CalgaryGuy
Enlightened
Hi, do you guys do a full discharge before recharging Ni-Cd batteries? If so, what's the best way to discharge a 1.2v?
Does Ni-Cd need a full discharge before recharge?
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Doug S
Flashlight Enthusiast
Contrary to common belief, no. There are a few special cases where it may be of benefit to do it once every 10 or 20 cycles. Doing it every time is counterproductive. This would be the case where the normal application rarely or never fully discharges the cell before recharge. If you must do it, an easy method for a single cell is to discharge with an ordinary diode and a resistor in series. This will discharge the cell down to about 0.6V.
SilverFox
Flashaholic
Hello CalgaryGuy,
I usually use my NiCd's in my lights until they start to dim, then put them on the charger.
My Vanson BC-1HU charger has a discharge function that takes care of the rest. My NiCd's are always discharged before charging on the charger.
I believe it is recommended to go through a full discharge/charge cycle about once a month. This is not necessary for cells in storage, just the ones you are using everyday.
I have found myself replacing NiCd cells with higher capacity NiMh cells, but still have a lot of NiCd's around. More of them are going into storage for a rainy day.
I do a discharge/charge cycle once per year on my NiCd's in storage.
Tom
I usually use my NiCd's in my lights until they start to dim, then put them on the charger.
My Vanson BC-1HU charger has a discharge function that takes care of the rest. My NiCd's are always discharged before charging on the charger.
I believe it is recommended to go through a full discharge/charge cycle about once a month. This is not necessary for cells in storage, just the ones you are using everyday.
I have found myself replacing NiCd cells with higher capacity NiMh cells, but still have a lot of NiCd's around. More of them are going into storage for a rainy day.
I do a discharge/charge cycle once per year on my NiCd's in storage.
Tom
SilverFox
Flashaholic
I see Doug got in ahead of me.
He probably knows more about NiCd's than I do, so listen to him.
I have always followed my procedure and now do it out of habit. I have not noticed any damage to the cells, but you must remember that they are only good for a certain number of cycles. I believe my system would be harder on the cells than what Doug is suggesting.
Tom
He probably knows more about NiCd's than I do, so listen to him.
I have always followed my procedure and now do it out of habit. I have not noticed any damage to the cells, but you must remember that they are only good for a certain number of cycles. I believe my system would be harder on the cells than what Doug is suggesting.
Tom
CalgaryGuy
Enlightened
The only reason that I'm using Ni-Cd is because that's the only type that I can find in a local store. They are 1/3 AA and I can charge them in my AA solar charger. It works great on the Arc LSH-P and it's truly guilt-free light /ubbthreads/images/graemlins/wink.gif
Ocelot
Newly Enlightened
I know I'm probably going to get flamed for this, but the "memory effect" as it relates to consumer use is a myth.
It was originally noticed in satellites, where the solar charge/discharge cycle was extremely repeatable down to seconds. That is where memory was first noticed.
The problem that consumers see is related to voltage depression where the chargers being used aren't "smart" in that they overcharge the batteries, by assuming that they need a full charge. This can overcook them, creating a voltage depression and an apparent loss of capacity.
My recommendation is to buy the best NiCd chargers you can find, which use a combination of methods to detect when a cell is charged.
Another common problem is when a battery pack becomes nearly fully discharged, reversing a cell in the pack. This happens when people use the pack in something which doesn't detect when the pack is getting low, or when they discharge the entire pack at once in order to avoid the "memory" problem. This reversed cell is often hosed.
If you have a cheap charger or still feel you "must" discharge, then Doug's suggestion of doing individual cells and using a diode is a very good one.
Scott
It was originally noticed in satellites, where the solar charge/discharge cycle was extremely repeatable down to seconds. That is where memory was first noticed.
The problem that consumers see is related to voltage depression where the chargers being used aren't "smart" in that they overcharge the batteries, by assuming that they need a full charge. This can overcook them, creating a voltage depression and an apparent loss of capacity.
My recommendation is to buy the best NiCd chargers you can find, which use a combination of methods to detect when a cell is charged.
Another common problem is when a battery pack becomes nearly fully discharged, reversing a cell in the pack. This happens when people use the pack in something which doesn't detect when the pack is getting low, or when they discharge the entire pack at once in order to avoid the "memory" problem. This reversed cell is often hosed.
If you have a cheap charger or still feel you "must" discharge, then Doug's suggestion of doing individual cells and using a diode is a very good one.
Scott
kitelights
Flashlight Enthusiast
Re: Does Ni-Cd need a full discharge before rechar
How can you get flamed for the truth? I agree completely.
How can you get flamed for the truth? I agree completely.
gwbaltzell
Enlightened
Re: Does Ni-Cd need a full discharge before rechar
[ QUOTE ]
kitelights said:
How can you get flamed for the truth? I agree completely.
[/ QUOTE ]
ditto - which if you're not old enough means I agree too!
[ QUOTE ]
kitelights said:
How can you get flamed for the truth? I agree completely.
[/ QUOTE ]
ditto - which if you're not old enough means I agree too!
Ocelot
Newly Enlightened
Re: Does Ni-Cd need a full discharge before rechar
Regarding flaming, lots of people still believe that NiCd batteries have "memory" under consumer use conditions and that you MUST fully discharge them.
When I've related what I said in my posting above, people often attack me and say I don't know what I'm talking about...
I discussed the issue extensively with battery engineers more than 15 years ago, and I've experimented myself over the years, and verified that memory is a myth, and a good charger avoids the voltage depression issue.
However, I ended up switching to NiMH and haven't looked back...!
Scott
Regarding flaming, lots of people still believe that NiCd batteries have "memory" under consumer use conditions and that you MUST fully discharge them.
When I've related what I said in my posting above, people often attack me and say I don't know what I'm talking about...
I discussed the issue extensively with battery engineers more than 15 years ago, and I've experimented myself over the years, and verified that memory is a myth, and a good charger avoids the voltage depression issue.
However, I ended up switching to NiMH and haven't looked back...!
Scott
LightScene
Enlightened
- Joined
- Sep 12, 2003
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Re: Does Ni-Cd need a full discharge before rechar
Rechargeables will last longer if they are charged more often rather than less often. That is to say, they should not be deep discharged if you want longevity.
However, if your charger has a tendency to overcharge (like if it's a dumb charger), then I suspect it's better to charge them less frequently, in order to avoid overcharging. This is the startegy I've used with my Sonicare toothbrush, and it's lasted for 3 years.
Trickle charging after the cells are fully charged probably shortens the battery life also.
I don't know where the advice to fully discharge them occasionally originates.
Rechargeables will last longer if they are charged more often rather than less often. That is to say, they should not be deep discharged if you want longevity.
However, if your charger has a tendency to overcharge (like if it's a dumb charger), then I suspect it's better to charge them less frequently, in order to avoid overcharging. This is the startegy I've used with my Sonicare toothbrush, and it's lasted for 3 years.
Trickle charging after the cells are fully charged probably shortens the battery life also.
I don't know where the advice to fully discharge them occasionally originates.
CalgaryGuy
Enlightened
Re: Does Ni-Cd need a full discharge before rechar
Maybe I'll try recharge very often to keep the capacity of my battery from 50% to 80%. Can't afford a top of the line Ni-Cd charger so I'll just do with my solar one. The good thing is that solar charger is very slow and I can easily stop it.
Maybe I'll try recharge very often to keep the capacity of my battery from 50% to 80%. Can't afford a top of the line Ni-Cd charger so I'll just do with my solar one. The good thing is that solar charger is very slow and I can easily stop it.
CalgaryGuy
Enlightened
Re: Does Ni-Cd need a full discharge before rechar
By the way, does anyone knows why Surefire uses Ni-Cd on their rechargeable? I though they would use Li-Ion or Ni-Metal.
By the way, does anyone knows why Surefire uses Ni-Cd on their rechargeable? I though they would use Li-Ion or Ni-Metal.
PeLu
Flashlight Enthusiast
Re: Does Ni-Cd need a full discharge before rechar
Ocelot: you right, except that it ocurred only in one single satellite and was fixed then. And the memory effect did nothing else than a slight (ok, we can debate what 'slight' means) voltage drop (about 0.15V).
Especially in batteries (that means more cells in series), a deep discharge is a bad thing.
Most NiXX cells do not die from a natural death, they are killed from repeated deep discharge and overcharging.
But it easy to have an usualy suspect to blame for all the malfunctions.
And the memory myth is actually an interesting piece to study human behaviour. People hear about it and beleive it (of course). So everything which goes wrong is balmed on it. So people ask for a remedy and the industry answers.
If, in some circles, the pressure from science was too high, so the just renamed another effect (voltage depletion) to 'memory effect'.
Actually in the older messages about memory, their contens was about:
1. symptom: due to memory, you cannot completly discharge your cell
2. remedy: discharge your cell completely
Not even such a simple contradiction made some people think.
Anyway, good NiCd cell can take a lot of abuse, even regular complete discharge. But it does not make the cells better.
Sometimes cacling the cells lowers their internal resistance (especially after long time storage), but it should also possible to cacle them only for half the capacity twice as often (but nobody does it).
I've written hundreds of pages about that topic
Ocelot: you right, except that it ocurred only in one single satellite and was fixed then. And the memory effect did nothing else than a slight (ok, we can debate what 'slight' means) voltage drop (about 0.15V).
Especially in batteries (that means more cells in series), a deep discharge is a bad thing.
Most NiXX cells do not die from a natural death, they are killed from repeated deep discharge and overcharging.
But it easy to have an usualy suspect to blame for all the malfunctions.
And the memory myth is actually an interesting piece to study human behaviour. People hear about it and beleive it (of course). So everything which goes wrong is balmed on it. So people ask for a remedy and the industry answers.
If, in some circles, the pressure from science was too high, so the just renamed another effect (voltage depletion) to 'memory effect'.
Actually in the older messages about memory, their contens was about:
1. symptom: due to memory, you cannot completly discharge your cell
2. remedy: discharge your cell completely
Not even such a simple contradiction made some people think.
Anyway, good NiCd cell can take a lot of abuse, even regular complete discharge. But it does not make the cells better.
Sometimes cacling the cells lowers their internal resistance (especially after long time storage), but it should also possible to cacle them only for half the capacity twice as often (but nobody does it).
I've written hundreds of pages about that topic
