Stinger discharged through unplugged cradle?

I have a Stinger cradle screwed into the wall. Recently had some power outages and other stuff and found out that it popped the breaker on the power strip the cradle was plugged into. Happened about a week ago and my XT was plugged in at the time. So, for the past week, the XT was sitting in the cradle which was effectively unplugged. Pulled it last night to do some work and found the battery pack totally flat.

Does the SL cradles lack a reverse current diode? It would appear to me that the pack discharged through the cradle when it was no longer receiving power. Has anyone had this problem?

I am not surprised it happened. I have never had that happen what happened to you i.e. the power failure. I know when I am not charging I don't leave my Stinger sitting in a unplugged craddle. If I did I think I would be asking for problems. I would think it would self discharge by sitting on the contacts of the charger... Maybe someone else with my experience could add his/hers two bits?

Dave

Nope, there should be no current coming from the light's charging contacts. It should'nt be drained by staying in the non-powered cradle.

--dan

My Poly Stinger clearly (well, through emperical testing) has a diode installed. Even with a fully charged pack, I can't measure any voltage at the body contacts. And it would be a hazardous situation to not have a diode - can you imagine tossing the Stinger into a toolbox with live contacts? In addition, the charger is putting out nearly 5 volts when the pack is fully charged; about a diode drop greater than what three nicad cells would normally be at when topped off.

Despite the fact your batteries went for some time with no charge, I assume they are O.K. now that your charger is back on line - correct?

Power will drain when outlet is not live, either house or auto. MagCharger has same problem.

Bill

Thought I would do a little test on my Magcharger. It's the latest model with the new style bulb.

First step - isolate a charger and flashlight contact. I used Solder Wick and Scotch tape:


Next - Snap the light into the charging cradle:


Now connect the power and verify the charge LED is not lit. (An open circuit exists):


Short out the open circuit to verify the charger works:


Now connect a DMM to measure the charging current:


Good - 227ma, just about what you would expect as an overnight charge rate for a 2.2AH Nicad pack.

Final test - disconnect power from the charger and measure how much drain is on the battery pack:


On my Magcharger, there is no drain when the charger is not powered. But designs change all the time, so this may not be true for earlier models. Also, nicad batteries lose 1 to 2 percent of their charge per day. After two months of sitting, most packs have pretty well drained themselves due to this self-discharge rate. If you leave your rechargable light in a unpowered charger, it would be easy to assume the charger had drained the battery.

Photos also prove that EvilLithiumMan has an electric plaque remover. But neither photos nor EvilLithiumMan's dentist have proof of said device having ever been used. /ubbthreads/images/graemlins/frown.gif

The batteries are bad or are possibly discharging in the flashlight. Check for corrosion or another conductive path in the light or charger. A bad switch may allow enough current to flow through the lamp. Test the charger, too, as EvilLith has done - no current should flow when unplugged.

Let us know what you found to be the problem.

Nice toothbrush! lol /ubbthreads/images/graemlins/hahaha.gif

What I was saying is that battery will discharge if you leave it plugged into wall and the power goes out. It will discharge probably overnite. The same thing for a car cigarette lighter DC outlet. If the outlet is not live, for example when you turn ignition off on some cars, the battery will discharge through the car's electrical system. Streamlight and Maglite recomment hard wiring charger to battery.

Bill

Well, I'll see about testing the charger and the flashlight contacts. I reset the breaker, overnight it charged up the light to full power again. I pulled the battery to test for swelling or other indication of a blown cell - stick looked okay and is only 2 years old. I've charged it and left it in a flashlight stuck in my toolbag for a month so I would think the stick is still okay or was until this problem. I'll do some more testing and see.

Hello Blackbeagle,

It is interesting to note that I was just reading the specifications of some battery chargers for NiCd and NiMh batteries, and they state that the batteries should be removed from the charger after charging because if the power is shut off, the batteries will discharge through the charger.

The batteries can be left on the charger as long as it is plugged in, but batteries should not be stored in the charger while it is unplugged.

Tom

Can anybody provide some technical insight on why a manufacturer would produce a charger where the batteries will discharge when the unit is unpowered. It's so easy and inexpensive to prevent that type of discharging that, perhaps, there is some other advantage to a circuit like that - one that I can't think of, however. Somebody, please, enlighten me. Thank you.

Hi Jayflash - I am no electrical expert(funny my father is a retired Design Engineer from General Electric). I have always assumed that while the item whether it be a flashlight, electric razor or whatever that anytime the item was not actually being charged it would not sit in the charging cradle. After all, the charging cradle is just that a charging cradle, says nothing about stowage. Anyway, I believe even my Tigerlight mention's that if you are not actually charging the light to take it off the cradle.

These of course are my own thoughts, nothing is set in stone just stuff I have run across through the years...

At this point I'm guessing the cost of another diode is saved in some chargers because the battery packs or lights already have one internally. Yet, the addition of a, second, diode in the charger would be a small expense. I've got an electrical background but cannot think of why a battery discharge occurs in an unpowered charger. Are these chargers supplying AC or DC to the flashlights? If the light or battery pack has a diode to rectify the current then that diode should prevent discharging. If the Diode is shorted and AC is supplied to the light then it won't charge in the first place. It could be that some regulator circuit designs will cause discharge when unpowered. I'd be interested to know if this problem has been definitely isolated to the charger or are the batteries dying when left in the light when it's not in the charger. Calling any electronic technicians or engineers!

I agree that it is good practice to not leave batteries in an unpowered charger. Why even do it? (Of course, if you were charging batteries and there was a power outage, the situation would unavoidable. But that is the exception and does not happen often in the U.S.)

I have a Digipower DPS-5000 and a Maha 401S I use for my Nimh 2200mah AA cells. I have the instructions for both of them and neither of them even mentions the subject. But just for fun, I measured how much drain was placed on the cells if left in the charger unpowered.

The Maha charger drained the cells at .65ma. Doesn't sound like much at first, but it adds up after a while. The DPS-5000 charger was much better. It's drain on the cells was only 50ua. (0.050ma) It was so low that I wondered if my if my $29 Radio Shack DMM was giving an accurate reading. So I ripped my Fluke 177 DMM out of another project and did a measurement. But it gave the same reading, 49.8 to 50ua.