On Fri, 29 Apr 2005 02:50:33 GMT, "Bill McKee"
wrote:


"Shortwave Sportfishing" wrote in message
.. .
On Thu, 28 Apr 2005 16:56:12 -0500, Richard J Kinch
wrote:

Tim writes:

Any mismatch is destructive, and eventually, they will mismatch.

I really don't know what you mean by "destructive"

Two equally good batteries should work fine.

No. Currents are at best unstably balanced. Any mismatch (difference)
in the cells (size, manufacturer, model, flooded/sealed/gel/etc, date of
manufacture, age, prior application, usage history) at the start or
developing over time will result in loads between the batteries
themselves, which over time will accelerate the mismatching process.

A shorted cell, not uncommon, will result in enormous currents that can
cause a fire or explosion.

I know it is done, but only as a compromise, and a bad one at that.

I would at least put fusible links in series with each battery before
the parallel connection. That will at least give some protection
against the fire and explosion hazard.

Think of it as yoking a strong horse and a weak horse to a cart side by
side. The strong horse will be spent dragging the weak one. The weak
one will be spent just trying to keep up with the strong. The power to
the cart is a fraction of what the team is exerting.

Whatever.

I guess I better disconnect the 2nd factory battery in my Duramax Diesel
pickumup.

Yes - I must go out and disconnect my diesel batteries in my pickup
truck right now - they might be unstable.

Oh, and my '50 MTA International tractor - can't have that being
unstable. I'll just have to figure out another way to start it -
maybe like pushing it downhill.

Oh, and the storage batteries that buffer the diesel generator for the
house and barn.

I forgot all those diesel electric subs - hell, subs are dangerous
enough, can't have unstable batteries.

They are all unstable, YOU HEAR ME!! UNSTABLE!!!

I also need to get to my professors - if they are still alive - and
tell them that parallel batteries are verboten because the circuit is
unstable.

Here's a quote and a reference:

"Failure mechanisms of deep cycle batteries are described on pages
14-97 thru 14-98 of reference 1. Grid corrosion and plate shedding are
the predominant failures. Neither is a result of parallel
connections."

http://www.amplepower.com/pwrnews/parallel/

Might want to take a look at this one while you are at it.

http://www.batteryuniversity.com/partone-24.htm

I just can't resist - here's one more.

http://www.wagonmaker.com/newbatt.html

And let's not leave a manufacturer out of this:

http://tinyurl.com/acvgb

I have no freakin' idea what this is all about, but it is described as
a Intra/Extra Dimensional Shift - anybody ever watch "Sliders"?

http://nadia.delicata.net/appendixVI.htm

Later,

Tom

Perhaps I wasn't clear. Paralleling lead-acid batteries is done, but
its not a good idea. If series is possible then use series. I believe
your reports of using them all over diesels where there is no other
option that cheap, but that doesn't mean it is a good idea for a little
trolling motor.

Shortwave Sportfishing writes:

"Failure mechanisms of deep cycle batteries are described on pages
14-97 thru 14-98 of reference 1. Grid corrosion and plate shedding are
the predominant failures. Neither is a result of parallel
connections."

A thoroughly shallow analysis, followed by ignorant opinions like: "a
cell rarely, if ever, shorts with a low resistance". All from somebody
trying to sell you something.

I suppose if you have never seen a car battery explode, you might not
believe the warnings, or at least you might not treat them with respect.
I know I didn't, until it happened. I still jump car batteries when the
need arises, but believe me, I do it with care and wearing protective
gear.

I'm not gonna get in a citation war. Look at lead-acid battery mfr
sites and you'll find they typically caution against paralleling if they
address the issue at all.

This religious advocacy of a poor practice reminds me of people who
advocate using suicide cords for portable generators. Yes, they work,
yes its done (and I have done it myself), but it isn't a good idea, and
it risks some serious problems.

On Sat, 30 Apr 2005 00:33:26 -0500, Richard J Kinch
wrote:

~` snippage ~~

I'm not gonna get in a citation war. Look at lead-acid battery mfr
sites and you'll find they typically caution against paralleling if they
address the issue at all.

Look, your position is ridiculous and silly.

Just admit it and move on.

Later,

Tom

I guess I better disconnect the 2nd factory battery in my Duramax
Diesel
pickumup.

Not a bad idea...LOL!
batteries can explode, I don't deny that. But if it was that great or
common of an issue, then there would be all kinds of govt regulations
checking for paralell and series battery applications to be in "code"

Almost all your diesel Semi-trucks have not only 2 but 3 and even 4
batteries and no "diodes" or "spark arrestors" installed. they are
however, mounted in a battery box which if I rememeber correctly is
Coast Guard mandatory on boats anyhow.

Richard is not so much being silly as he is being an expounder of a theory
with which he has fallen in love???

In practical terms he is full of it. Operating batteries in parallel is
virtually bullet proof. Clearly he has no practical experience or his
position would shift.

In some ways he reminds me of the K of Oz and DFI.

Butch
"Tim" wrote in message
oups.com...
I guess I better disconnect the 2nd factory battery in my Duramax
Diesel
pickumup.

Not a bad idea...LOL!
batteries can explode, I don't deny that. But if it was that great or
common of an issue, then there would be all kinds of govt regulations
checking for paralell and series battery applications to be in "code"

Almost all your diesel Semi-trucks have not only 2 but 3 and even 4
batteries and no "diodes" or "spark arrestors" installed. they are
however, mounted in a battery box which if I rememeber correctly is
Coast Guard mandatory on boats anyhow.

On Sat, 30 Apr 2005 14:23:28 GMT, "Butch Davis"
wrote:

Richard is not so much being silly as he is being an expounder of a theory
with which he has fallen in love???

In practical terms he is full of it. Operating batteries in parallel is
virtually bullet proof. Clearly he has no practical experience or his
position would shift.

In some ways he reminds me of the K of Oz and DFI.

I refuse to comment other than to say...

EXACTLY!!! :)

I'm sure Richard has something to contribute - on this issue I'm
afraid he's in a very small, and very wrong, minority.

Hey, everybody has an opinion - no harm, no foul.

Later,

Tom

Butch Davis writes:

Operating batteries in parallel is virtually bullet proof.
Clearly he has no practical experience or his position would shift.

We'll have to leave this as a distinct difference of opinion, then.

On Sat, 30 Apr 2005 23:44:19 GMT, Gene Kearns
wrote:

On Sat, 30 Apr 2005 00:33:26 -0500, Richard J Kinch
wrote:

Perhaps I wasn't clear. Paralleling lead-acid batteries is done, but
its not a good idea. If series is possible then use series.

I don't find any merit in what you offer as fact.

I don't want to get into a citation war either, but short of a
religious faith in safe vs. unsafe battery practices it would be nice
to have a little science to back up one's words.

I, too, have seen the explosion (and thermal runaway) of batteries,
but I believe it made not a whit of difference whether the battery was
paralleled or in series.

If you have some sort of objective scientific explanation reaching
beyond having seen a car battery explode and consequently becoming
afraid of them.... I'd like to hear it.

The only thermal runaway I have ever personally witnessed was an
industrial application in which temperature extremes caused a
situation in which the charger overcompensated starting for a low
temp condition and continuing through a high temp condition. The temp
compensator circuit was faulty. That was the only situation I have
ever watched personally. I've worked on investigations of thermal
runaway, but they almost always were caused by this same condition -
the temp compensation was faulty. You see this type of condition with
BBU systems also. These were/are not your everyday run of the mill
lead acid starting or trolling batteries though. They were rapid
charge/discharge batteries which are not seen in daily applications
being special purpose.

To give Richard his do, there have been some reports of AGM batteries
having thermal failure as a result of inappropriate application.
These have all been misapplication of the AGM technology rather than a
fault in the system themselves. In one reported case, a garage
mechanic just slapped a rapid charger on an AGM battery and it went
kablooey. These seem to be few and far between however and mostly
related to RVs which somehow figures.

To get back to the main discussion point - in basic service, with lead
acid batteries parallel circuits are as safe as can be and unless
somebody is a complete and total idiot, almost impossible to screw up
or blow up due to the basic nature of the circuit itself.

Later,

Tom

"Gene Kearns" wrote in message
...
On Sun, 01 May 2005 00:56:14 GMT, Shortwave Sportfishing
wrote:


The only thermal runaway I have ever personally witnessed was an
industrial application in which temperature extremes caused a
situation

In truth, the only thermal runaways I have ever witnessed were nicad
batteries designed for starting turbine engines......

.... not unheard of, but quite spectacular...


lead-acid explosions, I think, fall into another category...

--



Grady-White Gulfstream, out of Southport, NC.

http://myworkshop.idleplay.net/
Homepage*
http://www.thebayguide.com/rec.boats
Rec.boats at Lee Yeaton's Bayguide

The only lead-acid battery explosion I ever witnessed was about 42 years ago
and I removed the charger from the spare jumper battery at the service
station I worked in. Small spark, big bang. Luckily the battery blew out
the side away from me.

Gene Kearns writes:

If you have some sort of objective scientific explanation reaching
beyond having seen a car battery explode and consequently becoming
afraid of them.... I'd like to hear it.

The explanation is simply that batteries are more or less mismatched. See
my earlier posts. As long as there is a mismatch, you cannot get twice the
watt-hours out of a pair of batteries in parallel versus a single. One
will always load the other. There is also a risk of severe overload if a
cell should short; this risk is simply not present in a series arrangement;
thus my recommendation to insert fusible links in each parallel branch.
Aside from the output degradation, and the shorted-cell risk, yes, you can
put well-matched batteries in parallel. It is common in certain
applications as a compromise. If series is possible, then use series.