How do I test whether my battery is dying?
07-11-2002, 01:30 PM
#1
Registered User
Thread Starter
How do I test whether my battery is dying?
Over the past two days, I've noticed that the engine is cranking much more slowly than usual. Car runs fine once it's started, and only takes the normal couple cranks or two to fire up. My guess is that the battery isn't supplying enough voltage.
I don't have a voltmeter, but should I get one and check if the battery is putting out 12V?
How can I check if the alternator is working properly? No warning light has lit up on the dash, so I doubt it's that. Could the problem be with something else?
Thx.
I don't have a voltmeter, but should I get one and check if the battery is putting out 12V?
How can I check if the alternator is working properly? No warning light has lit up on the dash, so I doubt it's that. Could the problem be with something else?
Thx.
07-11-2002, 05:51 PM
#5
Originally posted by dhess
What voltage should a healthy battery read?
What voltage should a healthy battery read?
07-11-2002, 07:20 PM
#7
Registered User
The proper test of the battery is how much voltage is sustained when put under load. There is special equipment to do this, a voltmeter won't do. Many types of batteries keep 80% or more of their voltage even though they can't crank out the amperes. (Unlike alkalines which gradually lose their no-load voltage as they go dead)
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07-12-2002, 03:55 AM
#8
Registered User
A voltmeter can tell you something that you already will likely know - your battery is dead. Batteries die in 2 modes - acute death, usually when a cell goes bad, and slow death, when a battery loses its cranking power over time. In acute death and voltmeter will show that one cell is no longer functioning. My recently expired original battery read 10.2 V and obviously did not pass the load test at a local Batteries Plus store. Slow death occurs when the plates wear out over the life of the battery. At some point the battery will not be able to crank the engine properly even though it still shows near 12 V. This often happens in cold weather when batteries are weaker due to the low ambient temperatures.
07-12-2002, 05:50 AM
#9
I do add a tiny bit of distilled water to the cells to make up for evaporation. Here is all you ever wanted to know about batteries:
13.06 Current Events: Battery Evolution
The lead-acid wet-cell storage battery was invented in 1859, but it wasn't until 1912 that Cadillac introduced the first electrical cranking system, thus saving numerous wrecked backs and broken arms. The kick that starts your car today is still provided by lead and acid, but if you think that means not much technological development has gone into batteries, you'd better keep reading.
*Chem 101
A quick recap of battery theory and anatomy will help you understand energizer evolution. If two dissimilar metals are placed in an electrolyte that can attack them, voltage potential is created. Electrons will flow if a connection is made between the metals, and that's what electricity is.
In a wet cell, the metals are sponge lead (Pb) and lead peroxide (PbO2), and the electrolyte is dilute sulfuric acid (H2SO4). The reaction begins as sulfate (SO4) breaks away from the acid and unites with the lead of both the positive and negative plates to form lead sulfate (PbSO4). The oxygen (O2) is thereby liberated from the lead peroxide and joins with the hydrogen (H2 -- what's left over after the sulfate left the acid) to produce ordinary water (H2O), which dilutes the electrolyte.
Eventually, both the plates turn into lead sulfate, the electrolyte becomes very weak, and current stops flowing.
But reversibility is the wet cell's most important characteristic. When an outside power source pushes electrons through the cell in the opposite direction to that of discharge, sulfate separates from both plates to rejoin the hydrogen in the water, forming a new batch of sulfuric acid. The oxygen goes back to the positive plate to recreate lead peroxide, and the electrical potential is restored. If charging continues after all the sulfate has gone into the electrolyte, the water starts to decompose, releasing free hydrogen and oxygen, an explosive combination.
The traditional automotive battery has plates made of a mixture of lead and antimony impregnated with the metals involved in the reaction. The positive plates are separated from the negatives by sheets of porous material (balsa wood has been used) that insulates them electrically from each other, but allows the electrolyte to pass. Numerous plates of each metal are interlaced within one cell, but whether two or a dozen are used the cell produces a "pressure" of 2.1 volts. Six cells are connected in series to give the 12.6 volts almost all cars have needed since the '50s.
*Impossible maintenance?
One of the biggest departures occurred in 1972 when the maintenance-free battery appeared. Its plate grids are made of calcium lead alloy with no antimony, which reduces gassing by up to 97%, and cuts water loss and terminal corrosion. It also prevents thermal runaway, a condition wherein conventional plates destroy themselves by overheating when fed too much power. Also, there's very little self-discharge, so an M-F unit can retain enough wallop to start a car after sitting for up to a year.
Sounds great, right? But there's more to the story. As one expert tells us, "There's really no such thing as maintenance-free. Every battery will evaporate some water from heat, and gas a little from electrolysis." In the battery business, M-Fs with non-removable cell caps are frequently referred to as "maintenance impossible."
Which brings us to the low-maintenance type, also called hybrid or dual-alloy. This uses calcium for the negative grid, but retains a small amount of antimony in the positive. It gasses but very little, withstands deep discharges better than the calcium/calcium type, you can add water, and it requires lower voltage during charge, which reduces the potential for heat damage.
*Big burst
Maybe a decade ago, the equivalent of a horsepower race went on among battery manufacturers where CCA is concerned. Passenger car units with ratings of up to 1,000 were put on the market, and that's enough to crank a semi on a frigid morning.
But most people don't realize that there's a trade-off relationship between CCA (Cold Cranking Amps -- the number of amperes a full-charged battery can deliver a 0 deg. F. for 30 seconds without going below 7.2 volts) and RC (Reserve Capacity -- the number of minutes a new, juiced-up battery at 80 deg. F. can sustain a 25 amp drain before dropping to 10.5 volts) ratings. If the first is pushed up in a particular design, the second goes down, and vice versa. So, you might find a battery with robust CCA, but weak RC.
This is because the more numerous plates used to increase cold cranking are by necessity thinner, so the overall proportion of reactive material is smaller and reserve capacity is diminished.
Especially given today's increased parasitic loads, we usually choose a battery on the basis of a big RC number, figuring that CCA will be sufficient -- in case you hadn't noticed, new cars fire up instantly.
We should mention another problem with thin plates: They're more apt to buckle at high temperatures.
*Heat prostration
Speaking of heat, the manufacturers are addressing the fact that it's way up in today's cars, which causes all kinds of problems. Besides the buckled plates just mentioned, there's the chronic undercharge condition that occurs because a hot battery will produce higher voltage than a cool one at the same state of charge. The voltage regulator doesn't know the temperature, so it assumes the cells have a full dose of juice when in fact they may be down 25%. That's one reason Chrysler started using a battery temperature sensor and the logic module to control charging way back in '85.
High heat and a continual low state of charge makes hard sulfation build up, and crystallization starts breaking the bond between the active material and the grid. The lead becomes so soluble it attaches to the separators forming a "tree" that can short out the plates right through the pores in the plastic envelope. Specific gravity rises too far because the water evaporates while the acid stays, and separators can become "charred."
All this adds up to a surprising statistic: Average battery life is actually almost a year shorter in the south than in the north. So, there are batteries on the market designed specifically to combat heat, and they employ both new and old technology to do this -- efficient radial grids, but thicker plates. This lowers CCA, but who needs all that zero weather kick in the sunbelt? What's really necessary where warm weather prevails is plenty of HCA (Hot Cranking Amps -- the discharge load in amps a new, fully- charged battery at 32 deg. F. can deliver for 30 seconds while maintaining 1.2 volts per cell) and RC (130 minutes in a good example).
Another feature is a thermal insulation blanket made of a proprietary plastic foam that floats on top of the electrolyte, displacing the air so there's less gassing and evaporation.
*Forcing reconciliation
Ever hear of the recombinant battery? The idea here is to immobilize the electrolyte and keep the moisture level stable by forcing the hydrogen and oxygen to recombine into water. This is accomplished by using a different type of insulator and by keeping the interior of the unit under pressure. Because this type of battery is insensitive to severe angles, it's particularly applicable to marine and off-road use.
Early versions had problems with the relief valve that maintains pressure. It's hard to keep its calibration accurate in mass production, so sometimes you ended up with a battery that looked like a bowling ball.
The first recombinant to hit the market in the U.S. promptly failed, but perfected versions are now available. A prominent example is Exide's Orbital, which uses a paste-like electrolyte absorbed into glass matte separators to absolutely prevent acid leakage even if the unit is punctured or mounted upside-down. Another feature is the use of spiral-wound elements (each over a meter long when laid out) pressure-packed in individual "jelly roll" cells, which make the case resemble a six-pack. This configuration minimizes plate shedding and positive grid disintegration, two big reasons for battery failure.
*Goodbye dependable dozen
A big change we'll be seeing by 2002 or so is the adoption of 42-volt systems (that number refers to alternator output, but they can also be seen as 36-volt systems because they use 18 two-volt cells), something the Europeans are especially hot about. Why tamper with a standard that's been around for 45 years? Lots of reasons. First, those flywheel-mounted combination starters/alternators you may have heard about allow such quick, quiet starting that the engine can be shut down any time you come to a stop, which will save gas and cut pollution (no more idling in traffic jams), but they need plenty of voltage to do their job efficiently. Then there's the idea of using electric motors to drive such things as A/C compressors and rack & pinion steering gears, and that'll draw lots of power. Instead of resorting to gigantic cables to deliver sufficient amperage, increased voltage can be enlisted. Another possibility is solenoid-actuated engine valves, which concept will also require more moxie than 12 volts can offer.
Finally, are there any new combinations of active materials (called "couples" in the industry) that show promise as a practical replacement for lead-acid? In a word, no. As one battery engineer puts it, "I don't think we'll see a switch from lead-acid. Its cost is low relative to any other couple, nicad for instance. And lead-acid is eminently recyclable."
13.06 Current Events: Battery Evolution
The lead-acid wet-cell storage battery was invented in 1859, but it wasn't until 1912 that Cadillac introduced the first electrical cranking system, thus saving numerous wrecked backs and broken arms. The kick that starts your car today is still provided by lead and acid, but if you think that means not much technological development has gone into batteries, you'd better keep reading.
*Chem 101
A quick recap of battery theory and anatomy will help you understand energizer evolution. If two dissimilar metals are placed in an electrolyte that can attack them, voltage potential is created. Electrons will flow if a connection is made between the metals, and that's what electricity is.
In a wet cell, the metals are sponge lead (Pb) and lead peroxide (PbO2), and the electrolyte is dilute sulfuric acid (H2SO4). The reaction begins as sulfate (SO4) breaks away from the acid and unites with the lead of both the positive and negative plates to form lead sulfate (PbSO4). The oxygen (O2) is thereby liberated from the lead peroxide and joins with the hydrogen (H2 -- what's left over after the sulfate left the acid) to produce ordinary water (H2O), which dilutes the electrolyte.
Eventually, both the plates turn into lead sulfate, the electrolyte becomes very weak, and current stops flowing.
But reversibility is the wet cell's most important characteristic. When an outside power source pushes electrons through the cell in the opposite direction to that of discharge, sulfate separates from both plates to rejoin the hydrogen in the water, forming a new batch of sulfuric acid. The oxygen goes back to the positive plate to recreate lead peroxide, and the electrical potential is restored. If charging continues after all the sulfate has gone into the electrolyte, the water starts to decompose, releasing free hydrogen and oxygen, an explosive combination.
The traditional automotive battery has plates made of a mixture of lead and antimony impregnated with the metals involved in the reaction. The positive plates are separated from the negatives by sheets of porous material (balsa wood has been used) that insulates them electrically from each other, but allows the electrolyte to pass. Numerous plates of each metal are interlaced within one cell, but whether two or a dozen are used the cell produces a "pressure" of 2.1 volts. Six cells are connected in series to give the 12.6 volts almost all cars have needed since the '50s.
*Impossible maintenance?
One of the biggest departures occurred in 1972 when the maintenance-free battery appeared. Its plate grids are made of calcium lead alloy with no antimony, which reduces gassing by up to 97%, and cuts water loss and terminal corrosion. It also prevents thermal runaway, a condition wherein conventional plates destroy themselves by overheating when fed too much power. Also, there's very little self-discharge, so an M-F unit can retain enough wallop to start a car after sitting for up to a year.
Sounds great, right? But there's more to the story. As one expert tells us, "There's really no such thing as maintenance-free. Every battery will evaporate some water from heat, and gas a little from electrolysis." In the battery business, M-Fs with non-removable cell caps are frequently referred to as "maintenance impossible."
Which brings us to the low-maintenance type, also called hybrid or dual-alloy. This uses calcium for the negative grid, but retains a small amount of antimony in the positive. It gasses but very little, withstands deep discharges better than the calcium/calcium type, you can add water, and it requires lower voltage during charge, which reduces the potential for heat damage.
*Big burst
Maybe a decade ago, the equivalent of a horsepower race went on among battery manufacturers where CCA is concerned. Passenger car units with ratings of up to 1,000 were put on the market, and that's enough to crank a semi on a frigid morning.
But most people don't realize that there's a trade-off relationship between CCA (Cold Cranking Amps -- the number of amperes a full-charged battery can deliver a 0 deg. F. for 30 seconds without going below 7.2 volts) and RC (Reserve Capacity -- the number of minutes a new, juiced-up battery at 80 deg. F. can sustain a 25 amp drain before dropping to 10.5 volts) ratings. If the first is pushed up in a particular design, the second goes down, and vice versa. So, you might find a battery with robust CCA, but weak RC.
This is because the more numerous plates used to increase cold cranking are by necessity thinner, so the overall proportion of reactive material is smaller and reserve capacity is diminished.
Especially given today's increased parasitic loads, we usually choose a battery on the basis of a big RC number, figuring that CCA will be sufficient -- in case you hadn't noticed, new cars fire up instantly.
We should mention another problem with thin plates: They're more apt to buckle at high temperatures.
*Heat prostration
Speaking of heat, the manufacturers are addressing the fact that it's way up in today's cars, which causes all kinds of problems. Besides the buckled plates just mentioned, there's the chronic undercharge condition that occurs because a hot battery will produce higher voltage than a cool one at the same state of charge. The voltage regulator doesn't know the temperature, so it assumes the cells have a full dose of juice when in fact they may be down 25%. That's one reason Chrysler started using a battery temperature sensor and the logic module to control charging way back in '85.
High heat and a continual low state of charge makes hard sulfation build up, and crystallization starts breaking the bond between the active material and the grid. The lead becomes so soluble it attaches to the separators forming a "tree" that can short out the plates right through the pores in the plastic envelope. Specific gravity rises too far because the water evaporates while the acid stays, and separators can become "charred."
All this adds up to a surprising statistic: Average battery life is actually almost a year shorter in the south than in the north. So, there are batteries on the market designed specifically to combat heat, and they employ both new and old technology to do this -- efficient radial grids, but thicker plates. This lowers CCA, but who needs all that zero weather kick in the sunbelt? What's really necessary where warm weather prevails is plenty of HCA (Hot Cranking Amps -- the discharge load in amps a new, fully- charged battery at 32 deg. F. can deliver for 30 seconds while maintaining 1.2 volts per cell) and RC (130 minutes in a good example).
Another feature is a thermal insulation blanket made of a proprietary plastic foam that floats on top of the electrolyte, displacing the air so there's less gassing and evaporation.
*Forcing reconciliation
Ever hear of the recombinant battery? The idea here is to immobilize the electrolyte and keep the moisture level stable by forcing the hydrogen and oxygen to recombine into water. This is accomplished by using a different type of insulator and by keeping the interior of the unit under pressure. Because this type of battery is insensitive to severe angles, it's particularly applicable to marine and off-road use.
Early versions had problems with the relief valve that maintains pressure. It's hard to keep its calibration accurate in mass production, so sometimes you ended up with a battery that looked like a bowling ball.
The first recombinant to hit the market in the U.S. promptly failed, but perfected versions are now available. A prominent example is Exide's Orbital, which uses a paste-like electrolyte absorbed into glass matte separators to absolutely prevent acid leakage even if the unit is punctured or mounted upside-down. Another feature is the use of spiral-wound elements (each over a meter long when laid out) pressure-packed in individual "jelly roll" cells, which make the case resemble a six-pack. This configuration minimizes plate shedding and positive grid disintegration, two big reasons for battery failure.
*Goodbye dependable dozen
A big change we'll be seeing by 2002 or so is the adoption of 42-volt systems (that number refers to alternator output, but they can also be seen as 36-volt systems because they use 18 two-volt cells), something the Europeans are especially hot about. Why tamper with a standard that's been around for 45 years? Lots of reasons. First, those flywheel-mounted combination starters/alternators you may have heard about allow such quick, quiet starting that the engine can be shut down any time you come to a stop, which will save gas and cut pollution (no more idling in traffic jams), but they need plenty of voltage to do their job efficiently. Then there's the idea of using electric motors to drive such things as A/C compressors and rack & pinion steering gears, and that'll draw lots of power. Instead of resorting to gigantic cables to deliver sufficient amperage, increased voltage can be enlisted. Another possibility is solenoid-actuated engine valves, which concept will also require more moxie than 12 volts can offer.
Finally, are there any new combinations of active materials (called "couples" in the industry) that show promise as a practical replacement for lead-acid? In a word, no. As one battery engineer puts it, "I don't think we'll see a switch from lead-acid. Its cost is low relative to any other couple, nicad for instance. And lead-acid is eminently recyclable."
07-12-2002, 06:00 AM
#10
Chris,
Oooooh, back to chem 101!
Hey, about the battery in the S2000... I noticed it's a Panasonic in my '02, which was true in my '90 Miata. As I recall, the Miata's battery was unusual (not just the size). It used some sort of material in the cells which wasn't "wet" in the traditional lead-acid sense.
Is the S2000 battery the same technology (wish I could remember the details)? If so, it's supposed to last a damn sight longer than traditional batteries. And, that leads to the question of why Mark's battery would be running out of juice in just a couple of years.
If I'm off base here, just yell.
Oooooh, back to chem 101!
Hey, about the battery in the S2000... I noticed it's a Panasonic in my '02, which was true in my '90 Miata. As I recall, the Miata's battery was unusual (not just the size). It used some sort of material in the cells which wasn't "wet" in the traditional lead-acid sense.
Is the S2000 battery the same technology (wish I could remember the details)? If so, it's supposed to last a damn sight longer than traditional batteries. And, that leads to the question of why Mark's battery would be running out of juice in just a couple of years.
If I'm off base here, just yell.