We get this call every single Tuesday and Thursday morning, which is exactly when the swing flights land. You've been up north for two weeks, the car's been sitting at Perth Airport long-term or on the driveway at home, and now it won't turn over. Just that sad click-click-click and a dash full of lights.
Here's the thing that surprises people: nine times out of ten the battery isn't faulty. It's flat. Those are two completely different problems and they cost very different amounts to fix.
Your car is never actually off
Modern cars draw power constantly, even with the key in your pocket and the doors locked. The alarm is listening. The body control module is awake. The keyless entry receiver is checking for your fob every few seconds. The infotainment head unit keeps its memory alive. On a 2015-or-newer car that adds up to somewhere between 20 and 50 milliamps sitting there, 24 hours a day.
| Parasitic draw | Typical vehicle | Days until it won't crank |
|---|---|---|
| 15-25 mA | Older car, basic alarm | 35-50 days |
| 25-50 mA | Most modern cars, keyless entry | 18-28 days |
| 50-85 mA | Euro car, tracker or aftermarket alarm | 10-16 days |
| 85 mA+ | Dashcam wired to constant, faulty module | 5-9 days |
Look at that middle row. A normal modern car, a normal 2-week swing, and you're right on the edge. Add a battery that's already 3 years old and lost a third of its capacity to Perth summers, and the edge becomes the floor of the Domestic 3 carpark.
The dashcam killer
If you've got a dashcam wired into a constant-live fuse for parking mode, it's the number one drain we find on FIFO vehicles. Some pull 80-150 mA in parking mode. That'll flatten a healthy battery inside a week, and it'll do it every swing until you fit a proper voltage cut-off or move it to an ignition-switched fuse.
Why the airport carpark is worse than your driveway
Two reasons. First, that long-term carpark bakes — no shade, black bitumen, and the battery cooks all day at temperatures well above ambient. Heat accelerates self-discharge on top of the parasitic drain. Second, you drove straight there from home. A 20-minute run up the Kwinana or across the Tonkin doesn't fully recharge a battery, so you parked it at maybe 85% and then started the countdown from there.
Compare that to the bloke who parks in a garage in Canning Vale. Same car, same swing, and his starts fine. It's not luck, it's about 15°C of difference.
The three fixes, in order of how well they work
- 1A smart trickle charger, if the car's at home. A CTEK or NOCO runs about $60-120, plugs into a normal powerpoint, and holds the battery at full charge indefinitely without cooking it. Set and forget. This is the proper fix and it pays for itself the first time.
- 2A solar maintainer on the dash, if the car's at the airport. A 10-20W panel on the windscreen wired to the cigarette socket offsets most parasitic draw. Not as good as mains, but it turns a 2-week problem into a 6-week one.
- 3Disconnect the negative terminal. Free, works, and mildly annoying — you'll lose radio presets and some cars throw a wobbly about relearning the throttle body. Fine for a second car, not great for the daily.
What doesn't work: "I'll just start it and let it idle for 10 minutes before I fly out." Idling produces barely any charge current. You'll put back less than the starter took out. All you've done is make it worse and annoy the neighbours.
Flat vs cooked — how to tell which one you've got
This matters, because if it's just flat you don't need a new battery and nobody should be selling you one. Get a jump start, drive it for 30 minutes on the freeway, then check it the next morning. If it starts fine, the battery was only discharged and it's recovered. If it's dead again by Thursday, the battery has lost its ability to hold charge and it's genuinely done.
The faster way is a proper conductance test, which reads internal resistance and gives you a state-of-health percentage in about 30 seconds. That's what our battery testing gear does at every callout, and it's free whether you buy anything or not. A battery that's been deep-discharged three or four times across three swings is usually sitting at 50-60% health, and that's the point where we'd tell you to replace it before next swing rather than after.
Stop-Start cars are less forgiving
If you're in a modern ute or Euro wagon with Stop-Start, the AGM or EFB battery in it hates being deep-discharged even more than a standard one does. Two flat episodes can take a serious chunk of its life. It also has to be registered to the car's BMS when it's replaced — see Stop-Start battery replacement for why that matters.
What we do on a swing-return callout
We come to you — airport long-term, home driveway, wherever the car is sitting. We jump it, test the battery and the alternator on the spot, and tell you straight whether you need a battery or just a decent drive and a trickle charger. If it does need replacing we carry the stock in the van and do it there, so you're not paying for a tow or leaving the car another week. That's the whole point of mobile battery replacement — you've just done a fortnight of 12-hour days, the last thing you want is to organise a tow truck at 6am.
Call us on the way through the terminal if you want. We'd rather meet you at the car than have you standing in a carpark for an hour working out who to ring.
Frequently asked
How long can a car sit before the battery goes flat?+
Healthy battery, modern car, no accessories: about 3-4 weeks. Add a 3-year-old battery, a dashcam on parking mode, or a Perth summer carpark and it drops to 7-14 days. If you're doing 2-week swings you're living right on that boundary, which is why it seems to fail randomly.
Will a jump start fix it or do I need a new battery?+
Depends whether it's flat or cooked. If it starts after a jump, runs for 30 minutes on the freeway and is still fine two days later, it was only discharged. If it's dead again within a couple of days, the battery has lost capacity and it needs replacing. A conductance test answers it in 30 seconds instead of guessing.
Is a trickle charger safe to leave plugged in for weeks?+
A smart one, yes — that's exactly what it's designed for. Modern CTEK and NOCO chargers switch to a float or maintenance mode once the battery is full, so they can stay connected for months. Avoid the old dumb chargers that just push current constantly; those will boil a battery dry.
Can I leave a solar maintainer on the dash at the airport?+
Yes, and plenty of FIFO blokes do. Use one with a proper regulator, run it to the cigarette socket if that socket stays live with the key out, or straight to the terminals if it doesn't. It won't fully replace mains charging but it'll usually get you through a swing.
Common service areas for this guide