Rechargeable Batteries
Posted 17/05/2007 - 15:06
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Althought NiMH batteries often claim to be "memory effect free", in fact they are just less susceptible to this problem than NiCd batteries.
If you frequently charge any Nickel based cell from a partially charged state, it will eventually suffer from reduced capacity.
If this is the case and the situation has not become too serious, repeatedly totally draining and re-charging the cells can help. The cells which came with my re-chargeable mouse began to suffer from this a few months ago and I was able to save them by running them totally flat and fully charging them 4 or 5 times. Some high end chargers have a "reconditioning" mode which does this automatically, I just left the mouse off charge for a couple of days.
Also worth noting is that these batteries do have a finite lifetime, and the higher rated cells tend to die more quickly. I have a set of 1700mAh batteries which are something on the order of 5 years old and still work great, but these have seen only light use since they were about one year old. My more heavily used set of 2000mAh cells lasted about 4 years before refusing to charge anymore. It may just be time to retire your batteries in favour of new sets.
The Uniross Hybrio cells are very popular at the moment due to their minimal self discharge rate. I have also had very good use out of my 2600mAh cells from 7dayshop (own brand). They are very cheap and have surprisingly low self discharge for a classic NiMH cell.
I wouldn't use R-CRV3s because a lot of them produce 3.7V instead of 3V. It can be very hard to tell which are ok since the packaging frequently fails to mention this vital detail. For this reason Pentax specifically recommend against using R-CRV3s in any of their cameras.
If you frequently charge any Nickel based cell from a partially charged state, it will eventually suffer from reduced capacity.
If this is the case and the situation has not become too serious, repeatedly totally draining and re-charging the cells can help. The cells which came with my re-chargeable mouse began to suffer from this a few months ago and I was able to save them by running them totally flat and fully charging them 4 or 5 times. Some high end chargers have a "reconditioning" mode which does this automatically, I just left the mouse off charge for a couple of days.
Also worth noting is that these batteries do have a finite lifetime, and the higher rated cells tend to die more quickly. I have a set of 1700mAh batteries which are something on the order of 5 years old and still work great, but these have seen only light use since they were about one year old. My more heavily used set of 2000mAh cells lasted about 4 years before refusing to charge anymore. It may just be time to retire your batteries in favour of new sets.
The Uniross Hybrio cells are very popular at the moment due to their minimal self discharge rate. I have also had very good use out of my 2600mAh cells from 7dayshop (own brand). They are very cheap and have surprisingly low self discharge for a classic NiMH cell.
I wouldn't use R-CRV3s because a lot of them produce 3.7V instead of 3V. It can be very hard to tell which are ok since the packaging frequently fails to mention this vital detail. For this reason Pentax specifically recommend against using R-CRV3s in any of their cameras.
Posted 17/05/2007 - 15:21
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Thank you for some very clear and helpful advice.
Malcolm
Malcolm
Posted 17/05/2007 - 17:37
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In normal use you will never, ever, encounter the so called memory effect.
Memory effect is only seen in laboratory environments where they charge and discharge to the exact same level over and over again.
Since allmost all chargers use a -dV charging mode for determining the charge level they overcharge a battery a little everytime. This slight overcharging cancelles any form of memory effect if it would occur.
What most people think as being the memory effect is wear based on temperature and normal use.
Rechargeable batteries age quite quickly, you can't expect the same performance for two years or something.
For making the lifetime as long as possible you have to have a good charger which charges each battery individually and if you have the time to spare use a low charging current. Quick charging will make the life of the battery a lot shorter.
If you have a simple charger which charges the batteries in pairs or all four at a time then you have the added problem that the charger switches off when the cell with the lowest capacity is considered to be full.
So get a decent charger and charge the batteries with a low charging current. I use a 200mA current mostly.
Memory effect is only seen in laboratory environments where they charge and discharge to the exact same level over and over again.
Since allmost all chargers use a -dV charging mode for determining the charge level they overcharge a battery a little everytime. This slight overcharging cancelles any form of memory effect if it would occur.
What most people think as being the memory effect is wear based on temperature and normal use.
Rechargeable batteries age quite quickly, you can't expect the same performance for two years or something.
For making the lifetime as long as possible you have to have a good charger which charges each battery individually and if you have the time to spare use a low charging current. Quick charging will make the life of the battery a lot shorter.
If you have a simple charger which charges the batteries in pairs or all four at a time then you have the added problem that the charger switches off when the cell with the lowest capacity is considered to be full.
So get a decent charger and charge the batteries with a low charging current. I use a 200mA current mostly.
Camera:K20D|Ist*DS|Spotmatic II|MZ-10
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T
Posted 17/05/2007 - 17:39
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Quote:
In normal use you will never, ever, encounter the so called memory effect.
not true, as I have both seen and cured it in normal useIn normal use you will never, ever, encounter the so called memory effect.
I agree with NiMH's it is generally rare
Posted 17/05/2007 - 22:44
Link
From a very nice website on this subject:
http://www.dansdata.com/gz011.htm
What you have seen is NOT the infamous memory effect, it is most likely the voltage depression effect which you and the OP have seen or are seeing.
http://www.dansdata.com/gz011.htm
What you have seen is NOT the infamous memory effect, it is most likely the voltage depression effect which you and the OP have seen or are seeing.
Quote:
"Memory effect" is now used as a general term for anything that makes a battery not deliver its full capacity. What the term originally referred to, though, is a phenomenon that's probably never actually been observed in consumer hardware.
True memory only happens in sintered plate NiCd cells (which aren't necessarily the sort of NiCd you're using, and are of course completely different from any kind of NiMH cell), and it only happens when you precisely discharge a cell to exactly the same level over and over again, and recharge it without any overcharge. True memory effect happens in satellite power systems, electronics test labs, and practically nowhere else.
"Memory effect" is now used as a general term for anything that makes a battery not deliver its full capacity. What the term originally referred to, though, is a phenomenon that's probably never actually been observed in consumer hardware.
True memory only happens in sintered plate NiCd cells (which aren't necessarily the sort of NiCd you're using, and are of course completely different from any kind of NiMH cell), and it only happens when you precisely discharge a cell to exactly the same level over and over again, and recharge it without any overcharge. True memory effect happens in satellite power systems, electronics test labs, and practically nowhere else.
Quote:
"...What people nowadays call memory effect is a combination of two things.
One - cell aging. Batteries don't last forever. The older they get, the less capacity they have. Live with it.
Two - "voltage depression". Voltage depression is a problem with NiCd batteries and, according to some sources, also with NiMH, and it doesn't affect the battery capacity much at all. Rather, the battery voltage drops unusually quickly as it discharges. Gadgets that monitor their battery voltage therefore think the battery's flat earlier than they should. There may be lots of capacity left at the slightly depressed voltage, but the gadget doesn't know that and flashes its "low battery" warning.
Fully discharging cells cures voltage depression, but if you fully discharge a whole battery then the stronger cells in the battery will "reverse" the weaker ones. The weaker ones go flat first, and then get charged backwards by the others. This is very bad for the weaker cells, and will kill a battery pack quick smart. So don't do it..."
"...What people nowadays call memory effect is a combination of two things.
One - cell aging. Batteries don't last forever. The older they get, the less capacity they have. Live with it.
Two - "voltage depression". Voltage depression is a problem with NiCd batteries and, according to some sources, also with NiMH, and it doesn't affect the battery capacity much at all. Rather, the battery voltage drops unusually quickly as it discharges. Gadgets that monitor their battery voltage therefore think the battery's flat earlier than they should. There may be lots of capacity left at the slightly depressed voltage, but the gadget doesn't know that and flashes its "low battery" warning.
Fully discharging cells cures voltage depression, but if you fully discharge a whole battery then the stronger cells in the battery will "reverse" the weaker ones. The weaker ones go flat first, and then get charged backwards by the others. This is very bad for the weaker cells, and will kill a battery pack quick smart. So don't do it..."
Camera:K20D|Ist*DS|Spotmatic II|MZ-10
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T
Posted 17/05/2007 - 22:57
Link
interesting, I stand corrected
my apologies Golfdiesel, my earlier post was needlessly blunt even if I had been right.
from your sources it looks like it is definitely better to discharge cells in need of reconditioning using a clever charger rather than just running them flat in the device, although I imagine all the cells in a given set will be something close to the same condition if they have always been used as a set (eg the cells in my mouse which never leave it, or the ones in my *ist which I always use as a set of 4).
my apologies Golfdiesel, my earlier post was needlessly blunt even if I had been right.
from your sources it looks like it is definitely better to discharge cells in need of reconditioning using a clever charger rather than just running them flat in the device, although I imagine all the cells in a given set will be something close to the same condition if they have always been used as a set (eg the cells in my mouse which never leave it, or the ones in my *ist which I always use as a set of 4).
Posted 18/05/2007 - 07:42
Link
mongoose, no need to apologise.
This forum is especially good in providing usefull information and I think that we all learn every day here.
This forum is especially good in providing usefull information and I think that we all learn every day here.
Camera:K20D|Ist*DS|Spotmatic II|MZ-10
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T
Pentax Lenses: DA16-45|DA50-200|50A 1.7
Tamron Lenses: 28-200
Takumar Lenses: SMC 55 1.8
Sigma Lenses: EX DG 50-500 'Bigma'|EX 50mm Macro
Flashes: Metz 58 AF-1|Samsung SEF-36PZF|Pentax AF-220T
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63 posts
22 years
New Forest,
Hampshire
I have three sets and keep them well charged ready for use.
Recently, the camera's battery level meter shows a full charge for 10 or 20 shots and then moves to ½ charge where it stays for another 100 or so shots.
Is the quick reduction in power, and limited life, an identical fault with all three sets of batteries, or a problem with the camera?
Also, I am thinking of switching to rechargeable CR-V3 batteries. Is this a good move? Will they last any longer between charges?
Thanks,
Malcolm