We have a 2012 Nissan Juke, auto, 117k, 1.6 turbo. We’ve gone through 3 batteries in 6 years and each time both the battery and alternator tested fine - but since we couldn’t figure out why the battery kept dying we changed the batteries and that seemed to fix the problem for a while. This time when the battery died I charged it up and tested it and the alt. - they tested fine in my driveway, but this time I put one of those volt meters in the cigarette lighter and drove around and although it started reading fine (14.5 volts) - like it did when I tested in my driveway, after about 10 minutes the volts would drop down to 12.2 and my wife even saw it below 12 - and staying around there. So I figured I’d change the alternator - but I was still unsure because if it was the alt., how could it read 14.5 sometimes? After reading the manual about how to replace the alternator I saw how this car has a system where if it detects that the battery is fully charged it will tell the alternator to limit the charging of the battery (to save gas). Well, I disconnected the main current sensor (at the negative battery terminal) and now the meter reads a steady 14.5 +/- no matter how long I drive (but I’m still testing). So a couple of questions: Will driving around with the alt putting out 14.5 +/- all the time cause harm? Is this current sensor system connected to other systems and so disconnecting it will mess something else up? I figure at some point this will set an error code, but what are the downsides to driving like this? Has anyone else had this problem and what was your fix? Could this really be the solution or am I fooling myself? FYI - Nissan wants a couple of hundred dollars for a replacement part (so that is out of the question) and Nissan does have a TSB about dead batteries caused by the computer software but the dealer says it doesn’t apply to my VIN.
I’m curious why spending “a couple hundred dollars” would be “out of the question” on what I presume is otherwise a good car? Nissan did not spend money on equipping the car with this part for nothing. Leaving it disconnected could cause many unforseen problems.
The voltage shouldn’t drop below 11.6 volts
http://www.nissantechnicianinfo.mobi/htmlversions/2016_Feb_March_Issue_6/VoltageControl.html
Tester
Yes, it will overcharge the battery and could cause it to leak acid if it is a conventional flooded cell battery. Battery acid will eat through cables and sheetmetal.
The question I would have is- what is the designed trip point for the alternator to turn back on? I would think it is higher than 12.0 volts as that is fair amount of discharge. Seeing it below 12 and not triggering the alternator to output seems to be the issue.
At some point while you were running it, did it recover and start charging again? I suspect it must have or it would have died eventually. It might be interesting to watch for that trip point to see where it turns back on…