cordless drill battery

sendero · Jan 10, 2005

Soundguy, I'm under the impression that most cordless tools are still using NiCads. Sure, the newer batteries are out there and they are much better but they are also very expensive. If you didn't pay a boatload for your battery - unless it SAYS it is a NMiH or Lithium, I'd assume it is a NiCad.

NiCads are ok, but they DO IN FACT have a memory effect and they will go bad on you if you don't treat them right.

Now that I think of it, sorta like women /forums/images/graemlins/smile.gif

TWINKLE_TOES · Jan 10, 2005

Bill, NiCads are ok, but they DO IN FACT have a memory effect and they will go bad on you if you don't treat them right. 

Rat gave you the straight skinney on memory effect-myth. Even if it existed on todays batteries a single deep discharge and proper recharge will remove it.

I do agree that "treat them right"is necessary. If you look at your charger and it is a two terminal device, and capable of short time recharge, don't leave it plugged in indefinitely. If it has more terminals (temperature sensing) it's probably ok it will terminate on temperature rise.

Definition of memory effect:The property of nickel-cadmium (NiCad) batteries that causes them to lose their capacity for full recharging if they are discharged repeatedly the same amount and then recharged without overcharge before they have fully drained. The term derives from the fact that the battery appears to have a memory for the amount of charging it can sustain.

Proper recharging and todays batteries reduce this phenomena to insignificance.

Charging of a Nickel Cadmium battery is an endothermic reaction ( it gets cooler) The only way to increase the battery temperature is to discharge or overcharge the battery. NiCd batteries are somewhat tolerant to overcharge, they exibit a negative temperature coefficient of voltage in overcharge. Proper charge termination techniques are time, temperature, negative dv/dt dvsquared/dvt squared and combinations of all. High rate charging C, C/2 .. require some smart kind of charge termination or the battery is toast. Trickle charging C/10 or less can be dumb and continuous. Please don't provide a bunch of web references that perpetuate this myth.

bczoom · Jan 11, 2005

( I'd say that you have a defective charger then. Like a shorted or leaky diode... (avalanching prematurely)...

In normal situations.. that diode(s) shouldn't reverse conduct at the voltages these battery packs are charged to.

Soundguy )

OK, thanks. I've just made it a habit to charge then remove from the charger. The discharge "seems" nominal but it does seem like it's not 100% if it sat in an unplugged charger for a couple weeks. The battery is probably at 80%.

Brian

Soundguy · Jan 11, 2005

You're preaching to the choir... I've done alot of work with nicads.. especially in the 80's.

Soundguy

( Soundguy, I'm under the impression that most cordless tools are still using NiCads. Sure, the newer batteries are out there and they are much better but they are also very expensive. If you didn't pay a boatload for your battery - unless it SAYS it is a NMiH or Lithium, I'd assume it is a NiCad.

NiCads are ok, but they DO IN FACT have a memory effect and they will go bad on you if you don't treat them right.

)

Soundguy · Jan 11, 2005

( Rat gave you the straight skinney on memory effect-myth......Please don't provide a bunch of web references that perpetuate this myth )

The sad fact is, many low tech chargers are still floating around. Back in the 80's and early 90's you didn't see many of the chargers with conditioning or sensing circuitry. I remember in the late 80's "clippers" ( high voltage ) were a popular trend for nicads. Chargers that also discharged the battery first were also trendy... It's just old technology nowadays..

Soundguy

gsxr1100 · Jan 11, 2005

I hate to tell you it is not a myth. I have seen it on my R/C heli batteries. It does happen, period.

_RaT_ · Jan 11, 2005

Yeah, whatever you say, and all oil is the same too. /forums/images/graemlins/grin.gif
(I knew that would get you)

I'll stick with the scientific explanation though.

Guide to battery life. The comment at the bottom is what my carpenter friends would all do only with rubber bands. More myths.

Fine Homebuilding Article

TWINKLE_TOES · Jan 11, 2005

gsxr1100, Please explain the sequence of events surrounding your battery discharge and charge experience. If possible identify battery and charger manufacture and Ill bet I can show you that whatever you perceive to be "Memory Effect" is due to some other cause.

gsxr1100 · Jan 11, 2005

#1 it states in my 9-channel Futaba PCM manual about memory effect on its' own battery pack. page 3

#2 My GP3300 cells have had this happen since I fly my r/c heli, joker (.060 size) several times per week and have it happen with these cells. It is nothing new in the r/c world let alone on a $3,700 heli. I know these cheaper cells like the back of my hand, we need to for flight times.

Events are if you do not discharge them correctly they will have this effect (less charge) when charging at 3.5 amps; again nothing new. I know how my GP pack is when flying several hundred feet up in the air. I had had a 1-year pack give me less time (fail due to memory) and had to auto down. That is my example on how a $125 pack almost cost me $300 in repairs (main blades, tail blades, shaft, bearings, etc)!

#3 it does not happen with my lipo's battery pack, over $700 pushing over 50 amps.

You can show me this and that but I have had it happen in the real world, in flight. Thanks but no thanks.