Stock rechargeable batteries! This has long been dispensed as preparedness advice. The reasoning behind this advice is of course to have the ability to recharge the batteries for additional use once exhausted. If the stores are closed or you can’t get to them for more batteries at least you can rely on stash of rechargeable batteries. Depending on how the long the power is out, they may last you just long enough to get you by with a few modern conveniences like flashlights, headlamps and radios.
At present, there are four main types of rechargeable batteries that are commonly available for use in place of disposable batteries in electronic equipment. There is also larger Lead-Acid batteries (auto and RV) which are also rechargeable but for the purposes of this article I am only covering smaller consumer dry cell batteries. Rechargeable batteries are not all equal, each has it’s own positives and negatives, so which kind should you get? Keep reading and I will break down the different types of batteries for you below!
Non-Technical Battery Lingo for Normal People:
Voltage: Strength of power output of the battery. 1.5 volts is what disposable batteries commonly put out, so rechargeable batteries put out a little less, but are still within the range of what consumer battery appliances need.
mAh: Milliamps Hour (mAh) is important because it’s the easiest way to distinguish the capacity of a battery. The higher the mAh, the more power the battery stores and the longer it will last before needing to be recharged. The higher the number is usually better. Think of a car’s gas tank. Voltage is how much gas is being used, and mAh is the size of the gas tank (source).
LSD: Low Self Discharge; they won’t lose much energy while sitting around unused. Which means long shelf-life.
Charging Cycles: When a battery is completely drained and then completely charged up to full, or when a battery is partial drained and charged up to full that is one changing cycle. Batteries that can hold up to many changing cycles are usually preferred.
1. Nickel-Cadmium (NiCd) Batteries
These batteries used to be the only type of rechargeable batteries available, NiCad batteries are harder to get now due to restrictions on poisonous cadmium that is used in their manufacturing. However, NiCad batteries are still in use for low-drain applications such as solar yard lights, remote controls, smoke detectors and emergency radios.
Overcharging Ni-Cd batteries can reduce cycle life (the number of times the battery can be charged). Smart chargers know when the battery is full and stop charging. Dumb chargers run on a timer and will almost always overcharge or fail to fill up the battery. You can charge whenever you like, but constantly draining them completely before charging actually shortens their life but on the same hand if you don’t, NiCd batteries have been known to suffer from a “memory effect” which is when the battery remembers where it was last drained prior to recharging and from that time forward voltage drops as if the battery is going dead. In reality there is more power left to spare but voltage will drop as if the battery is going dead, while some manufacturers dispute this claim it remains widely reported. Occasional draining down to 1.0V is okay, and even recommended (source). A good brand of NiCd batteries you may recognize is Tenergy.
2. Nickel-Metal Hydride (NiMH) Batteries
The successors to Ni-Cd batteries, these commonly used and relatively inexpensive batteries are also the batteries that power some hybrid and electric vehicles. They can be relied on for most applications, but older batteries which have problems with self-discharge should never be used in smoke detectors as they can suddenly run out of power and leave you unprotected (source).
Remember that NiMH batteries come in two flavors: LSD and regular. LSD is “Low Self-Discharge”, which means long shelf-life (they won’t lose much energy while sitting around unused), vs. normal NiMH’s which go dead after a few months of sitting around. Given that, there’s not much incentive to get the normal NiMH’s, since they’re not any cheaper, and their capacity is only a little higher (2700 mAh for a normal NiMH vs. 2400 for a similarly-priced LSD NiMH). A good brand of Low Self-Discharge rechargeable battery is Eneloop, the Eneloop XXX batteries are one of the market’s best in capacity and charging cycles.
So how do you know whether a battery is the LSD kind or not? The easiest thing is to look for the good LSD-only brands: Eneloop and Imedion. You can also look for any of the marketing “code words” that indicate LSD, such as “Pre-charged” (since normal NiMH’s always require charging before use), “Ready to Use”, or “Hybrid” (source).
3. Nickel-Zinc (NiZn) Batteries
One of the newest types of rechargeable batteries for consumers, larger nickel-zinc battery systems have been known for over 100 years. Since 2000, development of a stabilized zinc electrode system has made this technology viable and competitive with other commercially available rechargeable battery systems. However because of their unique chemistry an voltage they require a special charger.
NiZn batteries are recommended for high-drain applications such as cameras, flashlights and outdoor equipment. The AA size NiZN batteries produce 1.6 volts which is higher than the voltage of disposable batteries as well as of NiMH batteries, which allows for better performance in motorized and light emitting equipment. However the main manufacturer of NiZn batteries discontinued production of them so they are no longer widely available. They also reportedly suffer from reliability problems, after only a few charging cycles the batteries self discharge considerably faster (source 1 and source 2).
4. Lithium Ion (Li-ion) Batteries
Li-ion batteries are sold as replacements for camera batteries, and they are also the most common batteries used in laptop computers, and some cell phones. Because they are easy to manufacture in different shapes, they are becoming the standard for use in personal electronics, and a built-in battery protection circuit keeps the battery operating safely preventing overcharge. They also store fairly well, therefore, having back-up battery packs for appliances that require them is not a bad idea. Unfortunately they are only available in the 3.6 voltage – accidentally using them in an appliance meant for standard batteries could easily fry the circuitry (source). Options for off-grid charging of lithium ion powered cameras, phones, GPS devices and tablets have expanded greatly in the past 4 years. Goal Zero’s solar recharging kit is one such highly recommended option that can be used to charge your USB capable devices and/or a pack of NiMH batteries.
5. Rechargeable Alkaline Batteries (RAM)
Less common than other types of batteries, rechargeable alkaline batteries are similar to single-use alkaline batteries but have a chemical composition that allows them to be recharged. They are best used in low-drain applications, but once charged they are known to hold their charge for longer than other types of rechargeable batteries. If they were commonly manufactured and easy to find this would make them ideal to have available for backup or emergency use. However they have been basically pushed out of the market by the newer (LSD) NiMH batteries. RAM batteries also require a special charger as NiCd and NiMH chargers won’t work (source).
Battery Chargers for Emergency Preparedness
If storing batteries and not using them, you may want to periodically test them to make sure that they have not discharged. Dead batteries are of no help in an emergency.
Ideally you want a charger that will charge both NiCd and NiMH batteries so that you will have the option of using them in everyday life right now and also some stored away for emergencies. There are many nice smart chargers on the market that can safely charge both NiCd & NiMH batteries, and even recondition them for additional use when plugged into a source of AC power, however, when you narrow the field down to solar chargers your choices are considerably slim. A regular wall charger is still useful to have especially if you start incorporating rechargeable batteries into everyday life. A solar charger is must for emergency preparedness as a battery charger that plugs into the wall wound be of little use in an event the grid goes down, therefore an alternative to that is solar power.
C. Crane makes an exceedingly affordable (under $30) and well rated a solar battery charger, that charges AA, AAA, C and D sized NiCd and NiMH batteries. While it is not a ‘smart charger’ the Solar 11 in 1 Battery Charger by C.Crane does have a very easy to read charge meter right on the front of it – a little vigilance is all that is required to make sure your batteries get a full charge. Another great charging option if you have the funds is the before mentioned Goal Zero Kit for AA and AAA batteries, which is actually a smart charger so you will not have to worry about over charging standard NiMH batteries (source). While Goal Zero will not endorse use of NiCd batteries with their product many reviewers have claimed the kit recharges them just as well. Since both these chargers are small in capacity my only advice is if you have the money, get two of them or in the case of Goal Zero to purchase an additional battery pack if necessary.
The Great Solar Yard Light Question
Can I use my solar yard lights as a solar battery charger?
You may have noticed some solar yard lights come with a replaceable AA or AAA rechargeable battery. The lights with these standard sized rechargeable batteries have become coveted items in emergency preparedness for their potential use as a super cheap battery charger.
The AA or AAA batteries that come in solar yard lights are typically NiCd batteries (some solar lights use NiMH batteries instead, but not many). NiCd batteries have different characteristics than the NiMH batteries and should not be used interchangeably in solar yard lights. Usually solar yard lights are specifically designed to recharge the size, type and capacity (mAh) of battery the lights originally came with. This is why the slightly lower capacity (600 mAh) NiCd “Moonrays”are usually recommended as replacement batteries for solar yard lights.
“Moonrays” are manufactured for solar yard lights with a slightly lower capacity which is better suited to the standard solar charge the lights usually give, so the batteries are not constantly under or over-charged. Always read the documentation that comes with your lights to see what type of batteries are needed; this well give you a better idea of what battery to keep on hand.
If the batteries you use for other appliances are compatible with your solar yard lights they do indeed make a handy recharger, but attempting to recharge a different type and/or capacity of battery could lead to over or undercharging issues (including overheating) unless you want to constantly test the battery all day to insure it gets a proper charge and is not damaged (source).
That being said, if I wanted to use solar lights to recharge batteries for use in other appliances I would go with the higher capacity Tenergy NiCd batteries (1000 mAh) and just be happy with whatever extra charge I got from the daylight over the Moonrays, knowing that they may end up always being slightly undercharged.
Rechargeable Battery Tip:
Battery spacers (pictured to the right) are a great way to turn small batteries like AAs into larger C or D size batteries so that you don’t have to buy all the battery sizes out there for emergency preparedness!
While there is still much to learn about rechargeable energy choices I hope this helps answer some of the most common questions about rechargeable consumer batteries.