Somewhat of a co-incidence, but I started thinking about our car batteries again, and this post is just over a year old, so a good time for an update/reminder. ...
Another update, 10 days later.
Battery was dead, dead, dead in my car on Sunday. Barely a click-click-click of the starter and dim lights. Put the charger on, and took DWs car out for the day.
Didn't want to leave the (ancient 'dumb') charger on overnight, so got ~ 8 hours in, but in the AM after a 'rest' it only read ~ 10.7V - not good.
I finally traced the problem to my driver side rear door not being fully closed when I took some stuff out, and the dome light was probably on for two days. I really thought newer cars would protect against this, and shut that stuff off before draining the battery. Apparently, that drain triggered a cell to go bad.
Oh well, this coming winter would be winter #6 for this (original) battery, so I was planning on replacing it anyhow, so no real loss. Actually, maybe a good thing, it was a nice fall day, so replacing the battery was not much of a chore (but they seem to be getting heavier, the older I get!), and not all that inconvenient in terms of timing.
Since I had the cables loose, I decided to check the standby drain. I have to do this carefully, to not exceed the 10A limit on my meter. Sometimes a fan will run, or the lights come on to "light your way" for 30 seconds or so. So I set up a jumper wire/clip so the meter was not connected until I could see/hear things settle down. Then I connected the meter and removed the jumper. I was surprised to see it was still at 2 amps! Another minute, and it dropped to 1A (still high!), but then 0.58A, then 0.12A, then finally (maybe 3 minutes?), I see it drop to 0.10, then quickly drop further to 0.008A (8 ma). That's a pretty low drain. I set the meter to MAX hold and waited over 10 minutes, and the peak was just 9 ma.
Car started right up, but the battery wasn't at full charge off the shelf (~ 12.37V ~ 70%). I put the charger on for ~ 4 hours, then measured the next AM after that rest, and it was ~ 12.65V so ~95%, so that's good.
Then I got curious about what NW-Bound said about reviving a bad cell by knocking the short loose. So I carefully lifted one end up ~ 1" and dropped it, and did that for each end a dozen times with no improvement. Wasn't interested enough to try to be more aggressive, a cracked case and spilled acid wasn't something I wanted to deal with. But, in an emergency, that approach might come in handy.
One more thing - someone (this thread or another) was saying the start-stop feature (optional on mine, I don't have it) is hard on batteries/starters. Well, I figure the starter is designed for it. But in looking for a new battery, I learned that the start-stop feature requires a heavier duty battery, which was at least $100 more. I wonder if the gas savings even reaches that level, cars just don't use much gas when idling at a stop light, and the lights aren't all that long. And if you are stuck in traffic, you can do it manually.
Oh well, all's well that ends well.
-ERD50
