Watts, Lumens, Kelvins, Amps, Li-ion, NiMH, Lead-acid.. which?

[Zundanc3]

Watts, Lumens, Kelvins, Amps, Li-ion, NiMH, Lead-acid.. what/which?

I'm looking at HID lights, but am a mere business major.

Could someone please kindly explain the terms above and which is best for diving?

I kind of understand for Watts, Lumens, Kelvins, and Amps that a higher number is better?
But, what's a good number for each?
And, what do these numbers mean in a practical sense?

As for the battery types, please list pros and cons.

I'd be using the light to communicate and to do some wreck, cave, and night diving.

 

[paintsnow]

watts is used as a measurment of how bright a light it, a 21W HID will be sufficient if not overkill depending on where you are diving, its also a unit of measuring how much electricity flows through the light/the light requires to burn at its set brightness

i know this can get confuzing because some companies refrence thier lights to be comparable to an 80 watt light of a different sort and all

lumens is a measure of intensity i would say, how much light it is giving out, almost like candle power.

kelvin is the color of the light and how bright it is colorwise

amps are again a measure of electricity used.

i might have messed up a few of those but others will chime in and fix any mistakes

you might want to post what your budget is so that we can point you towards some good lights and you can get peoples opinions, also if you already have a light in mind feel free to post it and see what people have to say

personally i like the nite rider products, although some will recommend salvos and other good quality lights

sorry if i made any mistakes up there or worded it badly, please chime in a fix it so the op isnt confused.

 

[H2Andy]

you really need to concentrate on watts.... the higher the wattage, the brighter the light. 10w is enough to light up the biggest caves in Florida ... anything above that is really just tweaking ... yeah, it's nice to have a 21w light ... but do you really need it? no ... Sheck Exley never had anything like that, and look at all he did

everything else (in my opinion, of course) is just secondary

as to batteries, oy vey... what can i say ... people are dead set it seems ..

a NiMH battery can have two to three times the capacity of an equivalent size NiCd, and the memory effect isn't as pronounced

but compared to a lithium-ion battery, the NiMH batteries don't hold their charge nearly as well nor can charge to the same level...

look, if a battery gives you four hours of burn time, and they all do, they're all good in my book ... go with price

(just my opinion)

 

[CompuDude]

The sort of diving you will be doing, under which conditions, should determine how many watts you need.

NEED is different from want. There are indeed situations where it is actually much better to have 21w over a 10w light (murky cold water in SoCal or the PNW, for instance), while in a clear cave the 10w may make more sense.

Budget is also a big determining factor. If you can only afford under $200, a UK light cannon is probably going to be among the best lights you can get that will serve well for most situations. (And may even be a little overkill... but still useable... for some warm clear tropical conditions.) If you can afford $1500, all kinds of canister light possibilities open up.

What waters do you dive? And what do your buddies have? Fill in your profile so we know more about where you are coming from and what to recommend for YOUR diving, else you'll just hear each person's preference, which may not be well suited to your needs.

 

[Benthic]

Watts, Lumens, Kelvins, Amps, Li-ion, NiMH, Lead-acid.. what/which?

I'm looking at HID lights, but am a mere business major.

Could someone please kindly explain the terms above and which is best for diving?

I kind of understand for Watts, Lumens, Kelvins, and Amps that a higher number is better?
But, what's a good number for each?
And, what do these numbers mean in a practical sense?

As for the battery types, please list pros and cons.

I'd be using the light to communicate and to do some wreck, cave, and night diving.

As others have said, more watts basically means more light. While this is usually a good thing, it also means that the lamp draws more current and may lead to backscatter problems in an environment with lots of particulate in the water.

Kelvin is the unit used to express (where lights are concerned) the color temperature of the light. A higher number means a 'whiter' light. For example 4000K is a yellowish light, while 5000K to 6000K is decidedly whiter. As you progress into the 10,000K to 12,000K range the light takes on a bluish cast, although I don't know of any dive lights that operate in that range.

Amps, or more correctly amp-hours (Ah), is a measure of battery duration. For example if you have a light bulb that draws one amp, and you connect it to a 10Ah battery, it will burn for 10 hours. If you connect a light bulb that draws two amps to that same 10Ah battery, it will only burn for 5 hours. To my knowledge, most 10w HID lamps draw one amp and the 18w/21w lamps draw two amps.

Ideally what you want is a light that will carry you through a day of diving on a single charge, is of a physical size/weight that you are willing to carry around, and won't break the bank. It's nice to have a similar size light (wattage) to those that you dive with frequently, but that's not necessarily a requirement.

Brian

 

[Zundanc3]

Hmm, not as many engineering nor physics majors out there aye?
Thanks Benthic.
I did some surfing and found these references also:

A watt is a measure of how much energy a light bulb consumes, not how much light it gives.
Wattage has nothing to do with the amount of light (lumens) you get from a light bulb.

Lumens, not watts, tell you how much light you will get from a light bulb.
For economy and efficiency, look for the highest lumens per watt.

A lumen is the amount of light you get from one candle placed one foot away from the center of the flame, or one foot-candle.

Stated again, a lumen is the amount of light which when distributed uniformly over a one square foot surface area, produces an illumination of one foot-candle on every point of the surface.

So, if I could get a 10 watt light that could put out 3000 lumens at 6000°K,
that would be better than a 24 watt light that only puts out 1500 lumens at 6500°K.
Right? The reasoning: The higher wattage just eats up more power quicker. The higher the lumens the brighter the light. And, a white light is preferable to a blue light?

As for Kelvins, here's a chart:

Seems white/direct sunlight is 6000-6500°K.
Higher you get blue light.
Lower you get amber light.

Next amps or mAh stands for Milliamp Hour, a term for how much power a battery will hold and how long a device will run before the battery needs recharging. Batteries with higher mAh values theoretically last longer without requiring a recharge.

And, here's a chart for the different battery types:

Seems Li-ion is the one for me due to better weight to power ratio?

However, these are all just book answers.

Do any of you have real-world diving experience with these different light specs and battery types?

 

[H2Andy]

Lumens, not watts, tell you how much light you will get from a light bulb. For economy and efficiency, look for the highest lumens per watt.

yeah, but realistically speaking, the more watts, the more lumens

for example, a DiveRite 10w light puts out 500 lumens, while a 21w light puts out 1,300 lumens

the 21w is brighter and more efficient at 61 lumens per watt (the 10w comes in at 50 lumens per watt)

you'll find the same results as you look into other lights. i don't know why or how, but more watts = more lumens = brigther lights

for me, the bottom line is price. i don't see the point in paying for a 21w light when a 10w works just as well. i don't need that much light in Florida caves

(as someone mentioned, your environment may be different)

 

[fppf]

1 out of 6 is not bad, ZunDac's last post hit it on.
Compare a 10W HID with a 10W Halogen, the 10W HID will blow the halogen away.

As for batteries, Li-ion does have the highest power density. But it also has the highest price and needs circuits to protect the cells during charge and discharge.
NiMH has good density, price, and ease of use, these are the most common today.
Lead Acid can give really high surge currents but has a low power density. Very cheap these days but very heavy compared to NiMH.

 

[H2Andy]

Compare a 10W HID with a 10W Halogen, the 10W HID will blow the halogen away.

:shakehead

next thing you'll say is that the world is a sort of sphere with the tops flattened a little and a bulge in the middle

 

[CompuDude]

I think the point is that wattage numbers are of barely any use when comparing lights... you have to be sure you are comparing apples to apples. 10W Halogen and 10W HID simply mean very different things and thus are not directly comparable to gauge the light's power (power consumption, yes, but output, no). However, comparing a 10w HID to a 21w HID and you actually can get a relative idea of how the two lights compare. Ditto for a 1w LED vs. a 3w LED or a 20w Halogen with a 50w.

In the real world, most (recent) rechargeable lights these days are using NiMH rechargables, be they rechargeable C-cells in a UK light or special packs in a canister light. Li-Ion is starting to pick up some steam, and does indeed have the highest power-to-weight ratio, but it slips behind in areas of price, and simply doesn't have the proven track record that NiMH has built up. Lead-Acid has other advantages, but severe weight and size penalties make it best suited for certain specialized applications (such as scooters) rather than for HID lights.

Color temp of any commercially purchased light, IMO, makes little difference, unless you are trying to use it as a video light or photo light, or match a friend's light. Any commonly-used/sold color temp within a reasonable range will do a decent job of lighting up the area.

In batteries, the more Amp hours (or milliamp hours=mah) the longer your battery will last. For HIDs, I see ~4.5 mah as popular for smaller, more compact lights at the expense of longer burn time (although this depends on the size of your light... they'll push a 10w HID a lot longer than a 21w), and ~9 mah battery packs seem to be the most popular.