Coast HP7 gets dimmer after short while.

I have recent bought HP7. I turn it on to maximum brightness, after a short while the batteries get warm and the light gets dims. I click the button three times, and the torch light switches back to maximum brightness and again gets dim after a short while as the batteries get warm. Is this normal or defective?

Short answer, yes. That would seem normal to me based off what I am seeing spec wise for this light. As a side note, I do not own this light and thus would not be able to tell you from experience.

Basically, here's what I am seeing that makes me say what I did. First and foremost, Coast tends to have direct drive like regulation patterns. This means the light output will begin to get dimmer the moment you turn it on and keep getting dimmer and dimmer until it dies. This isn't so bad as it allows the light to run longer than it other wise would and it let's you know when you need to replace batteries. Bad news is, if you needed that max brightness then you're not going to be very happy after about 5 to 10 minutes of use.

The other factor I am seeing is the battery configuration. AAA batteries will not be able to handle as high of a draw as larger cells and will cause the light to dim as the voltage in the cells sags under the loads. I don't know what LED Coast is using so I don't know how much current is being pulled from those batteries. Another factor that will multiply this almost infinitely is if you are using standard Alkaline batteries instead of quality NiMH rechargeables. Alkaline batteries can not handle any kind of high draw for any length of time.

If you are using Alkaline cells then you would get a marginal increase in performance out of NiMH cells. Eneloop is one of, if not the highest quality brand out there. You can find some of their cells rewrapped and sold under a different brand name. In example, Duracell uses them in some of their rechargeables which has earned those cells the nickname "Duraloop". You can find them cheaper that way sometimes.

Unfortunately, a lot of light companies tend to use regulation patterns like this as a way to market longer run times. Some companies that are known for this include: Maglite, Streamlight, Coast, Inova, etc...

That being said, it's pretty much a preference thing. There are a fair amount of people who prefer their lights to tapper in output as they go.

Hope this helps, :welcome:

That makes sense. Thanks. I guess the max brightness is 360 lumen. That is pretty high compares to other models and brands. The spec said it lasts 1 hour and 45 minutes. It probably lasts that long as the light gets dimmer.

Based on my experience with Coast lights, you would get more than a marginal improvement by going with NiMH rather than alkaline. Direct drive lights like Coast lights actually thrive on the constant voltage output of NiMH batteries. I have an old Coast PX25 kicking around that I used a few years back. And although the runtime of this light was never spectacular on 3xAAA batteries, it would at least not dim down with NiMH batteries. To me, this was a HUGE advantage (along with the fact that I didn't have to constantly buy batteries for a battery hog).

There is one thing I should say here that many might not like to hear. But if you run NiMH, I DON'T recommend Eneloops unless the light is only going to be used for short bursts and used for standby emergency use. These sorts of battery hogging lights need high capacity batteries to maximize their already short runtime. And unless the light is going to be sitting in a drawer most of the time, low self discharge is not very helpful because of the already short runtime. If you MUST run Eneloops (or other LSD batteries), Eneloop XXs are probably a better idea.

Hm, I wasn't sure how much of a performance increase NiMH batteries would have and I didn't want to overstate it.

Just to debate the whole battery thing right quick, Eneloops are very versatile as high draw cells and sag less than most others irrc. They don't really have much of a shorter run time than other cells.

Regardless, I agree that the XX series should be used for most people. You can find those cells rebranded as Amazon High Capacity 2500 mah cells. You can get 8 of them for just under 18 dollars when I got them. That's a great price for high performance cells like those.

I don't think the OP can go wrong whether he gets Eneloops or not if he upgrades batteries for his light.

SimulatedZero said:

Just to debate the whole battery thing right quick, Eneloops are very versatile as high draw cells and sag less than most others irrc. They don't really have much of a shorter run time than other cells.

Regardless, I agree that the XX series should be used for most people. You can find those cells rebranded as Amazon High Capacity 2500 mah cells. You can get 8 of them for just under 18 dollars when I got them. That's a great price for high performance cells like those.

I don't think the OP can go wrong whether he gets Eneloops or not if he upgrades batteries for his light.

Click to expand...

This light uses AAA batteries, not AA. That's the main reason why I don't like LSD batteries for this sort of light. My favorite NiMH AAA is actually the old Duracell 1000mAH. They were GREAT cells. And they provided a very noticceable boost in runtime vs Duraloop 800s. Unfortunately, you can't get them anymore.

Oh that's right. I don't know why I was thinking of AA cells.

Listen to Matt on this one, he's on the right page here. I'm off in the funnies section at the moment apparently.

i have this light. running duraloops primarily with great results

Primary lithium AAA work well in this light as well, but, the 360 lumen output lasts about 30 seconds or so on just about anything you load into this light....and starts dropping after that.

It will drop to half the claimed output in a matter of a few minutes on alkaleaks for example.

The claimed run time is to when its dropped to 36 lumens btw (10% of max output of 360 L)

I have the HP5 which is a single AA light and it does the same thing on high. On low mode it does pulse width modulation which is obvious from pointing it at a portable fan on low where it "freezes" the fan to the naked eye, a visual phenomenon known as "aliasing." It's sort of cool, and happens when the flicker fusion rate of the human visual system is not that far off of the frequency of the pulse width modulation. What can I say? Science in the home!

Ive had 3 HP7's and have never had this problem. Yes they dim after a bit but thats because they are non regulated

Tecboy said:

I have recent bought HP7. I turn it on to maximum brightness, after a short while the batteries get warm and the light gets dims. I click the button three times, and the torch light switches back to maximum brightness and again gets dim after a short while as the batteries get warm. Is this normal or defective?

Click to expand...

How long is the light on before you notice the dimming? I have the 250 lumen version of this light and it dims after I have had it on about 15 minutes. Mine, however, does not return to normal brightness after I turn it off and on. I am using 1000 mAh NIMH Duracell rechargeables in mine. If I just use it for brief periods of time a day (1 minutes or less) I do not notice a brightness drop until a few weeks later. In a nutshell, AAA batteries are a weak power source for a light that puts out this many lumens. That is the HP7's only flaw, in my opinion.

I bought the 360 lumens version from Lowe's on the 7th of this month. After using it a little bit, I noticed that it got very dim quickly. So w/ a freshly charged set of AAA Eneloops (1.46 volts off the charger), I put it on high and did a ceiling bounce test w/ my light meter. It dropped (quite a few noticeable 'steps') to half the LUX in two minutes. It did the same thing w/ NEW alkalines as well. Sounds like this is normal. Sigh, I may take it back today for a refund. If I can get a 251 lumens version somehow, I'll test it to see how long it takes to hit half the LUX vs. 2 minutes.

JohnnyBravo said:

I bought the 360 lumens version from Lowe's on the 7th of this month. After using it a little bit, I noticed that it got very dim quickly. So w/ a freshly charged set of AAA Eneloops (1.46 volts off the charger), I put it on high and did a ceiling bounce test w/ my light meter. It dropped (quite a few noticeable 'steps') to half the LUX in two minutes. It did the same thing w/ NEW alkalines as well. Sounds like this is normal. Sigh, I may take it back today for a refund. If I can get a 251 lumens version somehow, I'll test it to see how long it takes to hit half the LUX vs. 2 minutes.

Click to expand...

If the LED is being direct-driven from the batteries (which is sounds like it is), even a small sag in voltage is enough to cause a large drop in brightness. That's just the way LED's work. They'll work from about 2.5v to 3.5v. But they're really dim when you get near 2.5v, and really bright when you get near 3.5v.

I bought the HP7 (360) after reading this. Dratz!

So I just use it on medium, which is plenty bright for general use at 211 lumens.

Now my rechargeable (251 lumen) HP7 is pretty consistant using the rechargeable module. Haven't tried alkalines in it yet.

Edit:
Just found a pair of 251 lumen HP7's at Amazon. A silver one (easier to find) and a black one (looks cool). The 251 are rated to have a similar throw to the 360 version, hi/lo settings (no strobe) and about 4x the battery life. Still waiting the pair of 251's arrival.
(8/30/15 Edit: no more black 251's to be had and even though I got 'confirmed' one has yet to arrive. There are some titanium colored available at amazon sellers. I now have 2.)
While there bought some new eneloop pro 950 aaa's and a charger. The xx are now called pro.

I have the coast hl8 I run Amazon basic high capacity, I use it almost everynight for an hour, it will run two hours on high max Lumens is 390. The last 10 minutes is the only time I notice any drop in light output then it drops pretty quick.

^^ I like the HL7...but will try out that 8. Thanks for that info.

I wear it on a hard hat. When talking to coworkers the say "holy cow turn off that light."..I reach back, twist the slider a bit. I can still see, and they aint blinded. ;+/

Eneloop Pro 950's arrived. They made a big difference!!
Light was noticeably brighter vs about a half hour of on/off ocasional use of the supplied Duracells.

Left on a high a couple minutes and saw little to no dimming. WOW, what a difference.
I use it on medium (211 lumens) mostly (or even low at times) so it's nice to know it'll run on high for a little while if I choose to.

Ive had 3 HP7's 2 of the old ones and one of the new Pros. I use energizer ultimate lithiums and they crank like crazy for as long as I have the light on.....

My wife snatched up my titanium colored 360 model. So we had light wars one evening and my 251 model won.
Well, I cheated...hers had some regular copper tops and mine had eneloop pros...but she'll never know I had secretly switch battery pods before the test It being her burglar thwarter, I put back the pod with eneloops in hers after.

Like Celtic74 said, the lithiums he mentioned do the job too.

Coast uses that federal standard which times it from the point of begin to time it takes to be as bright as "1 moon light" brightness. So they are generally in compliance with these lights. As in after about 1 hour and 45 minutes it's still as bright as "1 moon light"...
In the dark, dark woods, where you look up and see a million billion stars on a clear night, that's bright enough. But in the city...it might as well not even be on, where I live.

So if you walk your dog for say 45 minutes on a lit street, and use supplied batteries, use medium on the 360 model for best results.