On Thu, 25 Jun 2009 16:41:55 GMT, "Lew Hodgett"
wrote:

2000/15% = 13,333 AH of battery bank is required for a 2,000 amp
charging rate.

Normal charging voltage is anywhere from 13.2VDC-13.8VDC.

Lew, I respectully disagree with both of those statements.

A recharge rate of 25% is normally acceptable for the bulk charging
phase, up to 70 or 80% of full charge.

13.2 to 13.8 is usually considered the "float" range where the battery
is being maintained at full charge.

"Wayne.B" wrote:

Lew, I respectully disagree with both of those statements.

A recharge rate of 25% is normally acceptable for the bulk charging
phase, up to 70 or 80% of full charge.

The operative word is "AVERAGE".

Yes, you can have 25% recharge rate for a portion of the cycle;
however, the 15% recharge rate is a design parameter given to me by a
Trojan application engineer who at the time was older than dirt, and
had forgotten more about wet cell batteries than either one of us will
ever learn.

IOW, the time to completely recharge will be Total AH/15%.

13.2 to 13.8 is usually considered the "float" range where the
battery
is being maintained at full charge.

Back in the days when I was in this business, regulators were set as
low as possible to minimize boiling.

Basic spec was 13.6 +\- 0.2.

Lew

On Thu, 25 Jun 2009 23:29:36 GMT, "Lew Hodgett"
wrote:

Back in the days when I was in this business, regulators were set as
low as possible to minimize boiling.

Basic spec was 13.6 +\- 0.2.

That's a good "float" voltage for a battery that doesn't get
discharged very much, like an engine starting battery. A deep cycle
battery which routinely gets disharged down to the 50% level would
take forever to recharge at 13.6 volts. That's why multi-stage
chargers have become popular on cruising boats.

"Wayne.B" wrote:

A deep cycle
battery which routinely gets disharged down to the 50% level would
take forever to recharge at 13.6 volts.

"Forever" is a relative term.

Just turning on the engine is beyond "forever" for me.

Basic reason I had provided for 16, T-105s and solar panels until the
money ran outG.

A L/N 4800 machine goes a long way to minimize engine time.

It will give you 120A @ 2,000 alternator RPM which BTW, is a "hot"
rating, not "cold" as most competitors offer.

Lew

On Thu, 25 Jun 2009 09:28:33 -0400, Wayne.B
wrote:

On Thu, 25 Jun 2009 18:50:25 +0700, Bruce In Bangkok
wrote:

Larry posted about people who had multiple 250 Amp alternators
installed. I simply asked how many volts it would take to charge a
battery bank at the installed 2,000 amps.

You seem to be saying that with 14.2 - 14.4 VDC the current flow will
be 2,000 amps, which would make the battery resistance about .00715
Ohms.

Somehow I don't think that is correct..

Actually it is because that is the voltage that *all* 12 volt lead
acid batteries get charged at. The point is, that to charge at 2,000
amps, you need to have about 8,000 amp-hours of battery capacity,
which is not very practical for a 12 volt system because of connection
and wiring losses.

You seem to be confused.

As far as the charger is concerned a battery is just a resister and
acts the same as any other resister. If you increase the voltage
output of the charger you will increase the amperage flowing through
the battery.

You also seem to have missed the point of the entire exchange between
Larry and myself which was a rather (I thought) understated bit of
sarcasm about people who seem to believe that installing massive
amounts of charging capacity is going to shorten significantly the
amount of time to charge a given sized battery bank.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Thu, 25 Jun 2009 10:58:42 -0500, cavelamb
wrote:

Bruce In Bangkok wrote:
On Thu, 25 Jun 2009 05:08:26 -0400, Wayne.B
wrote:

On Thu, 25 Jun 2009 14:40:38 +0700, Bruce In Bangkok
wrote:

O.K., if you want to be pedantic,
How much voltage do you need to pump approximately 2000 X ( 6.242 ×
1018^18) electrons per second into a battery.
If the battery is sized properly, 14.2 volts will get the job done,
maybe 14.4 for the first 70 or 80% if you're in a hurry.


Larry posted about people who had multiple 250 Amp alternators
installed. I simply asked how many volts it would take to charge a
battery bank at the installed 2,000 amps.

You seem to be saying that with 14.2 - 14.4 VDC the current flow will
be 2,000 amps, which would make the battery resistance about .00715
Ohms.

Somehow I don't think that is correct..

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

Hey Bruce,

Your math is correct.

The problem is that the internal resistance of a healthy battery is a lot higher
than that (which would limit current).

I know....
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Fri, 26 Jun 2009 00:28:39 GMT, "Lew Hodgett"
wrote:


"Wayne.B" wrote:

A deep cycle
battery which routinely gets disharged down to the 50% level would
take forever to recharge at 13.6 volts.

"Forever" is a relative term.

Just turning on the engine is beyond "forever" for me.

Basic reason I had provided for 16, T-105s and solar panels until the
money ran outG.

A L/N 4800 machine goes a long way to minimize engine time.

It will give you 120A @ 2,000 alternator RPM which BTW, is a "hot"
rating, not "cold" as most competitors offer.

I have a pair of these guys rated at 250 amps and running with dual
belts:

http://www.alternatorparts.com/Extreme%20Duty%20Dual%20Rectifier%20CS-144%20type.htm

They are performing very well so far and are much less expensive than
L/Ns.

"Wayne.B" wrote:

I have a pair of these guys rated at 250 amps and running with dual
belts:

http://www.alternatorparts.com/Extreme%20Duty%20Dual%20Rectifier%20CS-144%20type.htm

They are performing very well so far and are much less expensive
than
L/Ns.

Did they include an output curve?

High output at low RPM isn't Low cost.

Neither is a "hot" rating.

Lew

On Fri, 26 Jun 2009 01:46:44 GMT, "Lew Hodgett"
wrote:

Did they include an output curve?

High output at low RPM isn't Low cost.

Neither is a "hot" rating.

They do OK on both counts based on my observations. They're mounted
on DD6-71 diesels with about a 3 to 1 sheave diameter ratio. They
start producing full output at around 1200 engine RPMs which would be
3600 alternator RPM. I have not run any long term stress tests at
high temps but have measured them with an IR gun at about 170F while
producing 200 amps. I've only got about 50 hours on them at this
point so long term durability is still a question mark. At $450 I
can afford to carry around a spare however. They are also relatively
cheap/easy to rebuild.

"Wayne.B" wrote:

They do OK on both counts based on my observations. They're
mounted
on DD6-71 diesels with about a 3 to 1 sheave diameter ratio. They
start producing full output at around 1200 engine RPMs which would
be
3600 alternator RPM.

I would expect a high output alternator to produce about 80% of
nameplate at 2,000 alternator RPM and full output at no more than
3,000 RPM.

Based on your description above doubt they would meet those output
points.

Got any idea of output at 1200-1400 engine RPM?

What is top end of the DD6-71?

Difficult to tell from limited pics on web site, but it appears you
have a small case design, but that is just a guess.

Small case design offers the designer more challenges than larger
cases.

It's mostly a thermal problem.

I have not run any long term stress tests at
high temps but have measured them with an IR gun at about 170F while
producing 200 amps. I've only got about 50 hours on them at this
point so long term durability is still a question mark. At $450 I
can afford to carry around a spare however. They are also
relatively
cheap/easy to rebuild.

$450 seems a bit high, but then I haven't looked at a price for a few
years.

Lew