411man
02-27-2008, 02:25 PM
This from 230gr on another board.
An Overview of Current Rechargeable Battery Technology.
1. NiCd is the most durable battery chemistry, it has capacities ranging from 600-1000 [mil-Amp Hours] (mAH) It has the best temperature performance envelope, endures heat and over charge best, will operate with more cycles.
2. NiMH is the most common consumer cell these days, mostly due to the capacity advantage which run in the 1800-2700 mAH range at present.
3. NiMH low self discharge (LSD) cells. LSD cells are in the range of 2000-2100 mAH and have many advantages over traditional NiMH. They are new but current evidence indicates that they perform as advertised. The top brand, in my opinion, is Eneloops from Sanyo, it simply does the low-self-discharge thing better than the competition but there are a bunch of competing cells: Rayovac Hybrids, Hybrios, Titanium Enduros, and a bunch of others (2100 mAH).
In both types of chemistry, the higher capacity cells are more fragile than the lower capacity cells. It's an engineering trade off. The 2700 mAH whiz bang top-of-the-line cells are not your best bet for good durable cells, they are actually fairly fragile (chemically and physically) because of this trade off. Around 2000 mAH is not only cheaper (usually) but yields a cell that will see a longer service life, more cycles, and less likely to fail if dropped. Lower than 2000 in NiMH does not appear to hold significant advantage in durability in most respects. LSD cells appear to be at least as durable as their 2000 mAH NiMH counterparts.
Durability
1. Standard NiMH cells have an approximately life span of 3 years with increased internal resistance, lowered capacities, and higher self discharge with age. Cheaper brands may have less.
2. NiCd cells have about 5 year life span usually fails with internal shorts (complete failure) or excessively high resistance.
3. LSD NiMH cells currently have no data in this regard, they're advertised as having better longevity than regular NiMH cells. They've only been out for less than 3 years now. The oldest cells reported (1.5 years old) was lightly used and perform like new.
Self discharge
1. Standard; One of the biggest inconvenient things about rechargeable cell use and the standard NiMH cells discharge by themselves very quickly on the order of a couple of months when new and the rate increases significantly with age and use.
2. NiCd cells have about half the self discharge rate and this usually won't vary much up until cell death.
3. LSD NiMH cells shine in this regard, the self discharge slows down after a charge to almost a stand still in a little over a months time. LSD cells will retain around 85% (Eneloops) to 80% (rest of the field) charge after a year of storage at around 70 degrees.
Voltage Drop
Keeping the voltages up during use is important for many devices and one of the principle reasons rechargeables deliver poor performance in some devices. Many devices require a minimum voltage to operate correctly, if this minimum is above what your battery can deliver under load your device will shut down. That can be 1.2v per cell, and NiMH will often fail to meet this under less than ideal circumstances! If you experience significant performance difference between primary cells and rechargeable cells (especially older ones) this is likely the problem, especially combined with self discharge "usable capacity" drops very quickly.
1. Standard NiMH suffers from voltage sag over time. It will start out at a nice high 1.4 volts fresh off the charger but soon drops to1.3-to-1.2 v open voltage. If left on the shelf it will fall even more over time.
2. NiCd cells can suffer from a form of voltage sag, it is not as pronounced as NiMH but it can also happen in mid-discharge and is cell "memory". This problem can usually be corrected with a couple exercise cycles and a good top off charge.
3. LSD NiMH cells retain their voltage very well on the shelf, like their charge, and also deliver better than average voltages in normal use anyway. You will usually see much better performance from LSD cells in these voltage sensitive devices than NiMH or even NiCd. If you've been frustrated with rechargeables in the past in some of your devices give some LSD cells a try!
Poor Charging Practices- The most common method to kill cells.
1. Especially with NiMH cells, buy a good "smart" charger and never batteries to "cook" on a standard charger for far too long
2. Heat is bad! While it is normal for rechargables to get warm (not burning hot!) at the end of a charge cycle, if they continue to stay warm (or worse, hot) for several hours later, you have a [traditional "dumb"] charger that is cooking your cells.
a. The Maha-C9000 is a good, smart, high end slower charger that will not cook your cells if you leave them in the unit. The unit has options that allow you to easily exercise cells and see if they are improving. You can match cells to obtain the best performance from them and identify poor performing cells quickly. It also charges individual cells rather than pairs, which is better for them - especially a mismatched pair.
b. The Duracell 15 minute charger is a quality unit that does not cooked on the charger. They are rough compared to a good slower charge but are fairly energy efficient, reducing the power required to get a full charge. The most importantly, they give a reasonably charged battery very quickly when the need is now.
c. I would prefer to have both chargers available, the Maha-C9000 for normal, everyday charging and the Duracell 15 minute charger as a quick charge option.
d. Both chargers run on 12 volt DC input and can plug directly into 12 volt systems allowing for use in a car or directly off a battery based PV, wind system.
3. Cells below freezing (32 F/0 C) should not charge as it will damage them. If you really need a charged cell, warm it up in your pocket (preferably the charger too) and use the Duracell 15 minute charger . The charge cycle should provide enough heat to keep it above freezing until it's done.
4. Cells out of long term storage need "exercise". NiCds especially need fairly significant exercise before returning to full capacity. 5+ full cycles may be required, rule of thumb is exercise until you stop seeing capacity gains. This is easiest with a charger like the C9000 with capacity readouts. NiCds should be stored discharged. NiMH cells should be stored with a charge. LSD cells require significantly less maintenance and may not need any exercise at all and will likely have a serviceable charge intact after storage, depending on the length of time in storage and at what temperature.
5. NiMH cells like to be recharged gently and the more shallow the cycle the better so keeping NiMH cells topped off allows them to last the longest. Full cycles will wear on them the most but, occasionally, you may need to perform a deep cycle to restore some performance if the cell appears to be waning.
6. Advanced NiMH care systems like on the Toyota Prius reportedly keep cells at 60-80% capacity and only use about 20% depth in discharge cycles, which seems to be the most chemically repeatable and stable region.
7. NiCds stand up to abuse a lot better, in fact a regular full discharge is good for them and will help you avoid issues with the cells. It's not required for every charge, but once a month or so should keep it's performance high.
8. Earlier generation NiMH cells had a very poor temperature tolerance and struggle below freezing. The LSD appears to have better cold temperature performance limited testing down to 0 oF have found no appreciable drop in capacity.
9. C and D size rechargeable cells are not recommended as they are expensive, they take forever to charge, your charging options are more limited, and there are no LSD variants at present. Adapter sleeves readily available to make AA cells fit these sizes.
10. LSD NiMH tech has dramatically improve the performance, longevity, durability, and cycle life too. However, it is new and relatively unproven tech. For general use, the Sanyo Eneloops LSD NiMH seem the very best and there seems to be no reason to buy any non-LSD NiMH cells these days
11. NiCd cells are an old and proven for high power use tools and similar equipment. It maybe worth having a some NiCds around for special usages.
More on Sanyo Eneloop LDS NiMh
Eneloop is a rechargeable battery using latest Ni-MH technology. It does not contain any cadmium and, in comparison to other Ni-MH batteries, less cobalt.
1. Eneloop is rechargeable/reuseable 1000 times
2. Once charged, eneloop retains its charged capacity even after 6 or 12 months of storage (90% of Charged Capacity retained after 6 months, 85% Capacity after 12 months). A regular fully charged NiMH battery will lose about 1% of its charge per day just sitting on the shelf.
3. Memory Effect is a term used to describe the effects on the overall life of the battery when it goes through charge and discharge cycles. The eneloop battery does not experience the effects of "memory effect".
4. Not only do Sanyo eneloops hold their charge much longer than standard NiMH AA rechargeables, they run longer in most high power equipment but Eneloops are also suitable for long-running devices like this battery operated clock.
a. Regular NiMH AA rechargeable batteries giving 10 shots in a digital camera, regular AA alkaline batteries gave 90 buy Sanyo eneloops gave over 400 shots on a charge!
5. Keeping some charge in the battery, will require you to "cycle" the battery fewer times until it reaches its peak charge. If you store them with no charge, you will have to "cycle" the battery multiple times until it reaches its peak charge.
6. Though it is possible to charge an eneloop battery in a "Quick Charger", it is not recommended. We recommend charging eneloop batteries in a NiMh charger that is 2 hours or more. Charging eneloop batteries in a "Quick Charger" can reduce the overall life of the battery. It is strongly recommended to use eneloop, GE/Sanyo or Sanyo NiMh battery chargers.
For more information see: http://www.eneloop.info/ or http://us.sanyo.com/batteries/
LSN NiMh Testing *** 60 days Update ***
After two months of data, we finally got something substantial. The remaining capacity of the Eneloop & Enduro 2100 mAh finally surpass the 2500 mAh cells. It seems like the self-discharge of the LSD cells are tapering off, while the regular cells (like the bunny) are "still going".
Some other interesting data is that the average voltage is starting to show sign of degradation for the normal cells while the LSD cells changes are in the noise level.
Eneloop voltage underload is trully remarkable. Even after two months of resting the average voltage is above 1.2V
Standard NiMH cells
Energizer 2500 mAh
Titanium 2600 mAh
Titanium 2700 mAh
LSD NiMH cells
Titanium Enduro 2100 mAh
Sayco Eneloop 2100 mAh
http://img73.imageshack.us/img73/8588/capacitylossjj7.jpg
http://i109.photobucket.com/albums/n76/230gr/capacitylossjj7.jpg
For more information see: Eneloop & Enduro LSD Duration Testing - CandlePowerForums
http://candlepowerforums.com/vb/showthread.php?t=119003 or ImageShack.us
Summary of Plan:
1. Replace battery operated devices with low drain or no drain models.
2. Standardize to AA batteries (Buy battery adapters if an essential device is not AA compatible).
3. Buy quality smart [AC/DC] charger(s) with enough capacity to charge your battery needs for at least one day.
4. Buy quality rechargeable batteries (3 times the number you expect to use on your worst day).
5. Rotate batteries: Charge, store in freezer, then use them on a rotating basis.
6. Replace batteries when they drop below 50% capacity and can not be rejuvenated (roughly 500-1000 cycles for NiMH).
7. Rechargeable batteries may not work for all situations. If you keep some where they can not be regularly rotated, you should probably use lithium batteries.
Standard NiMH Battery Testing.
Run times with a resistive load and actual mAh measurements don't tell the full story: Watt-Hours are the real representation of how well the batteries will do powering an electrical device.
brand & rated capacity Watt-hours mAh Minutes
Sanyo 2100 9.66 2013 131.8
Uniross 2100 9.41 1867 124.0
Powerex 2000 9.04 1856 120.5
Nexcell 2100 9.00 1886 126.9
Nexcell 2000 8.91 1861 122.8
Sanyo 1850 8.89 1841 123.2
Energizer 1850 8.88 1827 121.7
Kodak 1850 8.84 1813 120.5
Jetcell 1850 8.81 1815 121.0
GE/Sanyo 1850 8.79 1823 119.4
Panasonic (Alkaline) 3.66 774 56.0
Duracell Ultra (Alkaline)3.66 781 57.0
Energizer (Alkaline ) 3.55 756 55.0
An Overview of Current Rechargeable Battery Technology.
1. NiCd is the most durable battery chemistry, it has capacities ranging from 600-1000 [mil-Amp Hours] (mAH) It has the best temperature performance envelope, endures heat and over charge best, will operate with more cycles.
2. NiMH is the most common consumer cell these days, mostly due to the capacity advantage which run in the 1800-2700 mAH range at present.
3. NiMH low self discharge (LSD) cells. LSD cells are in the range of 2000-2100 mAH and have many advantages over traditional NiMH. They are new but current evidence indicates that they perform as advertised. The top brand, in my opinion, is Eneloops from Sanyo, it simply does the low-self-discharge thing better than the competition but there are a bunch of competing cells: Rayovac Hybrids, Hybrios, Titanium Enduros, and a bunch of others (2100 mAH).
In both types of chemistry, the higher capacity cells are more fragile than the lower capacity cells. It's an engineering trade off. The 2700 mAH whiz bang top-of-the-line cells are not your best bet for good durable cells, they are actually fairly fragile (chemically and physically) because of this trade off. Around 2000 mAH is not only cheaper (usually) but yields a cell that will see a longer service life, more cycles, and less likely to fail if dropped. Lower than 2000 in NiMH does not appear to hold significant advantage in durability in most respects. LSD cells appear to be at least as durable as their 2000 mAH NiMH counterparts.
Durability
1. Standard NiMH cells have an approximately life span of 3 years with increased internal resistance, lowered capacities, and higher self discharge with age. Cheaper brands may have less.
2. NiCd cells have about 5 year life span usually fails with internal shorts (complete failure) or excessively high resistance.
3. LSD NiMH cells currently have no data in this regard, they're advertised as having better longevity than regular NiMH cells. They've only been out for less than 3 years now. The oldest cells reported (1.5 years old) was lightly used and perform like new.
Self discharge
1. Standard; One of the biggest inconvenient things about rechargeable cell use and the standard NiMH cells discharge by themselves very quickly on the order of a couple of months when new and the rate increases significantly with age and use.
2. NiCd cells have about half the self discharge rate and this usually won't vary much up until cell death.
3. LSD NiMH cells shine in this regard, the self discharge slows down after a charge to almost a stand still in a little over a months time. LSD cells will retain around 85% (Eneloops) to 80% (rest of the field) charge after a year of storage at around 70 degrees.
Voltage Drop
Keeping the voltages up during use is important for many devices and one of the principle reasons rechargeables deliver poor performance in some devices. Many devices require a minimum voltage to operate correctly, if this minimum is above what your battery can deliver under load your device will shut down. That can be 1.2v per cell, and NiMH will often fail to meet this under less than ideal circumstances! If you experience significant performance difference between primary cells and rechargeable cells (especially older ones) this is likely the problem, especially combined with self discharge "usable capacity" drops very quickly.
1. Standard NiMH suffers from voltage sag over time. It will start out at a nice high 1.4 volts fresh off the charger but soon drops to1.3-to-1.2 v open voltage. If left on the shelf it will fall even more over time.
2. NiCd cells can suffer from a form of voltage sag, it is not as pronounced as NiMH but it can also happen in mid-discharge and is cell "memory". This problem can usually be corrected with a couple exercise cycles and a good top off charge.
3. LSD NiMH cells retain their voltage very well on the shelf, like their charge, and also deliver better than average voltages in normal use anyway. You will usually see much better performance from LSD cells in these voltage sensitive devices than NiMH or even NiCd. If you've been frustrated with rechargeables in the past in some of your devices give some LSD cells a try!
Poor Charging Practices- The most common method to kill cells.
1. Especially with NiMH cells, buy a good "smart" charger and never batteries to "cook" on a standard charger for far too long
2. Heat is bad! While it is normal for rechargables to get warm (not burning hot!) at the end of a charge cycle, if they continue to stay warm (or worse, hot) for several hours later, you have a [traditional "dumb"] charger that is cooking your cells.
a. The Maha-C9000 is a good, smart, high end slower charger that will not cook your cells if you leave them in the unit. The unit has options that allow you to easily exercise cells and see if they are improving. You can match cells to obtain the best performance from them and identify poor performing cells quickly. It also charges individual cells rather than pairs, which is better for them - especially a mismatched pair.
b. The Duracell 15 minute charger is a quality unit that does not cooked on the charger. They are rough compared to a good slower charge but are fairly energy efficient, reducing the power required to get a full charge. The most importantly, they give a reasonably charged battery very quickly when the need is now.
c. I would prefer to have both chargers available, the Maha-C9000 for normal, everyday charging and the Duracell 15 minute charger as a quick charge option.
d. Both chargers run on 12 volt DC input and can plug directly into 12 volt systems allowing for use in a car or directly off a battery based PV, wind system.
3. Cells below freezing (32 F/0 C) should not charge as it will damage them. If you really need a charged cell, warm it up in your pocket (preferably the charger too) and use the Duracell 15 minute charger . The charge cycle should provide enough heat to keep it above freezing until it's done.
4. Cells out of long term storage need "exercise". NiCds especially need fairly significant exercise before returning to full capacity. 5+ full cycles may be required, rule of thumb is exercise until you stop seeing capacity gains. This is easiest with a charger like the C9000 with capacity readouts. NiCds should be stored discharged. NiMH cells should be stored with a charge. LSD cells require significantly less maintenance and may not need any exercise at all and will likely have a serviceable charge intact after storage, depending on the length of time in storage and at what temperature.
5. NiMH cells like to be recharged gently and the more shallow the cycle the better so keeping NiMH cells topped off allows them to last the longest. Full cycles will wear on them the most but, occasionally, you may need to perform a deep cycle to restore some performance if the cell appears to be waning.
6. Advanced NiMH care systems like on the Toyota Prius reportedly keep cells at 60-80% capacity and only use about 20% depth in discharge cycles, which seems to be the most chemically repeatable and stable region.
7. NiCds stand up to abuse a lot better, in fact a regular full discharge is good for them and will help you avoid issues with the cells. It's not required for every charge, but once a month or so should keep it's performance high.
8. Earlier generation NiMH cells had a very poor temperature tolerance and struggle below freezing. The LSD appears to have better cold temperature performance limited testing down to 0 oF have found no appreciable drop in capacity.
9. C and D size rechargeable cells are not recommended as they are expensive, they take forever to charge, your charging options are more limited, and there are no LSD variants at present. Adapter sleeves readily available to make AA cells fit these sizes.
10. LSD NiMH tech has dramatically improve the performance, longevity, durability, and cycle life too. However, it is new and relatively unproven tech. For general use, the Sanyo Eneloops LSD NiMH seem the very best and there seems to be no reason to buy any non-LSD NiMH cells these days
11. NiCd cells are an old and proven for high power use tools and similar equipment. It maybe worth having a some NiCds around for special usages.
More on Sanyo Eneloop LDS NiMh
Eneloop is a rechargeable battery using latest Ni-MH technology. It does not contain any cadmium and, in comparison to other Ni-MH batteries, less cobalt.
1. Eneloop is rechargeable/reuseable 1000 times
2. Once charged, eneloop retains its charged capacity even after 6 or 12 months of storage (90% of Charged Capacity retained after 6 months, 85% Capacity after 12 months). A regular fully charged NiMH battery will lose about 1% of its charge per day just sitting on the shelf.
3. Memory Effect is a term used to describe the effects on the overall life of the battery when it goes through charge and discharge cycles. The eneloop battery does not experience the effects of "memory effect".
4. Not only do Sanyo eneloops hold their charge much longer than standard NiMH AA rechargeables, they run longer in most high power equipment but Eneloops are also suitable for long-running devices like this battery operated clock.
a. Regular NiMH AA rechargeable batteries giving 10 shots in a digital camera, regular AA alkaline batteries gave 90 buy Sanyo eneloops gave over 400 shots on a charge!
5. Keeping some charge in the battery, will require you to "cycle" the battery fewer times until it reaches its peak charge. If you store them with no charge, you will have to "cycle" the battery multiple times until it reaches its peak charge.
6. Though it is possible to charge an eneloop battery in a "Quick Charger", it is not recommended. We recommend charging eneloop batteries in a NiMh charger that is 2 hours or more. Charging eneloop batteries in a "Quick Charger" can reduce the overall life of the battery. It is strongly recommended to use eneloop, GE/Sanyo or Sanyo NiMh battery chargers.
For more information see: http://www.eneloop.info/ or http://us.sanyo.com/batteries/
LSN NiMh Testing *** 60 days Update ***
After two months of data, we finally got something substantial. The remaining capacity of the Eneloop & Enduro 2100 mAh finally surpass the 2500 mAh cells. It seems like the self-discharge of the LSD cells are tapering off, while the regular cells (like the bunny) are "still going".
Some other interesting data is that the average voltage is starting to show sign of degradation for the normal cells while the LSD cells changes are in the noise level.
Eneloop voltage underload is trully remarkable. Even after two months of resting the average voltage is above 1.2V
Standard NiMH cells
Energizer 2500 mAh
Titanium 2600 mAh
Titanium 2700 mAh
LSD NiMH cells
Titanium Enduro 2100 mAh
Sayco Eneloop 2100 mAh
http://img73.imageshack.us/img73/8588/capacitylossjj7.jpg
http://i109.photobucket.com/albums/n76/230gr/capacitylossjj7.jpg
For more information see: Eneloop & Enduro LSD Duration Testing - CandlePowerForums
http://candlepowerforums.com/vb/showthread.php?t=119003 or ImageShack.us
Summary of Plan:
1. Replace battery operated devices with low drain or no drain models.
2. Standardize to AA batteries (Buy battery adapters if an essential device is not AA compatible).
3. Buy quality smart [AC/DC] charger(s) with enough capacity to charge your battery needs for at least one day.
4. Buy quality rechargeable batteries (3 times the number you expect to use on your worst day).
5. Rotate batteries: Charge, store in freezer, then use them on a rotating basis.
6. Replace batteries when they drop below 50% capacity and can not be rejuvenated (roughly 500-1000 cycles for NiMH).
7. Rechargeable batteries may not work for all situations. If you keep some where they can not be regularly rotated, you should probably use lithium batteries.
Standard NiMH Battery Testing.
Run times with a resistive load and actual mAh measurements don't tell the full story: Watt-Hours are the real representation of how well the batteries will do powering an electrical device.
brand & rated capacity Watt-hours mAh Minutes
Sanyo 2100 9.66 2013 131.8
Uniross 2100 9.41 1867 124.0
Powerex 2000 9.04 1856 120.5
Nexcell 2100 9.00 1886 126.9
Nexcell 2000 8.91 1861 122.8
Sanyo 1850 8.89 1841 123.2
Energizer 1850 8.88 1827 121.7
Kodak 1850 8.84 1813 120.5
Jetcell 1850 8.81 1815 121.0
GE/Sanyo 1850 8.79 1823 119.4
Panasonic (Alkaline) 3.66 774 56.0
Duracell Ultra (Alkaline)3.66 781 57.0
Energizer (Alkaline ) 3.55 756 55.0