Northwest Dive Club

Dashrynn wrote: I just want to clarify, I NEVER said anything about how much you use from the NIMH pack. I stated you can normally only use 80%-90% of its calculated capacity. This is mostly due to self discharging (20% or more in some, within first 24 hours).

Also I would like to note the venom 5000mah pack is 36 watts, not much difference between 32.4 and 36(unless we are talking nitrox ).

Uhuh whatever. Some of us buy 5 or 6 hour rated packs and only use them for 2 or 3 hrs for a reason. 80-90% blah blah doesn't matter to me. I am intentionally only using maybe 60% max of the pack capacity because I don't want to replace them. The can itself is only marginally bigger than something sized "just enough" anyway.

For the OP this is just a suggestion to buy more battery burntime than you think you need. You'll either grow into it, or it will last a nice long time.

CaptnJack wrote:
Uhuh whatever. Some of us buy 5 or 6 hour rated packs and only use them for 2 or 3 hrs for a reason. 80-90% blah blah doesn't matter to me. I am intentionally only using maybe 60% max of the pack capacity because I don't want to replace them. The can itself is only marginally bigger than something sized "just enough" anyway.

For the OP this is just a suggestion to buy more battery burntime than you think you need. You'll either grow into it, or it will last a nice long time.

That just reinforces my lithium battery idea. If you have already crammed all the nimh possible into a can, go lithium (or bigger can which is normally not possible).

And a fun fact, 80% of 36 watts is 28.8 watts. Which is basically 2 hours of (full power) burntime (as it drops in voltage total power drawn decreases = longer burn time/less bright). Using roughly half of the energy (as suggested) would mean 1 hour burn times. If someone doesn't fully understand they can PM me and I'll go more in depth, most people just want simplicity rather the math.

A little battery maintenance:
Using a NiMh pack to damn near dead is an excellent way to drain the weakest cell and produce a reverse polarity condition if you persist in keeping the power on. This WILL weaken that cell further and has a high possibility of killing it outright. This, of course, ruins the pack. When the light gets noticeably dim, shut it off.

Lithium does not like to be used beyond 80% capacity. If you over discharge some lithium you can readily and permanently ruin it in a single bad use. lithium iron phosphate (LiFePO4) is far more robust than lithium polymer in this regard. High output lithium polymer also does not take kindly to being stored in a fully charged state-50% is optimal storage (3.85v/cell). Lithium iron phosphate (LiFePO4) is MUCH more robust in this regard also. I think most of the lithium packs are LiFePO4. I don't think lithium polymer would be a good match for diving.

All rechargeable batteries tend to have a flat discharge curve. They attempt to keep up the voltage to the 'bitter end', then they just cave in. So, you may get little warning of the end unless you are paying attention or the manufacturer has put in protective circuitry .

As much as some commercial packs cost you want to take decent care of them if you can. Unfortunately a lot of lights have pretty limited info/support in that regard.

For folks wanting a LOT more information on batteries I suggest starting here-Battery University:
http://batteryuniversity.com/learn/

The big problem here is that unlike halogen or kripton bulbs is that led's do not dim when the power goes down. They may flicker or get brighter them dimmer then back again but they don't give you the warning that conventional bulbs do. Due to the fact that most LED's have a power controller that converts the power into what ever is optimal for the LED's there is no dimming until it's to late. Some circuits will automatically shift to a lower output setting if the unit has that capability. It is just a very good idea to treat your packs with respect like any any other piece of life support equipment. Like your gas supply you should never use that last 30%. Carry a spare(if practical) and change out well before needed. Always use freshly charged packs and that means charged within the last few hours. NiMh power packs self discharge meaning that the longer you wait the less power the pack has remaining. Also it is a good idea to always store NiMh packs fully charged not discharged because they will continue to lose power until completely dead and chances are destroy the pack or seriously lessen it's storage capacity and life cycles. Make it a policy to disconnect the battery as soon as you are finished diving and put it on the charger as part of your after dive routine.

Treat them well and NiMh will last a very long time. Treat them bad and they will fail you when you need them most.

Dusty2 wrote:The big problem here is that unlike halogen or kripton bulbs is that led's do not dim when the power goes down. They may flicker or get brighter them dimmer then back again but they don't give you the warning that conventional bulbs do. Due to the fact that most LED's have a power controller that converts the power into what ever is optimal for the LED's there is no dimming until it's to late.

I agree with everything you said BUT this. Led's will dim with lowered voltage, this is due to lower voltage input than what is needed to properly be driven at the constant current constant voltage the led requires. As the voltage goes down, it directly affects the amperage the led uses. The 5 xre led unit (unless you have a different driver but every driver I have owned does this) will begin dimming at 5.83(consuming 19.488 watts) volts, at 2.15 volts (consuming .294 watts) it will flicker. DON'T run your light til this starts, it WILL damage the battery.

95% of the drivers I have used will drop out of regulation within a certain voltage, meaning it goes from the driver dropping down the voltage for the led to direct driving the led with no regulation circuits needed.

I think the OP just wants a light...

+1

Dusty2 wrote:+1

+2 though understanding doesn't hurt.

Some people, when you ask them what time it is, will try and tell you how to build a watch.

Dashrynn wrote:

Dusty2 wrote:+1

+2 though understanding doesn't hurt.

But getting lumen and battery specs shoved down your throat does.

Happy New Year!

spatman wrote:

Dashrynn wrote:

Dusty2 wrote:+1

+2 though understanding doesn't hurt.

But getting lumen and battery specs shoved down your throat does.

Happy New Year!

+3, and Happy New Year!

Lumen and battery specs are interesting too!

fnerg wrote:Lumen and battery specs are interesting too!

The main reason i post like this; I bought a light that information wasn't correctly spec'd(edge light with a maglight led claiming 6-10 times what it's rated for). From that day forward I have been learning and bringing to light(pun intended) the true information behind lights and how they work. Though I'm not an expert, I do pass on everything I learn, and even what I read I cross check with my test equipment. I've devoted hours and days to research, all because someone :angry: me off.

Dashrynn wrote:all because someone :angry: me off.

I never would have guessed there was something personal going on. Keep it off the site, please.

Joshua Smith wrote:

Dashrynn wrote:all because someone :angry: me off.

I never would have guessed there was something personal going on. Keep it off the site, please.

Oh nobody on here that normally post's(this happened about 2 years ago), and i wouldn't post hate messages. Just facts.

Dashrynn wrote:

Joshua Smith wrote:

Dashrynn wrote:all because someone :angry: me off.

I never would have guessed there was something personal going on. Keep it off the site, please.

Oh nobody on here that normally post's(this happened about 2 years ago), and i wouldn't post hate messages. Just facts.

I think you know what I'm talking about. Give it a break. Happy New Year.