Lead-acid accumulators are made up of a number of cells which consist of two sets of lead plates separated by wooden or porous plastic separators, and filled with a dilute sulphuric acid solution called the electrolyte.
One set of lead plates (alternate plates) are the positive plates which form lead-peroxide and a chocolate-brown colour when the accumulator is fully charged.
The plates and separators are usually placed into a vulcanite, hard rubber, glass or plastic case sealed with pitch, through which the terminals protrude.
When discharged both the positive and negative plates form lead sulphate. This is caused by the chemical action during discharge when sulphur and oxygen are transferred from the electrolyte to the plates, reducing the specific gravity of the electrolyte.
Plates in a discharged condition are easily recognised by the appearance of lead sulphate (a white deposit) on both positive and negative plates.
Upon re-charging the lead sulphate is transferred back to the electrolyte and the specific gravity increases, provided the accumulator has not been left standing in a discharged condition for a long time when a hard core of lead sulphate forms. When the accumulators have been left in a discharged condition for too long the lead sulphate hardens and causes the plates to thicken and buckle, damaging the separators and casing and no longer function efficiently, if at all, in which case the batteries should be reconditioned or replaced.
The electrolyte consists of a solution of sulphuric acid diluted to correct specific gravity by distilled water.
The specific gravity will vary between 1,270 when fully charged and 1,150 when discharged. It is advisable not to allow the accumulate to discharge below 1,200 to prevent the formation of hard lead sulphate on the plates. Ideally the specific gravity should be maintained at approximately 1,250 by regularly charging them or by keeping them on float-charge.
The electrolyte should just cover the plates and maintained at that level by the additional of pure distilled water when the level drops below the top of the plates. The potential difference (voltage) of each cell should be 2,2 volts when fully charged and 2 volts when measured by a voltmeter on load.
The voltage of a bank of batteries for the Radiotelephone installation, normally 24V, should be indicated by a Voltmeter installed in the Radio Room so that the voltage can be ascertained at a glance. The voltage of a 24V bank of batteries should be maintained at 24 – 26 volts off load and approximately 24V on load. The charging voltage should be more than 24V, usually 25 – 30 Volts, depending on the condition of the batteries which should be checked daily.
The state of the batteries should also be checked by means of a Hydrometer which measures the specific gravity of the electrolyte, at least once a week.
- Ensure sufficient initial charge.
- Give batteries plenty of work and liberal charging.
- Do not charge too much or too little.
- Do not charge at too high a rate.
- Do not run batteries too low (voltage and specific gravity).
- Do not allow batteries to stand discharged too long.
- Charge batteries daily.
- Keep plates covered with electrolyte, using distilled water for popping up.
- Test specific gravity weekly.
- Keep terminals clean and coated with petroleum jelly or similar rating.
- Do not allow open lights including cigarettes near batteries.
- Keep batteries and battery box dry.
- Check casing for cracks.
- Ensure terminals are clean and tight.
- Earth connections should be properly connected.
- Vents in filler caps should be clean and open.
- The plates should not be buckled.
- The electrolyte should just cover the plates e.g.5mm.
- The batteries should not be over-filled with distilled water.
- Lead sulphate should not be allowed to form on the terminals on plates.
- Check voltages of batteries and cells on load.
- Check voltage at least once daily.
- Ensure that the power supply is switched on.
- Check that the voltage is correct.
- Check that the transmitter and receiver are on the correct frequencies.
- Check that the correct modes have been selected e.g. A3 A3H A3A A3J.
- Check that the aerial/aerials is/are connected.
- Check that the aerial/aerials is/are up and are not shorting anywhere.
- Check all switches and visible connections.
- Check fuses.
- If voltage is low check flat batteries and recharge.
- If voltage is correct but transmitter won't tune up check aerials and fuses.
- If transmitter tunes up OK and you are unable to establish communication check that you are calling and listening on the correct frequencies. When calling always say where you are listening.
- When calling on 2182 with a SSB transmitter check that it is on A3H.
- When listening on 2182 with a SSB receiver check that it is on A3H.
- When listening on SSB A3J you hear a strong whistle on incoming signals try listening on A3H.
- When the incoming signals are unintelligible try listening on A3J. If you don't have a SSB receiver try switching the BF0 on and then try to tune the signal in by changing the note or frequency slightly.
- Check earth connections e.g. when testing a portable lifeboat radio.
- Try alternative aerial if available e.g. for portable lifeboat radio.
- Check that artificial aerial is disconnected.
- If your transmitter is working satisfactory but you cannot establish communication check that you are within range of the station you are calling.
- Check that you are calling on the optimum calling channel, e.g. channel 16 and 2182 kHz for short range up to 100 miles, in the daytime, 4125 kHz for distances 100 – 1000 miles and 8257 kHz for distances 200 – 2000 miles, depending on the time of the day or night (greater distances at night). If you can't get through on the one channel you should try the alternative channels.
Additional Information on Batteries
- If you have no hydrometer to test the specific gravity of the battery, shine a torch into the filler holes and note the colour of the plates.
- Charged batteries: positive plate is light brown, negative plate is slate grey.
- Discharged battery: positive is whitish, negative light grey.
- While battery is being charged, the plates give off gasses causing bubbling, as it becomes fully charged, the amount of gas and bubbling increases.
- Batteries to be inspected once every 24 hours and to be kept fully charged.
- When making up the electrolyte always add acid to the water. (If water is added to the acid an explosion may occur.)
- A 12V battery when fully charged, should register about 13,5 volts when there is no load on it, and this value should drop slightly when there is a load on it.
- Check the battery for cracks or leaks when inspecting.