What is the most efficient driver

I am new to a lot of this but I am keen to do some mods to lights that I have. I already have lots of 6 volt and 12v batteries from my halogen lights. I dont know what driver to go for. I want to make some lights using Q5 at about 350ma to get good run times but also maybe P7 for mountain biking. Loved the light from jagge and packhorse. Packhorse is in my part of the world, New Zealand sometime seem a long way from a lot of parts.

The trouble with the Drivers is that they change efficiency depending their load and supply voltage.
Some of the DX and Kai drivers reach 100% efficiency as Vin drops to Match Vf and the LED gets direct drive. But those drivers are no good for voltages over 6v (and a 6V NiMh will be 7.2 fresh off the charger)

Given the difference between your supply and the led voltage and if you want an off the shelf driver then the sandwich shoppe or LEDSupply or Dotlight.de or LED1.de would all be a good place to start but they are all in the $15+ area

Nick

:welcome:

My thoughts:
1) If you are into designing, modding, building, etc. you should read this article by a former CPF member. This shows that with current drivers you can change the efficiency by changing the values and quality of some components.
2) If you want to buy an off the shelf product there are so many to choose from. Doh!Nut has given some good advice to start your quest.
3) The most efficient and most dangerous method is to direct drive with one or multiple LEDs.

An extra 3% is probably unnoticable and 10 to 15% extra runtime may not be that much. It is always advisable to know your flashlights and their capabilities. If unsure, keep extra batteries in your pocket.

Greetings OL.
The KD P7 driver seems the best option for 6-12v at the moment AFAIK.
If you are in Auckland I would be happy to show you my light close up.
I like the DX Q5 drop in module 3.5-18volt single mode. It seems quite efficient and has a nice beam.

To be honest Im not overly concerned about reaching max efficiency, just good efficiency. LEDs will always be better than the Halogens.

Thanks
I have got several drivers from DX and I am not happy with the effeciency. I was under the impression that boost was less effeciant so was staying away from them but is that not the case? The buck ones I tried were only 70% to 80%. One of the uses is for caveing where I do not want to carry any extra weight as I already tend to carry to much. I could easily want run times of 12 to 24 hrs. I sometimes take family and friends so have quite a few lights I do not want to spend $20US each on converting these.

Buck drivers are inherently more efficient. Depending in your voltage range, you can get efficiencies around 95% quite easily.. and even up to 98% if you're not too concerned about size or cost... especially with higher voltage situations.

I've tried a few single cell drivers from DX and KD and every one has been total BS, except the 3x7135 board, it doesn't seem too bad, but it's not constant output.

Re: What is the most efficient driver?

:welcome:

outer limits said:

I dont know what driver to go for.

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No disrespect, but if nothing in this list grabs your fancy you're probably hard to please. :thumbsup:

outer limits said:

One of the uses is for caveing where I do not want to carry any extra weight as I already tend to carry to much. I could easily want run times of 12 to 24 hrs. I sometimes take family and friends so have quite a few lights I do not want to spend $20US each on converting these.

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The issues you raise:

1. Caving weight. Use AA NiMH cells, not those SLAs. But you knew that, right? :kiss:

I've thought many times of lugging an SLA spotlight into one particular cave just to have a look across a large chamber, but the thought of all that weight always puts me off. Three AA cells will sit comfortably on the back of your helmet - much handier than lugging an SLA around.

2. Runtime. How much light do you want for that runtime? My main caving light at the moment has three modes (four if you include a glow ring around the reflector) which have very approximate runtimes of 6 hours, 20 hours, and 60 hours (and, um, "glow all night") from three AA cells. I mostly use medium, or low in tight passages. (When I'm not caving it'll go for about 2 hours, 7 hours, and 20 hours on three AAA cells.)

3. Conversion cost. NZ$15.35 (US$11) for said light including donor body, plus NZ$5.64 (US$4) for whipping up the external AA adapter. Very versatile, efficient enough, and it's simply a very elegant solution to my lighting needs, both caving and camping.

BTW, the AMC7135 constant current regulator drivers which have the really great efficiency IF the in and out voltages are about right can easily be used with 12V. Just use a couple of the LEDs in series with the board driving another LED. Make sure you use higher Vf LEDs to increase the efficiency. But with three suitable LEDs already you're heading toward US$20. Another reason to go with three AA cells.

IIRC the old Kennan board had an efficiency about 86% at 750 mA. (Above that and its efficiency drops markedly.) Even if you were able to find a board within budget with another 5-10% efficiency you would only have about 6-12% extra runtime. How much is that really worth?

That's probably enough food for thought for now.

A simple PWM driver is the most efficient but doesn't actually regulate the output.

Re: What is the most efficient driver?

I came to the conclusion about a year ago that drivers from the sandwich shop are the most efficient and as VanIsleDSM said, the buck drivers are more efficient than the boost.

Greater efficiency is achieved when the driver has to do less work ie, a buck driver will be more efficient if you drive an LED with 4.5V supply as opposed to 6V or a boost driver being powered by 3V will be more efficient than one being driven by 1.5V.

If you want really long runtimes, either get a higher capacity battery or use the light at lower levels. High efficiency is good but using light at lower levels is the best way to increase runtime.

Re: What is the most efficient driver?

eebowler said:

Greater efficiency is achieved when the driver has to do less work ie, a buck driver will be more efficient if you drive an LED with 4.5V supply as opposed to 6V ...

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Strangely enough the datasheet for the Kennan chip, at 700mA output, has its lowest point at 5V - just over 85% - and from 9V up to 18V is at or just over 86%. It's remarkably flat. At lower outputs what you say holds true. At 350mA it starts at 91% at 4V and drops to maybe 86.5% at 18V. At 100mA it's up at 94% at 4V but is under 80% at 18V.

I'd say it would make a great multimode driver with a suitable switch and the right set resistors. For longer runtime simply add any number of batteries in series or of course the right number in parallel. (I must get some more of these boards.) A couple of 4xAA holders with 2700 mAh cells on the back of a helmet would give 21 hours runtime with my present high mode!

eebowler said:

High efficiency is good but using light at lower levels is the best way to increase runtime.

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So it might be better to buy a more efficient LED than a more efficient driver. A Cree R2 in that Kennan light would be more than enough for most situations.