Answer SSEP Question 40
Q40.
With reference to a bank of emergency lead acid batteries:
A. State the
conditions of the battery bank if the specific gravity of a number of
cells in the bank is in the region of 1.11 with an ambient temperature
of 160°C;
B. Describe a systematic procedure for checking the conditions
of the battery bank if it is divided into section for charging;
C.
Describe the necessary routine maintenance.
Answer:
A. Conditions of the battery bank if the specific gravity of a number
of cells in the bank is in the region of 1.11 with an ambient
temperature of 16°C:-
SG of acid is temperature dependent. If the temperature is very cold or very hot this can lead to incorrect readings. The specific gravity of the electrolyte varies with temperature; consequently, hydrometer readings should be corrected as follows:
Note the Specific gravity values measured for lead acid batteries are based on an ambient temperature of 15°C. Corrections to the SG value at any other ambient temperature are as follows;
1. Add 0.007 to reading for each 10°C above 15°C
2. Subtract 0.007 from the reading for each 10°C below 15°C.
Given temperature is below 16°C, therefore there is not much of correction to the specific gravity measured.
The following shows the approximate state of charge at various specific gravities at 77°F / 25°C.
According to the table the charge on the battery bank ZERO and completely discharged.
B. Systematic procedure for checking the conditions of the battery bank If it Is divided Into section for charging: -
(a) If the batteries are connected into number of banks, It is recommended to conduct a test an wise, individual battery and as a whole set.
(b) Each bank shall be disconnected one by one and conduct load testing and capacity testing on each bank to ascertain the condition of that particular bank of batteries, any high deviation in voltage reading or internal resistance reading measure should be thoroughly checked by disconnecting each and every single battery from the bank and individual battery shall be tested.
(c) Un equal battery or a bank will not only cause less capacity but also reduces the life of batteries.
(d) Such tests shall be carried out in regular intervals to ascertain the conditions of battery/banks and replace the faulty ones immediately to protect the other batteries. Inspection shall include the following tests:
Visual Inspections
Impedance testing
Voltage recording
Specific gravity: recording/check electrolyte levels (flooded lead acid batteries)
Check for unintentional battery grounds
Load bank testing to verify proper operation of individual cells or blocks of cells
Constant KW or predetermined sustained current load bank testing to determine battery system capacity
C. Necessary routine maintenance:-
(a)Monthly check if the electrolyte level gets below the plates, electrolyte level below the plates will damage the batteries.
(b) Equalize the battery bank 4-6 times a year. Equalization is basically a controlled overcharge that extends your battery life by knocking deposits off the plates. Charge the batteries at your normal rate, but don't stop when meter shows full charge. Keep charging for 2 or 3 hours longer. You may take specific gravity readings 30 minutes apart and continue the process until the readings stop increasing.
(c) As a 3-monthly routine, turn off the main power switch and;
(d) Check the electrolyte level. Do this when the batteries are -not- discharged, and wait a couple hours after charging for the hydrogen bubbles to disperse.
(e) The batteries should have full and low marks--sometimes the full mark is an inner plastic "shelf" with a hole in it to see the electrolyte level.
(f) Wear safety goggles and rubber gloves Fill ONLY with distilled water to the "full" mark DO NOT add acid!
(g) Clean the battery tops with rags dipped in a baking soda and water solution. DO NOT let this cleaning solution get Into the batteries, be careful of the vent holes in the caps on each cell, as cleaning solution can enter the battery here.
(h) Check for corrosion on all the battery terminals, if any terminals are encrusted in green deposits, Make sure main power switch is off and all charging circuits, Carefully disconnect wires from the dirty terminal and clean off the gunk with a wire brush. Wear a mask if necessary. - Apply anti-corrosion paste to the terminal and Reconnect the wires.
SG of acid is temperature dependent. If the temperature is very cold or very hot this can lead to incorrect readings. The specific gravity of the electrolyte varies with temperature; consequently, hydrometer readings should be corrected as follows:
Note the Specific gravity values measured for lead acid batteries are based on an ambient temperature of 15°C. Corrections to the SG value at any other ambient temperature are as follows;
1. Add 0.007 to reading for each 10°C above 15°C
2. Subtract 0.007 from the reading for each 10°C below 15°C.
Given temperature is below 16°C, therefore there is not much of correction to the specific gravity measured.
The following shows the approximate state of charge at various specific gravities at 77°F / 25°C.
| Charged | Specific Gravity |
| 100% | 1.265-1.275 |
| 75% | 1.225-1.235 |
| 50% | 1.190-1.200 |
| 25% | 1.155-1.165 |
| 0% | 1.120-1.130 |
B. Systematic procedure for checking the conditions of the battery bank If it Is divided Into section for charging: -
(a) If the batteries are connected into number of banks, It is recommended to conduct a test an wise, individual battery and as a whole set.
(b) Each bank shall be disconnected one by one and conduct load testing and capacity testing on each bank to ascertain the condition of that particular bank of batteries, any high deviation in voltage reading or internal resistance reading measure should be thoroughly checked by disconnecting each and every single battery from the bank and individual battery shall be tested.
(c) Un equal battery or a bank will not only cause less capacity but also reduces the life of batteries.
(d) Such tests shall be carried out in regular intervals to ascertain the conditions of battery/banks and replace the faulty ones immediately to protect the other batteries. Inspection shall include the following tests:
Visual Inspections
Impedance testing
Voltage recording
Specific gravity: recording/check electrolyte levels (flooded lead acid batteries)
Check for unintentional battery grounds
Load bank testing to verify proper operation of individual cells or blocks of cells
Constant KW or predetermined sustained current load bank testing to determine battery system capacity
C. Necessary routine maintenance:-
(a)Monthly check if the electrolyte level gets below the plates, electrolyte level below the plates will damage the batteries.
(b) Equalize the battery bank 4-6 times a year. Equalization is basically a controlled overcharge that extends your battery life by knocking deposits off the plates. Charge the batteries at your normal rate, but don't stop when meter shows full charge. Keep charging for 2 or 3 hours longer. You may take specific gravity readings 30 minutes apart and continue the process until the readings stop increasing.
(c) As a 3-monthly routine, turn off the main power switch and;
(d) Check the electrolyte level. Do this when the batteries are -not- discharged, and wait a couple hours after charging for the hydrogen bubbles to disperse.
(e) The batteries should have full and low marks--sometimes the full mark is an inner plastic "shelf" with a hole in it to see the electrolyte level.
(f) Wear safety goggles and rubber gloves Fill ONLY with distilled water to the "full" mark DO NOT add acid!
(g) Clean the battery tops with rags dipped in a baking soda and water solution. DO NOT let this cleaning solution get Into the batteries, be careful of the vent holes in the caps on each cell, as cleaning solution can enter the battery here.
(h) Check for corrosion on all the battery terminals, if any terminals are encrusted in green deposits, Make sure main power switch is off and all charging circuits, Carefully disconnect wires from the dirty terminal and clean off the gunk with a wire brush. Wear a mask if necessary. - Apply anti-corrosion paste to the terminal and Reconnect the wires.
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