LED drivers

[TheWorkman]

Forget SLA.
NiCd is pretty out dated and offers no advantages over other types unless you have them already (thats why I still use them).

So then its NiMh or Lithium types.

Lithium Ion offers the highest energy density while NiMh may offer a longer life span.

For me the real reasons I choose one over the other is
A. Run time
B. Size/shape
C.Cost

1st decide how long you want your light to run for.

A P7/MCE run at 2.8 amps will consume about 10-12 watt including driver.

So if you want 4 hour burn time you need (12 x 4 =)48watt hours of battery power. Then add in efficiency, rule of thirds, manufactures "specs" etc and aim for say 80 watt hours.
You really should choose a batter pack that matches the VF of your LED and or driver. A P7 Vf is 3.7volt. The above mentioned driver is designed for 7.4volt input ideally. So your choices are...

2 lots of seriesed Li Ion batteries wired in parallel.
EG 8 Li Ion 18650 cells( 3.7v 2500ma each) 2S4P will give you a 7.4v 10000ma pack or 74watt hours. A little short of target so try a 10 cell pack (2S5P) at 7.4v 12500ma or 92.5 watt hours


Or you could try NiMh. If you go with D cells you could get 10000ma 1.2v cells.
10 in series or 10S1P ( Dont wire NiMh in parallel) you get 120 watt hour. Or 7 in series gives you 84 watt hour @ 8.4 volt.


All above options would work. 1st will offer most efficiency and get the most out of the driver ( eg low volt warning at 5.5 volt).

Use a different driver or if you use a different LED then it all changes.
The MC-E LED allows you to wire each of its dies independently. So you could wire all 4 in series (14.8Vf) or parallel(3.7Vf)or 2P2S (7.4Vf).

Since the P7 is 3.6 volts, would it be better to run it with a 3.7 volt 10000mah pack without a driver instead of a 7.2 volt pack with a driver??

 

[CBR-runner]

here is a multi-mode setup that is inexpensive.

Multi-level driver for SSC P7 under $8 ? - CandlePowerForums

I have used 3 of these to mod different maglites.

SSC P7 Buck Converter - CandlePowerForums

It is bigger than the first one, and the guy is making a multi mode one that should be ready soon.

 

[Packhorse]

Since the P7 is 3.6 volts, would it be better to run it with a 3.7 volt 10000mah pack without a driver instead of a 7.2 volt pack with a driver??

P7 has a typical Vf of 3.6v.
Some are higher some are lower.

Run a lower Vf P7 (I Bin) off a 3.7volt pack ( I assume you mean Li Ion which will be 4.2v at full charge) and wait for the magic smoke. My guess is you will see it with in 30 seconds.
You could use a amc 7135 based driver though. This will work well with a 3.7v pack. Or just use a resistor but then you get less efficency and no multi mode.

The driver I mentioned is best suited to 7.4v . Then you get 3 modes plus low battery warning.

 

[CBR-runner]

Pachorse am I going to run into you every forum I go to.

 

[350xfire]

Guys, I have used up to 4.5 volt alkaline batteries to direct drive the P7 on 2 different 3-D cell Maglites and have run them for a while with no problems.
My 3 SSCP7 is driven with 10 D cell NiMH pack and again no problems.
Need good heat sinking...
Just a thought.

 

[Packhorse]

But what bin were they?
D cell alkalines will suffer a huge voltage sag when trying to deliver 2.8 amps.
Try it with a 10 amp hour NiMh and you may get a different result.

 

[350xfire]

C bin running with 10D battery pack supposedly rated at 12,000 mah each.

 

[Packhorse]

C bin running with 10D battery pack supposedly rated at 12,000 mah each.

C is part of the lumen output bin.
is it CxxxI or CxxxJ
I being 3.25-3.5 Vf and J being 3.5-3.75Vf ( I think).

So you use no driver or resistor at all?

 

[350xfire]

I put the power supply to my P7 and got 3 amps at 3.6 volts. Packhorse I don't know the exact bin number, etc. They did not come with anyhting to identify. Nope, no driver or resistor at all. I have run my 3 SSC P7 light for over 4 hours combined total and no problems. My MagLites have run for hours as well.

 

[CBR-runner]

I just find it easier to use something that someone else has already produced and tested. all you need to do is get the battery pack to match it. :vintagediver:

I'm just a mechanic that knows some electrical theory (enough to be dangerous).

My dive light genie is up and running and is way bright with 3 p7's in series. Unfortunately not suited for a budget build. My light should still come in under $400 when all is said and done.