Battery cable selection

RST Engineering schreef:
Kirchoff is rolling over in his grave.
I guess that should read Kirchhof, should anyone wish to google it up.
For one example, see http://www.allaboutcircuits.com/vol_1/chpt_6/4.html

jan olieslagers schreef:
RST Engineering schreef:
Kirchoff is rolling over in his grave.
I guess that should read Kirchhof, should anyone wish to google it up.
For one example, see http://www.allaboutcircuits.com/vol_1/chpt_6/4.html

Hm. Actually it is Kirchhoff.
Nothing like German for spelling confusion.

not sooo fast, Mr.L'ectrzity!

supposed this guy got some bargain instuments (or radios, or starter or
whatever else) BUT these are 24 volt units then you could come to this
conclusion to join two batteries. In this case you will have half of the
current flow compared to a 12V system. So you can use half the cross section
of your cabling. Basic electics.


"RST Engineering" schrieb im Newsbeitrag
m...
Kirchoff is rolling over in his grave.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"oilsardine" wrote in message
...
no, it will see half the amperage at same wattage

"oilsardine" wrote in message
...
not sooo fast, Mr.L'ectrzity!

supposed this guy got some bargain instuments (or radios, or starter or
whatever else) BUT these are 24 volt units then you could come to this
conclusion to join two batteries. In this case you will have half of the
current flow compared to a 12V system. So you can use half the cross
section of your cabling. Basic electics.

That is not in dispute.

Look back to my answer. I said to use the same size as the main cable. It
(the jumper) would see the same amperage.

If the main cable is sized to carry the 24 volt load, it would indeed be
half the amps of the same 12 volt system.

The jumper would need to be the same size as the properly sized main cable.

THAT is basic "electics."
--
Jim in NC

"Morgans" schrieb im Newsbeitrag
...

....



The jumper would need to be the same size as the properly sized main
cable.



THAT is basic "electics."

No, it's not. Half the cross section is sufficient for same wattage.

I think I've got one or two seats left in my fall semester freshman
electronics engineering class. You might want to register today; those
chairs fill fast this time of the year.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"oilsardine" wrote in message
...

No, it's not. Half the cross section is sufficient for same wattage.

no need, got an Masters degree in Electrical Engineering myself, but thank
You for the offer.


"RST Engineering" schrieb im Newsbeitrag
m...
I think I've got one or two seats left in my fall semester freshman
electronics engineering class. You might want to register today; those
chairs fill fast this time of the year.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"oilsardine" wrote in message
...

No, it's not. Half the cross section is sufficient for same wattage.

oilsardine wrote:
got an Masters degree in Electrical Engineering myself...

Then I would have to assume that either eEnglish is a second or third
language for you or you have deliberately chosen to be a pendant. You
are right in that if the original poster intends to hook two 12V
batteries in series, but draw the same wattage over the same distance,
the conductor would require half the ampacity that would have been
mandated by a single 12v battery, since in order to provide the same
wattage the load would have to draw half the current at double the
voltage. The original poster never constrained the problem to the same
wattage -- and in homebuilt aircraft, I doubt that constraint ever
arises since the devices that one connects to the electrical system have
specific voltage requirements. Even if his system is exclusively
resistive loads, they are not likely to behave in purely linear fashion.

Charles

"Charles Vincent" wrote in message
...
oilsardine wrote:
got an Masters degree in Electrical Engineering myself...

Then I would have to assume that either eEnglish is a second or third
language for you or you have deliberately chosen to be a pendant. You are
right in that if the original poster intends to hook two 12V batteries in
series, but draw the same wattage over the same distance, the conductor
would require half the ampacity that would have been mandated by a single
12v battery, since in order to provide the same wattage the load would
have to draw half the current at double the voltage. The original poster
never constrained the problem to the same wattage -- and in homebuilt
aircraft, I doubt that constraint ever arises since the devices that one
connects to the electrical system have specific voltage requirements.
Even if his system is exclusively resistive loads, they are not likely to
behave in purely linear fashion.

Charles

Indeed, if the loads are purely resistive, and if the temperature is kept
constant to assist in keeping the performance linear, then twice the voltage
would mean twice the current and four times the power.

Peter

Gee, this discussion became convoluted. Your maximum draw on the circuit
would be when starting. Your battery may be rated in peak starting amps
capacity. One of the advantages of 24 volts over 12 is the ability to
use smaller diameter wires (weight savings). So, using the same diameter
for interconnection as was used for the 12 primary connection is
overkill. Low of mentioning of twice the voltage then half the wire
diameter...but I thought it was 1/4, but I am not an EE and it has a
loooong time since I have played with those calculations.{no, I don't
want to do the calculations right now! ;-) }

wrote:

I am putting two 12V batteries together
http://www.batterymart.com/p-hawker-...t-battery.html
to make a 24V battery.

What size cable should I use to make the serial connection?
http://shop.genuinedealz.com/Marine%...ttery%20Cable/

Thanks,
Karl