Battery Charger On Newer Cars

[chimpvalet]

Hello,

We've had trouble with a '21 Nissan Rogue failing to start and had the battery replaced on warranty at quite an early point in time. Cold weather operation, short trips and John Deere level revs don't sustain charge in the battery apparently. Since the new battery it's again acting oddly, this time shutting down 30 seconds after remote start and throwing the alarm system into action. Back at the dealer's once more. Looking ahead I believe it wise to run the car in Sport mode for such driving as this holds higher revs, so permitting better restoration of charge. In the event we can't start it due to low battery in future will it be risky to attach a battery charger to it? Uncertain as to how fragile modern auto electronics have become.

[Tom68]

Battery is a damper for the charger, just get an IU curve charger so it can't overcharge. Even a sealed lead acid battery charger off an alarm system will work.

[turbo camino]

What is the parasitic draw? What is the charging current from the alternator, at idle?

[Dan Timberlake]

A voltmeter in the lighter/power socket in the interior would give a helpful indication if the charging system is up to it.
I've had several cars where the lighter socket read .5 or so volts lower than probes on the battery posts.

Looks like "VPRW" ("vehicle power," or "battery voltage ") might be available real time with an OBD2 scanner that does live data.
https://www.nissanforums.com/threads/vp ... ng.275450/

[rebelrouser]

Charger should not hurt your Nissan Rogue with some common sense, I would not charge over 20 amps and what every you do don't hook up backward, most charger now have diode to protect but older ones might not. Never unhook charger without turning it off or unhook a battery cable while running. They just don't like voltage spikes. And I know 40 years ago you could unhook a cable while engine was running to see if the alternator was charging not anymore, and don't laugh still see people doing it all the time. But sounds to me it has an issue with battery draw or charging. Have a scan tool put on it, remember only issues that affect emissions will set the light on the dash, just because the light is off it may have codes to tell you exactly want the problem is. Good scan tool will let you max the alternator to check its output as well.

[chimpvalet]

Feedback from this community is greatly appreciated, thanks! Since the battery was replaced the car has run fine, though did kick the alarm into action in 2 successive remote start sessions. The dealer was unable to replicate but did update some firmware relating to the sonar anti-collision system. No further grief in minimal usage since.

What I'm inclined to conclude is as follows: car is started cold, drawing on the battery from that as expected; seat heat, cabin fan, defrost, and premium audio continue to draw down at idle and battery gets little recharge during wife's short trip at low revs. Next she fires it up again for return home and compounds the discharge situation. If this car is smart enough to detect an incipient problem it sure ain't smart enough to either head it off or advise us how to head it off. Buddy with a '14 M-B sedan says the thing not only flags emerging trouble but emails to him in addition to dash display. For us, I've advised wife to run short trips in Sport mode which spins up the engine more than Auto thus getting more from the alternator.

Cheers
Steve

[turbo camino]

Some quick checks with a clamp meter at various spots would be really useful (and non-invasive), it should not be able to discharge the battery even at idle even with all the major loads running.

[chimpvalet]

We are about 1 week away from taking her to the shop for seasonal oil and tire change, might persuade the boys there to check the load situation.

[turbo camino]

I have scopes and fancy meters and scan tools but for something like this, my favorite is this thing:
https://www.southwire.com/tools-equipme ... p/65031840

If there's more going out of the battery to the car than is coming out of the alternator, then fix whatever's wrong with the alternator. If battery current out and alternator current out are in balance, then go looking for a key-off parasitic draw.