direct drive versus converter runing time for 5W

Bob123

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Oct 8, 2002
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Poland
Hello to all,
I am interested to know and kindly asking you, members of CPF forum (for me famous forum about flashlight) what is better for usefull light working time:
1. LX 5W powered direct drive (for example from 9 V set of AA batteries)
2. LX 5W powered by converter supplied from 6 V battery

I am not interested so much about efficiency of each system. I am interested how long will light flashlight with power system 1 or 2 in full or down to let say 70% (I think that this difference is not easy to observe, if I am wrong please correct me) and later how many ours in moon mode.

Usually for comparison is taken only measuring in lux.

I am a still beginner here but I made battery holder (I call BBH1- Bob battery holder 1) from Aluminium for KL1 and Kroll switch. It holds two AA battery. It is anodising black but type II only. I did not find any company which can make type III - HA near my place. On the tube is (I forget how to named) engraving? for better grip.
Finally it is cheap version of E1x series (I sell few BBH1 to my friends for equivalent of 14 US dollars).
If any body interested I can put pictures. I will make also for 3 AA and for original switch assembly from E1 or E2 series.
Of course most important question is about runing time DD and converter.

There is also 3 possiblity:
3. LX 5W powered by converter supplied from higher Voltage 9 or 12 V battery.
What about that?

Sorry for my english and if I mention something about which you already had a topic sorry for that but I have limited access to forum.
 

kakster

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Feb 6, 2003
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London, UK
From what (very) little i know, direct drive will give you the longest run-time. If you use a convertor, you are adding more components, and each additional component will use up some of the batteries charge themselves.
Personally, id prefer a regulated light, and loose some overall runtime.
 

Doug Owen

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Jan 30, 2003
Messages
1,992
[ QUOTE ]
kakster said:
From what (very) little i know, direct drive will give you the longest run-time. If you use a convertor, you are adding more components, and each additional component will use up some of the batteries charge themselves.
Personally, id prefer a regulated light, and loose some overall runtime.

[/ QUOTE ]

It depends on what you call run-time, kind of a 'what your definition of 'it' is thing.

Basically DD lights (those will little series resistance to limit initial current) run very hot at first (to the limit of the design, typically) and decay in light output as the battery ages. Because of the numbers involved, this discharge curve (light against time) can have some interesting shapes. Typically battery voltage falls fairly quickly, but with lower voltage comes lower current. followed by still lower, and so on to the bitter end. Interestingly enough, the bitter end might not be all that dead, such cells might run in other flashlights, at least a bit. Anyway, the curve drops quickly and has a long, lingering 'tail'.

A regulated light can easily be set up to put out a quite reasonable level (say even as much as the mentioned 70% of DD 'full blast) from the start and therefore not pull as much current as the DD does at the start. Current we can use later, when the DD starts to dim too much. This, by definition, means longer run time. No matter how you define it. While some circuits can effectively suck the battery 'gin dry', the end comes relatively quickly. That is when the light starts to dim, the end is near and there won't be much hair splitting about when it's dark. But a regulated circuit, starting above your definition of 'bright enough' wins every time, against your terms.

Consider a circuit I've been fiddling with, takes advantage of the flat discharge of NiMH cells. Uses 3 of them and a low drop out linear current regulator set to 30 mA, drives a Nichia. It runs 50 hours straight (plus or minus an hour or two) on "1750" cells regular as clockwork.

And interesting things happen when you keep battery currents lower. If we 'save 100 mA per hour' in the first heavy current bit, we get more than that back. Inefficiencies in the cell 'cost us more' for each watt if the rate we draw it is higher. We also save in that the current now used is coming at a lower (more efficient) rate. We might get '150 mA's worth'. Check the batter specs, longest run times are for low draws to low voltages.

So yes, there is an increase in cost and 'power overhead' to use regulation, but it can more than make up the cost in preventing power waste up front.

I'm with you, I prefer one as well, and am confident we're not loosing runtime.

Doug Owen
 

Bob123

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Oct 8, 2002
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Kakster and Doug Owen
Thank you very much for explanation. Now I have better idea which mod I shall make in near future.
 

paulr

Flashaholic
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Mar 29, 2003
Messages
10,832
Re: direct drive versus converter runing time for

Hey Bob, welcome to CPF. Your BBH1 sounds similar to the Arc 2AA battery holder for their LS light, which will also fit the Surefire heads. The Arc 2AA pack is HA type III but much more expensive (I think 30 USD) than the BBH1. The McLux UBH (Universal Battery Holder) is also similar.

I agree with Doug, I'd rather have a regulated light.


If you can ship BBH1's to the USA and other countries, some CPF'ers would probably buy them from you. Also, I hope you'll offer your 5W lights for sale here on CPF.
 

Burnt_Retinas

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May 8, 2003
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Melbourne, Australia
Re: direct drive versus converter runing time for

Don't know if it helps, but anyway..

I have a constant current (boost converter) powered 5W LED, powered from NiMH's (3 D's). Other batteries shouldn't have any effect on the results relative to "moon mode" you asked about if you consider the below.

Assuming the regulator is a boost converter and battery voltage is less than the LED, there is NO moon mode. The MO of a regulated circuit is that it'll take whatever energy is left in the batteries to give full output, right up until the battery voltage hits the drop-out supply voltage of the regulator circuit. You get no warning, full brightness, then nothing. Well, in fact I get flickering as the boost converter kicks in and out as it loads up each restart.

Regardless, I too would prefer a regulated circuit.

Now, a micropuck 12V 5W job may be different as it's not a boost converter, I think?, but I haven't tested one of these so I just don't know how it would behave.

Chris
 

Bob123

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Oct 8, 2002
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Poland
Re: direct drive versus converter runing time for

Burt,
Thanks for your note. I did not think this way. I prefer light which give me sign about battery exhaust, not just leave me in dark. Now I think that I will make somthing like a direct drive but with current source or just resistor with protection device for overcurrent at the beginning. I designed something which have only 200 mV drop voltage and well stabilize current. Moon mode for me looks important.
I was thinking about using micropuck for 5 W LX but:
1. It is costly - flashlight will cost moore,
2. I do not have any experience with micropuck,
3. complicate design and final result is unknow (for me)

Thanks again for all info!
I think that I will make picture of mine BBH1 and put in CPF.
 

Slick

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Apr 24, 2002
Messages
1,264
Location
Nor Cal
Re: direct drive versus converter runing time for

Hi Bob, I know that I've mentioned that I favor direct-drive, but one thing I might not have mentioned is that I like NiMh rechargables. I know some poeple have had problems blowing up emitters using them.

I tried for a while and finally made it happen (blew up an emitter) using C cells right out of a charger - they were still quite warm! BUT - the thing I *really* like about NiMh batteries is their flat discharge curve. When I use NiMh, they run like they have a converter - in that they don't drive quite as hard when fresh, but keep driving well when they're near dead.. the brightness is very even from start to finish..

Oh, and I always meant to tell you that your english is MUCH better than my polish ! /ubbthreads/images/graemlins/thumbsup.gif
 

Bob123

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Joined
Oct 8, 2002
Messages
30
Location
Poland
Re: direct drive versus converter runing time for

Thank you to all for help.
Now I have a lot of information to start. I just get lenses from Elektrolumens then time to to work.....
 
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