"Roger Long" wrote in
:
How would you count a charge / discharge cycle according to this
article? When I use my two paralleled AGM's to start my little 15 hp
diesel, is that a cycle? I don't see how it could be since I sail
nearly every day during the summer and my batteries ought to be nearly
dead now. If the battery is good for 200 cycles and my draw down is
only 10% (In reality, it's probably less than that since my engine
lights of almost as quickly as a good car engine) can I expect to get
closer to 2000 charging cycles?
I believe he was referring to drawing down the battery in a deep
discharge cycle, not just a burst of starter current. Hell, we'd have to
put 4 batteries a year in my car if that were so...(c;
A good diesel fires on the 2nd TDC it rolls over. When Dan had the old
Hatteras 56, I told him I'd be afraid to jack over the 8v92TAs by hand as
they would probably start as soon as something moved. Both those engines
you just touched the starter and they popped up running...2-strokes,
gotta love 'em.
I think the 300 real cycles, using the batteries for lights and loads,
then recharging them properly to full charge SLOWLY is quite realistic
for lead acid AGMs or Gelcells. I just spent $70 putting 2 new 12AH AGMs
in my dock scooter. It's like driving a hot rod! Even at full throttle,
the status light stays green as soon as it comes up to speed. The acid
soaked gauze gets used up in about 200 cycles in the scooter....less than
a year the way I use it all summer.
There were very important graphs to study in this report that boaters
need to see, especially about charging....
I found the book for free on his website:
http://www.buchmann.ca/toc.asp
In figure 4-3 on pdf page 61, notice how the 3-stage charging is measured
in HOURS, not running the diesel for 30 minutes like boaters dream of.
Notice how the current drops very rapidly near the start of the charge,
not when the charge is near complete. My assertion of why it's stupid to
put a 140 amp alternator on a little sailboat diesel is obvious.
The accompanying text:
"A multi-stage charger applies constant-current charge, topping charge
and float
charge (see Figure 4-3). During the constant current charge, the battery
charges
to 70 percent in about five hours; the remaining 30 percent is completed
by the
slow topping charge. The topping charge lasts another five hours and is
essential
for the well-being of the battery. This can be compared to a little rest
after a
good meal before resuming work. If the battery is not completely
saturated, the
SLA will eventually lose its ability to accept a full charge and the
performance
of the battery is reduced. The third stage is the float charge, which
compensates
for the self-discharge after the battery has been fully charged."
See the time in HOURS, not MINUTES? He's especially talking about AGM
and Gelcell batteries boaters think are superbatteries because of the
awful prices. So, you're looking at charging them for several hours, not
just when the charging voltage pops up as is so often the case in a boat
trying to get that diesel shut down ASAP...shortening battery life in the
process by first overcharging, then not giving the chemistry TIME to
charge the cells. To quote the text, again:
"The charge algorithm for lead acid batteries differs from nickel-based
chemistry
in that voltage limiting rather than current limiting is used. Charge
time of a
sealed lead acid (SLA) is 12 to 16 hours. With higher charge currents and
multi-stage charge methods, charge time can be reduced to 10 hours or
less.
SLAs cannot be fully charged as quickly as nickel-based systems."
10 HOURS, not 30 minutes. Most sailboat captains would have a heart
attack....(c;
Of course, if you're headed back to the dock to plug in the little 10A
chargers...or a mooring with big solar panels or wind charger...that's
exactly what happens...HOURS.
I still prefer liquid electrolyte to gells and wicks. I can charge them
to a full charge and replace any electrolyte that vents. I can also
adjust their specific gravity to balance the cells over time to maximize
life. "Maintenance Free" just means you can't help them, once they start
down.
Larry
--
Why is it, in any city, all traffic lights act as if they have rotary
timers in them, like they did in 1955, and are all set to create
maximum inconvenience and block traffic movement, entirely?