Long ago I read that sulfate left on battery plates eventually hardens.
In addition, it’s good to have a battery well charged before hitting
the starter because the surge can knock sulfate off the plates,
shortening battery life.
I’ve been putting a charger on my car battery if it gets down to 12.55 V
or less. I take it off when the current tapers to a certain point. A
few days ago, I checked to voltage 8 hours after taking the charger off.
It was 12.78. It must be a Maintenance Free battery!
Because the cell covers appeared to be removable, I assumed it was Low
Maintenance (Sb/Ca) and not Maintenance Free (Ca/Ca). The two are
charged differently. Nowhere on the case does it say what kind it is.
Online, manufacturers of lead/acid batteries no longer seem to say which
model is which. (Nowadays, Maintenance Free batteries often have
On the farm, cars used to have Low Maintenance. I used a Standard
battery (Sb/Sb) in the truck because they were supposed to stand up
better to vibration. I used a Maintenance Free with cushioning for the
tractor because a Standard battery can self-discharge at 2% a day in hot
weather. The tractor could sit for weeks and be far from an outlet.
I’d charge any battery if I found the voltage down. The automatic
charger had a switch for Maintenance Free.
Somewhere, I got hold of the Battery Council International’s 1978
Battery Service Manual. It devotes 6 pages to Maintenance Free
batteries. A graph of “typical charge voltage characteristics” shows a
Standard battery being topped off at 14.6 volts and a Maintenance Free
battery at 15.7 volts.
My car’s regulator delivers 14.4 volts at normal temperatures. If it
were set higher, it would be bad for a Low Maintenance or Standard
battery. That explains why I need a charger to top my battery off. The
Service Manual says Maintenance Free batteries charge on a taper. That
explains why it takes hours to bring it up a little to 100%.
The charger I use now, has 2-millisecond pulses. It doesn’t say so on
the case, but I checked it with an oscilloscope. It seems that the
microprocessor determines the spacing of the pulses according to the
voltage between pulses. Apparently, this allows it to charge any kind
of car battery without a “Maintenance Free” switch.
If the battery is maint free, doesn't that mean
you put it in your machine, and don't need the
charger and volt check every few hours? Seems
like a lot of attention and action (maint) for
a maint free battery. Did I miss some thing?
My last was a 2-year battery that worked reliably for 13. As it was
being discarded when I picked it up, I was surprised.
I started checking batteries not to extend their lives but to avoid
trouble, like being unable to start a tractor 1/4 mile from any road.
Have you tried or used jumper packs? I saw
one used, and was so totally impressed, I
promptly bought one for each vehicle. Don't
waste money on Harbor Freight, the one I
got with the big 22 amp hour battery didn't
jump my truck, but the older Winchester with
17 amp hour did nicely. The HF was new, and
had charged overnight with the provided
charger. The day before I needed it.
I don't remember when I last needed a jump, but if I wanted to keep a
charged battery on hand, I think I'd get an AGM.
Last year, I took a chance and bought one for my riding mower. Then I
read an online recommendation not to charge an AGM over 120 F. Mine was
getting nearly that hot until I put in an insulating board.
I've occasionally checked the voltage and never had to charge it. AGM
takes a charge pretty fast, loses only 1-2% per month, and doesn't grow
sulfate crystals if kept charged. It's resistant to vibration, fairly
light, and doesn't leak.
I'll have to look into the possibility that my mower is overcharging it.
If the electrolyte dries up, that's all she wrote.
One time I boiled my battery dry on a motorcycle in Canada. The
regulator points had stuck.
I had a car that sometimes had a dead battery. I never figured out what
had been left on. I suspected that sometimes a door wasn't fully
closed, but when I'd walked past the before, the doors looked closed and
I didn't see any lights.
One morning when I jumped it, I connected the cables wrong. There was
something unusual about color coding of the positive and negative sides,
and I was sleepy. As soon as I clamped the cable to the ground of the
car, I knew it was wrong, but it was too late. The alternator didn't
work after that. It could have been worse.
As I recall, other than that, the problems were corrosion on posts,
batteries that hadn't been run enough, and batteries that should be
replaced. It was better to find out sooner, with a meter, than a few
weeks later, when it might fail to start.
Now I see why they quit labeling them maintenance free. Some consumers
took it literally. Good for sales, bad for a brand's reputation.
I suppose I put meter probes on the terminals every 1500-3000 hours. It
will probably be down, and I'll probably charge it.
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