CAMPING - POWER & LIGHTING
Before reliable solar/battery power became available, having a 240V inverter was a luxury few campers could imagine. Now, an inverter is pretty much compulsory camping gear.
We took the following inverter selection guidelines from the Enerdrive website and the only downside was the fact that the company just didn’t reply to our emails. We also tried to buy an evaluation unit, but after five emails we gave up.
We’d hate to think what would happen if we owned a unit and needed after-sales support.
For inverter novices, an inverter converts your vehicle’s, van’s or camper’s 12-volt, direct-current power to household-style, 240-volt, alternating current. An inverter allows you to operate household, 240V devices and appliances in your camping setup, provided you have sufficient 12V capacity.
Leonardo da Vinci knew that ‘everything is connected to everything else’ and that maxim has absolute applicability to appliance/battery/charger/inverter selection. If you expect to run your camping setup with all the 240V appliances you’re used to operating simultaneously at home, you’ll need massive battery and charging capacity.
By ‘staggering’ the operating time of 240V appliances, you can drastically reduce the capacity of your battery/charger/inverter setup. It’s sensible to decide on what you need to operate at the same time and size your battery, inverter and charging components to match that.
For example, if power is required for a few LED lights and a microwave at the same time, or a coffee maker and a few LED lights at the same time, the battery/inverter match would need to handle only the heaviest power consumer. In this case, it would be the 1200-watt coffee maker, not the 1000W microwave.
It’s important to note that the heaviest current users are usually those that generate heat, because heat produced by electricity isn’t a particularly efficient use of current. In contrast, the electric motors in fridges and electronics such as TVs are very efficient, normally needing only 100-120W.
So, the first step you need to make in sizing an inverter is determining what you need to operate simultaneously. Let’s say that works out at a demand for 1300W.
Choosing an inverter with the same power rating as your maximum demand isn’t wise, because the DC-AC current conversion generates heat and inverter output decreases rapidly as internal heat increases. In an inverter specification there’s often a time limit for rated output – five, 10 or 30 minutes.
That natural heat buildup also means it’s important to locate your inverter where it gets some ventilation.
It’s critical that some TVs and all computers are powered by a pure sine wave inverter, not a modified sine wave inverter.
Also, many appliances – particularly microwaves – have ‘peak’ loads as they start up, consuming additional power. To be on the safe side, your inverter should be capable of handling 50-percent more load than your estimated power demand.
That means the optimum inverter size for our hypothetical 1300W power demand is actually 2000W.
If you’re contemplating a DIY inverter installation, it’s best to select one that’s designed for installation without the need for an electrician, because most inverters don’t have an earth wire. Enerdrive’s RCD-GPO inverter models are designed for safe DIY installation.
Step two is determining how much battery capacity you have or are planning to have. It’s obvious from the chart that the practical minimum is 120 amp-hour battery size and preferable is 180Ah or even 240Ah.
Note that these estimates are based on fully charged lead-acid (flooded-type, AGM, calcium) batteries that are not discharged below 50-percent. Lithium batteries can tolerate a lower discharge than that, so while a 120Ah conventional battery is at best marginal for our desired 2000W inverter output, a lithium one would be better.
A conventional 180Ah or even 240Ah battery costs around the same as a 120Ah lithium, so cost isn’t an issue, but that conventional battery weighs around 40-50kg, compare with the lithium’s 11-15kg. Weight is always an issue with camping gear selection.
Another advantage of lithium is a much faster recharge rate, so the battery will recover more quickly than a conventional one.
If you’re regularly near mains power charging, the indicated battery sizes are OK, but off-grid travellers should double that battery capacity.
Inverters use power when on stand-by: enough to flatten your battery perhaps. It’s wise to get into the habit of turning on your inverter only when it’s needed.
Another issue can occur if someone plugs in an appliance that exceeds the inverter’s power output rating. Depending on type, the inverter will simply shut down and may emit a high-pitched warning sound, indicating that it’s not happy.
Of course, all this power will vanish without adequate battery charging gear. Solar is essential and you can’t have too much of it, going through a quality regulator. However, if there’s no sun, there’s no solar charge, so remote-area campers need backup.
Running a 4WD engine to provide alternator charging is a bad idea, because modern diesels, in particular, shouldn’t be run at low revs, at low exhaust gas temperatures, for more than a few minutes. However, old diesels, like Toyota and Patrol in-line sixes, are happy to fast-idle for an hour at a time.
The backup for other campers is a petrol generator, but not one of the Chinese ‘cheapies’ that needs to rev its tits off noisily. Get a good brand genny, with a low-noise, low-rev setting.