Seems ok, probably needs a heatsink added, but it states only max 2A out at 5V. That could be ok if I use two (one per LED).
-Garry
I dont know I can not be understood here.
If the drivers hava voltage adjustable why use two drivers instead of use a single driver and connect both leds in serie???
The converter is not capable of putting out that kind of power without additional heatsinking.
Even with only 2A output (at ~12V in ~7V out) the chip will rise easily 60K above ambient temperature in the PCB mounted variant and sooner or later go into thermal shutdown.
I'm no electronics expert. Perhaps that is the best way? Will the two LED's in series still pull 2A or will it drop lower? Or will it try to pull more than 2A and burn up the regulator? And isn't it preferred LED's be driven in parallel to be safer? (less likely to burn out an LED?)
-Garry
Internal current limiting of the converter can be up to ~7A (for input), and it might deliver that for a few pulses before shutting down or killing the LEDs. I would not consider that a desireable mode of operation. 
The LEDs will draw whatever the supply is capable of delivering if not limited.
If driven in parallel, all LEDs need some kind of current limiting. That might work in direct drive with the internal cell resistance of a battery as limiter, but I really would not try that with a switching regulator as source.
You could of course put the two LEDs in series, limit current with a handful of 7135 and use the converter as a pre-regulator. (Output voltage level set to 2x max LED forward voltage plus the drop for the 7135). It still would need a heatsink. But there seem to be a lot of vias underneath the chip, so one may get away with putting a heatsink on the bottom side. I have on of those chinese converters somewhere (without the rectifier), If I find it I can test how that works out.
I would likely use a regulator to then drive two of my drivers (the 3v - 18v input ones) and not wire the LED's directly from the regulator. I have two of these KD drivers (per E1320's suggestion).
-Garry
Please excuse the off topic question.
dave_ and ChangChungLeds, you both have very good English writing skills. Are your first languages German and Spanish, respectively?
This is very good way to do it, I dont read that… Do it that way…
Hi, thanks, my first language is spanish… I do my best…
@Garry
Oh sorry, I did not read that.
Then you have to put the two drivers in parallel on the converter of course.
The converter will not have to deliver that much current then. If I find mine when I get home, I will load it with a 12V 20W halogen lamp which should be a comparable load and look how adding a heatsink on the bottom works out.
(I actually bought that converter to test it up to destruction some times ago because they are so cheap I cannot believe they are made of genuine parts. It was less than 2€ I think.)
@ImA4Wheelr
Yes, German is my fist language.
I often struggle with finding the right words in English and I guess my grammer is a little strange sometimes, but I try to get better and am happy if it is half way understandable. 
Quite impressed. Like most typical US based Americans, I only know one language. My hat is off to both of you.
I apologize again for the off topic Garry.
Really? I thought I'd be pushing the limits on the converter's amperage output. Which converter exactly do you have dave_? I appreciate your testing for me! If I power my drivers off the regulator, what voltage would I adjust the regulator to output? Does it matter?
By the way, your English is just fine!
-Garry
The nice thing is that your drivers are buck converters too if i see it right (the inductor would indicate that). So their input current will be lower than their output current.
E1320 says they will deliver 2.5 amps to the emitter at 12V input, so in a perfect world they would have about 700mA input. Lets say they have only 75% efficiency, so they take 850…900mA current each. So let’s say 1.8A for both in parallel.
You say you have 18.25V AC, makes 25.8V rectified. Minus two diode drops for the bridge rectifier, you will end up somewhere near 24.5V DC at the input.
Now we look at page 26 of the datasheet (http://www.ti.com/lit/ds/symlink/lm2596.pdf#page=26&zoom=100,0,427.5).
The bottom graph shows temparature rise of an PCB mounted converter chip.
25V input, 12V output at 2A will give a temperature rise of ~62K. We know we draw less current, but it’s still quite some heat.
The upper graph shows the chip in another package on a little heatsink.
25V in, 12V out at 3A will give a rise of ~44K. We know we will draw way less current than that, so heatwise a little heatsink will be fine.
Output current is also within limits.
My fear is that the inductor has a to low saturation current, but there is only one way to find out :D. The caps are very likely to be crappy, maybe the diode too, but with a little luck they are good enough.
I have this converter http://www.ebay.de/itm/330882678355?ssPageName=STRK:MEWNX:IT&\_trksid=p3984.m1439.l2649 which is basically the same, just minus the rectifier and big input cap.
Well, best output voltage depends on several variables. How much will the input voltage drop under load? Do the drivers change output current with changing input voltage?
If all assumptions made so long are correct, 12V seems save. The drivers will output nice current then and the converter is in save operating area.
Thank you two!
English is a beautiful language and combined with modern technology a great opportunity to connect with all people in the world who have similar interests.
Well, we are forced to learn other languages here. Within a day’s drive I can get to places with maybe 6 or 7 different languages. Draw a 1000km circle on the US map and you barely will see it. 
English connects!
Thanks again… It is great that we can be connect for almost any part of the world and share, help and talk with other peoples…
This is a nice forum… With nice peoples…
Now I am that take my hat is off…
This is the right method to connect it with a perfect explanation…
Thank you dave_! So if your module works out (English link to dave_'s item) than your suggesting I can use this one which incorporates the AC to DC rectifier? Now what about going back to this one in the waterproof case rated 12V 2A max? That one would be really ideal already being in a case and waterproof (or at least water resistant)!
Thanks!
-Garry
By the way, here is RaceR86's test/review of the driver I have (I'm pretty sure it's the same). Be sure to look at post#9 though - it may not put out the 2+ amps I was expecting.
-Garry
Well, it has not the same inductor and caps, we have to trust the seller that they are good enough on that.
I can at least test heatsinking.
This waterproof module looks really nice!
If the manufacturer’s claims are accurate, it will fit perfectly.
Oh, it’s a shame the driver’s output ist that low. (But to be fair, product description says 1 to 1.2 A)
I found the waterproof one quite a bit cheaper. So you believe I could use one of these and connect my two drivers parallel off of it? I don't need two of these? Too bad we don't know what is on the inside of these to get an idea of quality.
-Garry
Nice, that’s really cheap!
RaceR86 measured about .7A input at ~12V, so two of the drivers in parallel will only be 70% of the max current it can deliver.
Should work really nice!
Even if you one day change your mind and want more light output, you could drive two LEDs in series at 2A with a linear driver or choose a different switching driver for even more. So I would say it’s hard to get more versatility for 8 bucks.
A dead heat as to whether you do your lawnmower first (think the momenteum has clearly shifted in your favor) w new lights or I do my snowblower for next season…?!
A quick call to any good power equipment dealer should get the answer (even though you tested) to whether you have AC or DC at the lights - I know only 12v DC in any lawn or outdoor equipment at the terminal* - and Dr’s suggestion to wire off the battery direct, w a fuse, is also the easiest and as noted, very reversible. I did this w my olde timey tractor mod for a friend, magnetic base LED lights, cigarette lighter style cords/plug ins and such… in business in a flash. And astonishing results.
- and aren’t the current bulbs 12v auto style?
Yes, the bulbs are #1156 12v bulbs (standard automotive bayonet socket). I don't know about the race to finish. I've been sitting on the other components since I started this thread (June 29th 2012)! Perhaps I'll take another look at the mower sometime and see if I change my mind on the direction to go with this.
-Garry