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.
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.
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.
(1) The voltage tolerance of the device (the V level that the device shuts
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.
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.
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.
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.