"James Hahn" wrote in message
news
"Meindert Sprang" wrote in message
...
snip


The other possibility is that due to a deeper discharge of one battery,
it
takes longer for the total voltage to reach the point where the charger
goes
from bulk to float. So while for the more empty battery the charge is
still
ok (bulk), the other one still gets the full bulk current too while it
should receive a float charge.
Deeper discharge of some cells in the string will not, of itself, mean
that the charge takes longer. The _difference_ doesn't matter. The amount
of charge required controls the charge time. Whether OP is running his
radio off one battery or both makes no difference to the ah used, and
therfore no difference to the charge time (except, of course, that if he
uses a converter he will be consuming more ah for a given usage than if he
uses just one battery).

Go and read my last post again. The charge doesn't magically share itself
according to need between the two batteries connected in series. Instead,
the charging current supplies equal charge to both batteries. If one
becomes fully charged before the other, then the only way that the partially
charged battery can get more charge is by overcharging the other. That
overcharge is "energy" which cannot be stored in the battery, but has to go
somewhere, and that somewhere is either/or elctrolysing the battery water to
oxygen and hydrogen, and heat. If the discrepancy is small, it probably
doesn't matter, but if not, then it certainly does.

Forget for a moment the issue of connecting a 12 volt load
to a 24 volt system.

Consider only the problem of properly charging two 12 volt
batteries in series with a single 24 volt charger. My
understanding is that unless the two batteries are identical
(goes way beyond same make or capacity) they will not be
charged to the same voltage. Two electrically non-identical
batteries will have different internal resistances (by
assumption)and thus charge to different voltages. As I
mentioned in an earlier post, Ample Power shares this
understanding and offers a 24 volt charger that is in
reality two 12 volt chargers, one connected to each of the
two 12 volt batteries (which are in series, of course).

If my understanding is incorrect, that would mean that a 12
volt marine battery and 8 AAA's in series would all be
properly charged by a 24 volt charger (with current limited
so as not to destroy the AAA's). An attempted reductio ad
absurdum.

My point is simply that with a real-world installation of
two 12 volt batteries in series, the two batteries will
probably measure different voltages. The greater the
differences between the batteries, the greater the potential
problem (no pun).

Without knowing the internal resistances, etc. of the two
batteries, it is not possible to know the precise effect of
placing a different load on one of the batteries. Doing so
would effectively place the added load resistance in
parallel with the internal resistance of the affected
battery. That could make the two batteries either more or
less alike, depending on the values involved.

All of this is hand-waving, of course, because a battery's
internal resistance is really not a constant, but a function
of the battery's chemistry, state-of-charge, etc. It is a
non-linear resistance, in that it varies with current. I
don't believe we miss the mark here by ignoring these
factors, however.

Regards,

Chuck









Pete Styles wrote:
"James Hahn" wrote in message
news
"Meindert Sprang" wrote in message
...

snip

The other possibility is that due to a deeper discharge of one battery,
it
takes longer for the total voltage to reach the point where the charger
goes
from bulk to float. So while for the more empty battery the charge is
still
ok (bulk), the other one still gets the full bulk current too while it
should receive a float charge.

Deeper discharge of some cells in the string will not, of itself, mean
that the charge takes longer. The _difference_ doesn't matter. The amount
of charge required controls the charge time. Whether OP is running his
radio off one battery or both makes no difference to the ah used, and
therfore no difference to the charge time (except, of course, that if he
uses a converter he will be consuming more ah for a given usage than if he
uses just one battery).


Go and read my last post again. The charge doesn't magically share itself
according to need between the two batteries connected in series. Instead,
the charging current supplies equal charge to both batteries. If one
becomes fully charged before the other, then the only way that the partially
charged battery can get more charge is by overcharging the other. That
overcharge is "energy" which cannot be stored in the battery, but has to go
somewhere, and that somewhere is either/or elctrolysing the battery water to
oxygen and hydrogen, and heat. If the discrepancy is small, it probably
doesn't matter, but if not, then it certainly does.

On Sat, 16 Apr 2005 10:12:46 GMT, "Pete Styles"
wrote:


"James Hahn" wrote in message
news
"Meindert Sprang" wrote in message
...
snip


The other possibility is that due to a deeper discharge of one battery,
it
takes longer for the total voltage to reach the point where the charger
goes
from bulk to float. So while for the more empty battery the charge is
still
ok (bulk), the other one still gets the full bulk current too while it
should receive a float charge.
Deeper discharge of some cells in the string will not, of itself, mean
that the charge takes longer. The _difference_ doesn't matter. The amount
of charge required controls the charge time. Whether OP is running his
radio off one battery or both makes no difference to the ah used, and
therfore no difference to the charge time (except, of course, that if he
uses a converter he will be consuming more ah for a given usage than if he
uses just one battery).

Go and read my last post again. The charge doesn't magically share itself
according to need between the two batteries connected in series. Instead,
the charging current supplies equal charge to both batteries. If one
becomes fully charged before the other, then the only way that the partially
charged battery can get more charge is by overcharging the other. That
overcharge is "energy" which cannot be stored in the battery, but has to go
somewhere, and that somewhere is either/or elctrolysing the battery water to
oxygen and hydrogen, and heat. If the discrepancy is small, it probably
doesn't matter, but if not, then it certainly does.


Pete is right on the mark. Reread his prior post. Also go back and
read Bruce's post on the subject. It is bad news to tap a battery
bank.

You can get away with it for a time but it will shorten battery life
because the two batteries do not get charged equally.
As Pete says, "in order to get the battery that is used the most
charged fully you must overcharge the other". There is no way around
that.

Overcharging a battery not only cause water loss but it can warp the
plates in the battery among other things.

Overcharging is the biggest killer of batteries.
Just ask anyone that still uses a feroresonant charger. They will tell
you batteries last only a couple of years.

Do it properly and use the inverter.

regards
Gary

"Gary Schafer" wrote in message ...
On Sat, 16 Apr 2005 10:12:46 GMT, "Pete Styles"
wrote:


"James Hahn" wrote in message
news
"Meindert Sprang" wrote in message
...
snip


The other possibility is that due to a deeper discharge of one battery,
it
takes longer for the total voltage to reach the point where the charger
goes
from bulk to float. So while for the more empty battery the charge is
still
ok (bulk), the other one still gets the full bulk current too while it
should receive a float charge.
Deeper discharge of some cells in the string will not, of itself, mean
that the charge takes longer. The _difference_ doesn't matter. The amount
of charge required controls the charge time. Whether OP is running his
radio off one battery or both makes no difference to the ah used, and
therfore no difference to the charge time (except, of course, that if he
uses a converter he will be consuming more ah for a given usage than if he
uses just one battery).

Go and read my last post again. The charge doesn't magically share itself
according to need between the two batteries connected in series. Instead,
the charging current supplies equal charge to both batteries. If one
becomes fully charged before the other, then the only way that the partially
charged battery can get more charge is by overcharging the other. That
overcharge is "energy" which cannot be stored in the battery, but has to go
somewhere, and that somewhere is either/or elctrolysing the battery water to
oxygen and hydrogen, and heat. If the discrepancy is small, it probably
doesn't matter, but if not, then it certainly does.


Pete is right on the mark. Reread his prior post. Also go back and
read Bruce's post on the subject. It is bad news to tap a battery
bank.

You can get away with it for a time but it will shorten battery life
because the two batteries do not get charged equally.
As Pete says, "in order to get the battery that is used the most
charged fully you must overcharge the other". There is no way around
that.

Overcharging a battery not only cause water loss but it can warp the
plates in the battery among other things.

Overcharging is the biggest killer of batteries.
Just ask anyone that still uses a feroresonant charger. They will tell
you batteries last only a couple of years.

Do it properly and use the inverter.

regards
Gary

I disagree. Two 12v batteries in series to make a 24v battery will self-level
with respect to charge.

They will self level even if one is tapped to run a VHF. No harm will come
to either battery. Voltage can be likened to pressure.

I hope this helps.

CN

"Capt. Neal®" wrote in message
...

"Gary Schafer" wrote in message
...
On Sat, 16 Apr 2005 10:12:46 GMT, "Pete Styles"
wrote:


"James Hahn" wrote in message
news "Meindert Sprang" wrote in message
...
snip


The other possibility is that due to a deeper discharge of one
battery, it
takes longer for the total voltage to reach the point where the
charger goes
from bulk to float. So while for the more empty battery the charge is
still
ok (bulk), the other one still gets the full bulk current too while it
should receive a float charge.
Deeper discharge of some cells in the string will not, of itself, mean
that the charge takes longer. The _difference_ doesn't matter. The
amount of charge required controls the charge time. Whether OP is
running his radio off one battery or both makes no difference to the ah
used, and therfore no difference to the charge time (except, of course,
that if he uses a converter he will be consuming more ah for a given
usage than if he uses just one battery).

Go and read my last post again. The charge doesn't magically share itself
according to need between the two batteries connected in series. Instead,
the charging current supplies equal charge to both batteries. If one
becomes fully charged before the other, then the only way that the
partially charged battery can get more charge is by overcharging the
other. That overcharge is "energy" which cannot be stored in the battery,
but has to go somewhere, and that somewhere is either/or elctrolysing the
battery water to oxygen and hydrogen, and heat. If the discrepancy is
small, it probably doesn't matter, but if not, then it certainly does.

Pete is right on the mark. Reread his prior post. Also go back and
read Bruce's post on the subject. It is bad news to tap a battery
bank.

You can get away with it for a time but it will shorten battery life
because the two batteries do not get charged equally.
As Pete says, "in order to get the battery that is used the most
charged fully you must overcharge the other". There is no way around
that.

Overcharging a battery not only cause water loss but it can warp the
plates in the battery among other things.

Overcharging is the biggest killer of batteries.
Just ask anyone that still uses a feroresonant charger. They will tell
you batteries last only a couple of years.

Do it properly and use the inverter.

regards
Gary

I disagree. Two 12v batteries in series to make a 24v battery will
self-level
with respect to charge.

They will self level even if one is tapped to run a VHF. No harm will come
to either battery. Voltage can be likened to pressure.
I hope this helps.

CN


Capt. Neal thinks I'm wrong.
I rest my case!
:-)
P.

In article ,
Capt. Neal® wrote:

I disagree. Two 12v batteries in series to make a 24v battery will self-level
with respect to charge.

They will self level even if one is tapped to run a VHF. No harm will come
to either battery. Voltage can be likened to pressure.

I hope this helps.

CN

bullcrap.... Better to leave the Blackgang stuff to the engineers that
know what they are talking about......

Me

"Me" wrote in message ...
In article ,
Capt. Neal® wrote:

I disagree. Two 12v batteries in series to make a 24v battery will self-level
with respect to charge.

They will self level even if one is tapped to run a VHF. No harm will come
to either battery. Voltage can be likened to pressure.

I hope this helps.

CN

bullcrap.... Better to leave the Blackgang stuff to the engineers that
know what they are talking about......

Me


I'm an electrician. Don't insult me with this engineer crap. I know how
batteries work and I know circuits - particularly DC circuits.

You idiots are only correct provided there is no circuit to which the
two 12v batteries in series are connected. In any yacht I've ever
been on the batteries are part of a circuit of there would be no
use to have them aboard other than as ballast.

In Nigel's case, tapping off one of two batteries connected in series in
a circuit to run his VHF will not cause only the tapped battery to discharge
as the voltage in the circuit will be lowered and not just the voltage
in the tapped battery.

Only if the two batteries were disconnected from the circuit would
the tapped battery discharge more than the untapped battery.

C'mon, folks, it doesn't take a rocket scientist to figure something
this basic out.

CN

I've never known an electricain that knew much about DC. Most deal with
nothing but AC and then only know about standard codes and
techniques related to household and industrial wiring. You would
get better mileage claiming you are a neurosurgeon, Neal.


"Capt. Neal®" wrote in message
...

"Me" wrote in message
...
In article ,
Capt. Neal® wrote:

I disagree. Two 12v batteries in series to make a 24v battery will
self-level
with respect to charge.

They will self level even if one is tapped to run a VHF. No harm will
come
to either battery. Voltage can be likened to pressure.

I hope this helps.

CN

bullcrap.... Better to leave the Blackgang stuff to the engineers that
know what they are talking about......

Me


I'm an electrician. Don't insult me with this engineer crap. I know how
batteries work and I know circuits - particularly DC circuits.

You idiots are only correct provided there is no circuit to which the
two 12v batteries in series are connected. In any yacht I've ever
been on the batteries are part of a circuit of there would be no
use to have them aboard other than as ballast.

In Nigel's case, tapping off one of two batteries connected in series in
a circuit to run his VHF will not cause only the tapped battery to
discharge
as the voltage in the circuit will be lowered and not just the voltage
in the tapped battery.

Only if the two batteries were disconnected from the circuit would
the tapped battery discharge more than the untapped battery.

C'mon, folks, it doesn't take a rocket scientist to figure something
this basic out.

CN

In article ,
Capt. Neal® wrote:

I'm an electrician. Don't insult me with this engineer crap. I know how
batteries work and I know circuits - particularly DC circuits.

You idiots are only correct provided there is no circuit to which the
two 12v batteries in series are connected. In any yacht I've ever
been on the batteries are part of a circuit of there would be no
use to have them aboard other than as ballast.

In Nigel's case, tapping off one of two batteries connected in series in
a circuit to run his VHF will not cause only the tapped battery to discharge
as the voltage in the circuit will be lowered and not just the voltage
in the tapped battery.

Only if the two batteries were disconnected from the circuit would
the tapped battery discharge more than the untapped battery.

C'mon, folks, it doesn't take a rocket scientist to figure something
this basic out.

CN

Like I stated before, if you paid any money for your electrical
education, you certainly should go back and ask for a refund,
because you didn't learn anything in DC Class......


Me

"Me" wrote in message ...
In article ,
Capt. Neal® wrote:

I'm an electrician. Don't insult me with this engineer crap. I know how
batteries work and I know circuits - particularly DC circuits.

You idiots are only correct provided there is no circuit to which the
two 12v batteries in series are connected. In any yacht I've ever
been on the batteries are part of a circuit of there would be no
use to have them aboard other than as ballast.

In Nigel's case, tapping off one of two batteries connected in series in
a circuit to run his VHF will not cause only the tapped battery to discharge
as the voltage in the circuit will be lowered and not just the voltage
in the tapped battery.

Only if the two batteries were disconnected from the circuit would
the tapped battery discharge more than the untapped battery.

C'mon, folks, it doesn't take a rocket scientist to figure something
this basic out.

CN

Like I stated before, if you paid any money for your electrical
education, you certainly should go back and ask for a refund,
because you didn't learn anything in DC Class......


Me

Sorry, I'm an expert yacht electrician and I used to teach 12v electrical
circuits at one time. I know of which I speak.

CN