Now that there is renewed talk of power outages, its time to remind everyone about what can be done to keep life tolerably comfortable during those hours of electricityless-ness. Many people will have purchased generators or inverters during the previous round f load shedding two years ago, and now might be a good time to check that everything is working properly. Here are a few tips that might be of value.

Generators

If you already own a generator, then it might be a good idea to check whether its still working. Generally, it is a good idea to run your generator at least once a month. It might also be a good idea to check the instruction manual and see how often it should be serviced. Some generators need an oil change after 100 hours. There are also things like air cleaner, spark plugs etc. which need attention. If you have a generator with a small battery to start it, you may need to replace the battery. We will have more to say about batteries later.

If you are considering purchasing a generator, remember that it should be situated in a position that causes the minimum of annoyance to your neighbours. Consider purchasing a good quality product with service and support readily available. For most families, a 2500 watt generator will provide enough power for lighting, TV etc. It will power most fridges – although I don't recommend using emergency power for fridges, since a well sealed good quality fridge will remain cold for 7 hours or more. A 2500 watt generator will supply a light and a hair-dryer, should you decide to dine out.

Inverters

Inverters convert battery power to 230 volts AC using devices called MOSFETs to step the DC voltage up to a high level using a switching action. During periods when there is power available, the inverter unit charges the battery or batteries. If you have already purchased an inverter, now would be a good time to check whether it still works. A good indication would be to switch off the power to the inverter, and switch on all the appliances connected to it. If it lasts as long as intended, then all is well. If not, there could be problems with the charging circuit, the batteries, or (most probably) both. Inverters are like most other items of electronic equipment, and can be damaged by nearby lightning strikes, power instability (i.e. spikes) on the mains supply.

If you are considering purchasing an inverter because it is quiet and requires hardly any maintenance, remember that they are not as forgiving as a generator when it comes to overloading. It might be a good idea to estimate the power required and then purchase an inverter capable of providing double that amount. For example, if you want to power 18 compact fluorescent lamps and a TV + PVR, then you need about 800 watts of power. You could purchase a 1500 Watt inverter (close enough to double) to power these appliances. Also – beware – most inverters can't operate fluorescent lights with a magnetic ballast. Either the inverter, the light, or both fail. Inverters of course, require batteries. To connect the inverter to the battery requires cables. Be sure to calculate the current drawn by the inverter correctly so that the cable doesn't melt, or lose all of the power that should go to the inverter. Remember that an inverter delivering 2400 watts from a 12 volt battery will be drawing more than 200 amps.

Batteries

Batteries for starting generators, or for powering inverters are invariably sealed lead -acid types. Lead-acid batteries need to be constantly on charge, and should never be discharged to less than about 1.8 volts per cell (say 10 volts for a 12 volt battery). Most inverters will stop automatically when the battery voltage falls to too low a level for the batteries good. Unfortunately, batteries that are just left alone will eventually self-discharge to too low a level and will have to be thrown away. The other thing that kills batteries is overcharging. Many inverters contain very complicated chargers designed to minimise battery deterioration. In my experience they tend to overcharge slightly (to prevent battery sulphation) and in our climate, this seems to lead to loss of electrolyte.

The batteries for generator starting will be of the “starting-lighting-and ignition or SLI type. These feature a different plate construction from the type of battery used for inverters. Batteries for inverter use must deliver quite high current for outage periods and then be recharged. Generally, “deep-cycle” batteries are most appropriate for this use and should deliver roughly 300 charge-discharge cycles. SLI batteries will only give you about 30. Be sure to get the correct size of battery to last the duration of your intended power outage. A rule of thumb is to select a battery with at least double the amp-hour capacity that you have calculated.

Change-Over switch

It is extremely dangerous to connect the output from your inverter or generator to the mains – even if you know there's a power cut. Many people still attempt this, and I even heard a radio listener phone in to 702 telling everyone how good an idea it was. If you are using a generator, then please install a change-over switch (transfer switch.) - please get an electrician to do it for you.

If you are installing an inverter, then the chances are good that it has a built-in transfer relay. One of the advantages of an inverter is the way that it will take over from the mains so rapidly that your computer won't even notice. Be sure to follow the instructions to the letter, or have an installer do the work for you.

Finally

Please contact us for any problems you may have regarding emergency power or inverter installations.