Long Term Care for Rechargeable BatteriesHow you store, maintain and recharge your batteries can have drastic impact on their long term viability.
- When storing NiCad batteries, be sure to pick a cool, dry place.
- The optimum temperature range for storing NiCad batteries is between −20° C and +45° C (−4° F to 113° F)
- When preparing to store NiCad batteries, be sure to discharge the batteries fairly deeply. The range in recommendations is between 40% and 0% charged when going into storage. NEVER short circuit a NiCad to drain/discharge, as this causes excessive heat and can cause hydrogen gas to be released, which can lead to an explosion. The self-discharge rate for NiCad’s is right around 10% at 20 °C, and rising up to 20% at higher temperatures.
- It is not recommended to store NiCads for an extended amount of time, without occasionally charging and using the batteries. During long periods of storage, the cadmium in the NiCd can form dendrites (thin, conductive crystals), which may bridge the gap between contacts and short out the cell. Once this happens, there is really nothing that can be done to fix it long term. The best way to prevent this from happening is frequent use (but at least once a year).
- When storing Nimh batteries, be sure to pick a cool, dry place.
- The optimum temperature range for storing Nimh batteries is between -20° C to +35° C (−4° F to 95° F)
- Can be stored indefinitely in either a charged or uncharged state.
- Recovery may take several cycles.
- During long time storage battery deactivation may tend to occur, and for this reason charging may stop early during recharging after storage. This problem can be solved by charging and discharging the battery several times.
- If a battery is stored for a prolonged time connected to a load, electrolyte fluid will leak, the battery will begin to deteriorate, and capacity will be impaired after storage.
Types of ChargersSometimes when we buy rechargeable batteries, they come with an included charger. Do you know what type of charger it is? Do you know how much charging current it provides? Do you know how long you should charge your batteries? There are 2 types of battery chargers, smart chargers and dumb chargers Smart Charger A 'smart' charger monitors each battery's status individually, and stops charging when each battery is full. This is the only way to ensure that your batteries are fully charged but not over-charged. It may also provide extra features such as Conditioning, Discharging and Testing. Dumb Charger (aka: Basic Charger, Value Charger, etc) A 'dumb' charger typically charges batteries in pairs only, and relies on a safety timer to terminate charging after 8-12 hours. These chargers are designed to output a certain amount of power over a certain period of time. Typically they have no charge termination mechanism and do NOT know how much voltage was in your battery when you inserted it, they do NOT condition the battery, nor do they really know when the battery is charged. They only know to turn on the indicator light (or start flashing) after X amount of hours, its up to you do do the math to ensure that your batteries are charged and not overcharged.
How long will it take to charge my batteries?We can use some quick math to estimate how long it will take. Simply divide the capacity of the battery by the charge rate of the charger. If everything was 100% efficient we could use this formula: Charge Time (hour) = Capacity (mAh) / Current (mA) Since nothing is 100% efficient, we compensate for that: Simply divide the capacity of the battery by the charge rate of the charger, then increase the amount of time by about 20% to allow for a certain amount of inefficiency. [ Capacity (mAh) / Current (mA) ] x 120% Example: a battery with a capacity of 1600 mAh will require about 9.6 hours to be fully charged by a charger with a charge rate of 200 mA. (1600 mAh/200 mA x 120%). Incidentally, this example would apply to a standard AA NiMH battery and a typical "rapid charger". Keep in mind that a battery that is only partially discharged will be recharged in less time. NiMH batteries can typically withstand over-charging at 0.1C current (which means 200mA for a 2000mAh cell) without immediate damage. If you forgot and left your batteries in a charger for an extra day, they are not going to leak or explode. But in the long run, over-charging will lead to reduced capacity and shorter lifespan.
How much Charge Current is my charger providing?You can find the charge charging current on the rear or bottom of most chargers or in the charger's documentation
What about Rapid Chargers or Quick Chargers?There is no standard in the industry, so manufacturers can use the terms in different ways. This means that both terms are essentially meaningless. One of the problems with terms like these is that the amount of time it takes to charge a battery is dependent on the capacity of the battery being charged. A charger that can charge a standard capacity AAA NiCD battery (180 mAh) in just one hour might take 8 hours to charge a high capacity NiMH (1500 mAh) battery. It's best to ignore such terms and make a rough calculation of how fast a charger can charge batteries. Fast charging is not good for batteries. Slower is better. Fast charging generates heat, which degrades the battery, reduces its life and in extreme cases can ruin it.
Recommended Smart ChargersAny smart charger is better than a non-smart charger (ok, dumb charger, I was trying to be politically correct), but there are 2 AA/AAA smart chargers that really lead the pack. Don't worry, you can use AA batteries in your C or D-cell devices with some battery adapters. La Crosse Technology BC-700 Alpha Power Battery Charger
- Battery charger for 4 rechargeable NiMH and NiCad AA and AAA batteries; with 4 modes: Charge, Discharge, Refresh, and Test
- Individual compartment for each battery with own LCD display and mode selection for multitasking
- 3 charging rate options of 200 mA, 500 mA, and 700 mA
- Detects overheating for safety
- Operates on 100-240-volt AC input for international use
- Four independent slots: It's like having four charger-analyzers for AA and AAA NiMH/NiCD batteries
- Large backlit LCD display: Digitally displays capacity, voltage, time and current
- Endless programming possibilities - over 10,000 ways: 29 selectable charging and discharging rate. Charging current from 0.2A to 2.0A and discharging current from 0.1A to 1.0A in 0.1A increments
- Delivers just the right charge: Independent negative delta V, temperature and timer protection eliminates over and undercharging
- Super light travel worldwide power supply and 12 V compatible: Worldwide 100-240 V switching adapter - light weight and small.
- Also compatible with 12 V input. Will work on car when used with the optional cigarette lighter adapter