Cordless tool batteries - don't overcharge

[arose62]

This morning I whacked myself across the noggin as a fickhead!

At 6:00 PM yesterday I put my cordless drill battery on charge, mentally noting the warning "Charge for 3-5 hours. Do not overcharge", and working out that I could turn it off around 9:00-10:00 PM before going to bed.

I forgot (again), and woke with a start at 2:00 AM, ran down to the garage and disconnected the rather warm battery, stubbed my toe, tripped over some kid's toy in the dark, and took ages to get back to sleep.

In the clear light of day, I wondered why the "obvious" solution has escaped me all these years - I now have the plug-pack plugged into a timer switch with the "On" period set for 4 hours. So, rotate the timer dial until it's ready to kick in, plug in, and I've got a whole day to remember without cooking the battery, as the timer will turn off the charger auto-magically.

I'm really, REALLY annoyed at myself, as I'm a bit of a fan of timer switches, and make sure I have a spare in my bits box.

Cheers,
Andrew

[blackhole]

I have even put it on a time and then forgotten about it for a few days, so the battery got charged every day.:(
thinking......
thinking..........:think:
thinking.............

I know what to do.......use two timers.
If I set one timer for 4 or 5 hours and plug it into another timer set for 4 or 5 hours then that should buy me about 5 or 6 days of forgetfullness.

Say I set both at 4 hours then for the first 4 hours both timers will be on, for the next 20 hours the timer with the battery charger will not only be in the off position but will be with out power so time will stand still. The next four hours the timer connected to the power will switch on and allow time to pass on the other timer with the battery. Then 20 hours off (time stands still again) so now 2 days have passed and the timer with the battery charger plugged in thinks only 8 hours has passed. If I follow this I think it means I can put the battery on charge Sunday night and it will be safe till next weekend.

OR
The timer manufacturers could make a timer that you set for so many hours of on and then it goes off, you know really simple like a kitchen timer that you twist the dial and the bell goes 'ding' when the cake is baked. In this case it would go 'off' before the battery is baked

Disclaimer:
I take no responsibility for any brain strain that may occur trying to follow my logic.

[bille]

I just tell my wife to remind me...... and she does, relentlessly every hour until I give in and switch the damn charger off :-)

[DavidG]

Buy a decent electronic timer that allows for a single on time followed by weekly times.

ie
4 hours on once only.
1/4 hour on once per week. Keeps the battery charged.

[hitch]

The cordless drill chargers I use - Markita & DeWalt - cut out when the batteries are charged. How did I get so lucky!!

[malb]

There is still a problem with charging for 4-5 hours, in that it doesn't take into account the original charge state of the battery, or its ultimate capacity, which will be in decline from the time of first use. So it is still possible to overcharge or cook batteries even with a timed charge.

Every rechargable battery family has some measurable characteristic to indicate that the battery is fully charged (i.e. will not absorb any further recoverable energy). With nicads, the battery voltage rises gradually, and drops a small amount at the max capacity point. It costs about $1.50 to detect this and terminate the charge electronically, but most manufacturers won't use this sort of technology. The only obvious reason is that they would loose sales of replacement batteries or equipment if the batteries had a reasonable life span.

As mentioned by others, some of the dearer brands do include decent monitored chargers which protect and actively recondition the batteries while charging. I have adopted a policy of not purchasing anything from brands which won't offer decent monitored charge facilities on the battery tools.

[Skew ChiDAMN!!]

And with all 3 of my el-cheapo drills, if I left the battery connected after switching the charger off it'd have discharged back through the damned charger, thus defeating the whole point of the exercise. :~

Those 3 drills are junk now - not because of drill or battery failure, but 'cos the chargers literally went into melt-down and I can't recharge the batteries unless I buy a decent charger that'll cost more than all 3 drills did in the first place... :sigh:

[Ashes]

Has anyone come across a decent timer that basically has a countdown function? eg. set for 4 hours, after 4 hours it turns off and doesn't come back on.

I was looking last weekend for one and couldn't quite find one that appeared to do this.

[FXST01]

Move the battery charger to your bedroom and place it beside your alarm clock. :2tsup:

[MICKYG]

Sounds like alziemers or oldtimers tablets may be needed:D:D:D:D:D.


Regards Mike

[chrisp]

There is still a problem with charging for 4-5 hours, in that it doesn't take into account the original charge state of the battery, or its ultimate capacity, which will be in decline from the time of first use. So it is still possible to overcharge or cook batteries even with a timed charge.

Malb is quite correct. The other issue with these "only charge of x hour" battery chargers is that that there is no equalisation charge after the bulk charge. Battery packs are doomed to early failure if not regularly re-equalised.

I'd steer clear of any cordless tool battery charger that has instructions like "only charge when fully discharged" and "only charge for x hours". These chargers are very primitive and don't recharge batteries properly - either with an external timer or no timer.

[Dusty Dave]

I have an 18V GMC hammer drill and I leave the battery on charge permanently, or at least until the battery on the drill goes flat. Sometimes that's within a couple of hours if I'm using it heavily, sometimes it will be weeks between uses. At least I know there will be a charged battery ready to go whenever I need it. The drill is now over 2 years old and I reckon I probably get just as much use out of a full charge now as I did when it was new.

In my experience taking batteries off the charger and letting them self-discharge over days or weeks is just as much of a battery killer as shallow cycling.

Any half decent cordless tool these days really ought to come with a charger which is at least smart enough to switch to a maintenance mode once the battery is fully charged.