Forums

Car battery matching with alternator

Started by cameo October 28, 2014
On Tue, 28 Oct 2014 11:24:46 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Tue, 28 Oct 2014 14:21:12 -0400, "Tom Miller" ><tmiller11147@verizon.net> wrote: > >> >>"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in >>message news:f6nv4ahtpa9svp9orefbijdvfvvk0ir16t@4ax.com... >>> On Tue, 28 Oct 2014 11:03:27 -0700, cameo <cameo@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. >>>>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. >>> >>> 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. >> >>Also need to match the terminal configuration. And maybe the holddown >>method. >> > >Yep, you might be a sick puppy and own one of those crap GM cars with >batteries with side terminals >:-} > > ...Jim Thompson
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
On 2014-10-28, cameo <cameo@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
On 2014-10-28, Tim Wescott <seemywebsite@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
On 29 Oct 2014 00:09:29 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

>On 2014-10-28, Tim Wescott <seemywebsite@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.
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 >:-} ...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.
"Jasen Betts" <jasen@xnet.co.nz> wrote in message 
news:m2pb7p$m36$1@gonzo.reversiblemaps.ath.cx...
> On 2014-10-28, Tim Wescott <seemywebsite@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 >
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.
On Tue, 28 Oct 2014 21:00:00 -0400, "Tom Miller"
<tmiller11147@verizon.net> wrote:

> >"Jasen Betts" <jasen@xnet.co.nz> wrote in message >news:m2pb7p$m36$1@gonzo.reversiblemaps.ath.cx... >> On 2014-10-28, Tim Wescott <seemywebsite@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 >> > >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. >
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> ...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.
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? > > I'd appreciate reading your learned opinions.
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.
On 10/28/2014 2:03 PM, 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? > > I'd appreciate reading your learned opinions.
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 $10 or so for the replacement. I think the first 3 years the replacement is free, then prorated over the next 6 years. I can't recall if they install batteries or not. I know the install tires of course. -- Rick
On 10/28/2014 8:09 PM, Jasen Betts wrote:
> On 2014-10-28, Tim Wescott <seemywebsite@myfooter.really> wrote: >> On Tue, 28 Oct 2014 11:03:27 -0700, cameo wrote: > >> >> The car has a dingus called a "regulator" in it somewhere (these days it's >> usually built into the alternator). This holds the voltage from the >> alternator to a reasonable value for battery charging, regardless of the >> speed of the alternator, the condition of the battery, or the electrical >> load. > > Actually the regulator doesn't control the voltage. The altenator is > a current source, the regulator controls the current produced by the > altenator, increasing the current when the battery is low, reducing it > when it is full, the battery keeps the voltage stable.
I think you are splitting hairs. I believe the voltage is what is sensed and so what is regulated. Yes, the current is controlled, but the two go hand in hand. The circuit is not high gain like in a power supply in your computer, holding the output voltage very steady. Instead when the voltage droops it pushes more current out to limit the droop, and vice versa when the voltage increases. -- Rick
On 10/28/2014 9:24 PM, Jim Thompson wrote:
> On Tue, 28 Oct 2014 21:00:00 -0400, "Tom Miller" > <tmiller11147@verizon.net> wrote: > >> >> "Jasen Betts" <jasen@xnet.co.nz> wrote in message >> news:m2pb7p$m36$1@gonzo.reversiblemaps.ath.cx... >>> On 2014-10-28, Tim Wescott <seemywebsite@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 >>> >> >> 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. >> > > 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>
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