Jim wrote in
ink.net:

I'm upgrading my charger to a Xantrex "True Charge" 40 amp, 3 stage
charger. The "Equalizer" function is important to maintain the
batteries.



The batteries only need 20A, so that leaves you with 20A of load current
while the charger is on.

The battery store guy should know better. 220 ampere-hours has nothing
to do with 220 amps. Ampere-Hour is a measure of the stored energy in
the battery. The "rating" only holds true for ONE load, the load that
drains it in 20 hours (that's about standard in the battery biz). 11
amps will drain it in 20 hours, so that would be the "standard load" for
this battery. The slower you discharge it, the more ampere-hours of
energy it will produce, way beyond its rating. The FASTER you discharge
it, more than 11 amps, the LESS its ampere-hour capacity is at that load.
This is caused by chemistry and physics. The chemistry is the speed at
which the acid can eat away at the soft lead plate's surface area.
Quickly discharging it with a heavy load, the acid by the plate is
quickly consumed into lead sulphate ions in suspension, blocking more
acid from attacking the plate surface. So, it's not some incredible
limit. Starting batteries overcome this problem with an incredible
number of plates producing an incredible surface area that can produce an
incredible instantaneous current.....but for a price. To keep the
physical battery size, the plates have to be very thin. Their amp-hour
rating is actually very low, as anyone who has been cranking a dead motor
for a few minutes when the lights go out can attest. Deep discharge
batteries use thick plates with lots of lead to eat and much more acid to
eat them....at a slower rate, 20 hours standard. At 50A, and I'm only
guessing as I don't have a chart in front of me but you can find them on
the net, the AH rating of the 220 AH battery is probably about half,
maybe a little more. Well, you get the picture. It's not a bottomless
pit of power, actually kind of small for its weight.

Nice charger, but you'll only see 40A charging them for a few minutes
before the charge quickly tapers off to a safe charging level below 20A.
If you never discharge them below specific gravity of 1.125, they'll last
a long time.

Larry wrote:
Jim wrote in
ink.net:


I'm upgrading my charger to a Xantrex "True Charge" 40 amp, 3 stage
charger. The "Equalizer" function is important to maintain the
batteries.




The batteries only need 20A, so that leaves you with 20A of load current
while the charger is on.


The specs call for the 20 to charge a bank 100 to 400 amps. the 40
calls for 400 +

I will have 440. I know it's ONLY 105 over . . .my thinking is to buy
the right one the first time.
The battery store guy should know better.

He said two 6v 220 amp batteries will give 12v, 440 amps.

220 ampere-hours has nothing
to do with 220 amps. Ampere-Hour is a measure of the stored energy in
the battery. The "rating" only holds true for ONE load, the load that
drains it in 20 hours (that's about standard in the battery biz). 11
amps will drain it in 20 hours, so that would be the "standard load" for
this battery. The slower you discharge it, the more ampere-hours of
energy it will produce, way beyond its rating. The FASTER you discharge
it, more than 11 amps, the LESS its ampere-hour capacity is at that load.
This is caused by chemistry and physics. The chemistry is the speed at
which the acid can eat away at the soft lead plate's surface area.
Quickly discharging it with a heavy load, the acid by the plate is
quickly consumed into lead sulphate ions in suspension, blocking more
acid from attacking the plate surface. So, it's not some incredible
limit. Starting batteries overcome this problem with an incredible
number of plates producing an incredible surface area that can produce an
incredible instantaneous current.....but for a price. To keep the
physical battery size, the plates have to be very thin. Their amp-hour
rating is actually very low, as anyone who has been cranking a dead motor
for a few minutes when the lights go out can attest. Deep discharge
batteries use thick plates with lots of lead to eat and much more acid to
eat them....at a slower rate, 20 hours standard. At 50A, and I'm only
guessing as I don't have a chart in front of me but you can find them on
the net, the AH rating of the 220 AH battery is probably about half,
maybe a little more. Well, you get the picture. It's not a bottomless
pit of power, actually kind of small for its weight.

Nice charger, but you'll only see 40A charging them for a few minutes
before the charge quickly tapers off to a safe charging level below 20A.
If you never discharge them below specific gravity of 1.125, they'll last
a long time.

Jim wrote in news:zpHrg.1717$vO.610
@newsread4.news.pas.earthlink.net:

He said two 6v 220 amp batteries will give 12v, 440 amps.


Nope....nice dream, though. Two 6V 220 AH in series gives you 12V at
220AH, not 440 AH. It's still only 220AH, just the voltage doubled. The
plates didn't get any bigger in the cells when you connected them in
series.

You can get 440AH at 6V by parallelling them....doubling the plate area....

Larry wrote:
. . .
Nice charger, but you'll only see 40A charging them for a few minutes
before the charge quickly tapers off to a safe charging level below 20A.

Hmm. Assuming 2 6v Trojan T-105s or equivalent (or an 8D), 220ah
capacity, discharged 50%, a 40 amp charge rate is only 20% of the
bank's capacity, quite safe. The bank probably won't even get warm.
If you're in a hurry, charging at a 40% rate, 80 amps (typical
alternator output), would shorten the life of the bank slightly, and
warm things up a bit, but still would be a "safe" charging rate.

A 40 amp charger should put out 40 amps for two hours or so, before the
rising voltage causes the charger to start tapering off (70%-80%
charged) down ultimately to 5 to 10 amps or so ( 2% to 5% of bank
capacity, depending on age and battery design), where it should stay
for a half hour or so (14.4 volts, Trojan says 14.8!), to gas the
batteries for a while to mix the electrolyte thoroughly and bring the
bank up those last few amp-hours to full charge. This is *not* an
equalization charge. Then you can either turn the charger off, or, if
it's smart, it'll drop back to a float charge, 13.2 volts or so, so you
can run stuff without discharging the bank.

OTOH, if you're hooked up to shore power and have all night to charge,
there's nothing wrong with charging at 10% of the bank's capacity (20
amps or so), which will prolong the bank's service life slightly. But
there's nothing *unsafe* about an initial 40 amp (20% of capacity)
charge rate on a discharged bank.

Sorry Larry, you have some misinformation here. First of all, a pair
of Trojan T105's will happily accept 40-50 Amps for an extended
period. I have 4 of them, and on a daily basis (when cruising) charge
them with a 110 Amp alternator. The charge rate starts at about 104
Amps, and slowly goes down. After about an hour it might be down to
65-70 Amps, which is where I'll usually stop. My 100 Amp charger also
hold the charge rate fairly high.

Secondly, although I don't often discharge at 50 Amps for an extended
period, most of my battery use is powering a DC fridge which draws 28
to 36 Amps. There is no evidence that this significantly reduces the
capacity of my bank. I normally discharge to about 50% (down 200-210
Amp-hours) and at that point the bank is still holding about 12 Volts
under load.

This affect is described empirically by Peukert's Equation. For each
battery design there is an exponent that allows you to predict a
battery's performance as you vary the load. Using 1.24 as a typical
"good" exponent means that 4 times the load drains the battery 5.6
times faster, implying an increase drain of a bit over a third.
Looking at the specs from Trojan:
http://www.trojan-battery.com/Produc...spx?Name=T-105
and Penn:
http://www.eastpenn-deka.com/products/pdfs/0248.pdf
it looks like they do about that. You would have to have a very high
discharge rate - close to 200 Amps - to reduce to capacity by half.
If you were actually interested in a battery for a high output
application, such as an electric car, you might look for one with an
exponent down around 1.1.

Its possible that my regime of high discharge and fast charging has
reduced the life of my batteries. But my first set lasted 7 years and
and may have gone a few more if illness had not interrupted their
proper care one winter. However, since a few phone calls turned up a
golf cart dealer that could supply them at $70 each, the cost was only
$40 per year. I have noticed that my new batteries perform better
than the old, but at 7 years the old set was probably only down 10-15%.


Larry wrote:
Jim wrote in
ink.net:

I'm upgrading my charger to a Xantrex "True Charge" 40 amp, 3 stage
charger. The "Equalizer" function is important to maintain the
batteries.



The batteries only need 20A, so that leaves you with 20A of load current
while the charger is on.

The battery store guy should know better. 220 ampere-hours has nothing
to do with 220 amps. Ampere-Hour is a measure of the stored energy in
the battery. The "rating" only holds true for ONE load, the load that
drains it in 20 hours (that's about standard in the battery biz). 11
amps will drain it in 20 hours, so that would be the "standard load" for
this battery. The slower you discharge it, the more ampere-hours of
energy it will produce, way beyond its rating. The FASTER you discharge
it, more than 11 amps, the LESS its ampere-hour capacity is at that load.
This is caused by chemistry and physics. The chemistry is the speed at
which the acid can eat away at the soft lead plate's surface area.
Quickly discharging it with a heavy load, the acid by the plate is
quickly consumed into lead sulphate ions in suspension, blocking more
acid from attacking the plate surface. So, it's not some incredible
limit. Starting batteries overcome this problem with an incredible
number of plates producing an incredible surface area that can produce an
incredible instantaneous current.....but for a price. To keep the
physical battery size, the plates have to be very thin. Their amp-hour
rating is actually very low, as anyone who has been cranking a dead motor
for a few minutes when the lights go out can attest. Deep discharge
batteries use thick plates with lots of lead to eat and much more acid to
eat them....at a slower rate, 20 hours standard. At 50A, and I'm only
guessing as I don't have a chart in front of me but you can find them on
the net, the AH rating of the 220 AH battery is probably about half,
maybe a little more. Well, you get the picture. It's not a bottomless
pit of power, actually kind of small for its weight.

Nice charger, but you'll only see 40A charging them for a few minutes
before the charge quickly tapers off to a safe charging level below 20A.
If you never discharge them below specific gravity of 1.125, they'll last
a long time.