Frequently Asked Questions about Batteries & UPS Systems

What are gel batteries or SLA batteries?
Gel or sealed lead acid batteries are basically the same chemistry as a wet (flooded cell) battery. The batteries' electrolyte is in a gelatin form and is absorbed into the plates and the battery is sealed with epoxies. These batteries may be used in any position and the batteries are exceptionally leak resistant. Battery uses are UPS, emergency lights, and camcorders. These batteries are 2 volts per cell so the common batteries are 4, 6, and 12 volt.

What are battery ratings and how battery ratings are used?
Some of the common battery ratings are
Amp-Hour battery rating This is a common battery rating of batteries. Amp-hour rating of battery capacity is calculated by multiplying the current (in amperes) by time (in hours) the current is drawn. Amp-hour battery rating is commonly used on sealed lead acid batteries used in UPS systems, emergency lights and camcorders.
For example A battery which delivers 2 amperes for 20 hours would have a 40 amp-hour battery rating (2 * 20= 40).
Cold Cranking Amperage battery rating CCA is the discharge load in amps which a battery can sustain for 30 seconds at 0 degrees F. and not fall below 1.2 volts per cell (7.2V on 12V battery). This battery rating measures a burst of energy that a car needs to start on a cold morning. This rating is used mainly for rating batteries for engine starting capacity and does not apply to NiCad batteries, NiMH batteries or Alkaline batteries.
Reserve capacity battery rating RC is the number of minutes a new, fully charged battery at 80 degrees F. will sustain a discharge load of 25 ahps to a cut-off voltage of 1.75 volts per cell (10.5V on 12V battery). This battery rating measures more of a continuous load on the battery.

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What is a battery cycle?
Battery cycle A cycle of a battery is a discharge plus a charge. For example, if your battery is full charged and you apply load (use) the battery and it discharges some (maybe completely) and then recharge to full battery charge; that is one cycle. Cycle life is the total number of cycles a battery yields. The cycle life is very important in battery applications such as laptop batteries and emergency light batteries. A Ni-cad battery has a cycle life of 500-1000 or more cycles.

What are deep cycle batteries?
Deep-cycle batteries typically feature thick plates with a high-density active material. The thick battery plates allow for reserve energy to be stored deep within the battery plate and released during slow discharge such as trolling or electronic instrument use. The high-density active material remains within the batteries' plate/grid structure longer, resisting the normal degradation found in cycling conditions. They are typically used where the battery is discharged to great extent and then recharged. For example, a battery powered trolling motor on a fishing boat.

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How does overcharging damage batteries?
Overcharging a battery occurs when the total capacity removed has been replaced by recharging and the battery remains on charge. This overcharging creates excessive heat which can cause the battery plates within the cells to buckle and shed their active material. The battery will react to the overcharge by producing an excessive amount of hydrogen and oxygen. These gases are the result of the breakdown of the water molecules within the electrolyte. The water that has been displaced by overcharging can be replaced in a serviceable (non-sealed) battery, but, in the maintenance-free sealed batteries, permanent capacity loss will result.
Excessive discharging a battery can also damage a battery. The amount of discharge a battery can have without damage depends upon the chemistry of the battery, but in general a lead acid battery will not tolerate as deep a discharge as a Ni-cad battery or Ni-mh battery. Sealed lead acid batteries function best if they are discharged to only about 85% of nominal voltage (10.2V on 12V battery).

What are some types of batteries?
A few types of batteries are Sealed Lead Acid, Flooded Lead Acid, Ni-Cad, Alkaline, Silver Oxide, Lithium, Mercury (not mfg in US any more), Manganese-Dioxide, Zinc-Air, and Ni-MH.

QUESTIONS ABOUT UPS SYSTEMS.
What is a UPS and how does is work?
An Uninterruptible Power Supply is a device that sits between a power supply (e.g. a wall outlet) and a device (e.g. a computer) to prevent undesired features of the power source (outages, sags, surges, bad harmonics, etc.) from the supply from adversely affecting the performance of the device.

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What is the difference between on-line and off-line?
On-line UPS implies that an electronic inverter is constantly supplying AC power to the load under all modes of operation. Off-line UPS supply input utility to the load during normal operation and revert to a battery-powered inverter during utility failures.

What is a bypass function?
In a UPS scenario, a bypass feature is in essence, a switch between the input and output of the device. It allows the routing or transfer of incoming power to the output bypassing any internal circuitry. The bypass function uses the A/C supply power as its standby source of power. This feature allows power to continue to flow to connected equipment if the UPS system encounters an internal error or overload condition. The UPS system will automatically transfer to the by-pass quickly to ensure that the connected equipment continues to operate.

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