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2025 Honda Civic — battery dies after the car sits for a weekend

CityMechanicish14Community StarterMay 31, 20262025 Honda Civic Sport Touring HybridBay Area
Battery passes a quick test and charging voltage looks normal, but after two or three days parked the car sometimes will not crank. What is the cleanest parasitic-draw test on a modern car that takes time to go to sleep? I would rather test this logically than replace parts.
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9 replies

FlatSixDailyCommunity StarterCommunity StarterMay 31, 2026permalink
I wouldn't throw parts yet. A pressure test beats staring at a dry driveway if the 2025 Honda Civic is losing coolant with no puddle. You'll know quickly if you're on the wrong tree. Run the total, not the monthly, before you commit. I've seen both outcomes, which is why I'd test instead of assume. Might be overthinking it, but I'd rather overthink than overspend.
TrackTraveler521Community StarterCommunity StarterMay 31, 2026permalink
I wouldn't throw parts yet. Capture voltage while the 2025 Honda Civic is actually failing — after it restarts you've lost the clue. You'll know quickly if you're on the wrong tree. A shop burned me once by skipping that step. Doing the boring step first on purpose.
FlatSixDailyCommunity StarterCommunity StarterMay 31, 2026permalink
I'd want a measurement, not a hunch. Write temp, speed, and in-gear vs coast when the 2025 Honda Civic does it — then decide on parts. Save the big job until that test fails. This is from a 2025 Honda Civic in Bay Area. If it doesn't change the out-the-door or the repair estimate, it's noise. Not interested in a five-hour wait for a shrug.
MarketBuyer633Community StarterCommunity StarterJun 1, 2026permalink
That's a good start, but I wouldn't stop there. Two 2025 Honda Civics can feel identical and have different causes, so measure before you copy someone else's repair. Don't erase codes until someone who can help has seen them. No need to make it theatrical. I've seen both outcomes, which is why I'd test instead of assume. I'll poke at it this weekend.
BrakeDIYerCommunity StarterCommunity StarterJun 2, 2026permalink
Agree — and I'd add this: Swap the cheap/easy piece first on the 2025 Honda Civic and see if the fault moves. That's the branch I'd chase this week. On “battery dies after the car sits for,” that was the fork that mattered for me. This is from a 2025 Honda Civic in Bay Area. Any freeze-frame data saved? If your situation is the opposite, ignore me. I'll update if anything new shows up.
WeekendEnthusiast75Community StarterCommunity StarterMay 31, 2026permalink
This is usually cheaper to test than to guess. A pressure test beats staring at a dry driveway if the 2025 Honda Civic is losing coolant with no puddle. That's the branch I'd chase this week. Happy to compare notes if your setup is different. Not interested in a five-hour wait for a shrug.
CanyonMiles540Community StarterCommunity StarterJun 1, 2026permalink
Log the conditions before you spend. Two 2025 Honda Civics can feel identical and have different causes, so measure before you copy someone else's repair. That's the branch I'd chase this week. On “battery dies after the car sits for,” that was the fork that mattered for me. Not gospel, but it saved me a headache. I'd rather pay for diagnosis than a second guess-repair.
V8Gal322Community StarterCommunity StarterJun 1, 2026permalink
If it were in my driveway, get a real battery/charging test on the 2025 Honda Civic, not just resting voltage, before blaming a module. If the cheap test changes it, stop and reassess. Just my two cents from doing this recently. I'd sleep better after that step, even if it finds nothing. Trying not to diagnose from the couch.
FlatSixDailyCommunity StarterCommunity StarterJun 1, 2026permalink
Ask what changed right before it started. Write temp, speed, and in-gear vs coast when the 2025 Honda Civic does it — then decide on parts. Save the big job until that test fails. Run the total, not the monthly, before you commit. Not interested in a five-hour wait for a shrug.
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