Battery cable selection

[[email protected]]

I am putting two 12V batteries together
http://www.batterymart.com/p-hawker-sbs-J16-aircraft-battery.html
to make a 24V battery.

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

Thanks,
Karl

[Morgans[_2_]]

> wrote in message
...
>I am putting two 12V batteries together
> http://www.batterymart.com/p-hawker-sbs-J16-aircraft-battery.html
> to make a 24V battery.
>
> What size cable should I use to make the serial connection?
> http://shop.genuinedealz.com/Marine%20Grade%20Wire/Marine%20Battery%20Cable/

Same size as the main battery cable. It will see the same amperage.
--
Jim in NC

[Philippe[_2_]]

wrote:

> I am putting two 12V batteries together
> http://www.batterymart.com/p-hawker-sbs-J16-aircraft-battery.html
> to make a 24V battery.
>
> What size cable should I use to make the serial connection?

Longer the cable, bigger the cable...
connect two batteries with a 1"cable: a 6AWG cable will work

flat copper bar will be better (less losses):
http://www.aircraftspruce.com/catalog/mepages/busbar.php

by
--
Volem rien foutre al païs!
Philippe Vessaire Ò¿Ó¬
** Posted from http://www.teranews.com **

[oilsardine[_2_]]

no, it will see half the amperage at same wattage

"Morgans" > schrieb im Newsbeitrag
...
>
> > wrote in message
> ...
>>I am putting two 12V batteries together
>> http://www.batterymart.com/p-hawker-sbs-J16-aircraft-battery.html
>> to make a 24V battery.
>>
>> What size cable should I use to make the serial connection?
>> http://shop.genuinedealz.com/Marine%20Grade%20Wire/Marine%20Battery%20Cable/
>
> Same size as the main battery cable. It will see the same amperage.
> --
> Jim in NC
>

[Vaughn Simon]

"oilsardine" > wrote in message ...
> no, it will see half the amperage at same wattage
>
Huh? You are joking...right?

Vaughn

[Capt. Geoffrey Thorpe]

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

No Jim was correct. The amperage is the same.

It is a series circuit - the amperage is the same throughout.

If you were wiring two batteries in parallel (and getting 12 volts from the
pair), then each battery would deliver 1/2 the amps (approx.)

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[RST Engineering]

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

[Dale Scroggins[_2_]]

"Philippe" > wrote in message
news:1770438.ul5SB0L1ai@GastonCoute...
> wrote:
>
>> I am putting two 12V batteries together
>> http://www.batterymart.com/p-hawker-sbs-J16-aircraft-battery.html
>> to make a 24V battery.
>>
>> What size cable should I use to make the serial connection?
>
> Longer the cable, bigger the cable...
> connect two batteries with a 1"cable: a 6AWG cable will work
>
> flat copper bar will be better (less losses):
> http://www.aircraftspruce.com/catalog/mepages/busbar.php
>
> by
> --
> Volem rien foutre al païs!
> Philippe Vessaire Ò¿Ó¬
> ** Posted from http://www.teranews.com **

A copper bar would indeed work much better than a short cable. If you plan
to join two standard aircraft batteries sharing the same battery box, a
well-fitted copper bar is easier to install than a cable.

You can make a bar by flattening a short section of 1/2" thick-wall copper
tubing (as used for refrigeration lines) in a vise and drilling two 5/16"
holes the correct distance apart (about two inches I think, but you should
measure). Coat it with grease each time it's installed or it will corrode
rapidly.

Beech Barons use a similar copper bar, tin-plated as I recall. You could
buy one.

[Peter Dohm]

"RST Engineering" > wrote in message
m...
> Kirchoff is rolling over in his grave.
>
> Jim
>
He obviously needs the exercise.... ;-)

Peter
Node theory sux!

[Dan[_12_]]

Dale Scroggins wrote:
>
> "Philippe" > wrote in message
> news:1770438.ul5SB0L1ai@GastonCoute...
>> wrote:
>>
>>> I am putting two 12V batteries together
>>> http://www.batterymart.com/p-hawker-sbs-J16-aircraft-battery.html
>>> to make a 24V battery.
>>>
>>> What size cable should I use to make the serial connection?
>>
>> Longer the cable, bigger the cable...
>> connect two batteries with a 1"cable: a 6AWG cable will work
>>
>> flat copper bar will be better (less losses):
>> http://www.aircraftspruce.com/catalog/mepages/busbar.php
>>
>> by
>> --
>> Volem rien foutre al païs!
>> Philippe Vessaire Ò¿Ó¬
>> ** Posted from http://www.teranews.com **
>
> A copper bar would indeed work much better than a short cable. If you
> plan to join two standard aircraft batteries sharing the same battery
> box, a well-fitted copper bar is easier to install than a cable.
>
> You can make a bar by flattening a short section of 1/2" thick-wall
> copper tubing (as used for refrigeration lines) in a vise and drilling
> two 5/16" holes the correct distance apart (about two inches I think,
> but you should measure). Coat it with grease each time it's installed
> or it will corrode rapidly.
>
> Beech Barons use a similar copper bar, tin-plated as I recall. You
> could buy one.
>
>


The truly energetic could tin the bar with solder or, wait for it, tin.

Dan, U.S. Air Force, retired

[jan olieslagers[_2_]]

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[_2_]]

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.

[oilsardine[_2_]]

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
>
>

[Morgans[_2_]]

"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

[oilsardine[_2_]]

"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.

[RST Engineering]

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[_2_]]

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.
>>
>>
>
>

[Charles Vincent]

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

[Peter Dohm]

"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

[Bruce A. Frank]

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-sbs-J16-aircraft-battery.html
> to make a 24V battery.
>
> What size cable should I use to make the serial connection?
> http://shop.genuinedealz.com/Marine%20Grade%20Wire/Marine%20Battery%20Cable/
>
> Thanks,
> Karl

[Dan[_12_]]

Bruce A. Frank wrote:
> 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! ;-) }
>

I don't blame you. Such calculations require higher levels math where
one leaves off counting on one's fingers and starts using one's toes.
This is called "algebra." Now, if one wants to use calculus...well,
calculus is found on one's teeth.

Dan, U.S. Air Force, retired

[RST Engineering]

Or you can simply go to www.rstengineering.com and then to Jim's Engineering
page and then open up the spreadsheet "wiretable.xls", put in the wire size
and length that you want and let the magic of rather complex algebra (for
the temperature rise) be invisible in the answers.

Jim
I *am* an EE and I play one at the college every day {;-)



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! ;-) }

[Philippe[_2_]]

Bruce A. Frank wrote:

> 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! ;-) }

battery is heavier... are you sure you gain weight?

For wire: section would be 1/2 as the amperage, diameter would be reduce
by 0,707.


--
Volem rien foutre al païs!
Philippe Vessaire Ò¿Ó¬
** Posted from http://www.teranews.com **