Help me choose a backup

[mjr0112]

Is runtime that big of a factor in the grand scheme? I'm only asking because I see that there is a big drop off in output with 1/2 worn batteries. So wouldn't I replace them before there completely depleted, to keep the light performing at its best? To make sure I'm understanding correctly, the disadvantage of using AAA as apposed to AA, is the AAA will become depleted quicker due to the smaller cell, assuming the voltage required for the bulbs are the same?
The only one that uses 6-AA is the Intova Ultra, and it has the lowest stated burn time (7hours). The Penetrater and Dorcy both use 6-AAA, and have 8 hour stated burn time. I would guess that the Ultra draws more wattage/amps/volts (dont know what correct term is here) and that would be the reason it has the shortest stated burn time, with the largest batteries of the 3.
The Ultra uses a 1 CREE Q5 LED, the Penetrater uses a CREE Q4 LED, and the Dorcy uses a K2 Superflux LED. Is there a preferred LED out of these 3? All 3 have a lumen output of 220. I was unable to find any other specs on the LED's on the mfg sites, to verify the reason for the shorter burn time on the Ultra.

 

[TSandM]

Can't answer your technical question, but my husband and I have been using the Dorcys for a couple of years, and have been very happy with them. The only complaint I have is that they're a little touchy about turning on with pressure, so you have to keep an eye on them on descent, to make sure they aren't burning down the batteries.

 

[Hatul]

Can't answer your technical question, but my husband and I have been using the Dorcys for a couple of years, and have been very happy with them. The only complaint I have is that they're a little touchy about turning on with pressure, so you have to keep an eye on them on descent, to make sure they aren't burning down the batteries.

That's where it's an advantage to use rechargeable batteries. Just recharge before diving and you can keep light on throughout the dive.

Adam

 

[Jim Lapenta]

I actually have one set to be on with pressure. I like being able to grab a light with one hand and have it on already. On night dives I turn on my primary and one back up on the harness before going under. They do not get turned off until the dive is over. And with 8 hour burn times I'm not too worried about how far the batteries will go down on a 1 - 1 1/2 hour dive. I would also not hesitate to recommend Pirahna for them. I got all of mine except the first one from them. I bought that one at a show and liked it so much I looked for them when I got home. The person I bought the first one from didn't have any more.

 

[mjr0112]

I would also not hesitate to recommend Pirahna for them. I got all of mine except the first one from them. I bought that one at a show and liked it so much I looked for them when I got home. The person I bought the first one from didn't have any more.

I thought you used the dorcy 180? Or am I just reading this wrong?

 

[gcbryan]

Is runtime that big of a factor in the grand scheme? I'm only asking because I see that there is a big drop off in output with 1/2 worn batteries. So wouldn't I replace them before there completely depleted, to keep the light performing at its best? To make sure I'm understanding correctly, the disadvantage of using AAA as apposed to AA, is the AAA will become depleted quicker due to the smaller cell, assuming the voltage required for the bulbs are the same?
The only one that uses 6-AA is the Intova Ultra, and it has the lowest stated burn time (7hours). The Penetrater and Dorcy both use 6-AAA, and have 8 hour stated burn time. I would guess that the Ultra draws more wattage/amps/volts (dont know what correct term is here) and that would be the reason it has the shortest stated burn time, with the largest batteries of the 3.
The Ultra uses a 1 CREE Q5 LED, the Penetrater uses a CREE Q4 LED, and the Dorcy uses a K2 Superflux LED. Is there a preferred LED out of these 3? All 3 have a lumen output of 220. I was unable to find any other specs on the LED's on the mfg sites, to verify the reason for the shorter burn time on the Ultra.

The Intova more than likely has the more accurate number and the rest (Penetrator/Dorcy) don't.

All of the led's are roughly equivalent (Cree XR-E Q5, Cree XR-E Q4, and Lumiled K2) and draw about 700 mA. Six AA batteries have twice the capacity of six AAA batteries.

The Ultra figures are about right regarding burn time based on 220 lumen output. The Penetrator should last about 3.5 hours at 220 lumen. However if they aren't regulated (and I don't think they are but am not sure) then they will gradually decline in output and therefore the Penetrator may actually last 8 hours but it won't be anywhere near 220 lumen. The Ultra either is regulated and burns at full output for 7 hours or it isn't regulated and should burn much longer than the Penetrator. The Penetrator can't be fully regulated and have a burn time of 7 hours however.

The Ultra must be larger than the Penetrator so consider that, the switching method, and the batteries.

I would probably get the Penetrator but both should work well for you. Regarding the twist head turning on with pressure...usually you can just back the head off enough to keep this from happening.

If you want the math regarding burn time...you have 18 wH capacity with 6 AA's and 9 wH capacity with 6 AAA. The led's in question are driven at approximate 2.5 wh (3.6v * .700ma = 2.52 wH)
So for the AA light you have 18/2.52 or 7.14 hours and for the AAA light you have 9/2.52 or 3.57 hours.

Those are are rough numbers and burn times would be less due to the power requirement for the drivers but you get the point.

There is currently no standard way for dive light manufacturers to advertise burn time so some do it at full power and some do it until the light quits and some do it somewhere in the middle. So in other words either do the math for yourself or just consider burn time as advertising in the same vein as "our light is the best!".

Keep in mind that for a backup you mainly just care that it turns on when you need it rather than how bright it is all the time so you really don't have to replace the batteries when they get a little dimmer. If the light isn't regulated it will get a little dimmer fairly quickly but you won't notice it. Having a regulated backup light probably isn't a good idea anyway. A truly regulated light would burn at 220 lumen until it just stops and this would give you no warning. This might work for a main light that you would keep charged before every dive but backup lights are usually just left alone until you need them.

 

[Jim Lapenta]

I thought you used the dorcy 180? Or am I just reading this wrong?

The dorcy is the penetrator! They changed body style a couple years ago and they are now called the penetrator. I have the older dorcy (3) and the new body style penetrator (2) but in the 180 lumen.

 

[mjr0112]

The dorcy is the penetrator! They changed body style a couple years ago and they are now called the penetrator. I have the older dorcy (3) and the new body style penetrator (2) but in the 180 lumen.

I figured there had to be something to it since the body is identical.

 

[mjr0112]

If you want the math regarding burn time...you have 18 wH capacity with 6 AA's and 9 wH capacity with 6 AAA. The led's in question are driven at approximate 2.5 wh (3.6v * .700ma = 2.52 wH)
So for the AA light you have 18/2.52 or 7.14 hours and for the AAA light you have 9/2.52 or 3.57 hours.

Thank you, it's always nice to see the actual numbers, I just don't always know how to get them.

 

[gcbryan]

Thank you, it's always nice to see the actual numbers, I just don't always know how to get them.

The quick answer to this is that you convert everything into watt or watt/hours. So volts * amps = watts

In the case of batteries it's just watt/hour instead of watt.

All alkaline batteries are 1.5 volt. The amp/hour is what changes. AA are 2 amp/hr, AAA are 1 amp/hr, C is 6amp/hr and D is 12/amp hr.

So 1.5 v * (amp hr of the battery * number of batteries) = w/H capacity of the batteries in question. Or...(1.5v * number of batteries) * amp hr of one battery...but the result is the same as in the first equation...it just depends on whether or not the batteries are wired in series or parallel but the power produced is the same.

For the led info you need to get that from the manufacturer but until you get into the leds that are more powerful than we are speaking of here a generic voltage value would be 3.6 V and most are driven at 700 mA or .7Amp. This is just a generalization and you need to check the specs.

So really for many of the lights in this category it's just 3.6v * .700mA = 2.52 wH

That what the led requires to power it for 1 hour....2.52 wH.

We just saw that 6 AA batteries provide 18 wH of capacity so you just divide that by the requirement of the led to get the run time...so 18/2.52 = 7.1 hours.

Once you do it a few times and learn a bit about the power requirements of some of the standard leds it's not hard to get approximate numbers just to see if the advertising is close or total BS and many times it is total BS