I think you mean WD40 was used. It's commonly used as a lubricating oil. WD40 stands for Water Displacement Formula #40. Because it coats everything with a thin film of oil, WD40 should never be used on anything electrical or electronic.
If the WD40 is used to "clean" corroded contacts, the corrosion material, which conducts electricity, becomes suspended in the oil. Sometimes, this thin film of oil, along with the suspended conductive material, will conduct a small amount of electricity. This small amount of electricity leaking through the oil could be the cause of your ground fault.
Battery Voltage
Consider the battery voltage as a readout showing the charge on the battery. If the voltage on a 24-volt battery has dropped down to 20 or 22 volts, the battery is almost completely dead; if the voltage on a 24-volt battery has climbed above 26.8 volts, the battery is almost full.
You can watch the battery voltage go up, or go down, depending on whether the battery is being charged or being used.
Battery Current
Usually, the finding out how much current a battery is able to produce isn't needed for Planned Preventative Maintenance (PPM); most fire alarm batteries can produce more than 20 Amps. Remember, when being used, the actual amount of current coming out of the battery is the same current that the panel uses; often 0.5 amps to 5.0 amps. When considering the current used in a fire alarm system, it's all about the current that the panel uses, not the current that the battery is capable of producing.
If the battery calculations are correct (the calculations are really only performed on paper), and there isn't anything wrong with the fire alarm system, there usually isn't any need to check the battery current.
Trying to measure the current that a battery itself is capable of producing will only burn out the fuse in the ammeter (if you're lucky). For purposes of measuring current, the ampmeter is basically a short. If the terminals of a battery are simply shorted, the short produces an extremely high current, and current can melt wires, or in extreme cases, cause a small explosion. That much current is dangerous. Don't create a real short on the batteries by trying to measure its current capability.
Battery Testing
In reality, when testing a battery, you are testing it to see if is good or bad. A bad battery could be:
- A battery that won't charge up
- A battery that has a shorted cell inside the battery
- A battery that has a cracked case
- A battery that has corroded contacts
- A battery that doesn't hold a charge
Won't Charge Up
When a battery doesn't fully charge, the charger in the fire alarm control panel will continually force current through the battery. Watt's Law is "Watts equals Voltage times Current". In this case, the wattage turns into heat, so the battery gets warm.
This is an easy test. When the battery is warmer than the panel it's in, the battery is bad. The battery is warm because the charger is continually trying to charge the battery. In rare cases, the charger itself is bad. More often, though, the battery is bad. Replace the battery.
When two 12-volt batteries are used to make 24-volts, always replace both batteries at once. Unless the batteries match, with the same manufacturer, model of battery, and date code, the batteries could cause later problems with the fire alarm panel. Keep the batteries matched.
Shorted Cell Inside the Battery
A 12-volt battery has 6 cells. When a shorted battery has one of its cells internally shorted, there are only 5 cells that produce voltage. Even if the battery is fully charged, it will always be less than 12 volts.
When a cell is shorted in the battery, the battery charger in a fire alarm panel will continually provide a charging current, trying to charge the battery. The battery will be warm.
When there are two batteries wired in series, like most fire alarm systems, the good battery and the cell-shored battery will both get this continual charging current, and both batteries will be warm.
Even what had been the good battery will be damaged by the excess charging current because it is being overcharged.
When two 12-volt batteries are used to make 24-volts, always replace both batteries at once. Unless the batteries match, with the same manufacturer, model of battery, and date code, the batteries could cause later problems with the fire alarm panel. Keep the batteries matched.
Battery with a Cracked Case
Once in a great while, a battery will crack its case. When it's cracked, a small amount of gel from inside one of the cells leaks out, and causes a ground fault. Sometimes, even with a visual inspection, the crack is hard to see.
Replace a cracked battery.
When two 12-volt batteries are used to make 24-volts, always replace both batteries at once. Unless the batteries match, with the same manufacturer, model of battery, and date code, the batteries could cause later problems with the fire alarm panel. Keep the batteries matched.
Corroded Contacts
Corroded contacts on a battery can be caused by a cracked case, or other problems. Replacing a battery with corroded contacts gets rid of whatever problem caused the corroded contacts. When the contacts are corroded, don't try to clean the contacts, just replace the batteries.
When two 12-volt batteries are used to make 24-volts, always replace both batteries at once. Unless the batteries match, with the same manufacturer, model of battery, and date code, the batteries could cause later problems with the fire alarm panel. Keep the batteries matched.
When Batteries Don't Hold a Charge
A real test to see if a battery holds a charge is to cut power to the panel, wait 24 hours, sound the alarm for 5 minutes or 15 minutes, and measure the voltage. The voltage at this time should never be below the manufacturer's minimum requirements. Read the instruction manual to find the minimum voltage, or call the technical support team for the manufacturer to find out.
The only other method of testing to see if the batteries hold a charge is to super-size the panel's internal battery test. This is how most fire alarm control panels and most Notification Appliance Circuit (NAC) power supplies test their installed backup batteries.
Panel's Internal Battery Test
Listen to the panel carefully. Every minute or so, there's a quiet relay click inside the panel. That is the panel checking its internal circuitry to make sure the whole panel is working. It's a type of watchdog circuit. Some panels only check for ground faults during that brief time.
One of the many things the panel is checking is status of the backup batteries. To check the battery's capabilities, the panel disconnects the charger from the batteries, puts a current load on the batteries, and watches the voltage drop. The voltage drops only a few hundredths of a volt, but if the voltage drops too much (because the battery doesn't have enough capacity), a trouble is shown, saying "Battery Trouble".
Because the time duration of the current load / voltage dropping test is extremely short, and the actual current load extended to the batteries is tremendously small, this is a very poor test. On the other hand, even though the test is very poor and doesn't show much about the true battery capacity, this test is far better than not having a test at all. If the panel is showing a battery trouble, count on the batteries being bad and just replace the batteries.
When two 12-volt batteries are used to make 24-volts, always replace both batteries. Unless the batteries match with the same manufacturer, model of battery, and date code, the batteries are not matched and could cause problems with the fire alarm panel. Keep the batteries matched.
PPM Battery Testing
You don't get away with the panel's internal battery test. Your Planned Preventative Maintenance (PPM) test, to test the battery's capacity has to be far better.
While there is no accurate method of testing backup batteries without using the 24-hour blackout method, a partial test can give some idea of whether the batteries are good or bad.
When performing the test for PPM, or any other time for that matter, write down the method and the results of the test in your CYA paperwork. Remember, no one reads your CYA paperwork, until something goes terribly wrong. Then, your CYA paperwork has better be there.
Testing the Capacity of a Battery Using a Current Load
Keep in mind, because the batteries aren't being tested over a 24-hour period, this is a shortcut method of testing batteries. Because there's no other accurate method of measurement, experience-based judgment is needed.
Also, the word "battery" is short for "battery of cells". A 12-volt battery is a "battery of six 2-volt cells". A 24-volt battery is a single "battery of twelve 2-volt cells". Whether it a single 24-volt battery or two 12-volt batteries wired in series, when a fire alarm system is using a 24-volt battery, it's using a "battery of twelve 2-volt cells".
Document the Battery Test
Starting out, you need to document both the method that you are using and the results of the testing. While most of the time, no one will ever read your CYA paperwork, if there's ever a time when something has gone horribly wrong, your CYA paperwork had better be there, or it will be assumed you didn't do your job. Write it down.
Each time you perform the Planned Preventive Maintenance for a fire alarm system, you need to specify in the write-up the method you are using. That way, anyone trying to figure out what was done will know the testing procedure.
Get a Reference Voltage
Before actually performing the test, start by measuring the voltage on the battery. This is is the normal voltage, the voltage of the battery when the battery is being charged. This is also your reference voltage. Write down this voltage.
Mimic a Blackout
Turn off the power to the panel at the circuit breaker. This mimics a blackout.
Measure the voltage again, and write it down. This voltage should be lower than the charging voltage, if the voltage is lower than the charging voltage, you've turned off the correct breaker.
Current Load on the Batteries
Now, keeping the voltmeter attached, put a current load on the batteries.
The easy way of putting a current load on the batteries is to sound the alarm. Extremely small systems, those with only one or two horns and strobes, will probably use less than 0.5 amps, while larger systems, with four NAC circuits and dozens of horns and strobes may draw over 5 amps of current. This is the system-in-alarm method.
Another method commonly used to test batteries is to use a large wattage value (25 watts or greater) resistor of, say, 20 ohms to 50 ohms, as a load; use the resistor to draw current from the batteries. This is a slightly harder to use technique because the batteries have to be disconnected from the fire alarm system while drawing current for a load. This is the resistor-as-the-load method.
When a technician sticks to one method, the system-in-alarm method or the resistor-as-the-load method, the technician gets used to seeing the results.
Measure the Drained Voltage
Watch the voltmeter as the current is being drained from the batteries. After :30 seconds to a minute, if the voltage on the battery is down to 24 volts, the battery capacity is questionable. At 23 volts, the battery is bad and needs replacement.
While this technique doesn't use the 24-hour blackout with 5 minutes or 15 minutes of alarm method, the technique does show some things about the batteries, especially if the technician is used to reading and interpreting the results.
Write down the results.
When two 12-volt batteries are used to make 24-volts, always replace both batteries at once. Unless the batteries match, with the same manufacturer, model of battery, and date code, the batteries could cause later problems with the fire alarm panel. Keep the batteries matched.
Using an Amp Hour Meter
Even though an Amp Hour Meter is a highly inaccurate method of field-measuring a battery, some owners or fire marshals require this instrument to show them that the real amp hour capacity of a battery is reasonably close to the amp hour capacity stamped on the side of the battery.
The meter, though, is very unreliable.
One reason that the amp hour meter is so unreliable is that it's extremely difficult to get a good connection between the meter and the battery. The alligator-clip connectors that come with the meter are designed for telephone wires; the alligator-clip connectors aren't designed for high-current use.
There's also no way of knowing if the connection is good, so you have to guess.
Yes: Most of the time, when the alligator-clips are used on the spade connectors of lower amp hour batteries, like the spade connectors on 8-amp hour batteries, the connection can be acceptable.
No: When the alligator-clips are used on the bolt-terminals of higher amp hour batteries, like the bolt connectors on 25-amp hour batteries, the connection doesn't make a clean - high-current connection, and the connection is un-reliable.
Calibration of the amp hour meter has to be adjusted for each size of battery. Read the manual that comes with the meter to find out how to adjust it. If the calibration isn't set correctly, the reading on the meter is useless.
The meter, when used correctly, is a comparison meter; it compares the conduction of a good battery to a tested battery of the same size. (Actually, the meter compares a good battery to a tested battery of the same manufacturer and model of the calibration battery.)
When there are two or more sizes of battery in the same building, the meter has to be re-calibrated each time the size of the tested battery is changed. That is not a fun way of testing batteries.
The amp hour meter has to measure batteries one at a time; one battery may test good and the other battery may test bad. When two 12-volt batteries are used to make 24-volts, always replace both batteries at once. Unless the batteries match, with the same manufacturer, model of battery, and date code, the batteries could cause later problems with the fire alarm panel. Keep the batteries matched.
If you are required to show the tested amp hours on the battery, remember, the real boss in this is not the NFPA; the real bosses are the building owners, the fire marshal, and the insurance representative. Perform the battery measurements the way they require; just be aware of the issues.
Every time you perform the test, make sure you write down the results in your CYA paperwork.
Douglas Krantz
