Frequently Asked Questions
Technical Questions
What is a deep cycle battery?
Deep cycle batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates than that of a standard battery.
What is a gel cell battery?
A gel battery design is typically a modification of the standard lead acid automotive or marine battery. A gelling agent is added to the electrolyte to reduce movement inside the battery case. Many gel batteries also use one way valves in place of open vents, this helps the normal internal gasses to recombine back into water in the battery, reducing gassing. "Gel Cell" batteries are non-spillable even if they are broken. Gel cells must be charged at a lower rate (max C/5) and voltage than flooded or AGM to prevent excess gas from damaging the cells. Fast charging them on a conventional automotive charger may permanently damage a gel battery. NEVER charge either AGM or GEL sealed lead-acid batteries with an automotive charger. The charger will damage the batteries.
What is a milliamp hour (mAH)?
Milliamp Hour is a term used to describe the capacity of a battery or the rate of discharge it is experiencing. The capacity of various chemistries is expressed in milliamp hours for smaller batteries and amp/hours for larger batteries; discharged over a specific period of time expressed in hours. The combination of the discharge rate (milliamp hours or amp hours), and the time to complete discharge, determine the capacity of the battery.
How is the rated capacity of a battery determined?
The capacity of a battery is typically expressed in milliamp-hours (mAH) or amp hours. For primary batteries, samples are discharged at a specific current drain (i.e. 25mAH) and time recorded to a cutoff voltage (i.e. 0.8 volts). The time (hours) it takes the battery to reach the cutoff voltage is then multiplied by the current drain to establish the mAH capacity of the battery. Rechargeable batteries (NiMH) are rated based on a C/10 charge followed by a C/5 discharge. Sealed Lead-Acid batteries are rated on a C/20 charge and discharge rate.
Can batteries freeze?
In a partially discharged state, the electrolyte in a lead acid battery may freeze. At a 40% state of charge, electrolyte will freeze if the temperature reaches approximately -16.0°F. The freezing temperature of the electrolyte in a fully charged battery is -92.0°F.
Do batteries self-discharge when not in use?
All batteries, regardless of their chemistry, self-discharge. The rate of self-discharge depends both on the type of battery and the storage temperature the batteries are exposed to. However, for a good estimate, deep cycle AGM or GEL batteries self-discharge approximately 3% per month, stored at 25°C (77°F).
What is the difference between a NiCd and NiMH chemistry battery?
The main difference between the two is the fact that NiMH batteries (the newer of the two technologies) offer higher energy densities than NiCd batteries. In other words, pound for pound, NiMH delivers approximately twice the capacity of its NiCd counterpart. What this translates into is increased run-time from the battery with no additional bulk to weigh down your portable device. NiMH also offers another major advantage over NiCd. NiCd batteries contain cadmium, a toxic heavy metal that must be recycled. NiMH does not contain any toxic components, and can be disposed of in the trash. However, the "green" movement encourages the recycling of all battery chemistries.
SLA Battery Article
Why did my lead-acid battery swell up?
Most of the time, this problem happens to sealed lead-acid batteries of either AGM (Absorbed Glass Mat) or GEL (gelled electrolyte) construction. These battery constructions are known as "recombinant" batteries, referring to the absorption of gasses generated by the chemical process of the battery. In order to absorb these gasses, the positive and negative plates must be as close together as possible and are usually only held apart by the thickness of the separator. A consequence of the necessity of gas absorption, the pack of plates (the element) is inserted very tightly into the cell cavity, resulting in a lack of space for any other components. In the situation of a swollen battery, the cell plate components expanded, and the force exerted on the case caused it to swell and most likely split at numerous points.
The expansion of the cell element is as a result of internal heat, and can be as a result of either overcharging of the battery or from a drastic shorting of the battery terminals. Either one of these situations will generate internal heat in the battery. Additionally, elemental lead natural has a high expansion rate when exposed to heat. Since the cells of a battery of AGM or GEL construction are deliberately manufactured with no extra room, the result is the individual cell casings will split from expansion pressure, and deform from high heat, destroying the battery due to the massive damage to internal parts.
This usually does not happen to the battery alone; usually the battery was either shorted or overcharged. The overcharging of the battery can be the result of a charger that is delivering too much current to the battery, or a charger of higher voltage than the battery was accidentally used-for example a 12V charger on a 6V battery. Regardless of the cause, the result is almost always the same; swelling and the destruction of the battery.
To avoid this particular accident, the end-user must consider the following points:
1) Is this charger meant to be used on this type battery?
2) Is this charger the right voltage for the battery I want to charge?
3) Is the maximum current of this charger within the charging range of this battery?
4) Do I have the right polarity connection between battery and charger?
5) Are the battery terminals shielded from possible shorting?
These questions must be considered to not only avoid the destruction of a battery, but also for personal safety because in worst case scenarios the heat could cause the battery to catch fire. Batteries are active devices and are reactive, not proactive, so they respond to the outside influences.
How can I test batteries to see if they're still good?
A battery tester (loaded voltmeter) is a simple and effective way to determine if a battery is "good" or "bad." Most testers place an appropriate load on the batteries and then read the voltage. A voltmeter without a load can give very misleading information and is not recommended for this purpose. Note that testers are typically not capable of providing reliable run time estimates.
Why is mixing batteries of different chemistries, brands or age a potential problem?
Mixing of battery types (different chemistries, brands and/or fresh vs. used) in a device is not recommended and can significantly increase the potential for leakage and reduced device run time. The primary concern is an imbalance in capacities or available energy between the installed batteries. As the weakest battery becomes exhausted, it will be force discharged by the stronger batteries to very low or negative voltage levels which drastically increases the potential for leakage.
What type of batteries can be recharged?
Only batteries that are labeled as rechargeable are capable of being safely recharged. Attempting to recharge non-rechargeable batteries greatly increases the potential for leakage and rupture. Charging must be conducted in chargers specifically approved for each product type which may vary depending on brand and model of both battery and charger.
Battery Safety
- - Do not short-circuit. A short-circuit may cause severe damage to the battery. Batteries can be short-circuited by metal items such as coins, keys, paperclips, etc. A battery that is subjected to a short-circuit can become very hot and increase the potential for leakage and personal injury.
- - Do not drop, hit or otherwise abuse the battery as this may result in the exposure of the cell contents, which are corrosive.
- - Do not expose the battery to moisture or rain.
- - Keep battery away from fire or other sources of extreme heat.
- - Do not incinerate. Exposure of battery to extreme heat may result in an explosion.
What is the "Memory Effect"?
NiCd batteries, and to a lesser extent NiMH batteries, suffer from what's called the "memory effect." If a NiCd battery is partially discharged on a continuous basis before re-charging, the battery "forgets" that it has the capacity to further discharge all the way down. To illustrate: If you fully charge your battery every time, and then use only 50% of its capacity before the next recharge, eventually the battery will lose its extra 50% capacity which has remained unused. Your battery will remain functional, but only at 50% of its original capacity. The way to avoid "memory effect" is to fully cycle (fully charge and then fully discharge) your battery at least once every two to three weeks. Batteries can be discharged by unplugging the device's AC adaptor and letting the device run on the battery until it ceases to function. This will insure your battery remains healthy.
Is it possible to upgrade my device's battery to a newer chemistry?
NiCd & NiMH versus Li-ion are fundamentally different from one another and cannot be substituted unless the device has been pre-configured from the factory to accept more than one type of rechargeable chemistry. NiCd and NiMH are very similar, except in capacity and charge rate. But those two differences preclude using the same charger on both. It is best to use the chemistry your device was designed for. Refer to your owner's manual to find out which rechargeable battery types your particular device supports, or simply use our BatteryFinder to find your device. It will automatically list all of the battery types supported by your machine.
My new battery isn't charging. Why is that?
New batteries are shipped in a discharged condition and must be charged before use. We generally recommend an overnight charge (approximately twelve hours). Refer to your user's manual for charging instructions. Rechargeable batteries should be cycled - fully charged and then fully discharged - 2 to 4 times initially to allow them to reach their full capacity. (Note: it is perfectly normal for a battery to become warm to the touch during charging and discharging).
New batteries are hard for your device to charge; they have never been fully charged and are therefore "unformed." Sometimes your device's charger will stop charging a new battery before it is fully charged. If this happens, simply remove the battery from your device and then re-insert it. The charge cycle should begin again. This may happen several times during your first battery charge. Don't worry; it's perfectly normal.
Should I recycle my old battery? How?
NiCd, NiMH and Li-ion batteries should be recycled. Be environmentally conscious - do NOT throw these batteries in the trash.
If you don't know where your local recycling facility is, call the Portable Rechargeable Battery Association at 1-800-822-8837. They will provide you with the address of the recycling center nearest to you.
Does rapid charging reduce the life of batteries?
No. Fast chargers will simultaneously rapidly charge and condition the battery thus extending the life of the battery. Overcharging and overheating a battery will adversely affect the life and performance of a battery.
