Why do car batteries go flat when the car’s just sitting?
Right, so picture this: you’ve left your car parked up at home in Flagstaff, or maybe it’s sitting at mum’s in Ngaruawahia while you scoot around in the work ute. Come back to it a week later, go to start her up… nothing. That sinking feeling, eh? Happens here plenty, especially if you’re not using the car often or it sits idle in one of those leafy Hamilton suburbs with all the stop-start commuting and short trips on streets like Peachgrove Road or Wairere Drive. Honestly, sitting is often what does them in.
The thing is, your car’s battery isn’t just “off” because the engine’s off. There’s always something drawing a bit of charge — alarm, clock, immobiliser, that sort of thing. Even if you don’t see a light left on, there’s what we call a parasitic battery drain. I can’t tell you how many times a Mazda Atenza or a newer Suzuki Swift’s come in after sitting at a mate’s place, battery flat as a pancake. Sometimes it’s just age, too, or you’ve got a wee radio upgrade wired in funny that drains more than it should.
Car charging system.
How long till a battery goes flat from sitting?
This one depends. Some cars last longer than others. A newer Hyundai i30 or those Honda Fits we see heaps of in Rototuna might go a decent couple of weeks parked up with no trouble. An old Peugeot 206 or a high-mileage Nissan Tiida? Couple of days, sometimes less, especially if it hasn’t had a decent run lately or the battery’s past its prime. European cars especially — little Audis, BMWs, all the gizmos ticking away even while they’re ‘off’ — can go dead after just a long Hamilton weekend.
Battery quality plays a part too; a decent premium battery can hold charge longer. Cheap battery? That thing will let you down faster than a flat on Cobham Drive on a Monday morning. If you want more details on how charging systems work, here’s a handy link: more on charging systems here.
What speeds up a flat battery?
Loads of things can drain your battery when not driving, and we see them all:
Switches or accessories left on: Not just lights. Phone chargers left in, dash cams, seat warmers… they all suck a bit of power. See it heaps with folks dropping kids off at The Base, forget to unplug the iPad, next morning — dead.
Old battery: If it struggles to start on cold Dinsdale mornings or after a few days at Raglan beach, odds are it’s time for a replacement. Got a Toyota Aqua that won’t hold charge after a big foggy Hamilton winter? Bring it in for a look.
Issues in the charging system: Could be the alternator, starter, or even a dodgy earth wire. Our techs caught a sneaky wiring fault in a Kia Carnival last week after the owner kept needing jump starts in Morrinsville.
Weather: Hamilton’s winters? Murder on batteries. If your car’s outside in the frost on Massey Street, those cold starts week after week will drain it fast. Hot dry summer on the other hand, like when you’re parked up on Lake Road for a few days, can cause fluid loss and wear out the battery, too.
Sorting out flat batteries in Hamilton
Dead battery after sitting at home or long-term parking at the hospital? No worries. Book in with Grimmer Motors and we’ll get to the bottom of it – whether you drive a late-model Corolla, a Mitsubishi Outlander, or something a bit rarer you’ve brought over from Papakura. Our team’s dealt with flat batteries from all over the Waikato, so you’re in good hands.
We cover everything from car battery diagnostics to replacement, car service Hamilton, hybrid repair, and more. Flick us a message or give us a bell – we’ll get you sorted and back on the road quick as.