12v supply from a 24v system

"Pete Verdon" wrote in message
> Capt. NealŪ wrote:
>
>> You need to learn how circuits work before you spew your nonsense,
>> Mr. Sprang.
>
> Hmm. Perhaps he should stop being a professional electronics engineer too, eh?
>
> Pete

He needs to go back to school!

CN
 >> Stay informed about: 12v supply from a 24v system 

"Capt. NealŪ" wrote in message

> Wrong, wrong, wrong, wrong, wrong, wrong and incorrect!
> How can some people's minds be so ineffective at thinking?

I know it is pointless to argue with you but:

> Perhaps you wankers would understand it better using flashlight D cells
> as an example. Take one D cell that is half charged (Ni-Cad) and put it
into
> a two-cell flashlight in the company of another NI-Cad) D cell that is
fully
> charged and turn on the switch. The bulb will light and current will
> pass through the circuit. As well as working to light the bulb, the
> fully-charged cell will discharge into the half charge cell until
> the voltage in both cells equalizes.

Perhaps you could try to envision in which direction current flows through
the empty cell in this example and next, try to envision in which direction
current flows when *charging* a cell. Or even better: try this example for
yourself.

> I hope this helps.

Certainly not.

Meindert
 >> Stay informed about: 12v supply from a 24v system 

"Nigel" wrote in message

> I have a 24v electrical set up on my boat, but need a 12v supply for my
VHF
> (amongst other things). Is there any reason why I can't just run a 12v
> supply from just one of a pair of batteries, or do I need to use a 24v/12v
> converter. I release this will draw charge from just one battery , but
won't
> the other just top it up and there by drain them both equally
> Thanks
>
>
At least everyone seems to agree that the problem (non existing according to
some people) is in the re-charging, not in the tapping off of the 12V.
It's interesting why so many people got it wrong. Perhaps it is because
they wrongly use the analogy with water. A water-flow through 2 unequally
filled reservoirs in series will cause the reservoirs to level, but not an
electric current through batteries. The total current has to flow through
both batteries. The difference with the example of the water reservoirs is
that the current itself does not charge the batteries, like the water does
to the reservoirs. It is the chemical EFFECT that the electric current has
on the batteries that charges them. The two unequally charged batteries have
different resistances and as they are in series they form a voltage divider.
During charging, the charger's voltage regulator senses the TOTAL Voltage of
the two batteries is series and adjusts the current to keep this at say 28.8
Volts during the absorbtion stage. The battery with the lower charge may be
charged with 14.2 Volts and the untapped one with 14.6 Volts. The latter
will gass and suffer and eventually fail, if this mistreatment takes place
on a regular basis.
During gassing, the full battery's Voltage will still rise, but slower than
the battery with the lesser charge.
This means that the lower battery will eventually reach near full charge,
but it will take long and at a great cost to the gassing battery.
To prevent overcharging and gassing of one battery, the charger should look
at the Voltage x 2 to of the higher Voltage battery. This can be achieved by
sensing only the untapped battery and using a 2x Voltage multiplier circuit.
By connecting the sense wire of the voltage regulator to this circuit, a
simple safety mechanism is built. Absorbtion charging will stop when this
battery reaches 14.4 Volts. It will protect the untapped (higher V) battery,
but it will take a long time for the tapped battery to reach near-full
charge state, as the full battery "puts the brake on". This not fully
charged state is less damaging than the gassing and is acceptable.
One way to compensate for this would be to connect a 12V solar panel to this
battery to top it up to full charge when the boat is not being used.
Wout
 >> Stay informed about: 12v supply from a 24v system 

On Mon, 18 Apr 2005 14:13:29 +1200, "Wout B"
wrote:

>
>"Nigel" wrote in message
>
>> I have a 24v electrical set up on my boat, but need a 12v supply for my
>VHF
>> (amongst other things). Is there any reason why I can't just run a 12v
>> supply from just one of a pair of batteries, or do I need to use a 24v/12v
>> converter. I release this will draw charge from just one battery , but
>won't
>> the other just top it up and there by drain them both equally
>> Thanks
>>
>>
>At least everyone seems to agree that the problem (non existing according to
>some people) is in the re-charging, not in the tapping off of the 12V.
>It's interesting why so many people got it wrong. Perhaps it is because
>they wrongly use the analogy with water. A water-flow through 2 unequally
>filled reservoirs in series will cause the reservoirs to level, but not an
>electric current through batteries. The total current has to flow through
>both batteries. The difference with the example of the water reservoirs is
>that the current itself does not charge the batteries, like the water does
>to the reservoirs. It is the chemical EFFECT that the electric current has
>on the batteries that charges them. The two unequally charged batteries have
>different resistances and as they are in series they form a voltage divider.
>During charging, the charger's voltage regulator senses the TOTAL Voltage of
>the two batteries is series and adjusts the current to keep this at say 28.8
>Volts during the absorbtion stage. The battery with the lower charge may be
>charged with 14.2 Volts and the untapped one with 14.6 Volts. The latter
>will gass and suffer and eventually fail, if this mistreatment takes place
>on a regular basis.
>During gassing, the full battery's Voltage will still rise, but slower than
>the battery with the lesser charge.
>This means that the lower battery will eventually reach near full charge,
>but it will take long and at a great cost to the gassing battery.
>To prevent overcharging and gassing of one battery, the charger should look
>at the Voltage x 2 to of the higher Voltage battery. This can be achieved by
>sensing only the untapped battery and using a 2x Voltage multiplier circuit.
>By connecting the sense wire of the voltage regulator to this circuit, a
>simple safety mechanism is built. Absorbtion charging will stop when this
>battery reaches 14.4 Volts. It will protect the untapped (higher V) battery,
>but it will take a long time for the tapped battery to reach near-full
>charge state, as the full battery "puts the brake on". This not fully
>charged state is less damaging than the gassing and is acceptable.
>One way to compensate for this would be to connect a 12V solar panel to this
>battery to top it up to full charge when the boat is not being used.
>Wout
>
>
>
Good explanation. As an added note,
not fully charging a battery is less damaging than overcharging but:

If just sensing the "untapped" battery and the charger shuts down,
goes into the float mode because that battery is fully charged, then
the "tapped" battery will never get a full charge. A battery that
never gets a full charge will sulfate and have a shorter life because
of it.
There is no way to win short of having individual chargers for each
battery. Or don't tap the battery bank.

Regards
Gary
 >> Stay informed about: 12v supply from a 24v system 

"Gary Schafer" wrote in message

> On Mon, 18 Apr 2005 14:13:29 +1200, "Wout B"
> wrote:
>
> >
> >"Nigel" wrote in message
> >
> >> I have a 24v electrical set up on my boat, but need a 12v supply for my
> >VHF
> >> (amongst other things). Is there any reason why I can't just run a 12v
> >> supply from just one of a pair of batteries, or do I need to use a
24v/12v
> >> converter. I release this will draw charge from just one battery , but
> >won't
> >> the other just top it up and there by drain them both equally
> >> Thanks
> >>
> >>
> >At least everyone seems to agree that the problem (non existing according
to
> >some people) is in the re-charging, not in the tapping off of the 12V.
> >It's interesting why so many people got it wrong. Perhaps it is because
> >they wrongly use the analogy with water. A water-flow through 2 unequally
> >filled reservoirs in series will cause the reservoirs to level, but not
an
> >electric current through batteries. The total current has to flow through
> >both batteries. The difference with the example of the water reservoirs
is
> >that the current itself does not charge the batteries, like the water
does
> >to the reservoirs. It is the chemical EFFECT that the electric current
has
> >on the batteries that charges them. The two unequally charged batteries
have
> >different resistances and as they are in series they form a voltage
divider.
> >During charging, the charger's voltage regulator senses the TOTAL Voltage
of
> >the two batteries is series and adjusts the current to keep this at say
28.8
> >Volts during the absorbtion stage. The battery with the lower charge may
be
> >charged with 14.2 Volts and the untapped one with 14.6 Volts. The latter
> >will gass and suffer and eventually fail, if this mistreatment takes
place
> >on a regular basis.
> >During gassing, the full battery's Voltage will still rise, but slower
than
> >the battery with the lesser charge.
> >This means that the lower battery will eventually reach near full charge,
> >but it will take long and at a great cost to the gassing battery.
> >To prevent overcharging and gassing of one battery, the charger should
look
> >at the Voltage x 2 to of the higher Voltage battery. This can be achieved
by
> >sensing only the untapped battery and using a 2x Voltage multiplier
circuit.
> >By connecting the sense wire of the voltage regulator to this circuit, a
> >simple safety mechanism is built. Absorbtion charging will stop when this
> >battery reaches 14.4 Volts. It will protect the untapped (higher V)
battery,
> >but it will take a long time for the tapped battery to reach near-full
> >charge state, as the full battery "puts the brake on". This not fully
> >charged state is less damaging than the gassing and is acceptable.
> >One way to compensate for this would be to connect a 12V solar panel to
this
> >battery to top it up to full charge when the boat is not being used.
> >Wout
> >
> >
> >
> Good explanation. As an added note,
> not fully charging a battery is less damaging than overcharging but:
>
> If just sensing the "untapped" battery and the charger shuts down,
> goes into the float mode because that battery is fully charged, then
> the "tapped" battery will never get a full charge. A battery that
> never gets a full charge will sulfate and have a shorter life because
> of it.
> There is no way to win short of having individual chargers for each
> battery. Or don't tap the battery bank.
>
> Regards
> Gary

Gary,
Going too early into float-mode is a general problem with chargers. I've
"doctored" my smart 3-stage alternator V-reg to prolongue absorption. If
the batteries are not all that new anymore the V- level jumps up very
quickly. Timed absorption stage with adjustable time is ideal, because the
age and state of the batteries can be compensated for. In my opinion,
provided that the gassing is prevented as described and provided that the
tapped battery is regularly brought up to full charge in some way, the
tapping is O.K., if it is only for electronics. Maybe install a simple
changeover switch to tap the batteries in turn. Very important is of course,
like someone else mentioned before, that the electronics that are run this
way have an isolated -wire, not connected to the 24V system's ground.
Regards,
Wout





Maybe the batteries need replacement a year or so earlier, but I think it
will work out cheaper. Many people leave their boats on the moorings for
weeks with half-charged batteries and they still seem to get years of use
out of them. A bit of "tapping", wisely done, A cheap solution would also
be to install a changeover switch, to tap the batteries in turn, but the
gassing-prevention has to be number 1.
 >> Stay informed about: 12v supply from a 24v system 

In article ,
Gary Schafer wrote:

> Of course maybe the "Capn" has some sort of magic battery in his boat.
>
> Regards
> Gary

The only thing Capt. Neal has on his boat is a lot of "Magic smoke"
that escaped his DC electrical Panel......


Me
 >> Stay informed about: 12v supply from a 24v system 

In article ,
Capt. NealŪ wrote:

> He needs to go back to school!
>
> CN

You Sir, are a complete, and utter Moroooon.... (Bugs Bunny Definition)
Now please take you DC Electrical Theories over to one of the
alt.engineering Newsgroups and see if they fly over there...... I can
hear the "Rolling on the floor, Laughing" already.....

We here have been vary patient with you, but your entertainment value
is about run it's course, and your noninformative posts could actually
cost unlearned folks, money and time. I only hope your Navigation skills
aren't on a par with you engineering skills.


Me
 >> Stay informed about: 12v supply from a 24v system 

"Me" wrote in message
> In article ,
> Capt. NealŪ wrote:
>
>> He needs to go back to school!
>>
>> CN
>
> You Sir, are a complete, and utter Moroooon.... (Bugs Bunny Definition)
> Now please take you DC Electrical Theories over to one of the
> alt.engineering Newsgroups and see if they fly over there...... I can
> hear the "Rolling on the floor, Laughing" already.....
>
> We here have been vary patient with you, but your entertainment value
> is about run it's course, and your noninformative posts could actually
> cost unlearned folks, money and time. I only hope your Navigation skills
> aren't on a par with you engineering skills.
>
>
> Me

Are you trying to claim that a battery in certain state of discharge cannot
be charged by a battery that is fully charged if the batteries are connected
in a circuit?

CN
 >> Stay informed about: 12v supply from a 24v system 

In message ,
=?Windows-1252?Q?Capt. _Neal=AE?= writes
>
>
>Sorry, I'm an expert yacht electrician and I used to teach 12v electrical
>circuits at one time. I know of which I speak.
>
Hmm..

...this little spat looks as though the 'great' are taking on the
'good'..

<.. to the consternation of those - like me - who would appreciate a
definitive answer..>

Any chance of MOBbing in an expert? This thread ain't gonna go away, is
it..?

--
Keith replace nospam with ilf0rd
 >> Stay informed about: 12v supply from a 24v system 

In message , Me
writes
>In article ,
> Capt. NealŪ wrote:
>
>> He needs to go back to school!
>>
>> CN
>
>You Sir, are a complete, and utter Moroooon.... (Bugs Bunny Definition)
>Now please take you DC Electrical Theories over to one of the
>alt.engineering Newsgroups and see if they fly over there...... I can
>hear the "Rolling on the floor, Laughing" already.....
>
>We here have been vary patient with you, but your entertainment value
>is about run it's course, and your noninformative posts could actually
>cost unlearned folks, money and time. I only hope your Navigation skills
>aren't on a par with you engineering skills.
>
>
>Me

Would you like to 'de-cloak' from your anonymous header? Or are you yet
another pontificating troll?
--
Keith replace nospam with ilf0rd
 >> Stay informed about: 12v supply from a 24v system 

In message , Me
writes
>In article ,
> Gary Schafer wrote:
>
>> Of course maybe the "Capn" has some sort of magic battery in his boat.
>>
>> Regards
>> Gary
>
>The only thing Capt. Neal has on his boat is a lot of "Magic smoke"
>that escaped his DC electrical Panel......
>
>
White smoke presumably?

He thinks he's the best thing since Go<no signal>
--
Keith replace nospam with ilf0rd
 >> Stay informed about: 12v supply from a 24v system 

In message ,
=?Windows-1252?Q?Capt. _Neal=AE?= writes
>
>"Me" wrote in message
>
>>>
>>> I hope this simple example will reduce your fogged thinking.
>>
>> and the Dufus chimes in again, with more off the wall BS.....
>>
>Why not refute my example instead of calling me names.?
>
I thought you were a pretty good troll, Cap'n..


The prat responding to you makes you look like a puking infant, if one
adopts trolling criteria..
--
Keith replace nospam with ilf0rd
 >> Stay informed about: 12v supply from a 24v system 

"Keith" wrote in message
> In message ,
> =?Windows-1252?Q?Capt. _Neal=AE?= writes
>>
>>"Me" wrote in message
>>
>>>>
>>>> I hope this simple example will reduce your fogged thinking.
>>>
>>> and the Dufus chimes in again, with more off the wall BS.....
>>>
>>Why not refute my example instead of calling me names.?
>>
> I thought you were a pretty good troll, Cap'n..
>
>
> The prat responding to you makes you look like a puking infant, if one
> adopts trolling criteria..
> --
> Keith replace nospam with ilf0rd



I'm not trolling here. I'm attempting to educate some folks who need it.

CN
 >> Stay informed about: 12v supply from a 24v system