Let Us Understand Battery Leak Testing
By the author of the Amazon Bestseller Book 'Batteries Demystified', Podcaster, & Expert in Lead Acid Battery Manufacturing Processes and Machines
After complete assembly, the air pressure testing of a battery before filling acid in the battery is done to check the quality of the sealing of the cover to the container. This test is done on lead acid batteries irrespective of the sealing method, i.e., it is to be done on bitumen-sealed and heat-sealed batteries. The only batteries on which this test was not mandatory were a specific type of 2-Volt stationary cells made in hard rubber containers. With the advent and popularity of 2-Volt stationary cells made in transparent SAN containers, which are of the sealed type and where the batteries are specified to be leak-proof, the Air Pressure Test is a mandatory requirement to be done.
The Air Pressure Test is a test to be done in a particular manner for a specified duration, subjecting the cells to a prescribed pressure such that the decay in pressure allowed after the specified duration lapses is minimal and within very narrow limits.
As such, the specified pressure is low but high enough to bulge the container's external walls and subject the intercell partitions to adequate pressure. The pressure decay allowed by the Indian and International Standards is similar, and the permitted range is a microleak.
Due to the above reasons, the equipment used for leak testing
• must be such that it is sensitive,
• must measure and display minor variations,
• must record and give audio-visual alarms for alerting the operator,
• must give printouts for analysis and corrective action,
• must aid in preventive action,
Since the standards prescribe that air leakage over 15 seconds needs to be monitored, it is necessary that the machine
fills the air to the prescribed pressure
stops filling after the required pressure has been reached
starts the test only after the cell has been sufficiently pressurized and after no air is coming in further
Keeps the test going on for 15 seconds
monitors the pressure drop
Relays the correct results
records the data for retrieval later
ensures that all the batteries that are manufactured are tested
provides printed data for records as well as analysis
Usually, in assembly line production, the heat sealing of a 12-Volt battery takes less than a minute. In most small industries with minimal production, say 50 to 200 batteries per shift, the testing is done on all six cells of a 12-Volt battery on a cell-by-cell basis.
Considering the process to be followed as explained above and to meet the test duration of 15 seconds per cell per Indian & International Standards, the minimum duration required to test one cell shall be theoretically 30 seconds. Thus, testing six cells must take at least 3 minutes.
However, we often observe that the operation is going on in a synchronized manner. The batteries being inter-cell welded and heat-sealed online within a minute are also air pressure tested within a minute, despite being tested for leaks on a cell-by-cell basis. Less than 10 seconds is allotted to each cell on line for air to fill, stabilize, test, and exhaust. The incoming air is probably only being filled, and it gets exhausted from the vent hole when the air pipe is fitted on for testing for the next cell opening. The entire test is a farce and does not give any indication unless there is a gross leak in the sealing.
The only way to complete Air Pressure Testing within a minute and to detect micro leaks and to know whether the leakages are through partitions or side walls is to have a tester which has two channels, such that the first channel fills air into alternate cells i.e. cells 1,3 and 5 first, completes the testing of these three cells, exhausts the air and then fills air into the cells 2,4 and 6 next, completes the testing of these three cells, exhausts the air and gives you reports of both the channels.
All medium-scale industries, large industries, and battery manufacturers that are aware of the test requirements mentioned in the standard specifications use only such equipment.
The testing of leakage attains importance because leakage of acid from the battery external walls, from between the container and cover sealing, can lead to
Spillage of acid → resulting in corrosion around the battery
lessening of electrolyte → resulting in a need for frequent top-up
frequent top up with water → resulting in reduction of acid sp gravity
reduction of acid sp. gravity → resulting in a voltage drop in those cells in which sp. gravity is low due to spillage and frequent water top-up
Thus, the battery ends up as a failed battery despite the battery.
Having excellent input materials
having been made with costly components from renowned vendors
The process of manufacture is being supervised properly
being made on good machines
Having a sufficient quantity of expensive material.
Further, let us presume that there is no leakage from the external walls from in between the container and cover sealing. During the testing process, after sealing, some industries put a soap solution in place to test the external leakage. However, no such physical test is possible for inter-partition leaks during such quick test methods. In cases where interpartition leaks are undetected and such defective automotive batteries fitted on vehicles are being used, the voltage of the 12-volt battery becomes 10 Volts when two adjacent cells behave as one cell due to their interpartition not being hermetically sealed.
To add to the battery manufacturer’s problems, the operators on many assembly lines, supervisors, and top management presume that heat sealing is a fully automatic process. They confidently say that once the parameters of time and temperature are set and the first few batteries roll out from the assembly line without any leakage, the entire day’s production is bound to be leak-proof. Hence, they check the first few batteries and accept the rest without testing.
The various other parameters that can go wrong in a heat sealing machine and which escape the battery manufacturer’s attention are
Change in input A.C. Voltage → leading to change in mirror temperature
Change in container/cover input → leading to Melt Flow Index variation, needing a change in material batch to temperature setting
Bent covers or containers bulging → leading to misalignment of the heating of the container/cover edges in or out
Bent containers partitions → leading to inter-partition leaks
Improper & tight assembly of some → leading to misaligned partitions and improper sealing of cells/ batteries at container partitions to cover partition edges
Hence, it is very important to ensure that 100% of the batteries produced are tested for leakage, not the first few batteries or sample batteries on a random basis.
The savings accrued due to proper battery leak testing—avoiding the quick test methods and testing following the prescribed standards—are substantial.
Equipment that prints a record of the number of batteries tested and the Sr. Nos. of the batteries, with a detailed summary tallying the number of batteries produced per shift, eliminates the supervision of the operator assigned to test the batteries. Such equipment ensures quality production and substantially reduces rejection.
If you would like more details on Air Pressure Testing methods, standards, test reports, and suitable equipment, you can contact the author of this article.
TO GRAB YOUR FREE COLOR COPY OF THE BATTERY MANUFACTURING PROCESS FLOW CHART, CLICK ON THE LINK BELOW:
✔️https://ramesh-natarajan.ck.page/1d1909eaef
You can visit my website to 👀read similar blogs and articles, 👂hear my podcasts, and 🎥see videos about batteries and related subjects by clicking the link below:
To ✍️ write to me with your comments and suggestions, please note my email below:
✔️ rameshnkailad@gmail.com
To buy my books 📒, please click on one of the links given below:
✔️https://relinks.me/9390661692 ️or https://relinks.me/B0BNXL1854