I have a 18V cordless drill (without instructions) and the charging base has both green and red LEDs. When a battery is being charged, the green LED is on. When should the red LED be on?
- posted
17 years ago
I have a 18V cordless drill (without instructions) and the charging base has both green and red LEDs. When a battery is being charged, the green LED is on. When should the red LED be on?
Err, when it's finished charging?
I would guess that it should be the other way around. Red= not charged, green=charged. If the battery was bought separately to the charger then it might not work properly. I have to use different chargers to charge different battery packs of the same make.
Yes that's the way mine works, perhaps the OP is trying to charge an already charged battery.
-- Mike W
The battery I'm trying to charge isn't charged but I am mixing and matching the charging base with mains chargers which is porbably why it doesn't work as it should (as described above, which makes sense).
My Dewalt charger has a single led... blinks while charging, constant light when charged and a third fast blink if the battery is kaput. I doubt that the red light is the kaput light but you never know!
Not a good idea unless everything is to original spec. Some chargers are incredibly crude and may only use a resistor to give an approximation of a constant current charge, and altering the PSU feeding that can only make matters worse. ;-)
They'll mean "power is applied" and "battery is connected" Unless it's a real charger, then you certainly _won't_ have a "charging complete" light.
Cheap chargers kill batteries. Your best option is to either replace it (which is certainly worth it if they're quality cells in there) or at very least to run it through a timeswitch and never run it for more than the recommended 5 hours. Personally I have an old half-hour "boost" timer that I use for this and charge the battery in a number of short blasts. This gives it a chance to cool down between bursts.
But those cheap chargers are just crude battery killers. Avoid them if you possibly can.
I've modified a few to constant current charge at 1/10th battery capacity
- ie approx a 14 hour charge. Overnight is really no more of a problem than 4 or five hours, and guarantees the longest cell life. It costs less than a quid for the components.
I have two 18v batteries- both seem to be the same spec and size but if I put one on the other charger then it does like you say. Both of mine (with the right batteries) go from red to green.
One of those old style 'pin' timers are good for this. Just have an off 'pin' say every 6 hours, then turn the dial as required (so 1 hr after a pin for 5 hrs charge) and switch on. Good for rechargable spotlights too.
The OP might find that the battery isn't pushed in properly, or the charger needs a 'third pin' on the battery and there isn't one.
cheers, Pete.
Ah, but how much does it cost for the expertise?! ;-(
David
Building something like that - ie the mechanics of it - should be well within the scope of the average DIYer who can solder. The circuit is extremely simple and the parts available from the likes of Maplin.
Is constant current charge critical then?
I've got another one where the base has no circuitry at all. It has an input for the mains charger and nothing else!
It's the traditional way, but modern chargers can be rather different. However, IMHO it's still the best way for long cell life.
The electronics can be built into the wall wart. More of a problem, size wise, with a high current charger. These tend to not be wall warts.
The message from "Dave Plowman (News)" contains these words:
Is that really true? With constant current as the cell approaches fully charged the voltage will rise and rise and rise as the charger tries to achieve a constant current. Doesn't sound like a good thing to do unless it's also got a temperature sensor and a cut-off at full charge.
Not worth it, IMHO. If you're going to faff with it, faff with it so you end up with a real and intelligent charger. The chipsets are cheap enough and it's simple enough that the manufacturer's data sheet (try RS) is enough guidance to work from.
The ones I modified were a few years ago when such chips weren't so readily available. And I had all the necessary bits in stock anyway.
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