What is a Gel Cell battery or Sealed Lead Acid battery?
Gel cell or sealed lead acid batteries have basically the same chemistry as wet or flooded cell batteries. The batteries' electrolyte is in a gelatin form and is absorbed into the plates. The battery is then sealed with epoxy. These batteries may be used in any position. They are exceptionally leak resistant. Applications include UPS devices, emergency lights, and wheelchairs. These batteries contain 2 volts per cell with common voltages of 4, 6, and 12 volts.
How are battery ratings used?
- Amp-Hour battery rating: This is the common rating of a battery. Amp-hour rating of battery capacity is calculated by multiplying the current (in amperes) by discharge time (in hours). Amp-hour battery rating is commonly when describing sealed lead acid batteries used in UPS systems, emergency lights and wheelchairs.
- 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 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 amps to a cut-off voltage of 1.75 volts per cell (10.5V on 12V battery). This rating measures more of a continuous load on the battery.
What is a battery cycle?
Cycle life is measured by the amount of times a battery may be charged and discharged. Every time a battery is charged and discharged, it uses one cycle. Cycle life is very important in battery applications such as laptop batteries and emergency light batteries. A NiCad 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 such as a battery powered trolling motor on a fishing boat.
How can batteries be connected?
Note: When interconnecting batteries (cells), they must be identical in voltage and amp rating!
- Batteries may be connected in series. The positive terminal of the first battery is connected to the negative terminal of the second battery; the positive terminal of the second is connected to the negative of the third, and so on. The voltage of the assembled battery is the sum of the individual batteries. The batteries are connected: + to - to + to - to + to -, etc. The capacity of the battery is unchanged.
- Batteries may also be connected in parallel. The positive terminal of the first battery is connected to the positive terminal of the second battery, the positive terminal of the second is connected to the positive of the third; the negative terminal of the first battery is connected to the negative terminal of the second battery, the negative terminal of the second is connected to the negative of the third and so on. The batteries are connected: + to + to + and - to - to -. In this configuration, the capacity is the sum of the individual batteries and voltage is unchanged.
- For example, (5) 6V 10AH batteries connected in series produces a battery array that is 30 Volts and 10AH. Connecting the batteries in parallel produces a battery array that is 6 Volts and 50AH. Ordinary auto batteries are designed in the same fashion. Six 2-volt cells are arranged in series to produce a 12v battery. Many NiCad batteries are arranged in the same way.
Does overcharging cause damage?
Overcharging occurs when the total capacity removed has been replaced by recharging and the battery remains on charge. This overcharging creates excessive heat that 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 battery discharging can cause damage to a battery. The amount of discharge a battery can have without damage depends upon its chemistry. In general, a lead acid battery will not tolerate as deep a discharge as a NiCad or NiMh battery. Sealed lead acid batteries function best if they are discharged to only about 85% of nominal voltage (10.2V on 12V battery).
What is sulfation of batteries?
Sulfation is the formation or deposit of lead sulfate on the surface and in the pores of the active material of the batteries' lead plates. If the sulfation becomes excessive and forms large crystals on the plates, the battery will not operate efficiently and may not work at all. Common causes of battery sulfation are battery inactivity in a discharged condition, operating the battery at excessive temperatures, and prolonged under or over charging.
What battery chemistries are available?
Sealed lead acid, flooded lead acid (automotive type), NiCad, alkaline, silver oxide, lithium, mercury (no longer available in the US), manganese-dioxide, zinc-air, and NiMH.