed it until now, feel free to PM me if a nice review slips by me.

Sorry for the late answer, I've been a bit busy the last few days. The batteries where fresh of the charger at 4,2V. After looking at the driver schematics and dusting off the knowledge from the basic EE course I had to take in university, I can see no obvious reason why removing the diode should increase the current through the LED.

You are right, as long as VBatt - VDiode - VMCU > 2,7V, the AMC should work as expected. Without a component level schematic of the AMC it's really impossible to tell what's going on here. All I can offer is an educated guess.

According to the data sheet, the AMC's OUT-pin needs to be buffered with a capacitor if the leads to and from the LED are longer than 10cm and 3cm, resp. The 101-AK is missing these caps and due to a seperate pill and reflector assembly in my torch, the leads are more than 10cm long. Maybe this caused some instability in regulation that vanished when Vdd was slightly raised? I should try soldering some 1µF SMD caps between the chip's OUT and GND pins...

I borrowed a friend's DMM and it has big 18 gauge leads (rated for 20A). Using his DMM I got about 2.8A and then using his leads on my meter I was getting about 3A direct driving the LED with a 18650 battery at 4.06V (at rest). So it's all in the leads. I won't have a chance to solder the drop-in back together and do tests on it for a little while, so for now just ignore my current readings because they are not right. I didn't realize it would make that big a difference. Also I kind of wonder if my DMM is calibrated somehow for its tiny leads and if I start using big leads, will I be getting numbers that are wrong in the other direction?

Best bet is to check it against something known, or at least something you can trust more. Low resistance in the meter and leads is not important for voltage measurements where you want the resistance to be as high as possible. For current measurements you want it to be as low as possible. When a meter is measuring current it is in fact measuring voltage over a shunt which is a (hopefully) high precision resistor with a low value, usually around 0.05-0.5 ohms. An external shunt is probably the best way to go and some nice heavy wire to connect the shunt into the circuit.

I think I will have to invest in new leads for my multi meter as well got my MC-E today shows 1.4a draw.

How bright is your light? Do you have other lights you can compare it to? Does it have that donut hole in the beam? Sorry for all the questions

These leads at DX seem like they are pretty good. I have some on the way now. The writing on the wires in the user picture shows 18AWG which would be 18 gauge wire. That should be plenty.

http://www.dealextreme.com/details.dx/sku.33451

I also bought some leads on eBay that look just like those, but even though they are listed as 10 amp leads, they have thick looking leads that are all insulation around very thin wires and can't measure the current either (I stripped the insulation and figure they are about 26 gauge wire). I told the seller about this and they agreed to send me 20 amp leads which they confirmed had much thicker copper inside. I got the 10A leads for $1.28 at auction whereas they sell the 20A leads for $6.99 so that was pretty nice of them (but they got me to change my negative review of them). Once I get some of the new leads I will do the tests again and post the results.

It is BRIGHT. When it stops raining I will do a comparison shots with it up against my R5's. Yes has a hole, but I suspect that can be fixed by removing alot of heat sink goop.(its everywhere emitter too high)

no worries

Ordering a better set leads from dx .

Got the new multimeter leads today and rechecked the draw on my MC-E shows 2.30A now. Its bright I'am happy

DX doesn't have any more in stock! I ordered on 8/16 and the status still shows

Processing - Awaiting Stock

I have been waiting for a cpl of drivers since 29/4/10 and I suspect you will get your 501b before I get the drivers..

I was so pleased with my DX 501B MC-E M bin that I bought three more to get the drop-ins to install in Solarforce or 504B bodies.The current drop-in seems to be just as good or the same as the original batch.I don't hear any whine like others have noticed and they don't seem to get any hotter than my DX R2s or my Solarforce R5s.They do have a small dark donut hole,but it is a small drawback considering the huge light output.I use them on bikes in tandem with a Solarforce R5 or R2 which fills any donut hole nicely.So be patient, DX is shipping them out!