"Larry" wrote in message
...
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.

My biggest load, when it's running, is the radar. All in all, if it's foggy
I'd rather just anchor out and wait, but if it comes down to it I should be
able to run the radar for a few hours straight without drawing down my bank
too much. After all, in this neck 'o it's only an hour or two to the next
anchorage or harbor anyway. And more likely than not, if it's foggy there's
no wind and to move the engine is running. No problem there.

With no refrigeration, no TV, no microwave, no electric appliances, I'm
mostly concerned with keeping enough energy to run my nav instruments and
laptop -- and the laptop has two batteries itself, running for quite some
time without needing a recharge. It's quite possible (likely, in fact) that
375 ah is overkill on Essie. But I like to stock up and feel that I have
enough to see me through hard times, and I can't see anything wrong with
stocking up on amp hours. And with your comments on charging, it's
comforting to know that I don't have to upgrade the alternator until it
actually NEEDS replacing.

"Larry" skrev i en meddelelse
...

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.

SNIP ...

Hi Larry, I've seen this rule of thumb before. But it cannot - in my
experience - be a valid general statement.

Today, my battery bank consists of two 70Ah batteries + a start battery
of 60Ah. If I spend - let's say - eight hours at sea using my
instruments, chartploter and autopilot, and the cooling compressor
running for 24 hours, I will have used something like 70Ah i.e. roughly
50% af the capacity of the bank ...

When I connect the land charger (in my case 220V) charging the 12V
batteries with 35A it does not take five times as long to "fill" the
battery bank back to close to 100% ...

What is the problem with the rule og thumb? Is there some kind of
"hidden assumption"? ... Or under what circumstances is the ratio 1:5
valid for charging the battery bank?

If I decide to increase the capacity of the bank to - say - 600Ah - will
I have to install a larger charger - i.e. giving more than 35A - in
order to give the batteries a full recharge - or is it just a matter of
time until the bank is "full" again? I have decided to add an alternator
to my Volvo Penta 2002. It will give 60A. This one - in combination with
the existing alternator - the total charge current will be around 100+A
.... with a bank of 600Ah, that should be no problem - right? I mean: No
harm to the batteries?

--
Flemming Torp
Gimle - DEN61

PS - I have seen som statements as to the power consumption of adding
another or larger alternator.
Some Danish friends have helped me defining the exact formula:

If we charge with 14V and 60A, and the efficiency factor is - say 50% -
the formula will be the following:

((14V * 60A)/50%) / 746 W/HP = 2,25HP.

A rule of thumb is given from
http://www.balmar.net/Page46-faq.html :

"What horsepower load will I put on my engine with a new alternator?

Typically, when an alternator is working at full output, it will
require approximately one horsepower for every 25 amps it produces. As
such, a 100-amp high-output alternator will demand up to four horsepower
to operate."

In this case, the rule of thumb seems to be quite accurate ...

In Jeff writes:

Larry wrote:

Has anyone had experience of fitting a 100A high output alternator to
a Bukh DV24 engine to either replace or supplement the 50A standard
alternator?
...

Doesn't matter if it's a 1000A alternator with 8 belts. Your batteries
will still charge about 25% of their AH capacity for about 5-8 hours to
recharge them. As long as the alternator has the capacity to drive the
loads plus 25% of the AH capacity of the house batteries (after the first
10 minutes when boaters DREAM the batteries are all charged up because
the current dropped off) the alternator is big enough. Overkill will NOT
recharge the batteries in 30 minutes, a pipe dream until the nanotube Ni-
Mh 3 minute batteries are delivered in the near future. THEN, you'll
need the 4000A alternator for 3 minutes to a 100% charge.

1920 lead-acid technology charges SLOWLY over HOURS not minutes....sorry.

80A is plenty....over 1100 watts, which would soon boil the electrolyte
and warp up the plates if the battery didn't prevent it at 14.2V.

Why are you so obsessed about this, Larry? Its gotten to the point
that you're just ranting nonsense!

The truth is that many cruisers have over 400 Amp-Hours of batteries.
My boat, for example, was designed to carry 4 6V golf carts (Trojan
T-105s), for about 450 AH as the house bank, or 520 AH if I use the
oversized T-145. A pair of 8D's will be in the same range.

I frequently charge with a 110 Amp Balmar and it puts out 105 Amps
when started, and it stays up of 90 Amps for quite some time. I
usually charge when the bank is down 200 AH, and bring it up 120 AH,
so I'm running for roughly 90 minutes. If I used a smaller
alternator, or a less aggressive regulator, that time would go up 10
or 15 minutes. While this might seem like a small thing, after
running for over 90 minutes one starts thinking the saving 15 minutes
might be worth some real money.

These aren't made up numbers; I've been doing this for about 6 weeks
every summer for the last 8 years, and with a similar but smaller
setup on my previous boat for 8 years before that. Lest you claim
that the high charge rate is cooking the batteries, there might be
some truth, but my first set of Trojans lasted 6 years, and might have
gone longer except illness prevented me from giving them proper care
one winter. Since the Trojans are cheap ($70 each) this is not a big
deal.

There's absolutely no reason why the OP shouldn't use a 100 Amp
alternator, assuming he has a large enough bank.

The point is, that if you increase your chargin capasity, then you have
to increase the battery capasity. The fastest chargin happens when the
batteries are relatively empty, there are "rules of thumb" like 40 - 80,
meanin that start charging when your batteries are almost half empty and
go until they are about 80 full. If the batteries go much deeper than 40
(you might have some other limits (30 or 50) it is not good for the
batteries and to fill them up to some 95 - 100 will take enorm time.
You have to have enough batteries that you do not regularly overstep the
limits, then your 100 A Balmar will be just fine.

- Lauri Tarkkonen

Lauri Tarkkonen wrote:
....

The point is, that if you increase your chargin capasity, then you have
to increase the battery capasity. The fastest chargin happens when the
batteries are relatively empty, there are "rules of thumb" like 40 - 80,
meanin that start charging when your batteries are almost half empty and
go until they are about 80 full. If the batteries go much deeper than 40
(you might have some other limits (30 or 50) it is not good for the
batteries and to fill them up to some 95 - 100 will take enorm time.
You have to have enough batteries that you do not regularly overstep the
limits, then your 100 A Balmar will be just fine.

You're right. While at anchor, I have little hope of fully charging
the bank. However, if we power somewhere for several hours, that does
bring it up close to 100%.

I try to avoid going below 50%, so that means I follow the now
traditional 50%-85% regime.

Jeff wrote in
:

Why are you so obsessed about this, Larry? Its gotten to the point
that you're just ranting nonsense!



http://www.batteryuniversity.com/partone-13.htm
Boiling the **** out of it isn't going to give it a saturated charge.
It's voltage comes up because the plate surface becomes coated, but
that's not charging it.....correctly.

http://www.batterystuff.com/tutorial_battery.html


http://www.bigginhill.co.uk/batteries.htm
which says:
"The Bulk Charge

In this first part of the charge the battery is allowed to have a large
draw on the available current. Usually the limit to this current level is
determined by the availability of a suitably sized mains outlet,
especially on large batteries. It is however, worth noting that that the
life of a battery will be greatest if even this first bulk phase of
charging is started off gently and the maximum current is limited. If the
current is too high the result will be excess heating within the battery
which is wasteful and could lead to buckling of the plates and
destruction of the battery. Sizing of the charger to suit the batteries
is important.

Finish charge

Once the bulk phase has been completed, the finish phase commences and
the battery charge is topped off. This phase is very important. If the
battery is not topped up gently it will overflow in the form of waste
heat and violent gassing of the plates which again can lead to the plates
buckling and the battery being destroyed. If the battery is not topped up
fully, it will become sulphated after only a few charges and the result
will be premature failure.

Equalization

In any cyclic application, a series of batteries will always need to be
equalized from time to time in order to ensure that the battery cells
remain at the same voltage throughout the pack.

No two battery cells or batteries are created equal. During both charge
and discharge each and every cell/battery will react in a minutely
different way to its neighbour. This could mean that each battery may be
holding a different quantity of charge. In order to get the most out of
the total battery pack it is necessary to make sure, as far as possible,
that each and every battery is holding a similar amount of charge.

During the charge cycle the voltages of the different batteries will
very. In order to bring them all to the same level it is necessary to
give some a slight overcharge in order to bring the other up to full
charge.

Equalization is done by allowing the voltage to rise while allowing a
small constant current to the batteries. The voltage is allowed to rise
above the normal finish voltage in order to allow the weaker
batteries/cells to draw more current. The stronger batteries will not be
adversely affected providing the current is gently and the period and
frequency of overcharging are not too high and great respectively. The
stronger batteries will absorb the overcharge by giving off heat by
gently boiling and gassing more heavily. Once the weaker batteries have
absorbed the required current, the equalization charge can be halted. The
equalization time should be long enough to bring all the batteries up to
a full state of charge. As the time factor will very the most reliable
way to check the charge states is by a voltmeter on each cell or
individual battery.

Really sophisticated battery charging and monitoring systems do not
require the use of an equalization charge and are able to charge all the
batteries fully including the weaker ones without overcharging the strong
ones.

In these systems, each battery is fitted with an electronic clamp, which
gradually reduces the amount of charge going into the fully charged
batteries as the finish charge progresses. This means that the weaker
batteries receive more current to bring them up to a full state of charge
and the strong batteries are prevented from being overcharged
unnecessarily. The drawback with these sophisticated systems is their
cost. The price of each battery clamp can be in the order of 1/5 the cost
of each battery."



Wishing it will charge in an hour is simply dreaming and really not good
for any lead acid battery, no matter how much it costs.

But, you have it YOUR WAY....(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.

Larry wrote:
Jeff wrote in
:

Why are you so obsessed about this, Larry? Its gotten to the point
that you're just ranting nonsense!



http://www.batteryuniversity.com/partone-13.htm
Boiling the **** out of it isn't going to give it a saturated charge.
It's voltage comes up because the plate surface becomes coated, but
that's not charging it.....correctly.

....

What's your point? If I can consistently charge my batteries at the
25% rate, and they last long enough so that the cost is under $50/year
what problem is there? You go on this rant every month or so,
assuming that everyone is trying to take a 100 AH bank from 0 to 100%
in ten minutes. Lots of people are running 100 Amp alternators
without cooking batteries.

Larry,

Thanks for that, but I've done my calculations...

My domestic battery bank is 315Ah. 25% is about 79A, plus running
load of say 10A gives a total required charging of around 90A. 100A
would seem a good choice as it means I don't have to run the
alternator at full speed.

Regards
Peter

"PeterS" wrote in news:1170197095.406328.242830
@l53g2000cwa.googlegroups.com:

Thanks for that, but I've done my calculations...

My domestic battery bank is 315Ah. 25% is about 79A, plus running
load of say 10A gives a total required charging of around 90A. 100A
would seem a good choice as it means I don't have to run the
alternator at full speed.

Regards
Peter


If you're buying, for that system, 100A alternator is plenty with room to
spare. Its starting bulk charge isn't dangerous to the plate
warping/gassing problems and leaves you plenty of overhead to pull a 10A to
30A load just fine. But, if you already have a perfectly good working 50A
charger, spending hundreds of dollars just to get 100A is nonsense.

Everyone is trying to get charged up in 30 minutes. I just don't care who
screams at me and calls me names....that isn't going to happen. The
chemical change in an old lead acid battery cannot be rushed. It LOOKS
like it charged, the voltage came up when we hit it with 250A for 30
minutes. But, do a load test and cycle it a few times and you end up with
plate sulfation and constantly dropping specific gravity, the only REAL
method of measuring the charge state of a lead acid battery...with a
temperature compensated hydrometer. Watching a bunch of meters, even like
a Link 10 AH meter (which has no facility to take into account overcharging
current rushing the chemistry, which is bogus) doesn't tell you how good it
is charged....

I can't wait until we dump all this ancient technology for:
http://www.eetimes.com/news/latest/s...leID=159907938

Check out this link page:
http://www.hobbyspace.com/Links/sciTech5.html
Buzz down the list until you hit LITHIUM and look at the various
technologies being done for the electric/hybrid car biz. Toshiba has its
own section of new items.

Your 1000AH nanotube Lithium house battery will be about the size of your
little starting battery, now. Nanotubes make them TINY. These are NOT
capacitors! They are chemical batteries, the same as your laptop and
cellphone. What's different is their PLATE SURFACE AREA, which is MASSIVE!

To charge IT, not them, your new diesel main engine will have a gear-
driven, oil-cooled alternator that can convert every HP of the engine into
DC current, not the wimpy 200A alternator boaters are dreaming of in this
thread. You will press the CHARGE button on the engine control panel. The
engine will be cranked by the charging computer in neutral. After a short
warmup to be safe for the engine to be heavily loaded, a full-load current
will be switched on the diesel by the computer which opens the throttle to
some maximum safe load. The huge conductors charging the little battery
will charge at thousands of amps, whatever the diesel can stand, for ONE
MINUTE. This will restore 80% of the battery's completely DEAD capacity.
The finishing charge will be about 60% of full load power and run for TWO
MINUTES, at which time the engine will shut itself down and a little beeper
will pleasantly beep while the CHARGED LED blinks for a minute to let you
know the house batteries are fully charged.

You'll smile as you have exactly what we've all been dreaming about since
we charged that first nasty lead acid way back in '62. The engine is now
ready for propulsion service and its transmission controls returned to
normal.

THREE MINUTES from DEAD to full charge. The technology now exists!

Consider what that means, though, to take advantage of it......

To charge a 1000AH house battery in ONE HOUR takes 1050A for an hour.
That's a hefty alternator, already! To charge a 1000AH house battery in 3
minutes takes 1050A divided by .05 (3min/60min) or 21,000A! That's going
to be hard to achieve!...(c; Reality will soon set in and quash the dream
of recharging in 3 minutes.....back to about 30 (2000A for 30 min?) or an
hour at 1000A. 2000A x 12V (about 4 cells of Lithium is 12V, but this new
technology doesn't get 3V/cell so it will probably be 5 cells if we stick
with 12V, which I hope we DON'T) 2000A x 12V = 24KW to charge it in 30
minutes. 29HP is about 21KW according to the Yanmar Saildrive website.
So, 24KW for charging it will be practical for a 35hp sailboat diesel and
up...charging the little beast in 30 minutes....VERY nice!

Nice to is Lithium-Ion batteries love float charging just as much as your
old house beasts, unlike Ni-Mh. You'll get used to the humming noise from
the 10KW charger plugged into the 100A service at the marina...(c;

The sooner the better! I'm gettin' heat for telling the truth about those
old crappers in the bilge!

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