Charging two batteries?

S

steamer

Guest
--Curious to know if there are any know downsides to stuffing an
extra 12v battery in a car, hooking it in parallel with the existing one and
expecting the alternator to charge both of them. I expect it would take
twice as long to charge 'em both, but is there a danger of screwing up the
alternator? Thx,

--
"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
www.nmpproducts.com
---Decks a-wash in a sea of words---
 
"steamer" <steamer@sonic.net> wrote in message
news:483a358d$0$34500$742ec2ed@news.sonic.net...
--Curious to know if there are any know downsides to stuffing an
extra 12v battery in a car, hooking it in parallel with the existing one
and
expecting the alternator to charge both of them. I expect it would take
twice as long to charge 'em both, but is there a danger of screwing up the
alternator? Thx,

--
"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
www.nmpproducts.com
---Decks a-wash in a sea of words---
Click to expand...
Why would you do that.
The car designer did a quite reasonable job of providing a battery suitable
to serve the car for the normal life of a battery.

If you have some extra use such as camping then you need to go to proper
separation of main and auxiliary and some of the Recreation news groups
would provide answers.

John G.
 
"steamer" <steamer@sonic.net> wrote in message
news:483a358d$0$34500$742ec2ed@news.sonic.net...
--Curious to know if there are any know downsides to stuffing an
extra 12v battery in a car, hooking it in parallel with the existing one
and
expecting the alternator to charge both of them. I expect it would take
twice as long to charge 'em both, but is there a danger of screwing up the
alternator? Thx,

--
"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
www.nmpproducts.com
---Decks a-wash in a sea of words---
Click to expand...
Why would you do that.
The car designer did a quite reasonable job of providing a battery suitable
to serve the car for the normal life of a battery.

If you have some extra use such as camping then you need to go to proper
separation of main and auxiliary and some of the Recreation news groups
would provide answers.

John G.
 
"default" <default@defaulter.net> wrote in message
news:1211804895_3174@isp.n...
On 26 May 2008 03:59:09 GMT, steamer <steamer@sonic.net> wrote:

--Curious to know if there are any know downsides to stuffing an
extra 12v battery in a car, hooking it in parallel with the existing one
and
expecting the alternator to charge both of them. I expect it would take
twice as long to charge 'em both, but is there a danger of screwing up the
alternator? Thx,

People with RVs do it all the time, likewise tow truck operators.
Marine batteries are frequently run that way - through a switch that
allows either or both to start the motor - but while under weigh both
are paralleled so they charge, then one or the other is running the
accessories keeping one in reserve.

The downside, from my boating experience, is when one of the batteries
has been abused it can sit there dragging down the good battery.
Click to expand...

That's why you should use isolation diodes.

Tom
 
"default" <default@defaulter.net> wrote in message
news:1211804895_3174@isp.n...
On 26 May 2008 03:59:09 GMT, steamer <steamer@sonic.net> wrote:

--Curious to know if there are any know downsides to stuffing an
extra 12v battery in a car, hooking it in parallel with the existing one
and
expecting the alternator to charge both of them. I expect it would take
twice as long to charge 'em both, but is there a danger of screwing up the
alternator? Thx,

People with RVs do it all the time, likewise tow truck operators.
Marine batteries are frequently run that way - through a switch that
allows either or both to start the motor - but while under weigh both
are paralleled so they charge, then one or the other is running the
accessories keeping one in reserve.

The downside, from my boating experience, is when one of the batteries
has been abused it can sit there dragging down the good battery.
Click to expand...

That's why you should use isolation diodes.

Tom
 
Tom Biasi <tombiasi@optonline.net> wrote:

That's why you should use isolation diodes.
--Understood. Yeah the application is a little nonstandard; nothing
Click to expand...
to do with an RV or other 'normal' app.

--
"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
www.nmpproducts.com
---Decks a-wash in a sea of words---
 
Tom Biasi <tombiasi@optonline.net> wrote:

That's why you should use isolation diodes.
--Understood. Yeah the application is a little nonstandard; nothing
Click to expand...
to do with an RV or other 'normal' app.

--
"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
www.nmpproducts.com
---Decks a-wash in a sea of words---
 
"steamer" <steamer@sonic.net> wrote in message
news:483a358d$0$34500$742ec2ed@news.sonic.net...
--Curious to know if there are any know downsides to stuffing an
extra 12v battery in a car, hooking it in parallel with the existing one
and
expecting the alternator to charge both of them. I expect it would take
twice as long to charge 'em both, but is there a danger of screwing up the
alternator? Thx,

--
"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
www.nmpproducts.com
---Decks a-wash in a sea of words---
Click to expand...
I had a diesel GMC Suburban that came with two batteries in parallel, no
isolation.
 
"terryc" <newssixspam-spam@woa.com.au> wrote in message
news:pan.2008.05.26.23.48.08.506154@woa.com.au...
On Mon, 26 May 2008 19:01:59 +0000, steamer wrote:

Tom Biasi <tombiasi@optonline.net> wrote:

That's why you should use isolation diodes.
--Understood. Yeah the application is a little nonstandard; nothing
to do with an RV or other 'normal' app.

Non-standard? Doubt it. double battery installations are fairly standard
these days. Basically, if you have anything you want to run off a 12V
supply whilst mobile or moving regularly, then installing a second battery
is fairly standard in all sorts of vehicles and "trailers".

Diodes are one method, relays are another. Isolation switches are commons.

Umm, jus make sure you get the correct type of battery. If you really just
want to install a second spare car battery, then it doesn't matter.
However if you are say touring and driving between places where you can
for a day or two and need to run a frigerator, medical machine, ham
radio, etc, etc, then make sure you get a proper deep-discharge battery.
Also read the LeadAcid FAQ on how to look after them properly for a long
life. Hint max 50% discharge at C/10 max rate.

AFAIK, "marine" batteries are a compromise between car battery and a
deep-discharge and not a proper deep-discharge battery.


handle boat shock
Click to expand...
"Handle boat shock"? What does this mean? Is this some type of alien command
like "Klaatu barada nikto"?

Bob
--
== NOTE: I automatically delete all Google Group posts due to uncontrolled
SPAM ==
 
On 26 May 2008 03:59:09 GMT, steamer <steamer@sonic.net> wrote:

--Curious to know if there are any know downsides to stuffing an
extra 12v battery in a car, hooking it in parallel with the existing one and
expecting the alternator to charge both of them. I expect it would take
twice as long to charge 'em both, but is there a danger of screwing up the
alternator? Thx,
Click to expand...
People with RVs do it all the time, likewise tow truck operators.
Marine batteries are frequently run that way - through a switch that
allows either or both to start the motor - but while under weigh both
are paralleled so they charge, then one or the other is running the
accessories keeping one in reserve.

The downside, from my boating experience, is when one of the batteries
has been abused it can sit there dragging down the good battery.

No expert on all forms of alternators . . . but the excited field
style tends to be relatively bullet proof. The circuit usually uses a
tickle charge from the battery to get the alternator pumping, but once
it is, the main current for the field winding comes from an extra trio
of diodes - so if the output is being dragged down, the voltage
available to the field is also dragged down - so it tends to be
current limiting.
--


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On 26 May 2008 03:59:09 GMT, steamer <steamer@sonic.net> wrote:

--Curious to know if there are any know downsides to stuffing an
extra 12v battery in a car, hooking it in parallel with the existing one and
expecting the alternator to charge both of them. I expect it would take
twice as long to charge 'em both, but is there a danger of screwing up the
alternator? Thx,
Click to expand...
so long as both batteries were in good order - you might consider
having a big diode to the +ve of the "spare" just to stop back feeding
- some kit I have used in the past has just this arrangement - a
switch can then be used to short out the diode when the power from the
spare battery is required back in the system - good idea to excercise
the spare every now and then.
 
On Mon, 26 May 2008 19:01:59 +0000, steamer wrote:

Tom Biasi <tombiasi@optonline.net> wrote:

That's why you should use isolation diodes.
--Understood. Yeah the application is a little nonstandard; nothing
to do with an RV or other 'normal' app.
Click to expand...
Non-standard? Doubt it. double battery installations are fairly standard
these days. Basically, if you have anything you want to run off a 12V
supply whilst mobile or moving regularly, then installing a second battery
is fairly standard in all sorts of vehicles and "trailers".

Diodes are one method, relays are another. Isolation switches are commons.

Umm, jus make sure you get the correct type of battery. If you really just
want to install a second spare car battery, then it doesn't matter.
However if you are say touring and driving between places where you can
for a day or two and need to run a frigerator, medical machine, ham
radio, etc, etc, then make sure you get a proper deep-discharge battery.
Also read the LeadAcid FAQ on how to look after them properly for a long
life. Hint max 50% discharge at C/10 max rate.

AFAIK, "marine" batteries are a compromise between car battery and a
deep-discharge and not a proper deep-discharge battery.


handle boat shock
 
On Mon, 26 May 2008 18:13:28 -0700, BobW wrote:

handle boat shock

"Handle boat shock"? What does this mean? Is this some type of alien command
like "Klaatu barada nikto"?
Click to expand...
Sloppy editing. I was going to say that I understood marine batteries to
have heavier plates to handle tinnies/tinnys bouncing around on the waves.
 
On 26 May 2008 19:01:59 GMT, steamer <steamer@sonic.net> wrote:

Tom Biasi <tombiasi@optonline.net> wrote:

That's why you should use isolation diodes.
--Understood. Yeah the application is a little nonstandard; nothing
to do with an RV or other 'normal' app.
Click to expand...
I don't know if I'd just throw in some isolation diodes and expect
everything to be hunky-dory. A tenth of a volt drop represents a lot
of amps to a battery under charge. But it all depends on the use -
long recharge period and the diode probably matters a lot less.

If the goal is/was running accessories - I think a nice elegant
solution would be a mosfet and active switch to isolate the battery
used for accessories.

I know tow truck operators use two in parallel with no ill effects and
plenty of military vehicles do the same. A relay is good for
isolation too, but it may be impractical to use one on a starting
circuit.

If you are planning on using diodes to isolate both batteries, I'd
bump the voltage regulation up by one diode drop.
--


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http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups
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default wrote:
On 26 May 2008 19:01:59 GMT, steamer <steamer@sonic.net> wrote:

Tom Biasi <tombiasi@optonline.net> wrote:

That's why you should use isolation diodes.
--Understood. Yeah the application is a little nonstandard; nothing
to do with an RV or other 'normal' app.

I don't know if I'd just throw in some isolation diodes and expect
everything to be hunky-dory. A tenth of a volt drop represents a lot
of amps to a battery under charge. But it all depends on the use -
long recharge period and the diode probably matters a lot less.
Click to expand...

I installed them on a pair of paddle boats at Lesourdsville Lake
Amusment Park over 35 years ago, and they were still working properly
when they went out of business, years later. The battery voltage was
monitored on a seperate wire from the lead charging the battery. The
diodes didn't change the charging voltage, at all. The second battery
was used to power a large inverter to run a cart machine and small
amplifier on each boat. They never had a dead batterey where the boat
wouldn't start from the sound system, and a single jumpper cabe between
the two positve terminals let them start when a battery failed from old
age.

http://mightymo.org/public_html/images/Projects/DelcoOneWire/DelcoSI.jpg
shows the older alternators.


--
http://improve-usenet.org/index.html


Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm
 
On Tue, 27 May 2008 09:48:08 +1000, terryc
<newssixspam-spam@woa.com.au> wrote:


AFAIK, "marine" batteries are a compromise between car battery and a
deep-discharge and not a proper deep-discharge battery.


handle boat shock
Click to expand...
"Marine" batteries may be either deep-cycle or starting types. The
difference between them and an automotive or other battery is
primarily in the terminal type, and the fact that they often have a
lifting handle, where a similar sized auto battery would not. I don't
think there is any internal difference between a marine starting
battery and an automotive starting battery.



--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
 
On Tue, 27 May 2008 18:53:33 -0700, Peter Bennett wrote:

"Marine" batteries may be either deep-cycle or starting types. The
difference between them and an automotive or other battery is
primarily in the terminal type, and the fact that they often have a
lifting handle, where a similar sized auto battery would not. I don't
think there is any internal difference between a marine starting
battery and an automotive starting battery.
Click to expand...
Well, in all I've read, that is the first bit that made it clear that
there are actually two different types of marine battery.
 
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