Rechargable tool batteries

[Barony]

Just a question by a weekend warrior about the right way to take care of my drill batteries. I have a Makita drill and have gone through about 4 batteries in the past 3 years. I purchased 2 more batteries last week and the salesperson told me that I am supposed to take the battery all the way down before thowing it on the charger. I guess that when I knew that I needed to use the drill, I would throw it on the charger the night before and it was ready the next day. He told me that I wrecked my batteries by doing that. What should I be doing?

[countryboy9799]

I read alot of woodworking mag's and they talk about this from time to time.

Don't worry about bringing them down all the way as this does not pertain to cordless drill's. A cordless drill does not have a constant drain so it does not get the memory effect like some batt's do. As soon as it get's low charge it up. Also another reason you should't do it is because the batt's are made up of rechargable C batteries wired in series so the more batt's the more voltage. If you bring them to a complete dead stage some of the indivial cell's can charge the wrong way, don't ask me how it's just something I have read many time's.

Heat is another enemy of batterie's. If you have been using them hard, let them cool down for 30 minute's before you charge them and let them cool down 30 minute's before using them afterward's.

Store them in moderate temp's, like not on the dash of your pickup or letting them freeze. These are the one's I can think of off of the top of my head and I am sure there are more.

You really shouldnt be going through that many batt's if you are a limited user in my opinion, I have had a 19.2 craftsman that I bought in 98, it has sat for the last couple of years because I bought another one and was quite suprised after I charged them up how well they hold, that doesn't happen to often to have luck like that with rechargable's.

Good luck.

[fivebucks]

I think you are way overcharging the batteries. I am still using a battery from 10 years ago. My drill batteries charge in about an hour or so. Leaving it on over night is the problem I believe.

[Giant_Jackpot]

It has nothing to do with the tool and everything to do with what type of battery it is. If they are NiCad (Nickel Cadmium) then you do want to discharge them before charging or you will get the memory affect as described previously. I went for 20 years on my 9.6 volt Mikita NiCad pack before replacing it. Most chargers shut off automatically but I would not leave them in the charger for more than 24 hours…..

[countryboy9799]

Like I said earlier, power tools do not discharge at a constant rate so they do not need to be drained all the way to avoid the memory effect, even with NiCad's. I trust the source's that I read that from.

[Giant_Jackpot]

I did 4 years as an engineer in the research and development department for a company that made battery chargers for all types of portable equipment. If you want to believe the woodworker magazines or me that’s your choice. It is possible that the batteries in Barony’s drill are not NiCads but I would bet they are. I will agree that overcharging is as bad or worse than not discharging them all the way prior to charge. Also, you do not have to deep discharge them every time but make sure you do it once every 4th charge cycle or so.

[SpecialK]

I stopped using Makita cordless products due to the battery issue. I ruined more of those Makita batteries by not draining them prior to recharging. Also make sure you have enough time to get a full charge on them before you start. They will also get a 'memory' if you only partially charge them back up.

[sparkyaber]

On the same topic, I have also heard that if you do not use the tools/batteries on a regular basis the batteries will not last as long- is this true? any one else have any thoughts? Maybe it is one for the Myth Busters.

[Gissert]

Any NiCad battery has the potential to develop memory. This is just their chemical nature. The reason that nicads are so popular is they have a pretty flat discharge curve for a longer period of time. Once they start to loose power, they go down fast. The flat discharge curve is the main reason why they are very common in commercial aircraft applications. Aircraft NiCad batteries are removed from service at shceduled intervals and run through a deep cycle test to prevent memory, and to identify and weed out cells that are loosing capacity. They function just like cordless tool batteries, only on a much larger (and more expensive) scale.

Most tool battery chargers have built in protection to prevent charging when a battery is too hot, or too cold. They also should cease charging when the battery is fully charged.

Lack of use is an enemy of all batteries. Some stand up to this better than others, but they will tend to loose capacity. Cold really saps capacity.

One side note - if you have some batteries that just are not lasting anymore, dont throw them away. I was shopping on hsolist for a couple of 18 volt DeWalts last winter. I found a place that rebuilt them, and they are good as new for half the price.

Nickel Metal Hydride (NiMH) bateries do not get "memory" issues like NiCads do. Many of the newer tool batteries are now NiMH units.

[united jigsticker]

I agree.

Nickel/Cadmium batteries will develop a memory, regardless of if there is a constant current draw or not.

You gotta run them suckers near dead to get the life out of them.

I think the biggest demise to lifespan for a battery is from the rapid chargers.

The quicker the charge, the more heat that develops. And heat will kill the integrity of any battery.

Also, alot of chargers have an automatic shut-off, but it is based on a timer calibrated to the average time to recharge a completely drained battery rather then the amount of resistance, so the battery does have the potential to over charge, though leaving it on the charger for 24 hours vs. 2 hours won't make a difference considering that most chargers timers will shut off before then.

If you want the "creme of the crop", get the lithium batteries. They do NOT develope any memory, they are lighter the Ni/Cd, and they last alot longer on a single charge.