My '90 LX is not a daily driver. I put a brand new battery in it when I purchased it four years ago. I would try to start it once a week, but sometimes wouldn't start it for a couple weeks. It got to the point that it would start dying by the time I would try to start it. When I started monitoring the voltage, I would notice it would get down to 11.98 volts, but would still start. While running, it would get as high as 14.5'ish and then would fall to 12.43 or so after sitting for a few hours. It would then lose .01 volts every few hours.
On Feb 9 at noon, the old battery was at 12.43v.
at 7:30 P.M. it was at 12.41v.
Next morning at 8:00 A.M. it was at 12.40v.
By 2:00 P.M. it was at 12.39v.
At 11:00 P.M. it was still at 12.39v.
On the 11th at 9:00 A.M. it was at 12.38v
At 10:00 A.M. I disconnected the battery cables and the battery read 12.43v.
This was the typical trend with this battery until it would drop to 11.98v and I would start it (thinking it wouldn't start), but it started up normally (not as strong at my new battery (which has about 50 more cranking amps), but it didn't struggle to fire up. I don't know how far it would drop when it wouldn't start (I wasn't measuring it at the time).
IS THIS ^ SLOW DROP IN VOLTAGE NORMAL FOR A BATTERY. AND, WHEN DISCONNECTING THE BATTERY, IS IT NORMAL FOR THE VOLTAGE TO GO BACK UP TO A "NORMAL" VOLTAGE. OR, DOES THIS SLOW DRAW INDICATE I HAVE A SHORT OR SLOW DRAIN SOMEWHERE THAT ISN'T NORMAL?
I then installed a new battery which measured 12.46v before connecting the cables.
On Feb 14, the new battery was at 12.42v at 10:00 A.M. (I didn't document this well, but I believe I purchased the new battery on the night of the 13th and measured it at 12.46 off the shelf. The next morning before installing the battery, it measured 12.42 before and right after attaching the battery cables).
At 5:00 P.M. it was at 12.41v.
On Feb 15 at 9:00 A.M. it was at 12.40v where it stayed for three days until
Feb 18 at 9:00 A.M it was at 12.39v.
Next morning it was still at 12.39v.
Yesterday, I pulled fuse #11 and #16 after running the car for 20-30 miles.
I parked it at 10:00 A.M. (didn't measure the voltage).
At 3:00 P.M. the battery was at 12.50v.
Last night at 9:00 P.M. it was at 12.50v.
I reinstalled fuse #16 (suspected offending circuit because this is where I pulled constant hot for my alarm recently).
Today at 9:00 A.M. it's flickering between 12.49 and 12.50v but steadied at 12.50v.
WHAT SHOULD I EXPECT FROM THIS NEW BATTERY IF THERE IS NO ABNORMAL DRAW ON THE BATTERY? SHOULD IT LOSE .01v OVER A FEW HOURS, OR A FEW DAYS? OR, SHOULD IT MAINTAIN A "NORMAL" VOLTAGE?
Since the battery stayed at 12.50v all day yesterday, I was thinking that if I installed fuse #16 and it only dropped .01v over the next few days, that that circuit probably isn't the problem. If I see a drop of .02v over the next day or so, that circuit might well be at least part of the problem. But, my question really is, should there always be a slow constant draw on the system? I'm suspecting yes, because if any car sits for long enough, it won't start. But, how quickly should the voltage be dropping???
(While taking all these measurements, I moved the probes of my multi-meter around to make sure my readying wasn't from a bad connection).
On Feb 9 at noon, the old battery was at 12.43v.
at 7:30 P.M. it was at 12.41v.
Next morning at 8:00 A.M. it was at 12.40v.
By 2:00 P.M. it was at 12.39v.
At 11:00 P.M. it was still at 12.39v.
On the 11th at 9:00 A.M. it was at 12.38v
At 10:00 A.M. I disconnected the battery cables and the battery read 12.43v.
This was the typical trend with this battery until it would drop to 11.98v and I would start it (thinking it wouldn't start), but it started up normally (not as strong at my new battery (which has about 50 more cranking amps), but it didn't struggle to fire up. I don't know how far it would drop when it wouldn't start (I wasn't measuring it at the time).
IS THIS ^ SLOW DROP IN VOLTAGE NORMAL FOR A BATTERY. AND, WHEN DISCONNECTING THE BATTERY, IS IT NORMAL FOR THE VOLTAGE TO GO BACK UP TO A "NORMAL" VOLTAGE. OR, DOES THIS SLOW DRAW INDICATE I HAVE A SHORT OR SLOW DRAIN SOMEWHERE THAT ISN'T NORMAL?
I then installed a new battery which measured 12.46v before connecting the cables.
On Feb 14, the new battery was at 12.42v at 10:00 A.M. (I didn't document this well, but I believe I purchased the new battery on the night of the 13th and measured it at 12.46 off the shelf. The next morning before installing the battery, it measured 12.42 before and right after attaching the battery cables).
At 5:00 P.M. it was at 12.41v.
On Feb 15 at 9:00 A.M. it was at 12.40v where it stayed for three days until
Feb 18 at 9:00 A.M it was at 12.39v.
Next morning it was still at 12.39v.
Yesterday, I pulled fuse #11 and #16 after running the car for 20-30 miles.
I parked it at 10:00 A.M. (didn't measure the voltage).
At 3:00 P.M. the battery was at 12.50v.
Last night at 9:00 P.M. it was at 12.50v.
I reinstalled fuse #16 (suspected offending circuit because this is where I pulled constant hot for my alarm recently).
Today at 9:00 A.M. it's flickering between 12.49 and 12.50v but steadied at 12.50v.
WHAT SHOULD I EXPECT FROM THIS NEW BATTERY IF THERE IS NO ABNORMAL DRAW ON THE BATTERY? SHOULD IT LOSE .01v OVER A FEW HOURS, OR A FEW DAYS? OR, SHOULD IT MAINTAIN A "NORMAL" VOLTAGE?
Since the battery stayed at 12.50v all day yesterday, I was thinking that if I installed fuse #16 and it only dropped .01v over the next few days, that that circuit probably isn't the problem. If I see a drop of .02v over the next day or so, that circuit might well be at least part of the problem. But, my question really is, should there always be a slow constant draw on the system? I'm suspecting yes, because if any car sits for long enough, it won't start. But, how quickly should the voltage be dropping???
(While taking all these measurements, I moved the probes of my multi-meter around to make sure my readying wasn't from a bad connection).