Dennis Pogson wrote:
Larry wrote:

Stephen Trapani wrote in news:nJrPf.263
:


Can I just charge both banks at the same time as I did before or do
I have to charge the banks separately?


I assume starting battery is on 1 and house batteries are on 2, right?

Any time there is a charging source, you may leave the switch in BOTH
to charge them all in parallel. The little battery will charge with
lots less current than the T-105s and when the voltage comes up to
14+, the currents will simply stop. The automatic charger will keep
pulsing the lot of them to keep them at full voltage, as will the
alternator. It'll work fine that way.

What I would do is connect the AC charger to the house bank, directly,
not the switch common. Once charged, the starter battery doesn't
need to be connected all the time to the charger, just occasionally,
but the house batteries do because you keep switching on loads in the
boat. Having the AC charger hooked directly to the house batteries
also means no matter what you do with that switch, even OFF, the
charger will NEVER be connected to the loads without a battery to
sink its output to 14V. Chargers and alternators can blow electronics
if there's no battery attached to them..not good. So, when you want
the AC charger to boost up the starting battery, just flip to BOTH
for a day or while the wild party is going on to maintain its charge.
Don't leave it in BOTH all the while.

I'd like to also put a plug into making TWO connections to the
starting battery....one to the switch with a HEAVY cable capable of
cranking the Yanmar...including the house battery cables so the house
batteries can also crank the Yanmar if necessary in the BOTH
position. But, make the starter cable connect directly to the
starting battery as short as possible. Run the starter off the
starting battery, direct, not the house battery switch. If the
switch goes bad, you're not stranded. If there's a short in the
house, your not stranded. WHEN, not if, the big switch gets all
corroded up inside because it's cheap boat crap, cranking the engine
won't pulsate all the expensive electronics, possibly destroying it,
because the engine has a direct path around the corrosion to the
starting battery, directly. Starting in BOTH when the starting
battery is dead is the same circuit as using jumper cables (from the
house batteries) in your car. Works fine.

For years, the two paralleled AGM starting batteries in my diesel
stepvan have been charged in parallel with my L-16H monster house
battery bank from one 80A alternator. Don't be alarmed you only see
35A, by the way. Actually I think that's a little high for charging
such small batteries as T-105s. They must have been discharged quite
a ways. The BATTERY, not the capacity of the alternator, determines
how much charging current there is. The CHARGER/ALTERNATOR sets the
VOLTAGE LIMIT with its regulator and its CURRENT LIMIT with its
internal resistance in series. Too many think if they swap out the
80A alternator for a 300A alternator their going to charge the house
batteries in 5 minutes, not hours. That would be fine if it weren't
for the chemistry and physics of lead-acid batteries. The slower you
charge them, the better they charge. What the big alternator does is
give you OVERHEAD, allowing you to use the difference current between
the alternator's capacity and the charging current at the moment to
run other stuff like radars/radios/lights/pumps/inverters/etc.,
without discharging the batteries....same as your car.

This will all change shortly with Toshiba's invention of the
amazingly- fast-charging Ni-MH nanotube cell. It charges to 80% in
ONE minute and 100% in 3 minutes....at such huge current levels the
Yanmar won't be strong enough to pull in short order. Those cells
will be like a dream, charging at whatever capacity the alternators
can put out for very short times (more than 3 minutes, I'm sure)
until they are fully charged. With their introduction and after
their debugging, I'm going to go for an electric or hybrid car with
them powering it. To date, traction motor braking has only recharged
current technology batteries a few percent. The new batteries will
allow traction motor braking to put ALL the power they produce as
generators back into the battery bank as you brake... Big oil will be
trying to squash this introduction with big bribes and big offers to
buy it up and hide it. Let's all hope they don't succeed.

Let's hope all vehicles, including the boats, dump this stupid 12V
power system for much higher voltages to get the currents down using
more economical wiring systems. I'm for 220 or 440 VDC, myself.
Your starter cable would be #12 wire at 440VDC. Its solid state,
brushless motor would never need brushes, as its armature isn't would
with wire. Your outboard motor stator driving the ignition system is
already in this voltage range, now! Low voltage DC is stupid.


He says his house batteries are connected in series. Is this an error?


Not if they are T-105s - they are 6V batteries