Frequently Asked Questions:
Q: Do you have general info for charging Ni-Cd batteries?
A: Yes, here it is: Care and Feeding of Nicad batteries
To utilize the high capacity of the NiCad battery pack it is recommended to charge the battery at the rate listed on the battery label. Results may vary according to charge rates and charging conditions.
To achieve a complete thorough charge the NiCad battery must be charged at a rate equal to or greater than C/10. Where C = cell capacity in mAh. For example: A 1000 mAh cell requires 1000/10 or 100 mA charge rate or greater. Charging at a lower than C/10 rate will not result in a completely charged battery no matter how long the charging process continues. The charge rate must exceed the minimum rate to effect the charge process. NiCad cells need to be charged at a rate equal or greater than the C/10 rate.
It is recommended that a “smart charger” designed for NiCad charging be used to charge NiCad cells. Using chargers not designed for NiCad cells may result in under charged cells, overheating, and or rupture of NiCad cells. Chargers that charge at limited selectable rates and or fixed charge times may result in incomplete or overcharge cycles to the battery pack with unpredictable charge capacities. NiCad batteries benefit from conditioning cycles. A conditioning cycle first discharges the battery pack to approximately .8 volt per cell followed by a complete charge cycle. Three discharge/charge cycles complete a conditioning cycle.
Conditioning cycles are recommended for a new battery pack before first being placed into service. Condition cycles are recommended when returning a battery pack to service after periods of inactivity or idle storage. Fast charge only FAST CHARGE-rated batteries. Non-fast charge batteries may be damaged or exhibit reduced capacity if subjected to fast charge stress. There are no warranties available for standard-charge batteries that are treated in this manner.
Soldering directly to battery cells is not recommended. Heat of soldering may damage battery cells and/or vent seals, under the positive contact. Soldering directly to cells voids any and all warranty or guarantees. Spot welded solder tabs are the accepted methods of making connections to battery cells. Cells with solder tabs are available from Batteries America.
Do not short circuit, over charge, dispose of in fire or puncture battery cells. Battery cells must be disposed of properly.
Q: A battery says it has 2000mAh. What does that mean?
A: It means that the battery is rated at 2000 milliamp hours of storage capacity. This measurement is in electrical terms, and as far as operating time, it depends on the power consumption rate of the device that the battery is attached to. For AA battery cells, 2000mAh represents good long running time.
Q: I charge my battery all night, and now it has hardly any running time. What is happening?
A: A number of things could be causing this problem. Either the battery is wearing out, or the charging circuit is faulty, or the charger itself is faulty, or the battery is faulty. Or it is a combination of any of the above factors.
Q: My cellphone battery is puffy. What is happening?
A: The battery, to put it mildly, has gone bad. What rendered it bad is another issue. This "puffing" symptom is usually associated with Lithium rechargeable batteries (Li-ION or Li-ION Polymer). The battery expands because the air pressure inside the cell or cells has greatly increased. This can be caused by inadvertent overcharging, or over-discharging; in either event, the cell's vacuum seal has likely been compromised. This eventually ruins the battery performance. The battery might still work, but it is likely nowhere near as good as it was new.
Q: After I charge a battery, how soon should it be used, or long can it be stored and still be charged?
A: A good rule of thumb is "Charge it today, use it tomorrow". Most Ni-Cd and Ni-MH batteries exhibit something known as "dissipation". They lose their charge if left on a shelf long enough. This is inconvenient, and usually frustrating; it is also, however, NORMAL. You may have noticed this when you go to pick up your cordless screwdriver or drill, and the battery is "dead". Stored current actually starts draining out of a Ni-MH or Ni-Cd battery as soon as it is removed from its charger. The reason that Ni-Cds and Ni-MHs don't hold their charge in storage is because they were simply not formulated to. The amount of time it takes for a battery pack to lose its charge depends on the particular cells it was made from. Low capacity cells actually have longer dissipation rates, so they could hold their charge longer; unfortunately, they are not ever going to perform as high-capacity, long-life batteries, whether they were in storage or not. High-capacity batteries (like the SANYO HR-3U 2700mAh AA Ni-MH cells) offer significantly long operating time, but ONLY they are used right after they are charged. There is a trade-off involved with very high capacity products. When properly charged, they run for a long time, provided they are used right after they are fully charged. The dissipation rate of extra-high-capacity cells is typically fast. They may require re-charging as soon as 1 week after being charged initially.
SANYO has addressed the needs of consumer demand for batteries that HOLD THEIR CHARGE while in storage. The answer, to a limited degree, is the "eneloop" cells; these are a specially-formulated Ni-MH type batteries that have extremely low dissipation rates. They are available in AA and AAA sizes. When they are charged up, and put in storage unused, they can hold up to 80% of that charge for a year. So when you pull them off the shelf and put them in your camera, they will WORK. As of now, these eneloop cells are not available in all sizes; they are not the highest-capacity batteries in existence; and they are not ideally suited for absolutely any application (actually, nothing is, for that matter). It is safe to say that whatever digital device was previously successfully operated with typical Ni-MH AA or AAA cells (as the device instruction would indicate & confirm) will run fabulously on eneloop cells.
Q: The battery I am putting in my model airplane says 1100mAh. Will I get 1100mAh of operation out of it?
A: The 1100mAh rating should be thought of as "gas tank size". Under ideal charging and measuring circumstances, the battery can hold 1100mAh of current. The battery manufacturers rate their cells for capacity based on complete thorough draining - down to 0.75VDC per cell. In real-world applications, we don't want to run the battery in a model airplane until it is completely empty; similarly, we don't want to drive our cars until the gas tank is completely empty. So really, when you use ANY battery, you are typically using a great deal of the stored current, then re-charging it (hopefully) before it completely dies. Even when a battery appears to "die" (i.e. your device stops working), it typically still has current in it. The problem is that the device is usually requiring a higher voltage level than the battery has left in it. So the device shuts itself off.
Q: Should I recycle my old batteries? What is the proper disposal method?
A: Local ordinances dictate the proper disposal methods; generally, all Ni-Cd batteries need to be recycled. They SHOULD be recycled - Cadmium is a heavy metal, and does not belong in landfills. Also, the steel canisters that batteries are essentially made with should be recycled also. Imagine how much steel is thrown into landfills every year. Billions of batteries worldwide are thrown out (that is NOT an exaggeration); in these times, that steel truly needs to be recycled. You can also visit www.rbrc.com (RBRC is short for Rechargeable Battery Recycling Corporation) to learn more about the importance of recycling old batteries.
Q: What rate should a Nickel Cadmium or Nickel Metal Hydride battery be charged at?
A: The "ideal" Slow-charging rate for Ni-Cd (Nickel Cadmium) or Ni-MH (Nickel Metal Hydride) batteries is 1/10 of the rated capacity of the battery pack. If a battery pack is 700mAh in capacity, the ideal charge rate is 70mA for 12-16 hours (12 hours for "constant current" chargers - which are relatively expensive, and 16 hours for "tapering current" chargers, A.K.A. wall warts/wall cubes, which are usually low-cost). Charging Voltage should be equivalent to the # of batteries in the pack X 1.5v. A 4.8volt pack (made of 4 cells) gets charged normally at 6 volts. “Smart” chargers usually set the charge Voltage automatically; wall cubes have a pre-set output voltage, and that output can vary from product to product. Furthermore, the POLARITY of the chargers vary from product to product, so GREAT CARE must be taken to confirm that the wall charger being used is the proper item for a particular battery pack.
Batteries will usually last longer if you Slow-charge them. In fact, almost ANY rechargeable battery will last longer if you can Slow-charge them. If a battery is constantly fast-charged, it WILL be ready for use quicker, BUT it will probably wear out faster (i.e. it will lose the ability to store current; i.e. it will stop taking a charge).
Q: A battery says it is "2700mAh" capacity. What does that mean, and will the battery provide all that capacity for any device?
A: 2700mAh means 2700 milli-amp hours. It is an electrical measurement. In the real world, it could mean that if some device requires 2700milliamps (also known as 2.7 Amps) of current to operate properly, a 2700mAh battery pack would run the device for about 1 hour, provided the minimum operating voltage level is maintained.
SANYO Corporation, as an example, determines their battery capacities by analyzing them under controlled lab conditions. A Nickel Metal Hydride battery cell is charged up to 1.47 volts, the peak is detected, and then discharge analysis begins. A common discharge rate is C/4. In the case of a 2700mAh battery, this means that the discharge current is 2700 divided by 4. The battery is discharged down to a measured voltage of 0.8 - 0.75VDC per cell. The test results eventually produce the capacity ratings that are assigned to the mass-production runs of the product.
So, the rated capacity of a battery is typically achieved under ideal circumstances. In any particular device, the actual expended capacity can vary. The variance depends on a number of things, such as:
(1) The voltage tolerance of the device (the V level that the device shuts off at)
(2) Whether or not the battery is fully conditioned and actually fully charged.
(3) The time that has elapsed since the battery was actually charged up.
(4) The actual real measureable capacity of the battery.
A digital device with strict voltage cutoff levels will probably never draw the full capacity out of a battery. The device will shut itself off, even though there is still useable current remaining in the battery. An analog device (such as a small radio) may very well deliver the full running time associated with the battery capacity. Analog devices without voltage cutoff will keep drawing current out of batteries until they aren't worth operating anymore. A high-amp electric motor will usually not draw the full stored capacity out of a battery, because they typically cause batteries to get hot, which causes the battery impedance to increase, which hinders the release of the current, which slows down the performance, and then usually convinces the person to stop operating the motor. There will almost certainly be current still stored in the battery or battery pack; it just isn't feasible to use it. The user will be better off letting the battery cool down, and then re-charge it.
Finally, it should be noted that high battery capacities are intended to imply "reliability". By this, we mean that they will typically run devices longer than other batteries with lower capacities. If you want to take more pictures with your digital camera, you should consider buying a higher capacity battery to accomplish the goal. The device will probably never use the absolute full capacity stored in the battery, due to voltage cutoff levels, but the improved performance is evident and achieved nonetheless.
Q: How should Ni-Cd and Ni-MH rechargeable batteries be stored when not in use?
A: It depends on the usage. IF the battery in question is a rechargeable flashlight or other emergency-type battery product, it is a good idea to have it on "trickle charge" at all times; this enables the battery to be KEPT at full charge, and makes it useable WHENEVER you need it.
IF the battery in question is not for emergency/immediate use, it should be stored UNCHARGED in a cool dry place. It will lose its charge after about 2 months, and it will have to be fully recharged when you bring it back out of storage.
Q:What is the difference between Nickel-Cadmium and Nickel Metal Hydride?
A: Nickel Cadmium rechargeable packs/cells have been on the consumer market since the mid-70s. They typically offer standard running times (known as "Capacity") for portable electronic devices such as Camcorders, Cellular Phones, Walkie-Talkies, Laptop Computers, etc.
Nickel Metal Hydride rechargeable packs/cells represent a newer chemistry, and have been on the consumer market since the early 90s. They provide longer running time without increasing physical size. Also, they contain no materials classified as "heavy metals", such as Cadmium. This means that they do not require the stringent disposal methods that Nickel Cadmium batteries do. They CAN, however, be recycled. Recycling regulations do vary based on location.
Q: Can my batteries develop a "Memory"?
A: This phrase relates to a internal symptom of some rechargeable batteries known as the "Memory Effect". This was confirmed to have existed in at some of the older generation productions of Nickel Cadmium batteries. Basically, if the battery was not effectively & fully discharged prior to recharging, it might not deliver the full expected run-time (capacity) during the next discharge cycle. It is important to understand that this lowering of capacity was and can be related to a number of other factors, such as: (1) charging time; (2) sensitivity of 'smart' chargers; (3) inadvertent overcharging; (4) charging current; (5) battery age. Any of these factors, alone or in combination, can give the impression that a battery has lost its capacity, whether the battery actually has a memory problem or not.
Q: What is Lithium Ion?
A: Lithium Ion is the catchphrase representing a new, lightweight rechargeable battery. Lithium Ion batteries are often supplied with cellular phones, laptop computers, and newer, compact handheld transceivers. Lithium Ion batteries typically offer even greater capacity (operating time) than Nickel Metal Hydride batteries of similar size or mass. It is important to note that Lithium Ion battery cells are usually not compatible with Ni-Cd or Ni-MH cells. Whereas a Ni-Cd or Ni-MH cell is 1.2 volts nominal (Alkaline cells are listed as 1.5v nominal), a Lithium Ion battery cell is 3.6v nominal. A Lithium Ion AA-size cell CANNOT be used in place of an Alkaline, Ni-Cd, or Ni-MH cell. Furthermore, the discharging and re-charging characteristics of Lithium Ion products are VERY DIFFERENT from anything else. Lithium Ion battery products should ONLY be recharged with approved, dedicated Lithium Ion chargers.
Q: What is Lithium Polymer?
A: Lithium Polymer is a new rechargeable battery product. It is very lightweight, while possessing high capacity. A Lithium Polymer cell is nominally rated at 3.7 volts, and the measured capacity varies with the physical size of the cell. The actual battery is a vacuum-sealed mylar-type exterior material, with thin synthetic & metallic sheets inside. There are usually 2 tabs extending out of the battery, one (+) and one (-). These cells are now being used in Cellphone battery packs, Palmtops, PDAs, and are also used in R/C hobby applications (such as receiver packs and slow-flight electric motor packs)
Q: My pack says 7.5 volts. Is that MORE voltage than 7.2 volts? OR, my pack says 10.8 volts. Will an 11.25 volt pack hurt my radio?
A: Short answer: 7.5 volts = 7.2 volts in performance. 10.8 volts = 11.25 volts in performance.
Long answer: Some manufacturers list a single rechargeable Ni-Cd or Ni-MH cell as 1.2 volts (Sanyo & Panasonic, for instance). Other manufacturers (Motorola, for instance) list a single cell voltage as 1.25 volts. In actuality, there is NO difference in the cell voltage. However, when a manufacturer declares the extra 5/100 of a volt per cell (it is certainly a permitted activity), it ADDS UP when you have a lot of cells in a battery pack. And the net result is a battery pack that APPEARS to have higher voltage than another. It looks impressive, and it is intended to. BUT, it is NOT actually a higher voltage.