Powered site or free camp: what your kids' devices actually cost you in amp-hours

Last school holidays, my nine-year-old asked why his tablet "died overnight" at a free camp near Barcaldine when it had charged fine the night before at a powered site in Longreach. Fair question. The honest answer is that our battery bank was already running the fridge, the water pump and two phones, and by 2am there just wasn't enough left for the tablet to top up properly. He wasn't wrong to notice. Most of us budget power for the fridge and lights and completely forget the device load two kids actually generate on a family lap.

This isn't a lecture about screen time. It's a power budget problem, and it's one I got wrong for about a year before I sat down with a cheap USB power meter and actually measured what our kids' gear pulls.

What kids' devices actually draw

A 10-inch tablet charging from empty draws roughly 10-12 watts at the wall, which through a 240V-to-USB adapter and then a 12V-to-240V inverter (if that's your setup) loses some efficiency along the way. Run it straight off a 12V USB port instead and you're looking at around 1-1.5 amps at 12V for an hour or so to get from 20% to full. A Nintendo Switch is thirstier again — its official charger is rated around 39 watts, which is about 3.2 amps at 12V while it's actively charging, tapering off as the battery fills. A basic e-reader like a Kindle is negligible, under 5 watts.

Multiply that by two kids with a tablet each, one shared Switch, a couple of adult phones and a laptop for the odd remote-work day, and you can genuinely be asking your battery bank for 8-10 amp-hours overnight just in device charging. That's before the fridge has done its overnight cycling, which on a decent compressor fridge in Queensland summer heat can easily be another 40-50Ah over 24 hours. I've written more on the fridge sums separately — see sizing your 12V fridge to your battery if you haven't done that maths yet, because it's the bigger number and it matters more than the device load, but the device load is the bit that catches families out because nobody accounts for it at all.

Lithium vs AGM makes this argument different for families

We ran two 100Ah AGMs for our first eighteen months and moved to a single 100Ah lithium after a trip through the Flinders where we were rationing charge every night. The practical difference for a family van isn't really about weight, it's about usable capacity. AGM gives you a genuinely useful 50% of rated capacity before you should stop drawing on it, so a 200Ah AGM bank is really 100Ah of usable charge. A 100Ah lithium battery gives you closer to 90-95Ah usable. That's roughly double the effective capacity for half the physical battery bank, which for us was the difference between "the kids' tablets can charge overnight" and "someone's tablet doesn't get plugged in tonight, sorry mate." We've covered the actual cost-per-amp-hour maths in detail in lithium vs AGM for caravans, and I'd say for a family running multiple devices plus a fridge, lithium earns its price premium faster than it does for a couple travelling light.

I'll admit I resisted the lithium upgrade for a long time because the sticker price annoyed me. In hindsight that was probably three years too long — the usable capacity difference is that stark once you've got two kids' worth of gear drawing overnight.

Where a DC-DC charger actually earns its keep

If you're doing shorter hops between camps — school holiday touring rather than months of free camping — your alternator is doing more of the heavy lifting than your solar. A proper DC-DC charger, wired to size (not the whatever-was-in-the-shed cable some install jobs get away with), will put a genuine 20-25A into your battery while you're driving, which recovers the overnight device and fridge draw in a couple of hours on the road. We've gone through the wiring specifics, including the cable gauge and fuse rating most installers skimp on, in DC-DC chargers explained. If your rig only has a basic trickle-charge lead off the tow vehicle, don't expect it to claw back what two kids' devices and a fridge used overnight, because it physically can't move enough current fast enough.

When a powered site is worth the extra twenty bucks

Here's where I'll say something a bit unpopular: I think a lot of grey nomad-oriented advice about avoiding powered sites doesn't translate well to family travel. For a couple with modest device use, a good solar and lithium setup will comfortably free-camp for a week without drama. For a family with two kids each running a device, a Switch getting flogged on a rainy afternoon, and possibly one of us trying to get an hour of work done, the numbers don't always add up, especially in winter when solar input drops and the fridge is working overtime in either extreme of temperature.

We now make a rough call every few nights: three or four nights free camping, then a powered site to fully top the battery, run the washing machine, and let every device charge without triage. At a place like Easts Beach Holiday Park in Kiama or Bright Holiday Park, the extra $15-25 for power buys genuine peace of mind, not just convenience. If you're weighing that decision generally rather than device-by-device, I went through the broader logic in caravan park or free camp: how to actually decide with kids in the van.

A simple overnight budget for a family of four

Rather than a spreadsheet nobody will maintain on the road, here's the rough shape of an overnight draw we actually see in mild weather with a 3-way or compressor fridge, two kids' tablets, a Switch, two phones and basic LED lighting: fridge 35-45Ah, devices and phones 8-12Ah, lighting and water pump 3-5Ah, which lands you around 50-60Ah total overnight draw. A 200Ah lithium bank with 300-400W of roof solar handles that comfortably through most of the year in decent sun. Drop into a cloudy stretch of the Victorian High Country or a few short winter days and that solar input can fall to a third of its summer output, which is where the device charging suddenly becomes the thing that doesn't happen.

The habit that actually fixes it

The single biggest change we made wasn't buying more solar. It was charging devices during the day when the sun's actually contributing, rather than plugging everything in after dinner when the battery is working from stored charge alone with nothing coming in. Kids' tablets sitting flat on the dash charging off USB while we drive, or on the picnic table in full sun on a portable panel, costs us nothing extra. It's a habit change, not a gear purchase, and it's the one thing I'd tell any family starting out before they spend money on a bigger battery they might not need.

None of this replaces knowing your actual numbers. A cheap battery monitor with a shunt tells you the truth about what's going in and out, rather than the voltage guess most of us relied on for years — worth doing before you assume the tablet "just died" is a device fault rather than a power budget one.