I just got some Of the Energizer/Sanyo 2300 batteries and one of my chargers (Digipower DPS-3000) says it goes into trickle charging after the cells are fully charged. It could be weeks between needing all these extra batteries so taking them out would probably lose alot of power from self discharge. How long is it okay to leave them in there without harming them? /ubbthreads/images/graemlins/thinking.gif
Leaving NiMH cells in charger safe?
- Thread starter Radiant
- Start date
Help Support Candle Power Flashlight Forum
It depends on the details, of course, but for sure it's not weeks.
The 'allowed full time rate' is C/300 from *some* makers (those that allow it) typical 'trickle' rates are 10 to 30 times that.
Charge 'em up and pull them when the light turns green....
Doug Owen
The 'allowed full time rate' is C/300 from *some* makers (those that allow it) typical 'trickle' rates are 10 to 30 times that.
Charge 'em up and pull them when the light turns green....
Doug Owen
Gold Peak specifies a trickle rate of 0.05 to 0.1C for continuous trickle with their nimh cells. Having said that, nobody recommends that batteries be left on the charger perpetually although over the weekend would be fine.
I would charge up all my cells and then do a touch up when the time came to use them if time permitted. If not, use them anyway and expect a decrease in your runtime.
Wilkey
I would charge up all my cells and then do a touch up when the time came to use them if time permitted. If not, use them anyway and expect a decrease in your runtime.
Wilkey
[ QUOTE ]
Ginseng said:
Gold Peak specifies a trickle rate of 0.05 to 0.1C for continuous trickle with their nimh cells.
[/ QUOTE ]
Indeed they do, but a couple of details need pointing out, first the standard for this continuous charge is "No conspicuous deformation and/or leakage", no word on what it does to service life.
And (under those conditions) there's a *manditory* voltage limit at 1.5 Volts (something I highly doubt is in the charger).
"Leave 'em in the charger until you need them" is a NiCd deal, not NiMH. If that's what you intend to do, best go that way. Hint, that's why 'modern' flashlights still use 'old fashioned' NiCds.....
Doug Owen
Ginseng said:
Gold Peak specifies a trickle rate of 0.05 to 0.1C for continuous trickle with their nimh cells.
[/ QUOTE ]
Indeed they do, but a couple of details need pointing out, first the standard for this continuous charge is "No conspicuous deformation and/or leakage", no word on what it does to service life.
And (under those conditions) there's a *manditory* voltage limit at 1.5 Volts (something I highly doubt is in the charger).
"Leave 'em in the charger until you need them" is a NiCd deal, not NiMH. If that's what you intend to do, best go that way. Hint, that's why 'modern' flashlights still use 'old fashioned' NiCds.....
Doug Owen
brickbat
Enlightened
[ QUOTE ]
Doug Owen said:
The 'allowed full time rate' is C/300 from *some* makers (those that allow it) typical 'trickle' rates are 10 to 30 times that.
[/ QUOTE ]
Are you aware of any NiMH cells whose specs say they can't be trickle charged at a very low rate? Anybody have any experience with this causing trouble? I'd like to build a VERY low rate charger (actually misleading to call it a charger, I just want to prevent self-discharge) operating at C/2000.
Doug Owen said:
The 'allowed full time rate' is C/300 from *some* makers (those that allow it) typical 'trickle' rates are 10 to 30 times that.
[/ QUOTE ]
Are you aware of any NiMH cells whose specs say they can't be trickle charged at a very low rate? Anybody have any experience with this causing trouble? I'd like to build a VERY low rate charger (actually misleading to call it a charger, I just want to prevent self-discharge) operating at C/2000.
I think I just said 'some makers specify C/300'....
Yup, that's what I said, all right.
Specifically:
Duracell NiMH charging
(amongst others...)
Doug Owen
Yup, that's what I said, all right.
Specifically:
Duracell NiMH charging
(amongst others...)
Doug Owen
kitelights
Flashlight Enthusiast
The guy that did the charger shootout (link is listed somewhere in this forum) set up a bank of trickle chargers that he leaves cells in. I've read that are safe rates that you can use, but why? If you get a fast smart charger like the 401 and your cells are nearly full and all you want to do is to top them off, it'll only take 10 - 20 minutes. Tests showed that the 401 charges to 98 or 99% when the charger cycles finished.
MrAl
Flashlight Enthusiast
Hello there Rad,
Another idea which had been discussed before here on CP
is the plug in timer.
You get one of those 120vac plug in timers and plug your
battery charger into that. You set the timer to come on
once per day for 1/2 hour. Thus the batteries get topped
once per day to keep their level up.
The charge level once it turns on is full charge assuming
the usual C/10 rate.
First, you should make sure the charger doesnt draw much
from the batteries when it's unplugged.
Take care,
Al
Another idea which had been discussed before here on CP
is the plug in timer.
You get one of those 120vac plug in timers and plug your
battery charger into that. You set the timer to come on
once per day for 1/2 hour. Thus the batteries get topped
once per day to keep their level up.
The charge level once it turns on is full charge assuming
the usual C/10 rate.
First, you should make sure the charger doesnt draw much
from the batteries when it's unplugged.
Take care,
Al
udaman
Banned
- Joined
- Feb 13, 2004
- Messages
- 381
[ QUOTE ]
Doug Owen said:
[ QUOTE ]
Ginseng said:
Gold Peak specifies a trickle rate of 0.05 to 0.1C for continuous trickle with their nimh cells.
[/ QUOTE ]
Indeed they do, but a couple of details need pointing out, first the standard for this continuous charge is "No conspicuous deformation and/or leakage", no word on what it does to service life.
And (under those conditions) there's a *manditory* voltage limit at 1.5 Volts (something I highly doubt is in the charger).
"Leave 'em in the charger until you need them" is a NiCd deal, not NiMH. If that's what you intend to do, best go that way. Hint, that's why 'modern' flashlights still use 'old fashioned' NiCds.....
Doug Owen
[/ QUOTE ]
Ok, we have these opinions, based on your experiences? Based on reading up on this topic? Based on reading of others experiences? If based on others experiences, can you provide links so we can read up on those?
A few points not mentioned here. Seems there is always some small risk of leaving these chargers unattended, what ever the type, NiCad, NiMH, and perhaps more risky(because of higher current capacities? or some other factor) the Li-ion/polymer formulations.
I see that while not conclusive, in the oft linked article below, the author likes to leave a set in the charger indefinitely for convinience sake. The Ultimate battery (NiMH AA) shootout
But if you read the FAQ link/answers at Thomas Distributing, they offer a caveat about charging/recharging an already fully charged set of batteries. But they offer no supporting evidence/proof of what they claim to be a 'truth'?.
Who do we believe? Is this just another 'urban legend' of overly cautious battery manufacturers? "and will PROBABLY cause damage to your batteries, charger or both."
And has Dave Etchells ever put a fully charged set of NiMh on the trickle charger by mistake, which may or may not be conclusive, to determine if this ever happens?
Doug Owen said:
[ QUOTE ]
Ginseng said:
Gold Peak specifies a trickle rate of 0.05 to 0.1C for continuous trickle with their nimh cells.
[/ QUOTE ]
Indeed they do, but a couple of details need pointing out, first the standard for this continuous charge is "No conspicuous deformation and/or leakage", no word on what it does to service life.
And (under those conditions) there's a *manditory* voltage limit at 1.5 Volts (something I highly doubt is in the charger).
"Leave 'em in the charger until you need them" is a NiCd deal, not NiMH. If that's what you intend to do, best go that way. Hint, that's why 'modern' flashlights still use 'old fashioned' NiCds.....
Doug Owen
[/ QUOTE ]
Ok, we have these opinions, based on your experiences? Based on reading up on this topic? Based on reading of others experiences? If based on others experiences, can you provide links so we can read up on those?
A few points not mentioned here. Seems there is always some small risk of leaving these chargers unattended, what ever the type, NiCad, NiMH, and perhaps more risky(because of higher current capacities? or some other factor) the Li-ion/polymer formulations.
I see that while not conclusive, in the oft linked article below, the author likes to leave a set in the charger indefinitely for convinience sake. The Ultimate battery (NiMH AA) shootout
But if you read the FAQ link/answers at Thomas Distributing, they offer a caveat about charging/recharging an already fully charged set of batteries. But they offer no supporting evidence/proof of what they claim to be a 'truth'?.
Who do we believe? Is this just another 'urban legend' of overly cautious battery manufacturers? "and will PROBABLY cause damage to your batteries, charger or both."
And has Dave Etchells ever put a fully charged set of NiMh on the trickle charger by mistake, which may or may not be conclusive, to determine if this ever happens?
qarawol
Enlightened
I would go by what the charger manual states. I use NiMH in my Surefire & Streamlight rechargeable Flashlights. Surefire chargers, not the constant charger only the rapid or semi rapid, and Streamlight states the battery can be left in the charger until needed. The longest I have left batteries in the charger, for a Flashlight I use, is maybe a week. It's rechargeable and you have spares, change the batteries every several days or so. BTW Streamlight SL series states the Flashlight can be left in the charger indefinately. I have a Streamlihgt multi bank charger and have left my SL's in them for about a year now. Maybe once every 4-5 months I use them for several minutes and once a year take the batts out to condition them on a Maha MH-C777 Plus. Even the Maha charger states the batteries can be left on it.
Enjoy...
Enjoy...
SilverFox
Flashaholic
Hello Udaman,
Welcome to CPF.
For my use, I never leave cells on the charger. I also do not leave rechargeable flashlights always on the charger.
I realize that nothing is free. If you use alkaline cells, you throw them away after use (or partial use) and live with that. If you use rechargeable's, you have to spend a little time managing them.
The basic problem with leaving cells on the charger is that you are shooting at a moving target. If the temperature varies, the optimum float voltage also varies. If you put a different capacity cell in, the float current varies. You will note that charging (and float) rates are given as a ratio to the capacity of the cell. Also, different cell manufacturers use different chemistry batches that react differently while charging. These differences can also be observed between batches of the same manufacturers cells.
I suppose that you could build a charger that varied voltage based on temperature and had a choice of outputs based on the capacity of the cell. This charger could discharge the cell and recharge it to get an idea of it capacity then maintain a float charge based on these results. Of course you would want to do several cells at a time, so each channel would have to be independent. I am not aware of a charger that can do all of this. I would think it would be pricey, but nice to have.
It is interesting to note that in the great battery shoot out article, one brand of cells were damaged while trickle charging. It was also mentioned that there is a big difference in the temperature rise of different cells in the same charger.
Doug has given you the Duracell link, PowerStream has this to say,
"Trickle Charging
In a standby mode you might want to keep a nickel metal hydride battery topped up without damaging the battery. This can be done safely at a current of between 0.03 C and .05 C. The voltage required for this is dependent on temperature, so be sure to regulate the current in the charger."
I can not explaine the order of magnitude difference, perhaps it is a difference in how the cells are made.
Perhaps you can do a detailed test and report back your results here...
Tom
Welcome to CPF.
For my use, I never leave cells on the charger. I also do not leave rechargeable flashlights always on the charger.
I realize that nothing is free. If you use alkaline cells, you throw them away after use (or partial use) and live with that. If you use rechargeable's, you have to spend a little time managing them.
The basic problem with leaving cells on the charger is that you are shooting at a moving target. If the temperature varies, the optimum float voltage also varies. If you put a different capacity cell in, the float current varies. You will note that charging (and float) rates are given as a ratio to the capacity of the cell. Also, different cell manufacturers use different chemistry batches that react differently while charging. These differences can also be observed between batches of the same manufacturers cells.
I suppose that you could build a charger that varied voltage based on temperature and had a choice of outputs based on the capacity of the cell. This charger could discharge the cell and recharge it to get an idea of it capacity then maintain a float charge based on these results. Of course you would want to do several cells at a time, so each channel would have to be independent. I am not aware of a charger that can do all of this. I would think it would be pricey, but nice to have.
It is interesting to note that in the great battery shoot out article, one brand of cells were damaged while trickle charging. It was also mentioned that there is a big difference in the temperature rise of different cells in the same charger.
Doug has given you the Duracell link, PowerStream has this to say,
"Trickle Charging
In a standby mode you might want to keep a nickel metal hydride battery topped up without damaging the battery. This can be done safely at a current of between 0.03 C and .05 C. The voltage required for this is dependent on temperature, so be sure to regulate the current in the charger."
I can not explaine the order of magnitude difference, perhaps it is a difference in how the cells are made.
Perhaps you can do a detailed test and report back your results here...
Tom
Udaman,
Howdy, welcome!
Your question of who and what to trust has a simple answer, at least to me (and my simple mind), go to the experts. With expert advice available, I see no need for opinions, urban or otherwise.
Battery manufacturers are far far from 'overcautious'. The are by nature risk takers in the competitive market. If one maker was even a little more conservative than necessary (say underrated their capacity in advertising) their competition would steal market share based on that. If, on the other hand, they were to overstate things they're sure to suffer as well.
FWIW, there's a lot of folks out there using Bourbon as a food group, dating married women and having casual unprotected sex without apparent mishap. I think the conventional wisdom is probably still right.
So for me, it's easy, follow the maker's instructions for use. As they're all basically the same it seems more like the truth than conspiracy to me.
Doug Owen
Howdy, welcome!
Your question of who and what to trust has a simple answer, at least to me (and my simple mind), go to the experts. With expert advice available, I see no need for opinions, urban or otherwise.
Battery manufacturers are far far from 'overcautious'. The are by nature risk takers in the competitive market. If one maker was even a little more conservative than necessary (say underrated their capacity in advertising) their competition would steal market share based on that. If, on the other hand, they were to overstate things they're sure to suffer as well.
FWIW, there's a lot of folks out there using Bourbon as a food group, dating married women and having casual unprotected sex without apparent mishap. I think the conventional wisdom is probably still right.
So for me, it's easy, follow the maker's instructions for use. As they're all basically the same it seems more like the truth than conspiracy to me.
Doug Owen
[ QUOTE ]
qarawol said:
I would go by what the charger manual states. I use NiMH in my Surefire & Streamlight rechargeable Flashlights.
[/ QUOTE ]
With some caution, I'd agree, as long was we're talking factory batteries. While I'm not sure what you're using, and have never looked into the SF, I recall the SL to be NiCd, not NiMH, right? Just like the AA cell that came with my new Sony minidisk player, top line, best quality *Sony NiCd* of 600 mAh capacity! Why? 'cuz you can continuously charge it. They sure didn't like having to include all the toxics stuff and living with the 1/3 run time they could have had with NiMH....
Still, the 'guys' that make the AA NiMH we use say 'remove it from the charger when charged'. So that's my practice and advice.
Doug Owen
qarawol said:
I would go by what the charger manual states. I use NiMH in my Surefire & Streamlight rechargeable Flashlights.
[/ QUOTE ]
With some caution, I'd agree, as long was we're talking factory batteries. While I'm not sure what you're using, and have never looked into the SF, I recall the SL to be NiCd, not NiMH, right? Just like the AA cell that came with my new Sony minidisk player, top line, best quality *Sony NiCd* of 600 mAh capacity! Why? 'cuz you can continuously charge it. They sure didn't like having to include all the toxics stuff and living with the 1/3 run time they could have had with NiMH....
Still, the 'guys' that make the AA NiMH we use say 'remove it from the charger when charged'. So that's my practice and advice.
Doug Owen
[ QUOTE ]
SilverFox said:
I can not explaine the order of magnitude difference, perhaps it is a difference in how the cells are made.
Perhaps you can do a detailed test and report back your results here...
[/ QUOTE ]
My *guess* is it's the difference between what you should do (if you're trying to replace lost charge) and the upper limit of what you can do (without causing damage). The C/300 number was defined as charge replacement, right?
And I agree, some first hand experimental results would be interesting. The makers have, of course, done this to distraction as has DOE at Sandia Labs. Rechargeable battery chemistry is a hot item in Material Sciences as you might guess. We've got one such research in Li cells at work in fact. Allowed charging regimes are part of the process from very early on in the R&D.
In the end it could well end up like overdriving LEDs, sure it cuts into the life span, but the owner deems the return worth it.
Doug Owen
SilverFox said:
I can not explaine the order of magnitude difference, perhaps it is a difference in how the cells are made.
Perhaps you can do a detailed test and report back your results here...
[/ QUOTE ]
My *guess* is it's the difference between what you should do (if you're trying to replace lost charge) and the upper limit of what you can do (without causing damage). The C/300 number was defined as charge replacement, right?
And I agree, some first hand experimental results would be interesting. The makers have, of course, done this to distraction as has DOE at Sandia Labs. Rechargeable battery chemistry is a hot item in Material Sciences as you might guess. We've got one such research in Li cells at work in fact. Allowed charging regimes are part of the process from very early on in the R&D.
In the end it could well end up like overdriving LEDs, sure it cuts into the life span, but the owner deems the return worth it.
Doug Owen
Don't believe any manufacturer's lies about how many cycles NiMH cells are good for (they claim 500-1000) or whether it's safe to trickle charge them (they say yes). They just want to sell you more cells.
In 10+ years of charging up rechargeable batteries several times a week (cell phones, laptops, digital cameras, cordless tools, etc.) I've never had any type of rechargeable cell last longer than 100-200 cycles. I'm convinced that 500-1000 is a pure fantasy, or at best achieveable only under perfect laboratory conditions.
Similarly with trickle charging, it seems to me that trickle charging for more than a couple of days kills NiMH cells (doesn't seem to be so bad for Nicads). I wiped out several cell phone batteries that way (Motorola so-called Intellicharger) before wising up and getting careful about disconnecting NiMH cells from the charger after charging them up. Li ion devices are generally smarter and do shut down charging completely after the cell is charged.
The other thing I find is that the self-discharge of Nicad and NiMH cells is not as bad as lots of folks think it is, and for li ion, it's worse than some people seem to think. If you charge up a set of NiMH cells and then leave them alone, they'll still have a reasonable amount of charge left (maybe 50%) even six months later. If you're leaving them alone for that long without recharging, maybe you don't need rechargeables in that device anyway.
Basic advice: use rechargeables in frequently used devices like your EDC flashlight. For less frequently used devices, either use non-rechargeables (longer shelf life), or make a point of charging up the cells every few months, or just let them discharge and accept the notion that you'll have to charge them up again before you can use that device.
In 10+ years of charging up rechargeable batteries several times a week (cell phones, laptops, digital cameras, cordless tools, etc.) I've never had any type of rechargeable cell last longer than 100-200 cycles. I'm convinced that 500-1000 is a pure fantasy, or at best achieveable only under perfect laboratory conditions.
Similarly with trickle charging, it seems to me that trickle charging for more than a couple of days kills NiMH cells (doesn't seem to be so bad for Nicads). I wiped out several cell phone batteries that way (Motorola so-called Intellicharger) before wising up and getting careful about disconnecting NiMH cells from the charger after charging them up. Li ion devices are generally smarter and do shut down charging completely after the cell is charged.
The other thing I find is that the self-discharge of Nicad and NiMH cells is not as bad as lots of folks think it is, and for li ion, it's worse than some people seem to think. If you charge up a set of NiMH cells and then leave them alone, they'll still have a reasonable amount of charge left (maybe 50%) even six months later. If you're leaving them alone for that long without recharging, maybe you don't need rechargeables in that device anyway.
Basic advice: use rechargeables in frequently used devices like your EDC flashlight. For less frequently used devices, either use non-rechargeables (longer shelf life), or make a point of charging up the cells every few months, or just let them discharge and accept the notion that you'll have to charge them up again before you can use that device.
