Lew Hodgett wrote in news:1QTpi.12042$zA4.313
@newsread3.news.pas.earthlink.net:

To replace 375 AH you will require 375/115 = 3.3 hours of engine time.



A pipe dream of battery chemistry. 375AH requires 5 hours (from 50%
discharge, not zero) at 38A, not 115. Batteries charge at 10% of AH
rating, not 30, if you want to convert the electrolyte, giving it time
for circulation.

The two batteries will recharge from 50% very nicely at moderate
temperature at 75A for 5 hours on the new 90A alternator. NO battery
will charge at 115A for very long before the interplate electrolyte has
been converted faster than it can be replaced by convection in the
electrolyte. This is why you see the current drop in the first
place....NOT because it has become charged. After the initial current
blast has reconverted lead sulphate into acid, that acid must move out of
the way to be replaced by more lead sulphate ions convecting in from
below by the heat of charging. There's quite a circulation. Charging
too fast, say at 115A trying to force it fast, only results in the
conversion of H2O into hydrogen gas and lead oxide, that violent gas
bubbling it's doing at high charger currents, once the initial lead
sulphate to sulfuric acid conversion has wained on the initial blast.

I suppose we could build a magnetic drive circulator pump into the bottom
of the cells under the plates and you could charge the hell out of it,
then....

Larry
--
Charging takes time.....the more time, the better.

Larry wrote in
:

Lew Hodgett wrote in
news:1QTpi.12042$zA4.313 @newsread3.news.pas.earthlink.net:

To replace 375 AH you will require 375/115 = 3.3 hours of engine
time.



A pipe dream of battery chemistry. 375AH requires 5 hours (from 50%
discharge, not zero) at 38A, not 115. Batteries charge at 10% of AH
rating, not 30, if you want to convert the electrolyte, giving it time
for circulation.

The two batteries will recharge from 50% very nicely at moderate
temperature at 75A for 5 hours on the new 90A alternator. NO battery
will charge at 115A for very long before the interplate electrolyte
has been converted faster than it can be replaced by convection in the
electrolyte. This is why you see the current drop in the first
place....NOT because it has become charged. After the initial current
blast has reconverted lead sulphate into acid, that acid must move out
of the way to be replaced by more lead sulphate ions convecting in
from below by the heat of charging. There's quite a circulation.
Charging too fast, say at 115A trying to force it fast, only results
in the conversion of H2O into hydrogen gas and lead oxide, that
violent gas bubbling it's doing at high charger currents, once the
initial lead sulphate to sulfuric acid conversion has wained on the
initial blast.

I suppose we could build a magnetic drive circulator pump into the
bottom of the cells under the plates and you could charge the hell out
of it, then....

Larry

Lew, try a little experiment to showcase my assertion:

Charge like hell until the voltage rises up and shut her down with NO
LOAD on the batteries. Wait 30 minutes. Charged batteries will still be
charged and immediately draw little current at float voltage.

Crank the alternator-from-hell back up and watch the current....It'll go
back to hard charging at lower-than-float voltage because the convection
in the electrolyte has replaced the supercharged electrolyte with
uncharged electrolyte to continue the replating process. The current
will drop and voltage will repeat its rise charging this hard as
electrolyte, once again, becomes saturated before convection takes place.

You can repeat the phenomenon over and over with no load on the battery
between charges.

Once the cells are TRULY charged, there will be a small current when
charging starts, but the voltage will already be high putting charging in
float mode almost immediately.

Larry
--
SLOWLY.....we recharge SLOWLY.....

Larry wrote:


A pipe dream of battery chemistry. 375AH requires 5 hours (from 50%
discharge, not zero) at 38A, not 115. Batteries charge at 10% of AH
rating, not 30, if you want to convert the electrolyte, giving it time
for circulation.

Spoken with the vision of a person with his head squarely placed where
the moon doesn't shine.

Plonk

Lew

Lew Hodgett wrote in news:FPWpi.11839$Od7.10372
@newsread1.news.pas.earthlink.net:

Larry wrote:


A pipe dream of battery chemistry. 375AH requires 5 hours (from 50%
discharge, not zero) at 38A, not 115. Batteries charge at 10% of AH
rating, not 30, if you want to convert the electrolyte, giving it time
for circulation.

Spoken with the vision of a person with his head squarely placed where
the moon doesn't shine.

Plonk

Lew


Sorry you feel that way. Telling them they can recharge by shoving current
like hell into it in 3 hours is still a pipe dream.

Larry
--
While in Mexico, I didn't have to press 1 for Spanish.
While in Iran, I didn't have to press 1 for Farsi, either.
While in Florida, I had to press 2 for English.
It just isn't fair.

* Larry wrote, On 7/26/2007 12:36 AM:
Lew Hodgett wrote in news:1QTpi.12042$zA4.313
@newsread3.news.pas.earthlink.net:

To replace 375 AH you will require 375/115 = 3.3 hours of engine time.



A pipe dream of battery chemistry. 375AH requires 5 hours (from 50%
discharge, not zero) at 38A, not 115. Batteries charge at 10% of AH
rating, not 30, if you want to convert the electrolyte, giving it time
for circulation.

You've made this assertion many times, and its still completely false.
Or possibly, I have magic batteries. I have 4 Trojan T-105's for a
total of 450 Amp-hours. The 110 Amp alternator, controlled by a Link
2000R generally charges at about 90 Amps, slowly dropping to around
75. At that point, its around 80% full. Continuing to charge, it
goes down to 50, when I figure its close to 90%. The first set of
batteries last 6 years, and were really killed by a sever winter. The
new set is on its third year.

BTW, I don't have double belts, but I cook at least one year.

Larry wrote in
:

A pipe dream of battery chemistry. 375AH requires 5 hours (from 50%
discharge, not zero) at 38A, not 115. Batteries charge at 10% of AH
rating, not 30, if you want to convert the electrolyte, giving it time
for circulation.

I note that my batteries (2 Caterpillar 153-5720 8Ds) are speced at a max
charging rate of 5% of their CCA, which is 1500 A. That works out to 75 A.
Each of the batteries have a rating of 210 AH, which based upon Larry's
math, would be 21 Amps, or 42A for both of them.

That said, this whole discussion doesn't make a lot of sense to me. I
watch my 3 stage regulator charging rates, and it spends very little time
charging at full throttle. When initially turned on, the charger goes into
bulk charging mode and attempts to get the charging voltage up to the bulk
charging voltage. This voltage depends upon the battery temperature and I
have a thermocouple which sends the battery temperature back to the
charger. I've specified a temperature coefficient in the charger (which is
specified in mV/degree C) and as the battery gets warmer, the bulk charging
voltage drops.

Anyhow, I try not to let my batteries get below 12.5V. When I charge the
batteries I see my charger outputting at its maximum charge rate (110A) for
about 15 minutes and then it typically has reached the bulk charging
voltage. Then the charging rate drops as it maintains that voltage. My
typical charging cycle runs for about 1 hour, and at the end of that hour
I'm only outputting about 20A. It will take several more hours for the
rate to drop to 0.

Thus, this talk about charging at some rediculously high rate for X hours
doesn't seem to have much to do with real charging systems

-- GEoff

Geoff Schultz wrote in
:

I note that my batteries (2 Caterpillar 153-5720 8Ds) are speced at a
max charging rate of 5% of their CCA, which is 1500 A. That works out
to 75 A. Each of the batteries have a rating of 210 AH, which based
upon Larry's math, would be 21 Amps, or 42A for both of them.

That said, this whole discussion doesn't make a lot of sense to me. I
watch my 3 stage regulator charging rates, and it spends very little
time charging at full throttle. When initially turned on, the charger
goes into bulk charging mode and attempts to get the charging voltage
up to the bulk charging voltage. This voltage depends upon the
battery temperature and I have a thermocouple which sends the battery
temperature back to the charger. I've specified a temperature
coefficient in the charger (which is specified in mV/degree C) and as
the battery gets warmer, the bulk charging voltage drops.



The 3-stage charger bulk charges the initial load of electrolyte between
the plates that WILL take a tremendous current and charge with it until
it has been converted back to acid and replated the lead. Then, as you
say, it drops back to give the battery time to recover its electrolyte by
convection back between the plates with a much lower charge current
(stage 2) after the voltage rises from the recharge I alluded to in stage
1. State 2, a more sedate charge rate that prevents you from warping the
plates with 100+ amps by melting them, possibly causing a
short/explosion, continues unabated with short periods of zero current
for charge testing, then turns back on until the test period voltage
remains higher than the natural voltage of the cells, indicating nearly
full charge. It then switches to stage 3 which is a very slow topping
off charge.

Investigating Lew's 115A at 14V massive charge for 3 hours shows 115 X
14V = 1,610 watts being shoved into the battery. At first, this will be
absorbed a lot by the chemical reaction converting back to acid. But, as
the charge between the plates quickly completes and he goes into the
gassing phase converting his water into hydrogen, this power starts being
turned into heat, heating the electrolyte and plates, which are soft to
begin with, an possibly, probably, warping the plate structure,
especially if the cells aren't straight up vertical, such as being heeled
over with sail aloft of sloshing about in the waves. 1,610 watts is a
lot of DC power to pour through a rubber or plastic case...and will not
just go off easily sealed away in those tight battery boxes that insulate
the battery from any air cooling....making the heating problem worse.

He didn't want to hear my sad story, so I hope the rest of you will think
about what I'm saying before the big bang coats your boat with
acid....not a pretty sight at all!

Larry
--
Cursing me won't change physics or chemistry.....