Batteries

This week, we worked on a bettery at the workshop. The battery on the car is to supply electrical current to the stator motor which cranks the engine and to all accessories while the engine is off.

There are a number of different batteries, conventional, maintenance free, gel cell, etc, the one we worked on was conventional lead acid batteries.

To understand a lead acid battery better, .there are 6 plates inside of the battery casing when you remove the battery cover, 3 positive and 3 negative are alternated, each set of 6 plates has a charge of 2.1V (volts), 6 sets which total to 12.6V



to inspect the battery, first you must first check the battery specifications, take visual checks, check the electrolyte levels, battery open voltage (OCV) test battery electrolyte specific gravity, high rate discharge test using a load tester. seems like a lot? may be, but it must be done!


lets start with the battery specifications, these are labelled on a sticker on the side of the battery, the battery specs which i got were.
make: Repco
battery number: NS402L
Battery capcity in Cold Cranking Amps (CCA) :310
type of battery: Conventional
Electrolyte accessibility: Yes

Visual check
terminals are tight and clean: No
does the battery show signs of swelling? (caused by over charging): No
Check for corrosion under mounting clamps: No
what areas need attention? terminal corrosion need to be sanded off, electrolyte leakage needs to be cleaned with soda water.

Electrolyte levels
while carrying out this test, make sure you have thick rubber gloves and safety glasses, that no part of your skin is exposed (acid burns is no joke!), that there is a water supply to clean your self if anything should occur.
to check the electrolyte level, you must remove the cell caps and use the srynge to check, they will either be high, ok or low

Our group findings
cell 1ok cell 2ok cell 3ok cell 4ok cell 5ok cell 6ok

OCV test
before taking an OCV test, you must remove the surface charge, you can do this by turning the headlights on for about 1 minute. after that, use a voltage meter set to DC, take a reading over the terminals. set the range on the meter to 20V (unless you have an autoranging meter). i had received a measurement of 12.9V, this is overcharged.

Battery Electrolyte Specific Gravity
to check the electrolyte specific gravity, use the srynge to perform a hydrometer test, write down the readings for each cell and also the colour (clear or murky/white'ish)
our readings were

Cell: cell 1 cell 2 cell 3 cell 4 cell 5 cell 6

reading: 12.25 12.25 12.50 12.50 12.50 12.25

colour: murky murky murky murky murky murky

the specific gravity variation i got from my test is 0.025, which is allowable since the specification of the battery is 25-50

high rate discharge test using a load tester

to do this test, the battery must be atleast 50% charged (12.4V) to be able to supply cranking voltage, if it isn't, charge the battery using a quick charger.

firstly, you must first determine the load current to apply, we have got 155A (1/2 of the CCA of 310)

the specified voltage to be held while load is applied is 9.5V, i had 10.8V

you apply the load for 10 seconds

We also used a Digital Battery Tester. It is a hand-held tool, designed to test lead-acid batteries used in the modern motor vehicle. its ranges include Capacity in cold cranking amps(CCA)'s, Voltage, Temperature in which the tester will operate correctly, Minimum voltage a battery must be able to deliver before a successful test can occur. To check the battery with it, turn the ignition key off, not in the accessories position, then connect the red clip to the positive and black clop to the negative terminals. So then the digital gauge will automatically show up.
The reading shows SAE with 460CCA's. then we move on to the cold test by simply push the cold test button. O.C.V of the battery is 12.86V with 300CCA's which shows pass.