I'm not sure that the reading of a voltmeter says it all. What do you see on an oscilloscope? (Same remark about car alternators. High current peaks seem to counter sulfation.)
Groetjes Albert
-- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- being exponential -- ultimately falters. albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst
On Saturday, December 2, 2017 at 10:12:35 AM UTC-8, Albert van der Horst wr ote:
I wish I had an oscilloscope and could view the charging waveform. The cha rger does appear to use a switching regulator. Even so, I have a feeling t hat the average voltage and average current would still be meaningful in te rms of charging the battery. This particular charger does not have a Desul fate Mode which would also be very interesting to view on an oscilloscope.
That's a very interesting comment on alternator rectified current peaks hel ping to counter sulfation!
Here is a new data point that might be of interest. My car had not been dr iven for a full two weeks and the battery voltage only dropped to 12.59 vol ts. I connected the Black & Decker 2 Amp Charger/Maintainer and it stayed on charge for 3.25 hours. If the charger maintained 2 Amps during that per iod, it would have put 6.5 Amp Hours into the battery which is rated at 52 Amp Hours. That would suggest that the battery had a 12% discharge while s itting idle for two weeks. The battery had been fully charged prior to dri ving the car. Temperatures were in the range of 50-70 degrees F.
When the car is shut off, there is a small current load to run the keyless entry receiver, the burglar alarm system, etc. The battery drain is usually less than 50 milliameres. If you let the car sit for two weeks, and the drain was 50 mA, the total amp-hours would be
50e-3 * 24 * 14 = 16.8 amp-hours.Since the B&D only put back 6.5 amp-hours, your idle current drain would be
(6.5 / 16.8) * 50e-3 = 1.93e-2 = 19.3 mA
However, we don't know how well the B&D is calibrated, and what condition determines shutoff, so all estimates are only approximate.
But it looks like your battery and alternator are fine. Keep the charger so you can help out your cute neighbour when she leaves an interior light on overnight.
I recently discovered that my driving pattern causes sulfation (seemingly, not fatal). Frequent short starts to move the vehicle (~daily), infrequent trips adequate to charge the battery (>10 mins).
It's just marginal enough (whether because of my driving pattern, or if it's a weak alternator) that it takes 5 years to develop.
It's a '95, not a particularly new car, so it's missing some of the features you noted.
Full recovery (in terms of ESR; capacity unknown) was obtained after floating the battery at 14.4V for 48 hours. This drew very little current overall, less than 10 amperes at first, dropping to 0.3A through the last day.
Will see if it behaves for the rest of the winter (solid so far), and if it still acts like new next winter.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
I'm retired and only drive 1,500 kilometers per year. It's a bunch of short trips for groceries and parts from the hardware stores, with lots of sitting in between. The battery is a couple of years old, and I often monitor the quiescent voltage before starting. Oddly enough, the battery measured 12.4 volts when I bought it instead of the normal 12.6 volts as mentioned in numerous web sites such as the Battery University. It still measures around 12.4 V, but varies with temperature.
I though the battery was bad when I purchased it, but it seems to be holding up quite well. It has no trouble starting the car in -30c weather after several days of cold soak.
I'm not surprised you are seeing a dropoff in capacity. Around here, battery warranties seem to expire in 3 years, so they expect the battery to die soon after. Most sites recommend a new battery after 6 years of service, so you may be due for a new one.
I don't think you can attribute your performance to sulfation - the battery has to be almost dead and sitting for guite some time. Then it won't accept a charge.
I'd check the voltage under light and heavy loads. If there's not much difference, your alternator is probably OK.
My previous car was a Ford Taurus. It was designed to destroy the battery, and often charged at around 13.5 volts or less. I finally had to remove it after each trip and put it on a constant current/constant voltage lab supply.
I set the voltage to 14.5 Volts and 5 A. Like you, it measured 5 Amps at the start, then it quickly dropped to several hundred mA after about 5 minutes. So I think the battery was OK.
How do you measure ESR?
A mechanic once told me. There are TWO four letter "F-Words". He allows his children to say the first one, but not the word FORD. (Unless the first four letter F-Word, precedes the word FORD).
I have two of them, a convertible stick-shift Mustang (my car, which I love) and a turbo-four Fusion (my wife's car, whose dashboard displays I cordially dislike, but which makes her happy). No worries so far.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
Drive it through a known load and measure voltage and current at energization, and the ESR will be in series with that and should be determinable with those instantaneous readings.
Doing so with small, medium, and heavy loads would allow one to dial it in even more precisely.
gy
I agree if the voltage regulator settings allow it. The problem today is t hat new cars are often light on charging to reduce alternator load and incr ease fuel economy. My car is in that category and the highest alternator v oltage I've seen after a cold start is 14.25 volts and that was on a cold d ay. As soon as the engine warms up the voltage drops to the range of 13.5-
13.8 volts. I may only see ten minutes where the charge current would be a dequate for charging the battery. Ten minutes appears to be fine if the ba ttery is in good condition and near full charge. It's a different story wi th a discharged battery or a sulfated battery. I think others have stated that automotive charging systems today are not designed to recharge a disch arged battery.I also wonder if there is a secondary problem with the temperature compensa tion typically used with voltage regulators. If I restart my car after a s hort trip, the engine is still warm and the alternator voltage may be 13.8 volts or less. The battery may still be relatively cool inside and need a higher alternator voltage to charge adequately.
Does it begin with F and end with U-C-K?
Although that's a nine letter word, hmm.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
I've seen figures of 10 years being typical, but I'm not sure if that was because the people saying so were in more temperate climates.
I got 5 or 6 years out of the last battery (according to its sticker; I didn't install it, it came with the car). Didn't try floating it, unfortunately; might've been another year in it!
"Sulfation" in a weak sense, in that, that's simply how a lead acid works (PbSO4 and Pb Pb and PbO2), but that it's probably nonuniform enough to cause problems (high ESR) but apparently not beyond the point of no return.
Have been meaning to measure it some time, see if it's low or nominal. Probably not far off, given that it's good for whole years at a time.
I momentarily apply a heavy (~200A) load to it and measure the voltage by ear. :^)
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
I have two, also. My wife's car is also a convertible Mustang (though a 6-speed auto) and I drive an F-150 (bought both the same week ;-). She had a Mercury Sable (same car as the Ford Taurus) and had no problems with batteries. We were in Vermont at the time and got seven years out of the original). Great vehicles. The only crappy Ford I've had was the '73 Rustang-II (i.e. Pinto, in drag). OTOH, every Chrysler product I've had was crap.
We had a '94 Dodge Grand Caravan, which was great until it finally rusted out circa 2003. It had far and away the most comfortable seats of any vehicle I've ever driven, and it was very reliable mechanically.
OTOH my '92 Saturn SC lasted twice as long before succumbing to corrosion. (It was old enough to drive itself.)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
I had '85 and a '90 voyagers. Both rusted badly. The '85 went through a head gasket every 30K miles (you could set a watch by it). Both rusted out before 100K miles (about six years). The NE is hard on car bodies but they weren't that much better than the Rustang-II.
I also had a '93 Eagle Vision TSI and a '96 Chrysler Intrepid. Nice comfortable cars but they fell apart. The final nail for both was transmissions.
Have some mercy. The poor thing sacrificed itself to prevent you from having to drive it any longer. ;)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Car restorers/collectors buy engines from the Northeast and bodies from Arizona or Southern California. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
It's what you learn, after you know it all, that counts.
The equation we are interested in is
Pb(s) + PbO2(s) + 2H2SO4(aq) --> 2PbSO4(s) + 2H2O(l)
Both plates get sulfated. This is not bad if the battery gets fully charged before the sulfur crystals have time to harden. Here are some articles that describe it better:
BU-804b: Sulfation and How to Prevent it
Applying ways to minimize sulfation.
Sulfation occurs when a lead acid battery is deprived of a full charge. This is common with starter batteries in cars driven in the city with load-hungry accessories. A motor in idle or at low speed cannot charge the battery sufficiently.
Electric wheelchairs have a similar problem in that the users might not charge the battery long enough. An 8-hour charge during the night when the chair is not being used is not enough. Lead acid must periodically be charged 14 - 16 hours to attain full saturation.
This may be the reason why wheelchair batteries last only 2 years, whereas golf cars with the identical battery deliver twice the service life. Long leisure time allows golf car batteries to get a full charge overnight. (See 403: Charging Lead Acid.)
Solar cells and wind turbines do not always provide sufficient charge for lead acid banks, which can lead to sulfation. This happens in remote parts of the world where villagers draw generous amounts of electricity with insufficient renewable resources to charge the batteries. The result is a short battery life. Only a periodic fully saturated charge can solve the problem. But without an electrical grid at their disposal, this is almost impossible.
An alternative solution is using lithium-ion, a battery that prefers a partial charge to a full charge. However, Li-ion is more than double the cost of lead acid. Although more expensive, the cycle count is said to be cheaper than that of lead acid because of the extended service life.
What is sulfation? During use, small sulfate crystals form, but these are normal and are not harmful. During prolonged charge deprivation, however, the amorphous lead sulfate converts to a stable crystalline and deposits on the negative plates. This leads to the development of large crystals that reduce the battery's active material, which is responsible for the performance.
There are two types of sulfation: reversible (or soft sulfation), and permanent (or hard sulfation). If a battery is serviced early, reversible sulfation can often be corrected by applying an overcharge to an already fully charged battery in the form of a regulated current of about 200mA. The battery terminal voltage is allowed to rise to between 2.50 and 2.66V/cell (15 and 16V on a 12V mono block) for about 24 hours. Increasing the battery temperature to 50 - 60C (122 - 140F) during the corrective service further helps in dissolving the crystals.
Permanent sulfation sets in when the battery has been in a low state-of-charge for weeks or months. At this stage, no form of restoration seems possible; however, the recovery yield is not fully understood. To everyone's amazement, new lead acid batteries can often be fully restored after dwelling in a low-voltage condition for many weeks. Other factors may play a role.
A subtle indication whether lead acid can be recovered or not is visible on the voltage discharge curve. If a fully charged battery retains a stable voltage profile on discharge, chances of reactivation are better than if the voltage drops rapidly with load.
Several companies offer anti-sulfation devices that apply pulses to the battery terminals to prevent and reverse sulfation. Such technologies will lower the sulfation on a healthy battery, but they cannot effectively reverse the condition once present. It's a "one size fits all" approach and the method is unscientific.
Applying random pulses or blindly inducing an overcharge can harm the battery by promoting grid corrosion. There are no simple methods to measure sulfation, nor are commercial chargers available that apply a calculated overcharge to dissolve the crystals. As with medicine, the most effective remedy is to apply a corrective service for the time needed and not longer.
While anti-sulfation devices can reverse the condition, some battery manufacturers do not recommend the treatment as it tends to create soft shorts that may increase self-discharge. Furthermore, the pulses contain ripple voltage that causes some heating of the battery. Battery manufacturers specify the allowable ripple when charging lead acid batteries.
Last updated 2016-09-22
In the discharged state both the positive and negative plates become lead(II) sulfate (PbSO4), and the electrolyte loses much of its dissolved sulfuric acid and becomes primarily water. The discharge process is driven by the conduction of electrons from the negative plate back into the cell at the positive plate in the external circuit.
The total reaction can be written as
Pb(s) + PbO2(s) + 2H2SO4(aq) --> 2PbSO4(s) + 2H2O(l)
Sulfation and desulfation
Lead - acid batteries lose the ability to accept a charge when discharged for too long due to sulfation, the crystallization of lead sulfate.[27] They generate electricity through a double sulfate chemical reaction. Lead and lead dioxide, the active materials on the battery's plates, react with sulfuric acid in the electrolyte to form lead sulfate. The lead sulfate first forms in a finely divided, amorphous state, and easily reverts to lead, lead dioxide and sulfuric acid when the battery recharges. As batteries cycle through numerous discharges and charges, some lead sulfate is not recombined into electrolyte and slowly converts to a stable crystalline form that no longer dissolves on recharging. Thus, not all the lead is returned to the battery plates, and the amount of usable active material necessary for electricity generation declines over time.
Sulfation occurs in lead - acid batteries when they are subjected to insufficient charging during normal operation. It impedes recharging; sulfate deposits ultimately expand, cracking the plates and destroying the battery. Eventually so much of the battery plate area is unable to supply current that the battery capacity is greatly reduced. In addition, the sulfate portion (of the lead sulfate) is not returned to the electrolyte as sulfuric acid. It is believed that large crystals physically block the electrolyte from entering the pores of the plates. Sulfation can be avoided if the battery is fully recharged immediately after a discharge cycle.[28]
A white coating on the plates may be visible (in batteries with clear cases, or after dismantling the battery). Batteries that are sulfated show a high internal resistance and can deliver only a small fraction of normal discharge current. Sulfation also affects the charging cycle, resulting in longer charging times, less efficient and incomplete charging, and higher battery temperatures.
SLI batteries (starting, lighting, ignition; ie, car batteries) suffer most deterioration because vehicles normally stand unused for relatively long periods of time. Deep cycle and motive power batteries are subjected to regular controlled overcharging, eventually failing due to corrosion of the positive plate grids rather than sulfation.
There are no known, independently verified ways to reverse sulfation.[8][29] There are commercial products claiming to achieve desulfation through various techniques (such as pulse charging), but there are no peer-reviewed publications verifying their claims.
Sulfation prevention remains the best course of action, by periodically fully charging the lead-acid batteries.
So when you go to Walmart or some other battery store, you may see racks of batteries waiting to be sold. The reason they don't sulfate is because they were fully charged before being placed on the racks, and they don't stay there long enough to become discharged.
With the proper charging voltage, the battery recharges quickly after starting the engine. The actual drain current to keep the battery charged is very low. However, when you have a high load current from headlights, heatd seats, rear window defrost, stereo, and other loads, the alternator only charges on the peaks, and the battery has to supply the total load current between the peaks.
The alternator output is three phase bridge rectified, so there are 6 voltage peaks per cycle. This means the ripple voltage is pretty low, so the alternator is taking the full load for a large part of the cycle. But the battery has to supply the load the rest of the time, and it needs to be in good shape. Especially if you are stuck in traffic at night with the healights on and the air conditioning full on. My battery died in Toronto one night under these same conditions, and it was a real pain trying to get it out of the traffic and get the engine started again.
Older cars had the voltage regulator inside the alternator. Since the alternator was bolted to the engine, it quickly attained the heat from the engine. After warmup, the regulator reduced the charging voltage regardless of the actual battery temperature. The battery became depleted and would begin to sulfate. This happened on my old Taurus.
Newer cars meaure the intake manifold air temperature to estimate the battery temperature. This is a bit more accurate, but the temperature sensor can absorb heat from the engine while you are shopping. This throws off the estimate of battery temperature and the battery can be overcharged or undercharged depending on conditions.
Seems like less of a problem nowadays. We just got rid of a 2004 Hyundai XG350 because the fenders rusted out, but it had 180k on it and didn't owe us anything--apart from one engine computer and a set of struts it worked fine till the day we traded it in on the Fusion.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
The concept of measuring battery voltage to indicate state of charge may no t be very precise. This morning I measured my battery voltage at the batter y terminals 36 hours after removing my battery maintainer. The voltage read 12.70 volts. I then opened the driver side car door which apparently resul ts in some current flow. The battery voltage dropped to 12.60 volts and the n drifted down to 12.48 volts within a few minutes.
After closing the car door, the voltage drifted back up to 12.68 volts afte r about 25 minutes. I've checked this battery on quite a few occasions and temperature also seems to be a factor. It's not clear if voltage readings a re any more meaningful at lower states of charge. The table I have been ref erencing shows 100% charge at 12.7 volts, 75% charge at 12.4 volts, 50% cha rge at 12.2 volts, 25% charge at 12.0 volts, and 0% charge at 11.9 volts.
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