Lead acid battery

Hi Gova

Before we can help further, we need to know what type of cells your battery consists of - tubular plate vented, flat plate vented, Planté type, etc. If you don't know, contact the manufacturer. If you cannot, give us some details of the make/model if avaialable.

I'm a bit rusty on battery maintenance, though we also used them (I'm not directly involved with substations any more!). They are the hidden heart of a substation. From what I remember:

1. Exact trickle charge requirements depends on the load and the way your charger measures the charging current. We don't boost charge our cells (see 6 below), but different types may require it - check with the manufacturer.
2. Ensure that your ripple current at full charge is relatively low - a figure of <15% ripple Amperage rings a faint bell? Otherwise the plates could be damaged.
3. Your battery should be fuse-protected against accidental short-circuits.
4. Your battery should be protected against under-voltage (typically it must cut-out at 75% of full voltage, depending on your manufacturer's specifications). Voltages below that can severely reduce the life span of your battery, and may impact on the correct operation of your substation protection.
   
5. We also measure the positive-to-earth and negative-to-earth readings monthly, these should be (in our specialised traction substation case) below 15V to ensure integrity of the protection system.
6. Charging voltages and current are extremely important. We only use so-called Constant Voltage - Constant current chargers. For a 300Ah set that would mean charging a flat battery at no more than 30A until the correct voltage is reached (118,5V for Planté cells only, I think - different voltage for other types - check with manufacturer!). Then the voltage remains at say 118,5V and the current gradually reduces until full charge is reached.
7. Ensure that the battery room does not exceed 25°C if possible - higher temperatures reduces battery life of certain types of battery.
8. Clean terminals as they get dirty and corroded and apply petroleum jelly or whatever the latest technology is.
9. Check water levels monthly or weekly and add as required. Excessive water use is probably an indication of overcharging. Charging voltages should be set with an accurate digital multimeter (if not fitted to the charger) - analogue dials are too inaccurate as a rule.
10. We are not too fancy when it comes to recording, so we have a "battery book" that we record data in - every 3 months we take s.g. (specific gravity) readings and voltage readings of each cell, as well as the temperature of cell 1. Differences of cell voltage or s.g. is a warning that certain cells are about to fail. Protective eye wear and long rubber gloves are to be used when this is done. We also record charging voltage and current monthly.
11. Also check for sedimentation 3-monthly, as excessive sedimentation at the bottom of a cell is indicative of a problem, and it could short out the cell or severely reduce it's Ah rating.
12. Battery rooms are to be kept scrupulously clean, with an emergency water supply in case of acid spillage or explosion. Good ventilation (natural or flame-proof if forced?) is also essential.

We don't skimp on batteries - problems and shortcuts here can cost the unwary a substation if the protection is compromised!

Hope this guides you in the right direction.

Gideon