A battery as we had earlier mentioned, is made up of cells connected in a series. In a series connection, when one cell fails, it affects the whole connection and the battery may fail. For such failures to be detected a battery intercell connection test can be conducted.
Such cases of battery failure due to a weak intercell connection are more common in lead posts which can cold-flow.
The plates in the cells make up the battery hardware and they need to be tightened to the low end of torque as per the guidance of the manufacturer.
It is always better to perform an electrical test of the cells using instruments. Torque wrenches are a mechanical means of tightening the mechanicals. The tests done before commissioning the battery will try to obtain low electrical resistance.
Importance of Battery Intercell Connection Test
The most commonly used equipment to test the intercell connection is the MOM tool or DLRO tool which easily confirms whether the connections have been done right. The main objective of doing the intercell connection test is to make sure that the intended discharge rates are met.
These tools apart from doing the intercell connection test, can help in identifying other errors in the battery that might have caused future failures and damage to equipment.
Why Perform an Intercell Connection Test?
The two objectives to be achieved through this test are:
- Validating the resistance of the intercell connection.
- Finding errors in top lead internal to the cells and therefore validating the intercell connection resistance.
The intercell connection resistance variation should be less than 10%. This is according to the IEEE recommendations. 10% approximates to 7 micro-ohms on a 70 micro-ohm intercell connection resistance.
Internal connections should be tested annually and the 10% of intercell connections should be tested quarterly. This is also according to the IEEE recommendations.
Measuring Intercell Connections In Multiple Post Batteries
For you to be in a position to identify errors in cell-to-lead connections this is what you need to do. Measure straight across both connections and then have the measurements taken diagonally so that the balances in the cells and connections are checked.
When you do the measurements only on one side straight across, you will not test for either intercell connection resistance defects or gross top lead defects.
Final Thoughts
Proper sizing of current-carrying components both in the cell and external to the cell needs to be done perfectly well when the current drawn is high. Batteries meant for power backup are made in such a way that they can handle high discharge rates of between 15-20 minutes.
Telecommunication CO battery, however, has a capacity of 500 Amp even though the discharge rate is low and can discharge for up to 8 hrs.
The bottom line is that in both cases, when an improper size and improperly maintained cell is used, the effects can be really dangerous.