I have a Coast HP7 that I've really depended on for many years. Had to put it to emergency use this past week during an electrical outage and ran into a problem. When I turn it on it's as bright as it's ever been. But the longer it is on, the weaker the LED becomes and will eventually go completely out. If the ambient temperature is low, the light lasts longer and if it's warm it doesn't last long at all. It's as if the warming of the LED dims it. Anyone have any idea what might be causing this? Is the flashlight just old and needs to be tossed, or is this something I can remedy?
Why does Coast HP7 dim?
- Thread starter Chris C
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It's known as direct drive. Dang near every incan flashlight was direct drive. Many LED flashlights are "regulated" to stay the same brightness.
Now sometimes that means sudden lights out when fuel supply cannot keep up with required voltage to keep a steady brightness. The HP7 dims as voltage drops.
Heat does cause an LED to dim but in your case it's probably more about batteries not being able to keep up with the amount of electricity the LED wants from the batteries. The 360 lumen version was famous for dimming greatly when using alkaline batteries.
Try some energizer ultimate lithiums or eneloop pro rechargeables which can better keep up with the demands of that Coast. Rayovac Fushion do ok also. The biggest downfall of an otherwise great flashlight, the HP7 is the fuel supply being triple a batteries.
Next time you need extended use try clicking it to low as that is still fairly bright but draws a lot less demand from the batteries.
Welcome to the site Chris.
Now sometimes that means sudden lights out when fuel supply cannot keep up with required voltage to keep a steady brightness. The HP7 dims as voltage drops.
Heat does cause an LED to dim but in your case it's probably more about batteries not being able to keep up with the amount of electricity the LED wants from the batteries. The 360 lumen version was famous for dimming greatly when using alkaline batteries.
Try some energizer ultimate lithiums or eneloop pro rechargeables which can better keep up with the demands of that Coast. Rayovac Fushion do ok also. The biggest downfall of an otherwise great flashlight, the HP7 is the fuel supply being triple a batteries.
Next time you need extended use try clicking it to low as that is still fairly bright but draws a lot less demand from the batteries.
Welcome to the site Chris.
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Thanks, bykfixr. I'm using CopperTop batteries..................just as I always have. They've always lasted as long as the "need". However, this light will completely extinguish in less than 5 minutes and I'm using brand new batteries. That's why I find it surprising. The light is an older model and only has one brightness level so that's not an option. Of all the LED lights I've owned over the years, I like this one the most. Guess I'll try new batteries before tossing this in the trash. Hate to do that.
WalkIntoTheLight
Flashlight Enthusiast
Alkaline batteries die extremely fast when used at high loads. They're basically useless if you draw more than 0.5 amps out of them, and even at that modest drain, they only have about half their capacity compared to lower drain.
Use Eneloops, instead. They're good up to about 5 amps, and you can recharge them hundreds of times.
Use Eneloops, instead. They're good up to about 5 amps, and you can recharge them hundreds of times.
Definitely don't toss it. And don't store it long periods with alkalines inside.
You just need a better fuel supply.
You just need a better fuel supply.
Seems strange that it would shut down after 5 min. if the batteries are new and this didn't happen in the past. Might be a temperature sensor that went bad and is shutting the light down because it thinks the light is getting too hot. It also could be really bad batteries.
AAA alkaleaks are notoriously "springy" in that under a light load they will be a decently high voltage but under a heavy load as they are used up the voltage drops a little and they become a lot more springy in that they sag more but come back to voltage after resting.
This behavior is rather frustrating for sure as on lower modes they perform fine in a light but higher modes they do well till that batteries are partially used up and have more sag and spring back. If the batteries are not Alkaleaks but some sort of heavy duty or carbon zinc then it can get even worse and even under light loads can spring tons. I had a remote that came with batteries that kept acting up and I would use a voltmeter to check them.... 1.5v put them in the remote quit working after a minute. Finally I tested them on a battery tester with a load on it.... 0.1vdc under a light load..... no load 1.5v.
Another very problematic issue of 1.5v batteries in series is on occasion one cell depletes a lot faster than the rest and if you have 3 cells that normally would measure 4.5v new and half used about 3.6v or so, but if one cell goes depleted instead of it contributing 1.2v it contributes nothing so you get 2.4vdc. Using 4 cells you would have 3.6v if one cell goes flat and under load that could be way below what is needed to power an LED at a significant output.
Uneven cell depletion happens at times that is why a lot of us have gone to lithium ion cells as a single cell can do a bunch.
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Well bykfixer, I thought you were crazy...............but I went out and bought some Energizer Ultimate Lithiums like you suggested. I've had the light sitting on my desk for the past 10 minutes and it's still pretty bright...............not anywhere near as bright as it was when I first turned it on, but bright enough to be more than useful in the dark. This whole process has been a surprise to me, especially since the light has always worked well in the past with Copper Top batteries. Oh well, it looks as if I'm back in business. Thanks for your help. Like this light and didn't really want to discard it. I'm going to replace all my LED flashlight batteries with these lithiums.
WALKINTOTHELIGHT, with so many things in my life on batteries, you're probably right I should invest in some rechargeables and a charger. I used to have some, but that was many years ago and the recharging life cycle was mighty low back then. Should be better now............some 30 years later.
WALKINTOTHELIGHT, with so many things in my life on batteries, you're probably right I should invest in some rechargeables and a charger. I used to have some, but that was many years ago and the recharging life cycle was mighty low back then. Should be better now............some 30 years later.
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One cool thing about eneloops is they hold their charge a good long time. Used to be rechargeables would be halfway dischrged in a couple of weeks but eneloops stay at least halfway charged a year or more.
The hydrogen gas that chemical reactions in alkaline cells escapes and in time a white powder forms and coats parts.
https://www.consumerreports.org/batteries/whybatteriesleak/
Here's an explanation
https://www.consumerreports.org/batteries/whybatteriesleak/
Here's an explanation
The huge advantage of rechargeables is you can top them off anytime that way you know how much power is in them when you need it. With primary batteries you can get more runtime when full but once you start using them you have to keep track of how much power is left.. if you can and end up sometimes with dead batteries when you need to use something.
Okay, you guys have me convinced. So it's Eneloop rechargeable batteries. Is there a recommended charging station? I've noticed some will charge both AA and AAA batteries at the same time. Seems as if that would be a good choice since I do still have some AA requirements around the place.
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Chicken Drumstick
Flashlight Enthusiast
I don't know enough about the Coast light you have. But it may also have a regulation program that dims the light to extend runtimes. If you notice it dimming, trying cycling the light by turning off and on again. It might come back bright.
It's a direct drive light CD. No regulation at all. That's why it dims so badly using Duracell triple a batteries.
That brings it back to bright..........for a split second. This crazy LED would actually dim down so low I'd have to cup my hands around the lens to see the minor glow of the LED. I'm talking "dim" here! Anyway the new Energizer Ultimate Lithiums work fine. I don't walk around with this flashlight.............just use it now and then. So if I get good usable light for 10 minutes or so I'll be satisfied. So I'm sure all is well. When I get my rechargeable batteries and charger it'll even work better.
lightfooted
Flashlight Enthusiast
- Joined
- May 6, 2010
- Messages
- 1,017
You said you have other LED lights but ...I don't think you understand yet, just how deep this rabbit hole is.
Back in the early LED light days they came out with boost circuits using less than 3 cells (alkaleaks). Some lights would actually start strobing when the alkaline battery got depleted. The strobing was caused by the circuit kicking in/out when the voltage would rise under no load and fall when hit with the circuit load and continue on till it was unable to spring back.
We have threads and threads of vampire lights, that is lights that can essentially drain a primary battery dead of power. These lights work down to the lowest voltage level there is without shutting down. The circuits are more efficient at very low current and lumen level outputs unlike many lights who put out a lot of lumens. You could take the AAAs out of your dead light and put them in another light and use it perhaps for days at very low levels of output.
What you probably need to invest in is a battery tester that incorporates a load. A load battery tester can show if alkalines or other primary batteries are depleted as the load defeats the springy voltage recovery of the cells that a volt only test will not be able to show a battery is depleted.
