"KLC Lewis" wrote in
et:

Essie has a Model 20 Universal (5416) 16hp Diesel, fitted with a 50
Amp alternator. The biggest alternator I can put on this engine,
according to my research, is an 80 Amp. When I install my new
batteries this year, I'll have 375 ah aboard, being charged by that
small alternator and supplimented by my two 35 watt solar panels. I
have no illusions that I will be able to fully-charge that bank with
my onboard charging capabilities -- my aim is to set out with as much
amp-hours as I can get so that I don't draw-down my batteries as much
as I would if they were smaller. Back in the slip, the 50 Amp
shorepower charger can complete the job. The 80 Amp alternator, if I
fit it, will be close to 25% of bank capacity, but not quite. The 50
Amp alternator is only 15.5% of capacity, which will probably prompt
me to go ahead and upgrade the alternator. But that's not exactly
cheap.



The discharge-charge cycle is a ratio of 1:5. It takes 5 times as long
to CHARGE a lead acid battery as it does to DISCHARGE it. That ratio
hasn't changed in my lifetime. It's chemistry.....a slow chemical
reaction. The only difference is your initial charge rate will be lower.
375AH batteries CAN, but don't have to be, charged at 375 x .25 = 93A.
This bulk charge is the constant current phase and your 50A alternator
will run 50A for about twice as long. It's plenty adequate, but will
simply take longer. That small engine uses so little diesel fuel, relax!
Let everybody take a show from the hot water tank while charging, if it
has a hot water heat exchanger attached to it.

Now, discharge the battery bank down to 12.25V (at 70F). Turn off all
loads and crank The Beast. Watch the ammeter and see how long it will
hold 50A before it bumps its voltage regulator, the second phase of the
charge whereby the VOLTAGE is regulated to around 14.3VDC and the battery
sets the current load. There's the switch point between a 50A bulk
charge and the finishing phase, which is just as important, even more so
if you'd like to keep the cells from sulfating. When the current drops
to near zero, the charging is complete.....NOT when you see it start to
drop off 50A....as wishful boaters charging at 200A for 1.5 hours will
tell you theirs is charged....total nonsense.

A lead acid battery CANNOT be rushed to get a proper charge. Your 50A
alternator will never endanger your battery banks with gassing and
warping the plates from excessive heat....as long as its voltage
regulator works properly. Simply reduce your DC loads as much as is
practical during the bulk phase, then you can turn them back on during
the finishing phase when you have extra amps to spare the battery's not
using up....(c;

Larry
--
Democracy is when two wolves and a sheep vote on who's for dinner.
Liberty is when the sheep has his own gun.