dr bob

Karl--

The charging available in the cute little maintainer I got recently has all the characteristics of the 'desulfators'. It pulse-charges, varies the rate of charging, etc. The only missing part is the small discharge-recharge part of that cycle.

Lead sulphate is somewhat conductive, and if allowed to build up into the plates it will eventually 'kill' an individual cell. Sometimes a heavy charge current will 'unkill' the cell by either returning some of the deposits back to solution, or warping the plates so they lose contact with the deposits. hard charging abuses all the cells in the battery, since the current to 'fix' the bd cell has to pass through all the good ones. Bottom line though is that the lead has been leached from the plates and the sulphur has been borrowed from the electrolyte, and both of those things affect total battery capacity. Keep the electrolyte concentration correct by maintaining levels with distilled water, and you go a long way toward minimizing sulfation. Keep the charge level correct and you can help keep the lead in the plates and the sulphur doing its job in the electrolyte too.

BYW, some of those mosquito gadgets really do work. The propane catalyst kind that generate CO2 will actually attract them, and it then takes only a little maze or chemical to trap and kill them. I never understood the practice of putting the attractor near where people congregate. Good News is that, if you believe the experts, the CO2 is causing Global Warming, raising water levels, and creating more breeding areas for the mosquitos.

The de-sulfaters may or may not work, depending on how far gone your battery is when you use it I suspect. To your original question...

MGW-Fla

Just replaced my previous Duralast 49-L with another one, it lasted 2.5 yrs. My car is in the garage, not driven too often. Prorated it cost about $45, with them taking the core to save $12. The wife's S4 has a Duralast I put in almost 2 yrs ago, still going fine & its driven almost daily.

depami

Not a duralast but I just replaced the battery in the '82.

It was a Die Hard and I paid $89 in June 2004. I just paid $150 for the same battery!

Mark SF

I was just at Walmart yesterday. My battery had died so I went there to exchange it.

The basic battery, which is the one in my car, is the Everstart 40-R3 with 590CCA. It costs $67 plus $8 core. There is also a better one called Maxx 48.

I am sure the 40R3 fits but haven't tried the Maxx48.

dr bob

I suspect the Wal-Mart battery comes off the same assembly line at Johnson Controls. Plus the Wal-Mart warranty network is pretty extensive.

----

With a new alternator, the latest Duralast is keeping its head barely above water. SPG of the fluid is low but the car still cranks and starts. Symptoms worse in hot weather when the alternator output is limited, but we survived the summer OK. So hot nights with lights, AC, etc, still have the dash gauge at 12V or a little less at hot idle. I'll probably get this onereplaced soon, before I have to start paying money on the exchange. If I wasn't bought in so deep on this one for warranty, I'd probably try the Wal-Mart version. The cost is the same as three of the sven pro-rated years on the Dura-Last. Makes it a pretty good deal!

dprantl

Isn't the alternator supposed to limit charge rate during hot conditions because a hot battery should be charged less? In that case, since the 928 battery is at the back, shouldn't the alternator's regulator be back there too, instead of right on the alternator? I'm sure it's much cooler back there than in the engine bay on a 100 deg F day...

Dan
'91 928GT S/C 475hp/460lb.ft

danglerb

If you are cheap like me, those prorated warranties really lock you into the product. Still its hard to complain too much with the Duralast Gold 84 month and 3 year free replacement, as long as the basic quality of the battery remains good. Die Hard I eventually got sick of and switched to Duralast Gold. One 928 is still locked into the PepBoys Bosch prorated warranty, first two of which didn't last at all, but most recent is still fine with a 3 yr free replacement.

AFAIK the battery in all cars is directly wired to the main power buss, where voltage varies by engine speed and demand from maybe just a few volts during cranking, whatever the battery voltage is at idle, and about 14.5v once the engine rpm gets high enough to meet demand. Most of the car "likes" 14.5v, so the trick of any smart battery charging system would be how to isolate the battery for charging, but still deliver full battery power when drawing from it. Batteries also act like a BIG capacitor to smooth the voltage removing alternator and other noises, so if they aren't directly on the main buss, something else like a big capacitor would be needed to keep the ripple and noise down.

Its amazing after the technology has been around for so long that nothing I have found could remotely be considered a good test of battery desulphating. Lots of anecdotal evidence says it does work, with the caveat that all of the commercially sold products are very low power pulses, and may not be close to as effective as some of the kit products.

dr bob

Dan,

The actual generating capability of the alternator is limited so you don't damage insulaion when it gets real hot. On the battery side,higher temps actually cause greater charge efficiency right up to when you boil electrolyte and/or warp the plates. So the protection is coincidental but good. And FWIW, the battery box is probably at least as warm as the ducted alternator. Gearbox, muffler and crosspipe on my car are by the battery, albeit with some heat shielding. No AC hose to the spare and batterywells.

dr bob

Spent the better part of an hour yesterday "negotiating" with the local Autozone manager about replacing the latest 13-month old battery. My specific-gravity and voltmeter tests showed that it was at 50% capacity. Autozone's tester showed the same, but the manager thought that recharging it would make it OK. It had been on my charger all morning, but it wasn't their charger... So it sat on their charger for an hour. Immediately off the charger, his voltmeter showed it at 12.25 volts. He said that that's a 'pass'. I suggested that he wait an hour and let the surface charge bleed off, then test again. But he was done with me and went to wait on other customers.

Autozone keeps a list of manager's phone numbers on a sign at the door. A call to the regional manager's office (lowest number on the list), got me a call back 10 min later from the district manager. I explained my case and my diagnostic method. He immediately agreed that it should be replaced, and told the store manager to do so. The manager wasn't real happy about it but did replace it. That's the good news.

The not-so-good news is that the battery from the shelf, tagged 12/10, has a marginal (barely passing) fluid SPG right there on the shelf. I showed the store manager, who shrugged and said that they sell what they get from the manufacturer.

So my history with these has been poor. This is the fourth battery in the car in six years now. Each has lasted less than 18 months. New alternator last fall with all connections maintained. Charging voltage on a SoCal winter afternoon at idle measures 14.3 at the battery terminals, so the battery is not suffering with low charging voltage at all. Car starts right up so no extended-drain abuse either. It's the slow cranking and the dash computer resetting that flags the tired-battery problem in my case.

I'm in the same situation Mike mentioned above, where the replacement under prorated warranty cost ($21) is so much less than a new better battery that I've gone the Duralast route once again. This one will likely fail in the free warranty replacement period as the others have. The one after that will start costing more than the negotiation time at the store, and at that point I'll probably just bite the bullet and fit an Optima, NAPA or Interstate replacement and be happy for years instead of months at a time. Optimas are often on the rack at Costco stores; they have a no-quibble replacement protocol that has got to be better than what's going on at my local Autozone store. Plus they have a reputation for lasting a while compared with conventional batteries.

dprantl

It seems my 10 month old Duralast is also resetting the dash when cranking cold. There is normal minimal drain with the car off and it will not do it if I put the charger on it overnight. Charging voltage when running is 13.8 - 14.0V.

Dan
'91 928GT S/C 475hp/460lb.ft

H2

My Interstate battery is going on 5 years...cost me $110 though.

dr bob

Harvey-- I'm ready for that next time around.

Dan-- I can put the charger on it all night and get a good start or two out of it in the morning. By the third or fourth start it's spinning noticeably slower. It never stranded me, but I'm not quite ready to wait until it does. If I'm gone for more than a few days in a row, I put the maintainer on it. Keeps terminal voltage between 13 and 14 when it's attached. The car can sit for weeks without the maintainer and still start OK, but why abuse the battery with the deep discharge cycling? Maintainer plugs in too easily. In parallel, I'm kind of in the middle of designing a bracket to put a disconnect/isolation switch next to the jump post to isolate most of the CE panel from the battery while the car is parked. Everything else still attached to the battery is isolated by relay contacts except for the alternator and the fan controller, so that switch --should-- kill off all the normal current leakage when it's open. Take the key out of the switch and the car won't run.

dprantl

Yup, same here. Two or three good starts and then not so good anymore, or if the car is not started for 36 hours or so, happens right away. Can't be normal for a good battery. Funny, I was also thinking about wiring a convenient place to hook up a maintainer to.

Dan
'91 928GT S/C 475hp/460lb.ft

JPTL

Maintainers are a must for non daily-drivers: boat, cycle or car.
My Duralast w/maintainer didn't last as long as it should have, IMO, so I changed to an Optima Red Top. Although it's only been < than a year, I have a good feeling about this Optima and its longevity. I think you can still get these for $100 delivered to your doorstep.
But since this is a Duralast thread, Nick, to answer your question, go here for Optima Red Top info.

MGW-Fla

My wife's Duralast has started to get slow. I was wondering when I had last replaced it, guess from my post above it was three years ago. Her alarm started randomly going off once or twice a week. We had recently starting locking her shark up at night in the garage & I was guessing that was enough of an additional drain on the battery to cause the problem. Quit locking it at night & the alarm hasn't gone off in a couple weeks, but the battery is still not as strong as I want. So I'll probably end up replacing it pretty soon.

I can confirm the problems with Autozone regarding the attitude on their batteries. Never had any problems in the past. A few months ago, my 928 battery was weak, since it'd been sitting. I wanted to make sure there wasn't any problems with the battery. The guy 'helping' me at Autozone said he'd not even consider replacement without charging it & acted like he was doing me some big favor. Ok, fine. So he took it to charge it up, but never did so. When I called later that day to see if it was charged, I spoke to a different employee. He told me the guy never hooked up my battery and he had even asked him about it. He then offered to charge it for me. I told him I'd just come pick it up & get it charged back up on my own, which I did. Its been fine since then. Jury is still out on whether I'd buy another Autozone battery, after I've bought at least four for four different cars. I'll wait & see how my wife's progresses.

I also am not impressed with the Walmart batteries either. After three years with the previous battery, I put one in my daughter's former VW Jetta VR6. The battery lasted less than six months before I had to use their free replacement. That part was easy, but I'm guessing there's a reason for the free three year replacement warranty they have. Doubt I'd buy another one from them, even with their low prices.