Frequently Asked Questions (FAQ) About Batteries
- How are batteries rated and what do the ratings mean in battery selection?
- How does the Cold Cranking Amperage rating help me select a battery?
- What does the Reserve Capacity rating mean and how does it apply to deep cycle batteries?
- What is battery cycle life?
- What is the difference between deep cycle batteries and starting batteries?
- What is the difference between series battery connections and parallel battery connections?
- Does overcharging damage batteries?
- Does over-discharging damage batteries?
- How can I evaluate the health and charge state of a battery?
1) BATTERY RATINGS
How are batteries rated and what do the ratings mean in battery selection?
The most common battery rating is the AMP-HOUR RATING. This is a unit of measurement for battery capacity, obtained by multiplying a current flow in amperes by the time in hours of discharge. (Example: A battery which delivers 5 amperes for 20 hours delivers 5 amperes times 20 hours, or 100 ampere-hours.)
Manufacturers use different discharge periods to yield an different Amp-Hr. Rating for the same capacity batteries, therefore, the Amp-Hr. Rating has little significance unless qualified by the number of hours the battery is discharged. For this reason Amp-Hour Ratings are only a general method of evaluating a battery's capacity for selection purposes. The quality of internal components and technical construction within the battery will generate different desired characteristics without effecting its Amp-Hour Rating. For instance, there are 150 Amp-Hour batteries that will not support an electrical load overnight and if called upon to do so repetitively, will fail early in their life. Conversely, there are 150 Amp-Hour batteries that will operate an electrical load for several days before needing recharging and will do so for years. The following ratings must be examined in order to evaluate and select the proper battery for a specific application: COLD CRANKING AMPERAGE and RESERVE CAPACITY are ratings used by the industry to simplify battery selection.
2) COLD CRANKING AMPERAGE:
How does the Cold Cranking Amperage rating help me select a battery?
(CCA) is the maximum amperes that can be continuously removed from a battery for 30 seconds at 0°F before its voltage drops to unusable levels. A 550 CCA battery can supply 550 amperes for 30 seconds at 0°F. This rating is only useful in the selection of engine starting batteries.
NOTE: Do not confuse Cold Cranking Amperage (CCA) with Marine Cranking Amperage (MCA) or Cranking Amperage (CA). MCA and CA is a higher battery rating measured at warmer temperatures.
3) RESERVE CAPACITY
What does the Reserve Capacity rating mean and how does it apply to deep cycle batteries?
Reserve capacity is the number of minutes a battery can maintain a useful voltage under a 25 ampere discharge. The higher the minute rating, the greater the battery's ability to run lights, pumps, inverters, and electronics for a longer period before recharging is necessary. The 25 Amp. Reserve Capacity Rating is more realistic than Amp-Hour or CCA as a measurement of capacity for deep cycle service. Batteries promoted on their high Cold Cranking Ratings are easy and inexpensive to build. The market is flooded with them, however their Reserve Capacity, Cycle Life (the number of discharges and charges the battery can deliver) and Service life are poor. Reserve Capacity is difficult and costly to engineer into a battery and requires higher quality cell materials.
For instance, Rolls, Surrette and Lifeline use thicker lead grids (the plate's skeletal structure) to support additional positive plate oxides which are compressed into a denser form in order to add battery reactive material for greater Reserve Capacity and Cycling Performance. In addition, these plates are separated by indestructible separators. These mats hold the active oxides tightly in place during the cubical plate expansion which occurs during deep discharging, instead of allowing the oxides to shed off and precipitate to the bottom of the battery. Construction materials such as those raise the Reserve Capacity of a battery and increase the battery's Cycle Life.
4) CYCLE LIFE
What is battery cycle life?
One cycle of a battery is a discharge from full charge to full discharge and a return to full charge again. The total number of cycles a battery can perform before failure is called its Cycle Life. Most battery manufacturers will not discus the Cycle Life of their product. Many advertised Deep Cycle batteries have not been tested, or, which is the case with cranking batteries, were never designed for long Cycle Life .
5) DEEP CYCLE BATTERIES
What is the difference between deep cycle batteries and starting batteries?
Unfortunately, the term Deep Cycle has been overused by the battery industry as a sales tool to imply a heavy duty product. This has led to confusion and difficulty in battery selection. One must understand that any battery may be termed deep cycle as all batteries may be fully discharged and charged. However, a true deep cycle battery, such as Rolls or Lifeline, is capable of thousands of these hard cycles during its life without losing its capacity. Comparatively, many advertised deep cycle batteries composed of thin plates, excessively porous separators, and low density plate oxides will suffer permanent capacity loss after a few dozen cycles and will shortly sulfate or shed plate material and fail. Batteries without substantial materials designed for true deep-cycling will lose more than half of their capacity after only a few cycles. A 200 Amp-hour battery will shortly become a 100 Amp-hour battery for the remainder of its shortened service life. What initially may seem to be an inexpensive battery to purchase, now costs twice as much per Amp-hour. True Deep cycle batteries will perform well as cranking batteries, however, cranking batteries will not survive deep cycle use.
Deep cycle batteries can be used in any application and exhibit a long service life, while cranking batteries are limited to starting applications only. Cranking batteries exhibit poor service life in cycling applications.
6) INCREASING CAPACITY THROUGH SERIES AND PARALLEL CONNECTIONS
What is the difference between series battery connections and parallel battery connections and how do they increase battery capacity and voltage?
In the SERIES CONNECTION, batteries of like voltage and Amp-Hour capacity are connected to increase the Voltage of the bank. The positive terminal of the first battery is connected to the negative terminal of the second battery and so on, until the desired voltage is reached. The final Voltage is the sum of all battery voltages added together while the final Amp-Hours remains unchanged. The bank's Voltage increases while its Amp-Hours, Cranking Performance and Reserve Capacity remain unchanged.
In the PARALLEL CONNECTION, batteries of like voltages and capacities are connected to increase the capacity of the bank. The positive terminals of all batteries are connected together, or to a common conductor, and all negative terminals are connected in the same manner. The final voltage remains unchanged while the capacity of the bank is the sum of the capacities of the individual batteries of this connection. Amp-Hours Cranking Performance and Reserve Capacity increases while Voltage does not.