Interesting Lead Acid Battery facts
"purple_stars" wrote in
oups.com:
Recently these batteries have degraded to the point that they won't run
the radio equipment over an entire night (10 hours let's say) before
they go completely dead. Now of course those "completely dead"
dicharge cycles are rapidly eating the batteries and sucking out what
life they had left in them, because it's a bad thing to completely
discharge lead acid batteries.
I used to run a rather powerful HF station mobile:
Yaesu FT-900 remote mounted in trunk
Highly modified TenTec Hercules II, 120 amps from golf cart beasts with
650 watts output to a 15' tall, trailer-hitch-mounted, homebrew using
Henry Allen's Texas Bugcatcher's biggest coil and 8-spoke, 36" capacitor
hat. On 20M, my favorite band, the coil was shorted out, completely, and
the whip on top was tuned so only the capacitor hat was used, pulling the
current lobe way up the mast for more H field. Maybe some day I'll put
it back in the car when the sun cooperates better....
I, too, drove the car every day and didn't really tax it much with much
transmitting power, except on long trips with ham friends. The big
batteries got weaker over time and it took me a while to figure out what
was going on.....
Like you, my daily drive was around 25 miles of city driving, which is
part of the problem. I used a continuous duty solenoid to connect the
ham batteries in parallel with the diesel starting battery in the finest
ham radio car (zero electrical noise) ever invented, the 1973 Mercedes
220Diesel with no electronics, at all. I still drive it. I restored it.
The car has a 80A alternator, plenty of juice, and a huge starting
battery for the diesel.
I started tracking the specific gravity and plotting it after a long
overcharge (2 days) from 1.280 sg. Each day, upon arriving home from the
driving, I got out my hydrometer and recorded/plotted the gravity, the
only REAL means of measuring cell condition in lead acid batteries.
The chart started falling from that first day. Well, maybe it'll level
off at some point, as we did start with a really full charge. Nope, it
never did. The 25-45 mile drive each day in stop and go traffic never
produced enough charging TIME to recover the gravity all the way up to
full, or even close. It looked good on the voltmeter, 14.5 volts
charging, until I stopped or keyed the beast around 140A (with the radio)
on packet or rtty. There simply wasn't enough charge TIME to cause the
chemistry to reverse.
I gave up the test around 1.180, defeated.....
The solution was quite simple. Leave a drop cord by the car and mount a
10A automatic shutoff battery charger in the trunk by the
batteries....and simply plug in the car all night. Specific gravity
recovered the first day from the SLOW, SLOW recharging at 3-4A and each
morning the charger would by slowly cycling on with long off periods as
the battery's high gravity voltage held it off very nicely.
I remoted the charger's AC plug to under the trailer hitch to make
connecting it as easy an painless as possible. The batteries went from
lasting a year and a half to five and a half years, same batteries, same
manufacturer....lots less unrecoverable sulphation.
Boats that have a little charger plugged into the dock and water their
batteries with DISTILLED ONLY get that gravity back up after the abuse of
dreaming you're going to charge them at 50A for 30 minutes on the engine
at sea. Same effect....charging happens very SLOWLY OVER TIME.
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