BATTERIES

Frequently Asked Questions

For some battery terms, see the battery glossary

1. What are Gel Cell or SLA batteries?

Gel cell 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, long-life telemetry units, and camcorders. These batteries are 2 volts per cell so the common batteries are 4, 6, and 12 volt.

2. 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.

   

3. 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.

4. 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. 

5. How can batteries be connected?

Note: When interconnecting batteries (cells) they must be the same batteries (cells)!

Ways to connect batteries:

• 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, etc. The voltage of the assembled battery is the sum of the battery voltages of the individual batteries. So the batteries are connected: + to - to + to - to + to -, etc. The capacity of the battery is unchanged.

• Batteries may 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, etc. and 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, etc. So the batteries are connected: + to + to + and - to - to -. In this configuration, the capacity is the sum of the capacities of the individual batteries and voltage is unchanged.

  • For example, if you take 5 6V 10AH batteries and connect the batteries in series, you would end up with a battery array that is 30 Volts and 10AH. If you connect the batteries in parallel, you would end up with a battery array that is 6 Volts and 50AH. By the way, this is how ordinary auto batteries are made. 6 2volt cells are put in series to give 12v battery and the 6 cells are just enclosed in one case. Many ni-cad batteries are done the same way.

6. 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 tolorate 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).

7. 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 standing a long time in a discharged condition, operating at excessive temperatures, and prolonged under or over charging.

8. 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.

Battery Glossary

Battery: Two or more cells connected together.

Cell: An electrochemical system which converts chemical energy into electrical energy.

Primary cell: An electrochemical device which is discharged only once and then discarded. AA alkaline battery is great example.

Secondary cell: An electrochemical device which may be discharged and recharged a number of times. For example, Ni-cad batteries in a cellular phone.

Battery Capacity: The ampere hours available from battery.

Battery Float Voltage: A constant voltage applied to a battery to maintain the battery capacity.