[SwissXC90]

Yes you can eliminate the battery. Everything you tested showed the battery is perfectly good.

So to test for parasitic draw you could get a CTEK Battery Sense and monitor the battery state over a few nights and see how it drops, or go through the laborious tests for parasitic drain, which can take many many hours, and you may find all is well


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[SwissXC90]

PS you should also check battery terminations for tightness, and ground cables in turn and on engine for tightness and cleanliness (corrosion).


Any corrosion can cause voltage drop... causing many weird issues


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[John C]

Again, if the battery can start the car then either it should run until you shut it off (or you run out of gas) or there is an issue with the charging system.

 

[leoxdeng]

Want to give you guys an update - I drove the car for 15 miles round trips daily for 1 week, never needed to charge battery with a charger, no problem at all, and no 'low battery' message popped up. This included driving in moderate traffic (not heavy traffic though, as I've yet to experience that).

The only 'driving behaviour' I modified was - before I start ignition I leave the headlights to off position, and sat nav unplugged (dashcam still plugged in). When I get stuck in slow traffic, I unplug the sat nav charger cable, and switch off heating fan if I feel warm enough. Maybe this helped?

After 1 week daily trips (30 miles per day), I left the car parked for 5 days, and night temperature dropped to sub zero for these 5 days. Then started the car on day 6 on a morning when everything was iced over - again no problem and ignition started really quickly. When I had the old battery, it tended to show 'low battery' warning on cold mornings.

So all seems to point to the most plausible theory - that the problem was due to 1) low battery voltage to start with, 2) all appliances plugged in, including headlight and fan, and 3) heavy traffic when the alternator struggled to keep up with amp demand at low rpm - all three causes combined over a period of 30~60mins caused the car to shut down electronics to preserve minimal battery voltage for running CEM/ECM/TCM.

I disagree the only job of the battery is to start the car. It serves another important purpose - as back up electricity supply when alternator does not generate sufficient charge in low rpm.

 

[leoxdeng]

Again, if the battery can start the car then either it should run until you shut it off (or you run out of gas) or there is an issue with the charging system.

What are the main functions of car battery?

Car battery is a power reserve, that supplies necessary juice to the car's starting motor and shovels electricity to the car's ignite system. Read more.

www.caasco.com

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[John C]

I disagree the only job of the battery is to start the car. It serves another important purpose - as back up electricity supply when alternator does not generate sufficient charge in low rpm.

Yeah, but, that should never happen. If it does that means there is a limit to how long you can idle the car, and there isn't. This was a problem when we had DC generators that didn't start charging until 1500 RPM or so, but those days are long gone. Today's alternators are sized so that they can always supply enough current to run the car. You should not have to worry about what loads are on, starting or otherwise, unless you know the battery has been abnormally discharged, e.g. from playing the radio at the drive-in. Now, if you have a 2000 watt subwoofer installed and you like to go around rattling windows, that may be a different story.

Monitor the system voltage. As long as it stays over 12.8 volts you are not discharging the battery.

One other important purpose of the battery is to provide a sort of buffer between the alternator and the loads, but that has no bearing on your problem.

If your battery was bad then it could be sucking up too much of the alternator's output without charging enough, although I find that hard to believe.