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Car Forum / Ford / Ford Explorer / December 2004Battery question.
The battery on my Explorer died a couple of weeks ago. It was 6 years old but showed no signs of illness before it wouldn't crank the engine anymore. So I got a new battery from Pepboys which is supposed to be 650 cold cranking amps. Just to be sure I also took the truck over to AutoZone to get the charge system checked. They said it was fine but the battery showed only 250 cold cranking amps. Is it like that with new batteries ? will it charge more ? The battery dial in the dash shows just under half and the engine cranks just fine. Should I be worried ? 650 sounds like a pretty small battery, but since you already bought it, I would not worry about it as long as it cranks ok. >The battery on my Explorer died a couple of weeks ago. It was 6 years old >but showed no signs of illness before it wouldn't crank the engine anymore. [quoted text clipped - 10 lines] > >Should I be worried ? Wouldn't worry about! You've got to kidding me!!!! Take that junk battery back. Get yourself a "real" battery. At least a Diehard. In my Explorer I run a 900 CCA Diehard SUV and my Toyota has an Optima battery. The Toy gets more of an electrical workout, with the winch and the lockers and the entertainment system so thats why the Optima Red top. But YES I would definately worry about a battery that is supposed to be 650 and putting out less than half that. Searcher1 > 650 sounds like a pretty small battery, but since you already bought > it, I would not worry about it as long as it cranks ok. [quoted text clipped - 16 lines] >> >>Should I be worried ? Searcher, You have got to be kidding me!!! You just like to waste your money, don't you? Once you exceed the amps required to turn your engine over the excess cold cranking amps are as useful and extra spare tires! How many spare tires do you carry, 10 or 12? The brand new 2005 F-550 with a V-10 gas engine comes with one 78 Amp/HR, 750-CCA battery. The brand new 2005 Explorer comes from Ford with a 72 Amp/HR, 650-CCA battery. 650 Cold Cranking Amps is Plenty for all most all automotive applications. When you misinform people you do more harm then help... > Wouldn't worry about! You've got to kidding me!!!! Take that junk battery > back. Get yourself a "real" battery. At least a Diehard. In my Explorer I [quoted text clipped - 26 lines] > >> > >>Should I be worried ? > Wouldn't worry about! You've got to kidding me!!!! Take that junk > battery back. Get yourself a "real" battery. At least a Diehard. In my [quoted text clipped - 7 lines] > > Searcher1 Consumer Reports had a car battery issue recently. You might want to check with them, because diferent makers make diferent sizes and the best for Chevs might not be the best for Fords. One thing, they almost all lie on their specs. -- Riki --Those who live by the sword get shot by those who don't. A battery's amp-hour rating is a maximum specification, much like the horsepower rating of an engine. If you have an engine rated at 400 horsepower, that is its maximum rating at a specified RPM. Assuming that said rating is taken at the rear wheels, if you put the vehicle on a dyno and run it at that specified RPM, you should read 400 hp. If you operate the vehicle at a different RPM - say you're driving at 25 mph - you will see far less than the rated HP. However, unlike a horsepower rating, which is an instantaneous quantity, amp-hours represent energy (which is power over time), divided by voltage. You can't specify a maximum current output for a battery without some assumptions. The amount of current (in amperes) that is actually drawn from the battery will depend on the resistance of the load (in ohms) connected across its terminals. The relationship between voltage (V), current (I) and resistance (R) is V = I times R, otherwise known as Ohm's Law. Then I = V/R, so if R=0 (a dead short), I will attempt to go to infinity. Of course, a real battery can't produce an infinite current! Obviously, you could short the terminals together with a conductor, but if you did this, the current draw would create so much heat that the battery would be destroyed, if the conductor doesn't melt first. As Rastis Fafoofnik states in his post below, you have to test the battery using a carbon pile (which is nothing more than a high-wattage resistive element), so that the battery will be adequately loaded, but the amount of current flow will not damage it. During the test, the voltage has to stay within an acceptable range (if it's +/- 10%, then the range is 10.8 to 13.2 volts), and ideally you will read a current that will stay constant for a certain period of time, say 250 amps for 2.5 hours, until the battery is exhausted. If you multiply 250 and 2.5, you get 625 amp-hour. 125 amps for 5 hours gives you the same rating. Of course, in the real world, the voltage and current will gradually diminish as the battery loses charge, but you get the idea. The battery has to be adequately loaded for the test to be meaningful; a battery in poor condition with little or no load might still read 12 volts across its terminals, but as soon as any substantial load is connected across it, the voltage drops way down, below the minimum acceptable voltage. I'm an electrical engineer and I've specified lots of batteries for power substations. It's basically an addition and multiplication problem. Substations have batteries so that supervisory and protective devices can be operated in case of an outage (if everything runs on AC, and your station goes down, you have no power and are SOL). You first decide how long you want the power to last (typically 8 hours), then you add up the load you need to connect to the batteries. Finally, you multiply that load by the time you want everything to run, and voila - there's your battery specification. I'd add 10 or 15% to that to allow for the tendency of that amp-hour rating to diminish with time (like 10 or 20 years), but you get the method. HTH >> Wouldn't worry about! You've got to kidding me!!!! Take that junk >> battery back. Get yourself a "real" battery. At least a Diehard. In my [quoted text clipped - 17 lines] > -- Riki > --Those who live by the sword get shot by those who don't. http://www.uuhome.de/william.darden/ > However, unlike a horsepower rating, which is an instantaneous quantity, > amp-hours represent energy (which is power over time), divided by voltage. Bzzzzt! Wrong answer... Horsepower is a unit of work over time. Torque is the instantaneous measurement. <http://vettenet.org/torquehp.html> But thanks for playing! -Fred W Sorry Fred, but I'm afraid that you are wrong on this one. Horsepower is *not* a unit of energy, but horsepower-hours are. You may be more familiar with the watt as a unit of power, and a kilowatt-hour as a unit of energy. One horsepower is equal to 746 watts. One horsepower-hour is equal to 1 kilowatt-hour. Electric utilities will bill you for energy used in kilowatt-hours. They don't bill for kilowatts. Torque is a unit of force over distance, for example newton-meters or foot-pounds. These concepts are easily confused. In addition to working as an engineer for an electric utility, I occasionally teach electric circuits and statics classes at the local community college. I find that students confuse power, energy and torque frequently. >> However, unlike a horsepower rating, which is an instantaneous quantity, >> amp-hours represent energy (which is power over time), divided by [quoted text clipped - 10 lines] > > -Fred W Whoops - meant to say that 1 horsepower-hour equals ).746 kwh. Sorry. > Sorry Fred, but I'm afraid that you are wrong on this one. Horsepower is > *not* a unit of energy, but horsepower-hours are. [quoted text clipped - 27 lines] >> >> -Fred W kW or W Are you sure it's 746kwh or just 746 watts. How many horsepower is your vacuum cleaner, garbage disposal? | Whoops - meant to say that 1 horsepower-hour equals ).746 kwh. Sorry. | [quoted text clipped - 29 lines] | >> | >> -Fred W 1 hp = 746 watts= 0.746 kW > kW or W Are you sure it's 746kwh or just 746 watts. How many horsepower > is your vacuum cleaner, garbage disposal? [quoted text clipped - 37 lines] > | >> > | >> -Fred W Thanks, I didn't think I was nuts....of course it is standard measure for most technical disciplines. Mine happens to be computers and electronics. |1 hp = 746 watts= 0.746 kW | [quoted text clipped - 39 lines] | > | >> | > | >> -Fred W Yeah, and I didn't help matters any by typing a parenthesis instead of a zero! > Thanks, I didn't think I was nuts....of course it is standard measure > for most technical disciplines. Mine happens to be computers and [quoted text clipped - 51 lines] > | > | >> > | > | >> -Fred W > Sorry Fred, but I'm afraid that you are wrong on this one. Horsepower is > *not* a unit of energy, but horsepower-hours are. Yep, you're right. I was wrong. > Torque is a unit of force over distance, for example newton-meters or > foot-pounds. But the distance is not the distance of the work, but rather it's the distance of the leverage applying the force to convert it to rotational energy, right? -Fred W Fred: By "the distance of the leverage", I think you mean the moment arm. That's the length of a wrench handle, for example. If I apply 100 lb. of force to a 1 ft moment arm, I get 100 ft-lb. If I have a five foot moment arm (like a breaker bar), I only need to apply 20 lb. of force to get that same 100 ft. lb. So yes, you're correct - when we say force over distance, that distance is indeed the length of the moment arm. Kevin >> Sorry Fred, but I'm afraid that you are wrong on this one. Horsepower is >> *not* a unit of energy, but horsepower-hours are. [quoted text clipped - 9 lines] > > -Fred W Definitions of Cold Cranking Amps on the Web: A performance rating for automobile starting batteries. It is defined as the current that the battery can deliver for 30 seconds and maintain a terminal voltage greater than or equal to 1.20 volts per cell, at 0degrees Fahrenheit (-18Celsius), when the battery is new and fully charged. Starting batteries may also be rated for Cranking Amps, which is the same thing but at a temperature of 32F (0C). > Fred: > [quoted text clipped - 6 lines] > So yes, you're correct - when we say force over distance, that distance is > indeed the length of the moment arm. Thanks. One more thing, and I appreciate your patience with me... Most of the "definitions" I see about horsepower include the element of time in the calculation. example: one HP = 33,000 ft/lbs per minute. Yet you have indicated (and I have found some corroboration)that horsepower is a measurement of power and does not express "power consumption". How can this be if the formula for horsepower already contains the element of time in it? -Fred W Fred, glad to help. I enjoy helping others learn, which is why I teach classes occasionally. And as I said, these concepts are easy to confuse. First of all, 1 hp = 33,000 ft-lb/min, not ft/lbs per minute. That's important because you can get a good idea of the relationship between these quantities from their units. Remember that the units of torque are ft-lb (force multiplied by distance). Since horsepower has the units of ft-lb per minute, then this tells you that horsepower is torque divided by time. Mathematically, this means that if you draw a curve with torque on one axis versus time on the other axis, and took the first derivative of that curve with respect to time, you would get the horsepower at that instant in time. If calculus isn't familiar to you, another way to say it is that if you take the slope of the torque curve (by drawing a straight line tangent to the curve at an arbitrary point on the curve), that gives you the horsepower at that point in time. If you take the slope at every point on the torque curve, you end up with the horsepower curve. It's the same thing as the relationship between distance (meters), velocity (meters/sec) and acceleration (meters/sec squared). Since we know that power multiplied by time equals energy (kilowatt-hours, for example), and if torque divided by time equals horsepower (ft-lb/min), you realize that torque has units of energy. That's where the time relationship comes in. If you study engineering, you find that distance, time, energy, power, etc., are more interrelated than is intuitively obvious. So horsepower-hours and Newton-meters are both units of energy. In fact, according to my references, one hp-hour equals 2,684,520 Newton-meters. There's a really good little conversion program available, called convert.exe. You can get it for free at http://www.joshmadison.com/software/convert/. I use this program at home and at work. I hope that this makes sense. If you want more help, drop me an email at cyclist1@verizon.net. I imagine that most everyone else is rolling their eyes or sound asleep by now! Cheers, Kevin >> Fred: >> [quoted text clipped - 19 lines] > > -Fred W Mathematically, this means that if you draw a curve with torque on one axis versus time on the other axis, and took the first derivative of that curve with respect to time, you would get the horsepower at that instant in time Darn - made a small boo-boo. If you draw a curve with torque on one axis versus time on the other axis, and took the first derivative of that curve with respect to time, you'd get a continuous horsepower curve, over the same length of time. Sorry about that. Kevin >Mathematically, this means that if >you draw a curve with torque on one axis versus time on the other axis, and [quoted text clipped - 8 lines] > >Kevin Oh, well, yeah. I make that mistake all the time. :-0  SignatureBill Funk Change "g" to "a" > The battery on my Explorer died a couple of weeks ago. It was 6 years old > but showed no signs of illness before it wouldn't crank the engine anymore. [quoted text clipped - 10 lines] > > Should I be worried ? This is why you DONT trust your car to idiots like Autozone/Poop-Boys! How the hell can he tell it's only producing 250 COLD cranking amps? He might have seen 250 amps being drawn from the battery when you crank the starter. 250 Amps is a reasonable amount. Unless this guy put the FULLY CHARGED battery on a carbon loadpile and pulled power until he dropped the terminal voltage down to 10 volts he cant tell what the real "COLD Cranking Amperage" is. OLD high compression V-8's (GM and Ford) would pull 400 Amps easy. Your Explorer wont pull that much. Amp/Hr ratings CAN be deceiving. 65AH/Hr means 65 amps for ONE hour. You can interpolate this any way you like.65Ah/Hr also means 130Amps for 30min,650Amps for 10 minutes (you will blow the top off it).It also means 1 Amp for 65 hours, DOESNT mean it will start the car!!! The higher the AH/Hr rating the longer it will last with the lights left on, the longer it will be able to start the car after sitting. DON'T be terribly concerned with "COLD CRANKING AMPS" unless you have a diesel, high compression or a rust bucket thats hard to start. On the voltmeter you want to see 13.8 to 14.2 volts while running at driving speeds NO more or less.On a lot of cars the meter is not calibrated, get used to where it stays, if it moves a lot higher or lower trouble is near.... Hope this helps. Sign me...... Tired of Poop-Boys and AssholeZone Damn... What an argumant I started. So far the baterry works just fine so I guess it's ok. > The battery on my Explorer died a couple of weeks ago. It was 6 years old > but showed no signs of illness before it wouldn't crank the engine anymore. [quoted text clipped - 10 lines] > > Should I be worried ? |
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