Thread: Discharging cordless drills before recharging.

If the batteries are NiCad, it most certainly helps to do it from time to time.... not good to do it tooo often.
Remember the one thing that NiCads hate is heat above all.
Charging them in the fridge works.
Giving them the freeser treatment works.

Some of the fancier chargers do it all for you.

If the batteries are NiMh... aparantly there is no point.

cheers

With the Makita that I have they say to change the battery over once the charge starts to go, not to keep using as it can affect the battery.

Will have a look tomorrow for you and let you know type of battery it has.

I read somewhere with NiCad batteries that they shouldn't be made dead flat but just to the point where it has lost its sting.

Originally Posted by apricotripper

Personally find having to rap triggers with rubber bands etc annoying.

Been doing that a lot at work lately.

My battery drills came in sets with torches and spare batteries. I discharge the batteries by putting them in the torches and switch them on and come back later for them.


Peter.

I've been advised to not discharge batteries totally. Let them wind down a bit, but when they lose their sting (as BW said), take them off. But, I've been told that it is more important to not put them immediately on the charger - let them cool down for 30 minutes first. And also, if you've had the charger going, switch it off and let it cool before putting a new battery into it. I've been told that the quickest way to kill a battery is take it off the drill and put it straight onto charge. I've just bought a couple of new ones for our workshop and I've made the rules - give them a 30 minute rest after taking them off the drill. Give the charger the same rest after charging a battery. Switch the charger off once the battery is charged.

What Soundman said. Different types of batteries have different requirements... apparently deep-discharging Lithiums (Not that I've seen them in a cordless drill yet) is a sure-fire way to destroy 'em.

I've always fully discharged my NiCd and was getting around 3 years life out of 'em. One or two exceptions, but that's par for course, and even then 'twas only single cells failing which were easily (and cheaply) repaired. Actually, I've had more problems with the cheap bloody chargers melting than batteries! (I think it's the old Transistor Radio syndrome... the designers come up with something bullet-proof, then the buggers in Accounting pull components out until it fails, plug the last piece back in and declare "this is what we'll build." )

My last drill came with NiMH's and has, in big red letters, DO NOT FULLY DISCHARGE printed on the battery sides. Do ya think that might be a hint?

Originally Posted by Skew ChiDAMN!!

My last drill came with NiMH's and has, in big red letters, DO NOT FULLY DISCHARGE printed on the battery sides. Do ya think that might be a hint?

I do stupid things like that everyday. I've given up feeling embarrised about or angry at myself. dont care anymore

Used to get most embarrised at the butchers spending a good 10 seconds trying to push open a door that says pull in big RED letters right in front of my eyes to the amusement of the people inside.

I must find out what to do with his makita drill batteries.... Noones really bothered to have a good look at the manuals.

Soundman........... Do you really stick the charger in the fridge with the cord hanging out past the door ? ..oh you mean, stick the batterys in the fridge when there hot......when there cold again stick them in the charger thats outside the fridge.

Just don't charge the Nicads when they feel warm in your hand ? yes ?....That hasn't happened much over the last couple of months yet though with the Makitas at work. Been working them non stop. Does that mean there probably not Nicads ? .....I'll just check today.

What does the owners manuel say?

My recently bought Rigid set has a smart charger and these thing are unimportant. It even detects if the battery is to hot to charge and waits to start the charging cycle.

ron

When mine [NiCad] starts to lose its sting I tie the trigger back with a velcro strap and just sit it on the bench until it changes tone - let it cool off and then recharge.

My Milwaukee Owners Manual specifically warns against deep discharging the Nicads.

Amost without exception batteries do not like beeing fully discharged HARD.

the exception is NiFe.... which are very obscure and should be stored flat & shorted.... or so it used to be.

NiCad will not respond badly to being discharged fairly hard, but they shouldn't be left connected to a load for any significant period when flat.
You don't need to discharge them all that hard anyway....just near flat.

with the wraped up trigger in the drill method, pull em out when the motor isn't running freely... yeh it will slow down lots.... lots...... I've let mine stop in the past... no grief... but don't leave it that way.
with the torch whip the battery out as soon as the lamp dosnt glow any more.
bear in mind an unloaded drill is quite a light load, and a piddling torch lamp is even lighter. so you arent hitting them all that hard.

If you get into the technicalities there are specified cell voltages and all that but if you have the time & the means to measure, I'm sure you can find all that out.

Indeed as mentioned before a hot NiCad is an unhappy nicad...in whatever situation a nicad will perform less efficeintly the hotter it gets... they are happiest arround 1 or 2 deg C and will keep working fine down to about -10degC.

YES I most certainly have put the battery charger and all inside the fridge... just make sure it stays dry.

Adfmitted I don't hammer mu battery drills as hard as I once did but I have a perfectly servicable battery with a 2001 date on the side.

I habitualy date things like batteries and fluro tubes when they go into service, just so i know how they went.

There is no specific life span for NiCad... their projected life is expressed in charge cycles.
Unlike lead acid batteries such as in the car that have always had a projected life span of 2 years... If yiu treat them well you and are lucky you might get 5 years.

to maximise the life of your NiCad batteries.....
above all keep them cool
don't discharge them too deeply or too heavily too often.
store them charged.
don't leave them without use or charging for extended periods of time charging at least once a month is a minimum.
Avoid discharging them to the same point & then recharging them.
avoid too many shallow cycles.
do deep cycle them OCASIONLY..... once a month should be plenty.
give them a holiday in the freezer once in a while... they seem to like it.
and yess wait for them to cool before charging them.

If it is anything but a crude charger..... "like it has a light that indicates finished" you should be fine to leave the battery in the charger.

Oh did I say keep them cool.

now a bit of information
most of the battery drill chargers that fast charge terminate charge based on temperature of the cell... thats what the third contact is a temp sensor.
Why... because they want to hit the battery as hard as they can without damage and to get as much in without damage.
As the battery reaches full charge the excess charge is disapated as heat in the battery... if there is no supervision the cells would very rapidly overheat and die bigtime.
so starting with a cool battery is an advantage... keeping the battery cool is a big advantage..... remember the limiting factor with NiCad is heat.

trivia
take your typical AA NiCad.. not one of the fancy types or high capacity types stoco 1.2V 700mAh AA.
How much current do you recon you could pull out of that?


Well a good one... 15 to 20 amps....... Nicads are capable of delivering huge amounts of current for their size & weight......a such they can be dangerous if the equipment isn't designed right.

story of danger
There was a popular battery belt pack for a portable video light common in TV news gathering
It ran a heap of "F" cell nicads that are like a "D" cell but half as long again, powering a very high power halogen head.
the problem was there were no fuses or protection in the pack and the interconnecting wiring.... could have been heavier.
Also the belt had a double tounged buckle.
A nimber of news crew members were badly hurt when the wiring in the packs and the batteries overheated and wnet int melt down.
You have this quite heavy thing straped arround you middle that strats burning you... to get it off you have to pull it tighter and then get both toungues of the buckle to let go.... not a happy thing.
To this day most news crew will not wear a battery belt except by slinging it over their shoulder..

anyway.

cheers

Originally Posted by Wizened of Oz

My Milwaukee Owners Manual specifically warns against deep discharging the Nicads.

I'm sure my Dewalt manual says to recharge when the battery starts to lose power. However I often will swap batteries at any time so I have a fresh fully charged one in the tool, nothing worse than climbing onto a roof or up a ladder only to screw in 2 or 3 screws and the battery goes flat and then have to climb back down to change it.
I've been using rechargable tools for about 20 years and I don't think this fussing around trying to make the batteries last longer makes any difference to the life of the battery(if your lucky you might get an extra month).

My recollection was that NiMH benefitted from regular discharging. I thought it was not required of Lithium Ion batteries.

There are plenty of sources on the internet which cover this discussion in detail. One is listed here:

http://www.ebikes.ca/batteries.shtml

Cheers,

Tom

As someone who works in battery research and holds patents on batteries and rapid charging, I wouldn't advice fully discharge any battery pack in a coldless tool - the reason why is that there will be some cell imbalance in any battery pack and fully discharging will almost certainly reverse polarise a cell in the pack and stuff it up big time.

I would recommend using the tool until it starts to slow under load. When it starts to slow - stop - and change the battery pack. Don't rest it and continue to use it! To discharge beyond this would be considered "over discharging" and will shorten the life of the battery pack.

The memory effect in NiCds is unlikely to be present under high-load high-recharge rates that most cordless tools operate under.

I've actually worn out a Metabo cordless drill (chuck wobbles about like hell) but the original batteries are still going strong in a new Metabo drill.

A good charger is very important to battery life - but don't abuse the batteries by over discharging them.