Car battery matching with alternator

[cameo]

I wonder what you think about the following problem:

A car's battery needs to be replaced but the exact capacity battery is
not available, though smaller or larger ones are.
My feeling is that the battery capacity is matched by the manufacturer
with the alternator's charging capacity, so the replacement battery
should also closely match the OEM battery's capacity.
Is my assumption correct, or it makes not much difference to use
somewhat larger capacity replacement battery than the original?

I'd appreciate reading your learned opinions.

[Jim Thompson]

On Tue, 28 Oct 2014 11:03:27 -0700, cameo <ca...@unreal.invalid>
wrote:

All you need to "match" is the case size... 24, 24F are typical
passenger car sizes.

I would tend toward a higher amp-hour rating when replacing... the
"capacity" is _draining_, not charging... the alternator regulator
will charge the battery as needed.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

[Tom Miller]

"Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> wrote in
message news:f6nv4ahtpa9svp9or...@4ax.com...

Also need to match the terminal configuration. And maybe the holddown
method.

[David Platt]

The matching of total battery capacity, to instantaneous maximum
charging current available from the alternator, is not as critical as
you seem to feel.

Basically, the battery capacity is going to give you a measure of how
much starting power you can pull out of the battery (over a prolonged
period of cranking) before the voltage starts to drop. Larger is
(again, to a first approximation) better.

Once you start the car, the charge control system (alternator and
control logic) is going to supply current to recharge the battery.
Typically, these systems are designed as (fairly crude) "constant
voltage" supplies - the alternator output is allowed to float upwards
to higher voltages, but is limited by the control system to no more
than around 14.4 volts (nominal). If the battery is heavily
discharged, the battery will draw about as much current as the
alternator can supply; the alternator's voltage won't reach 14.4 and
the limiting won't occur. Once the battery is largely recharged, its
terminal voltage will rise and it will draw less current from the
alternator, and the charge-control system will prevent the alternator
voltage from rising above 14.4 volts.

If you put in a higher-capacity-than-before battery, then (if you
don't deep-discharge it) starting the car will draw out a smaller
proportion of the battery's stored charge. Its terminal voltage won't
drop as much as would be the case in a smaller battery. It'll
probably draw just about the same amount of recharge current as a
smaller battery would, though, and so the alternator won't really
"notice" a difference.

Under conditions of really deep battery discharge, the higher-capacity
battery might be able to "take" more current than your present
alternator can supply. I don't believe this is harmful, though... the
alternator's output voltage will simply drop (due to e.g. resistive
loss in the alternator windings) and this will automatically reduce
the current into the battery to what the alternator is capable of
supplying. The same thing happens with your current battery, if the
vehicle is idling and the alternator isn't running very quickly... its
output voltage drops, the headlights dim a bit, and everything
balances out.

Unless there's something really unusual about your car (I believe),
replacing an OEM battery with a new one having even twice the capacity
shouldn't present any sort of problem (other than the physical size of
the battery).

[Jim Thompson]

Yep, you might be a sick puppy and own one of those crap GM cars with
batteries with side terminals >:-}

[RobertMacy]

On Tue, 28 Oct 2014 11:21:12 -0700, Tom Miller <tmille...@verizon.net>
wrote:

>>> ...snip....

> Also need to match the terminal configuration. And maybe the holddown
> method.
>
>

told by mechanics: larger battery as long as it physically fits in there.

hold down method! EXACTLY, envision an autocrash and that 50 pound battery
becomes a projectile with lethal strengths.

[Tim Wescott]

Actually, alternators are usually sized to the electrical load that the
car designers think the car will present -- cars with little electrical
equipment can get by with smaller alternators, cars with lots of
electrical equipment need bigger alternators. You'll find camper trucks
out there with alternators up to 100A (or more: 100A in a 4-wheeled road
vehicle is where my brain fuzzes over).

The car has a dingus called a "regulator" in it somewhere (these days it's
usually built into the alternator). This holds the voltage from the
alternator to a reasonable value for battery charging, regardless of the
speed of the alternator, the condition of the battery, or the electrical
load.

This, in turn, means that as long as the charging system is in good shape
you can have a wide range of battery capacities and be perfectly fine.

The bottom line is: if you get a battery the correct physical size for the
car, you should be OK. Even if you go much larger, you should be fine.
If you go much smaller the battery may not have enough oomph to start the
car, but if you're getting the correct sized battery then that probably
won't happen.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

[Tim Wescott]

All done by going into your local auto parts store and telling them what
car you have. If they're competent, what comes across the counter should
fit right in and work just fine.

[Jim Thompson]

Yep. I just jump start, drive to Batteries Plus, and wait in the
air-conditioned waiting room ;-)

[Tom Miller]

"Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> wrote in

message news:konv4ahpd2pm3qscr...@4ax.com...

Yep. Bought it new in 2004. Never again will I buy another GM product. It is
a real piece of shit.
Did I say GM is crap? GM is crap.

[Martin Riddle]

It's the Lead washer used between the double leads on a side terminal
battery, that causes problems. It thermal cycles and causes a bad
connection. Tightening it compresses the washer such that the bolt
eventually protrudes into the battery and causes a leak.
The bad connection usually causes the diodes in the alternator to go
kaput.
I replaced mine with a brass washer and never had a problem since.

As for the battery, largest that will fit and the longest warranty
available.


Cheers

[Jasen Betts]

On 2014-10-28, cameo <ca...@unreal.invalid> wrote:
> I wonder what you think about the following problem:
>
> A car's battery needs to be replaced but the exact capacity battery is
> not available, though smaller or larger ones are.
> My feeling is that the battery capacity is matched by the manufacturer
> with the alternator's charging capacity, so the replacement battery
> should also closely match the OEM battery's capacity.

nah, car battery size is a trade-off between weight and lifetime.
they have little intrinsic leakage. that would require a larger
charging system,

If you fit the smaller battery it might not be strong enough to start
the engine and will probably die sooner, but you car will be lighter
and therefore, if it runs, use less fuel.

If you fit the larger battery you'll take a fuel efficiency hit.
starting will probably be easier, or at-least no harder than with the
reccommended battery, and battery the will last longer.


The charging capacity of the engine is matched to the drain that the
automobile systems present so a larger nattery would not be harder to
maintain in a charged state than the regular one.

--
umop apisdn

[Jasen Betts]

On 2014-10-28, Tim Wescott <seemyw...@myfooter.really> wrote:
> On Tue, 28 Oct 2014 11:03:27 -0700, cameo wrote:

>
> The car has a dingus called a "regulator" in it somewhere (these days it's
> usually built into the alternator). This holds the voltage from the
> alternator to a reasonable value for battery charging, regardless of the
> speed of the alternator, the condition of the battery, or the electrical
> load.

Actually the regulator doesn't control the voltage. The altenator is
a current source, the regulator controls the current produced by the
altenator, increasing the current when the battery is low, reducing it
when it is full, the battery keeps the voltage stable.

--
umop apisdn

[Jim Thompson]

Sonnuva gun, I didn't know that, patents...

3,496,447 Alternator Voltage Regulator Responsive to Temperature

3,505,590 Temperature Responsive Output Voltage Apparatus

3,522,482 Temperature Compensated Voltage Regulation

3,546,563 Alternator Voltage Regulation Utilizing A Constant Current
Source

>:-}

[Tom Miller]

"Jasen Betts" <ja...@xnet.co.nz> wrote in message
news:m2pb7p$m36$1...@gonzo.reversiblemaps.ath.cx...

No, it is a constant voltage regulator with current limiting. Lead acid
batteries like to be charged with a negative temperature coefficient
compensated constant voltage.

[Jim Thompson]

The alternator _is_ a current source, _but_ it is a voltage-controlled
current source, with a temperature compensation...

<http://www.analog-innovations.com/SED/AlternatorRegulatorTC.pdf>

[miso]

I always put in the highest capacity battery that will fit.

Car batteries have got crappy in the last decade. About the only cheap
battery worth buying is Duralast Gold. They are just the house brand of
Autozone and made by Johnson Controls.

If you want to go high end, Deka makes some good batteries. Odyssey
(Enersys) is as good as it gets.

Besides size and terminals, watch out for batteries where the positive and
negative are not in the same location (left & right) as your stock battery.

[rickman]

Costco batteries are very cost competitive and have a great warranty. I
don't think the batteries are any different though. Mine went out after
a bit over three years and it only cost me $10 or so for the
replacement. I think the first 3 years the replacement is free, then
prorated over the next 6 years. I can't recall if they install
batteries or not. I know the install tires of course.

--

Rick

[rickman]

I think you are splitting hairs. I believe the voltage is what is
sensed and so what is regulated. Yes, the current is controlled, but
the two go hand in hand. The circuit is not high gain like in a power
supply in your computer, holding the output voltage very steady.
Instead when the voltage droops it pushes more current out to limit the
droop, and vice versa when the voltage increases.

--

Rick

[rickman]

Would that temperature compensation be the battery temperature? How is
that measured? Is it assumed that the battery temperature is the same
as the air in the engine compartment?

--

Rick

[Jim Thompson]

Yep, that is the assumption... a bad one. Back in the '60's, when I
was designing alternator regulators for _all_ of the American car
companies, I tried to get the sensing portion put at the battery, but
the companies were too cheap... takes an extra wire :-(

I did come up with an interesting scheme that could do remote sense
_without_ an extra wire, but it was also deemed too expensive.

[DecadentLinuxUserNumeroUno]

On Wed, 29 Oct 2014 09:03:02 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> Gave us:

Funny how now, they wouldn't hesitate to, and would even give a
watertight line and term caps for it.

[DecadentLinuxUserNumeroUno]

On Wed, 29 Oct 2014 09:03:02 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> Gave us:

This is why, as you say, it is a voltage driven current source.

It will drive into the load only up to the max driving voltage of 14.8
VDC, OR the alternator's max design driving amperage at that voltage or
below, whichever comes first.

The added voltage actually places the battery under a charging state,
and makes up for small cable drops as well. When all one has is 14.8 at
the alternator terminals, minus cable drop, every half volt of that drop
matters a bit.

Long starter cables pose problems at times for that task too.

That is why good, solid terminal connection cinching is one of the
most important elements in power circuits and their connection and feed
elements.

[cameo]

Thanks for that detailed explanation, as well as the less detailed ones
from other respondents. My car's battery uses 24F terminals on the top.
The old battery was an Interstate MT-24F model that had 600 CCA and 5 yr
warranty. Because the same model was not in stock, I had it replaced
with Interstate MTP-24F model, which has 800 CCA and has a 6 yr
warranty. But is also 5 lbs heavier. BTW, the car is a 20-year old Honda
Accord that still runs very well, despite the 320 K miles in it.

[rickman]

On 10/29/2014 12:03 PM, Jim Thompson wrote:
> On Wed, 29 Oct 2014 02:50:37 -0400, rickman <gnu...@gmail.com> wrote:
>>
>> Would that temperature compensation be the battery temperature? How is
>> that measured? Is it assumed that the battery temperature is the same
>> as the air in the engine compartment?
>
> Yep, that is the assumption... a bad one. Back in the '60's, when I
> was designing alternator regulators for _all_ of the American car
> companies, I tried to get the sensing portion put at the battery, but
> the companies were too cheap... takes an extra wire :-(
>
> I did come up with an interesting scheme that could do remote sense
> _without_ an extra wire, but it was also deemed too expensive.

There is also the rule, "If it ain't broke, don't fix it!" The current
method seems to work pretty well. What would the consumer get from a
more accurate battery temperature measurement?

--

Rick

[Jim Thompson]

Because of temperature mis-match most charging systems over- or
under-charge the battery.

Over-charging shortens battery life by overheating and
water/electrolyte loss.

"The current method" is still what I designed almost 50 years ago ;-)

[rickman]

On 10/29/2014 2:49 PM, Jim Thompson wrote:
> On Wed, 29 Oct 2014 14:38:36 -0400, rickman <gnu...@gmail.com> wrote:
>
>> On 10/29/2014 12:03 PM, Jim Thompson wrote:
>>> On Wed, 29 Oct 2014 02:50:37 -0400, rickman <gnu...@gmail.com> wrote:
>>>>
>>>> Would that temperature compensation be the battery temperature? How is
>>>> that measured? Is it assumed that the battery temperature is the same
>>>> as the air in the engine compartment?
>>>
>>> Yep, that is the assumption... a bad one. Back in the '60's, when I
>>> was designing alternator regulators for _all_ of the American car
>>> companies, I tried to get the sensing portion put at the battery, but
>>> the companies were too cheap... takes an extra wire :-(
>>>
>>> I did come up with an interesting scheme that could do remote sense
>>> _without_ an extra wire, but it was also deemed too expensive.
>>
>> There is also the rule, "If it ain't broke, don't fix it!" The current
>> method seems to work pretty well. What would the consumer get from a
>> more accurate battery temperature measurement?
>
> Because of temperature mis-match most charging systems over- or
> under-charge the battery.
>
> Over-charging shortens battery life by overheating and
> water/electrolyte loss.
>
> "The current method" is still what I designed almost 50 years ago ;-)

I think that is the point. It works plenty well enough so that I can't
remember the last time I bought a battery. I just know my 17 year old
truck is on its third battery.. well, fourth if you count the one that
was replaced under warranty after just 3.5 years. There is no problem
to solve, so don't try to fix it.

--

Rick

[Jim Thompson]

You clearly don't live in Arizona.

[cameo]

What's wrong with incremental improvements over time? That's what the
whole car industry has been doing ever since Henry Ford.

[rickman]

Nothing is wrong with incremental improvements. But what improvement
is needed? Will this make the batter last longer? I've yet to read
anything saying that.

--

Rick

[Jim Thompson]

You missed my post ?>:-}

[rickman]

No, I read it. Didn't see anything to reply to.

--

Rick

[DecadentLinuxUserNumeroUno]

On Thu, 30 Oct 2014 14:18:37 -0400, rickman <gnu...@gmail.com> Gave us:

What about the alternator? They fry too.

Decades ago, lead acid batteries were dirt cheap, and slapping in
another of those was cheaper and easier than a new alternator. Now,
both the task complexity, and the price are closer together, so
longevity needs to be engineered in to both in a more focussed manner.

One does not see '73 Cadillac batteries in a '15 Chevy Monte Carlo.
The charging gear differ too, and the watchdog charge manager on that
alternator did not previously exist.

[John S]

Damn! And I thought the horse was dead.

[Jim Thompson]

Cretin.

[DecadentLinuxUserNumeroUno]

On Thu, 30 Oct 2014 14:40:25 -0400, rickman <gnu...@gmail.com> Gave us:

>No, I read it. Didn't see anything to reply to.

A simple face mashing would not be enough bludgeoning to lesson up an
immature, hard wired, retarded asswipe like you.

Your fucktarded mother and zero effect father should be in prison for
the piece of shit result you are.

Now, analyst (sic... NO SICK!)... Tell me the difference between what
I said to you here, and the horseshit you spewed, to which I gave this
reply?

You pathetic, cringing little milksop! ... no... WORM!

[Jim Thompson]

rickman is your typical smug ignoramus. I had been giving him some
slack, but I decided to put him back into the do-not-retrieve gmail
cretins folder.

[rickman]

That is your way of explaining why you are asking where I live?

--

Rick

[John S]

On 10/30/2014 1:57 PM, DecadentLinuxUserNumeroUno wrote:
> On Thu, 30 Oct 2014 14:40:25 -0400, rickman <gnu...@gmail.com> Gave us:
>
>> No, I read it. Didn't see anything to reply to.
>
> A simple face mashing would not be enough bludgeoning to lesson up an
> immature, hard wired, retarded asswipe like you.

You do seem to use the asswipe and -tard sub-fix a lot. Probably
something you grew up hearing from your progenitors (not to mean that
you had actual father and mother in the usual sense).

> Your fucktarded mother and zero effect father should be in prison for
> the piece of shit result you are.

And you are an angel, you think.

> Now, analyst (sic... NO SICK!)... Tell me the difference between what
> I said to you here, and the horseshit you spewed, to which I gave this
> reply?
>
> You pathetic, cringing little milksop! ... no... WORM!

Why aren't you busy backing up your little brother, Big Jamie, as usual?
Not enough challenge for your vile look-up vocabulary? Your nose is not
brown enough yet?

[rickman]

On 10/30/2014 3:05 PM, Jim Thompson wrote:
> On Thu, 30 Oct 2014 11:57:07 -0700, DecadentLinuxUserNumeroUno
> <DL...@DecadentLinuxUser.org> wrote:
>
>> On Thu, 30 Oct 2014 14:40:25 -0400, rickman <gnu...@gmail.com> Gave us:
>>
>>> No, I read it. Didn't see anything to reply to.
>>
>> A simple face mashing would not be enough bludgeoning to lesson up an
>> immature, hard wired, retarded asswipe like you.
>>
>> Your fucktarded mother and zero effect father should be in prison for
>> the piece of shit result you are.
>>
>> Now, analyst (sic... NO SICK!)... Tell me the difference between what
>> I said to you here, and the horseshit you spewed, to which I gave this
>> reply?
>>
>> You pathetic, cringing little milksop! ... no... WORM!
>
> rickman is your typical smug ignoramus. I had been giving him some
> slack, but I decided to put him back into the do-not-retrieve gmail
> cretins folder.

Lol. Dude, all you needed to do what explain what the heck you were
talking about.

--

Rick

[Maynard A. Philbrook Jr.]

In article <m2u2v8$9jv$1...@dont-email.me>, Sop...@invalid.org says...

I don't need any backing up, I am impervious to shit heads like
yourself.

I don't drag others into my problems, it just shows weakness.

If you can't take the heat, get out of the kitchen, in this case, get
out of the thread.

Jamie

[sms]

On 10/28/2014 11:03 AM, cameo wrote:
> I wonder what you think about the following problem:
>
> A car's battery needs to be replaced but the exact capacity battery is
> not available, though smaller or larger ones are.
> My feeling is that the battery capacity is matched by the manufacturer
> with the alternator's charging capacity, so the replacement battery
> should also closely match the OEM battery's capacity.
> Is my assumption correct, or it makes not much difference to use
> somewhat larger capacity replacement battery than the original?

Your assumption is incorrect. The manufacturer considers the CCA (Cold
Cranking Amps) and AH (Amp-Hour rating) of the battery. The AH rating is
of lesser importance since the alternator keeps the battery fully
charged unless you're operating electrical equipment with the vehicle off.

[sms]

The batteries in my truck, from Costco, rarely last more than three
years, probably because I don't drive the truck very often. So I always
get a warranty replacement. It's not really free, you get a refund of
the price you paid then you buy a new one at a slightly higher price.

[rickman]

Life gets a whole lot better when you ignore the misbehaving children.
They really aren't our problem. If their parents couldn't teach them,
what hope do you think we have?

--

Rick

[rickman]

Usually a battery replacement is free for the first year. The battery I
bought at Costco extended that free replacement to three years and
prorated after that. All in all it is a pretty good warranty and the
second battery is working fine after more than three year... I think. I
really can't recall just how long it has been.

--

Rick