What is HCA rating?
The full form of HCA is hot cranking amperes. It is the same thing as the MCA or the CA or the CCA, except that the temperature at which the test is conducted is 80°F.
What is the Amp Hour (Ah) rating?
An amp-hour is one amp for one hour, or 10 amp for 1/10 of an hour and so forth. It is amp X hours. If you have something that pulls 20 amp, and you use it for 20 minutes, then the amp-hours used would be 20 (amp) X .333 (hours), or 6.67 AH. The accepted AH rating time period for batteries used in solar electric and backup power systems (and for nearly all deep cycle batteries) is the "20 hour rate". This means that it is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours it supplies is measured. Sometimes ratings at the 6 hour rate and 100 hour rate are also given for comparison and for different applications. The 6-hour rate is often used for industrial batteries, as that is a typical daily duty cycle. Sometimes the 100 hour rate is given just to make the battery look better than it really is, but it is also useful for figuring battery capacity for long-term backup amp-hour requirements.
What is OHM'S Law?
OHM'S Law expresses the relationship between volts (V) and amperes (A) in an electrical circuit with resistance (R). It can be expressed as follows: V= IR Volts (V) = Amperes (I) x Ohms (R). If any two of the three values are known, the third value can be calculated using the above equation.
How can a standard automotive or marine battery's state of charger be accurately measured?
The state of charger of a lead acid battery is most accurately determined by measuring the specific gravity of the electrolyte. This is done with a hydrometer. Voltage also indicates the level of charger when measured in an open circuit condition. This should be done with a voltmeter. For an accurate voltage reading, the battery should also be allowed to rest for a period sufficient to let the voltage stabilize.
