Battery Terms and Abbreviations - Glossary
When describing batteries and their features and characteristics, many abbreviations are used. Knowing their meanings is very important, because that is the difference between getting the right battery and the wrong battery. And the wrong battery often can cause much more damage than its money worth ...
Here are several, most common abbreviations used to describe marine ant other batteries and their characteristics:
Capacity (Ah or mAh - Ampere/Amp hours) - this value describe how many Amps (A) or milli-Amps (mA) battery can provide for 20 hours, before the voltage drops below certain level (drop-off or cut-off voltage). Draining the battery below cut-off voltage could cause permanent damage to the battery - cut-off voltage primarily depends on the battery chemistry, but also on the battery construction and design. While small button cell batteries have capacity in the mAh range, large deep cycle marine/RV batteries have capacity values in the range of 100s of Ah.
For example, the capacity of lead-acid batteries is determined by how many amps of current can new, fully charged 12V battery at 80°F (~25°C), deliver for 20 hours without its voltage falling below 10.5V.
RC (Reserve Capacity) - this value is number of minutes that a new, fully charged battery (at 80°F, ~25°C) can deliver 25A current and maintain voltage above its cut-off value (10.5V for lead-acid batteries). RC value is important for deep cycle batteries used in marine applications (for trolling motors, for example), RVs (in-house batteries), solar systems (off-the-grid applications) etc.
CA (Cranking Amps) or MCA (Marine Cranking Amps) - maximum current that a new, fully charged, 12V battery can deliver for 30 seconds, with the voltage NOT dropping below 7.2V at 32°F (0°C). Lead-acid battery packs having other nominal voltages (6V, 8V, 24V etc) generally calculate their cut-off voltage for MCA value by using 1.2V per single cell. MCA value shows how good is the battery for marine cranking/starting applications. Although 30 seconds appear too long for starting applications, note that this is the value for brand new, fully charged battery - in real life, battery must perform properly even after being used for some time and without being fully charged!
CCA (Cold Cranking Amps) - maximum current that a new, fully charged, 12V battery can deliver for 30 seconds, with the voltage NOT dropping below 7.2V, at 0°F (-18°C). Cold Cranking Amps (CCA) is value more important for cars, trucks and other vehicles during winter than Marine Cranking Amps - even when the sea is frozen, only the surface is frozen, allowing the boat's battery compartment (which is usually low in the vessel) to be relatively warm (at least warmer than outside temperature).
HCA (Hot Cranking Amps) - maximum current that a new, fully charged, 12V battery can deliver for 30 seconds, with the voltage NOT dropping below 7.2V, at 80°F (27°C).
If you are looking for a lead-acid battery that has only the CCA rating, and you want to know it's MCA or HCA value, it is good to know that CCA, CA/MCA and HCA are related (approximately):
CCA = HCA X 0.60 = MCA x 0.80
HCA = CCA x 1.66 = MCA x 1.33
MCA = CCA x 1.25 = HCA x 0.75
This is logical, since CCA describe performance of AGM/gel cell/flooded cells lead-acid batteries at lower temperature and lead acid batteries are more efficient and perform better on higher temperatures (up to the point, of course).
Flooded (wet) lead acid batteries use liquid electrolyte, which can be spilled out. Depending on the use and temperature, distilled water must be periodically added to keep the batteries function properly and to avoid the damage. Although flooded cell batteries have certain advantages, SLA batteries are IMHO the way to go for most of the applications.
Valve-regulated lead–acid (VRLA) batteries have safety valve inside battery which opens at certain pressure and let oxygen flow from positive plate to negative plate to recombine with hydrogen and create water. Such VRLA Sealed Lead Acid (SLA) batteries are maintenance free batteries and are used more and more on various vehicles, off-the-grid applications, boats and yachts.
Gel Cell lea-acid batteries use electrolyte in the form of gel - diluted sulfuric acid is mixed with fumed silica to create gel which is placed between battery plates. Gel cell lead-acid batteries are non-spillable batteries and most of them can safely operate regardless of the position.
Absorbed Glass Mat (AGM) lead-acid batteries use electrolyte that is held in the glass mats made out of woven, very thin glass fibers. As such, AGM lead-acid batteries are also a type of non-spillable batteries and most of them can safely operate regardless of their position.
Maximum drain current is maximum current that battery can regularly provide for certain period of time without being damaged. This value is indicator if the battery is optimized for power, for endurance, or it is of balanced design.
Maximum pulse drain current is maximum current that battery can periodically provide for short period of time without being damaged. This value is provided in Amperes and seconds, for example, 15 Amps for 3 seconds, 30 Amps for 1 second and similar.
Maximum charging current is the maximum current that can be used for charging the battery without it getting damaged. Certain battery chargers prevent damage by featuring forced cooling of the batteries, but nonetheless, one should NOT use larger than recommended currents for charging the batteries - better safe than sorry.
Maximum charging voltage is the maximum voltage that should be applied during the charging. When the battery reaches maximum charging voltage, charging should stop in order to prevent any possible damage to the battery.
There are many other terms and abbreviations used in technical documents when describing the features and functionalities of the batteries, but, these are the most common ones.
Knowing these terms and abbreviations can help significantly when looking for the right battery equivalent and replacement.