Braille’s Batteries are individually tested proir to shipping. Find out how the final step before shipping helps make a more reliable and better performing battery for you. Conductance testing is now a part of the IEEE standard for testing sealed valve regulated lead acid batteries. Braille uses the World’s most popular testing company, Midtronics to test and calculate data to provide true performance numbers for your application.

What is conductance?
Conductance is a unique electrical measurement that determines the ability of a battery to transmit current through its internal structure. As such, it gives a direct relationship to battery power. Internal conductive battery components include battery grids, active material and connectors that conduct electronic current as well as sulfuric acid electrolyte that conducts ionic current between and within the plates and plate separators.
Conductance is measured by probing the battery with a small AC current ripple that generates a small AC voltage response. Conductance is the relative ratio of the variation in current with the variation in voltage. It is a powerful tool for providing rapid and pertinent battery information without the need of discharging the battery with high currents that can be dangerous and leave the battery in a depleted condition.
In standby applications, various test data have shown that at low frequencies, the conductance of a battery is an indicator of battery state-of-health showing a linear correlation to a battery’s timed-discharge capacity test result. This can be used as a reliable predictor of battery end-of-life.



What is ohmic testing technology?
In simplest technical terms, “ohmic” technology is based on Ohm’s law, which expresses the relationship between changes in voltage, current and resistance or conductance in an electrical circuit. Ohm’s law can be expressed as follows:
ΔV = I x R or I / G
where ΔV is a change in voltage in a circuit
I is the current in amps
R is the resistance in ohms
G is the conductance in siemens
Thus, ohmic technology in batteries attempts to use measured resistance or conductance values to determine the discharge characteristics of a battery under load. Lower conductance equates to a reduced ability to transmit current for a given drop in battery voltage. Thus the measurement of ohmic factors can be used to assess battery load performance.



Why test conductance?
Through years of laboratory and field-based research, conductance has been found to correlate directly with battery capacity as measured in a timed discharge test. This correlation is nearly linear, meaning that if conductance can be measured, timed-discharge capacity can be predicted as a function of the change in conductance. Since voltage and specific gravity testing are not predictive, timed discharge testing is very time-consuming and expensive, and impedance testing does not correlate directly and linearly with timed discharge capacity. Conductance testing is a very rapid, effective and economical alternative.


How is the conductance test performed?
Simply by connecting the two test set leads to the positive and negative posts of the cell or battery under test, a measurement is taken in a matter of seconds. There is no need for additional leads to be connected to the ends of the string, or for clamp-on current measurements. A conductance measurement, often abbreviated as “G”, is displayed in Mhos or Siemens.


What is the difference between Mhos and Siemens?
None. Mhos and Siemens are interchangeable terms for the same thing - the unit of measure of conductance.


How can conductance readings be used?
A significant number of tests on a variety of valve regulated lead acid (VRLA) batteries demonstrate that conductance is predictive of battery state-of-health. Since conductance is directly related, and very nearly linear, with timed-discharge capacity, a reading of the percentage of a known conductance reference value of a new, good battery is a reliable predictor of a capacity test result. The conductance tester gives a quantitative measurement in Mhos (or Siemens), as well as a qualitative indication (percent of reference) of a battery as related to a standard.


Are conductance readings difficult to interpret?
Unlike other testing techniques that require interpretation and mathematical calculation, conductance readings can be read instantly and can be related directly to the condition of the battery being tested.


Since the qualitative conductance test requires a standard, how can that standard be established?
The most effective method for the establishment of a standard requires the performance of a timed discharge test to locate a cell or battery that performs to 100% of the rated discharge capacity. A conductance test can then be performed and a reference established. A sample of 30 or more new batteries can also be used to establish a standard. Without a set reference value, conductance testing can still be utilized to trend state of health, as batteries can be monitored through periodic conductance readings and the observation of deterioration over time.


Will the battery manufacturer have reference numbers for my batteries?
Many battery manufacturers now publish conductance reference or base-line values. If not, a specific reference value can be established during installation for a new, healthy battery. An average can also be used from a sample of batteries of the same model, manufacture date, installation date and service history as detailed in the operating guidelines and instruction manuals. Midtronics testers also provide tools for the establishment of reference values. Refer to the instruction/operating manual for more information on these features.


What if the batteries I am testing are really old? How do I determine what to use for a reference number?
For older batteries, combine conductance testing with a full physical inspection for any visible faults. Utilize the highest measurement as an initial benchmark and the string average as a starting point for comparison. If any batteries deviate by 30% below the highest jar, consider a discharge test to determine actual run-time.


Can conductance testing be used to evaluate the quality of inter-cell connections?
Yes. Since a conductance reading of a cell plus an inter-cell connection can easily be related to the conductance of the cell alone, conductance provides a very simple and reliable indication of the system’s inter-cell connection quality.


Can Midtronics conductance testers measure the condition of sealed valve-regulated batteries as well as flooded cells?
Yes. Correlation studies have been performed on a significant number of valve regulated AGM cells. These studies have shown that conductance test results are very predictive of battery timed discharge capacity, while voltage measurements are shown to be of little value. This data has been presented to a number of international organizations.

Can Conductance testing measure CCA?
The actual SAE J537 Cold Cranking Test is a manufacturing process control test applicable only on new, fully charged batteries. It does not produce an actual value of cold cranking amps (CCA), but is a pass/fail test based on the battery’s CCA test rating. The CCA rating is the discharge load, in amps, that a new, conditioned battery can supply for 30 seconds at 0°F/-18°C while maintaining a voltage of 1.2 volts per cell (7.2 volts per battery) or higher. Thus, the CCA test sets the minimum power requirement for a new battery as rated, which means that a battery rated at 500 CCA must measure 7.2 volts or above for 30 seconds when a load of 500 amps is applied at 0°F/ -18°C.
In automotive applications, the conductance of a new, fully charged battery under normal conditions can be directly related to its rated CCA, the industry gauge of starting power. Therefore, conductance can be translated into working units of CCA so that the power level of a battery can be compared to its cranking rating. The Midtronics CCA value derived from conductance does not, however, determine the actual Cold Cranking Amps of the battery because that test includes a lengthy discharge of 30 seconds at a very high current rate. The conductance CCA corresponds better to the starting current that the battery can normally deliver for a second or less normally needed to start a vehicle. In this regard, the conductance CCA can be considered even better than the cold cranking test. Cold cranking tests run on batteries taken from service often give poor results because they cannot sustain the long duration of discharge (30 seconds) that is not required to start a vehicle. The Midtronics CCA values are designed simply to mimic the initial starting characteristics of new batteries with a given CCA rating under the same operating conditions.
For example, if a battery that is rated at 600 CCA is measured at 500 CCA, it can be thought of as having similar starting characteristics of a new battery having a rating of 500 CCA if that battery is substituted with the test battery. It does not mean that the battery will pass a Cold Cranking Test at 500 CCA. It should also be remembered that the cranking power of all batteries increases with temperature and decreases with discharge and degradation.