I've got a 2005 XLT 5.4 that seems to have trouble charging the battery fully. It never has gone dead but I notice that the engine turns over slower about once a week until I put the Battery tender on it, then it takes about 3 hrs or so to get back up to float charge status(green light). Then it spins over fine until about a week goes by. This has been going on about 3 months now.
I've had the truck since new and never had this problem before. I do mainly just drive around town but my trip length has been the same the entire time owning the vehicle so that would seem to rule out the problem of too short of a trip to pull battery back up to charge.
Had the system checked at Advance and they say everything checks good on the charging system and the battery. In fact the guy said the alternator was perfect, 14+ volts at idle no load and same with lights and heater fan on high, etc. No parasitic drain with key off either. The battery is a 3yo Everstart, had WalMart check it last Dec just before it went out of warranty(3 yrs) and they said it was fine. All connections are clean and tight, no corrosion seen anywhere.
Despite what WalMart and Advance Auto are telling you you have a problem---this you already know.
Frankly I'd suspect that battery. Were it me I'd find a good and well respected independent repair shop and pay them to completely diagnose your charging system.
A good battery that's accepting alternator output and able to store it properly will survive a few short trips a week. If you're force to trickle charging it over night often then that only reinforces the battery is suspect.
I pay right at $100 for an NAPA "premium" battery that typically lasts at least 5 years, sometimes considerably longer. That trumps any WalMart cheapy that needs overnight charging, IMHO anyway.
One thing about electrical connections (not just batteries) is that looking at them doesn't tell you anything. By the time you CAN see corrosion then that connection has probably failed altogether, or close to it. But can't count the number of times simply disconnecting and reconnecting a "clean" electrical connector cleared some weird gremlin. I use lots of NO-OX-ID and dialectic grease these days on my newer equipment after seeing how well it works on the older stuff.
Sounds like your battery might have some sulfation though. Try turning your headlights on for five minutes (engine off) and wait ten minutes. Measure your voltage at the battery posts, should be 12.8 volts at 80F with a maintenance free battery. Once a battery gets sulfated the tenders are gonna choke, they will automatically switch to float.
If you have an old school charger you can try a low ampere charge rate for a couple days and see if it will hold a charge and deliver rated current. Another easy test is measure voltage drop at the posts when cranking for 15 seconds, should not drop below 9.6 volts.
Thanks for the replies! I have already cleaned the easy connections, that is the battery cables at the posts. I have an old Schauer 4 amp charger with "tapering charge" capability. Is that "old school" enough, haha? Are you saying I should hook it up to battery for a couple days?
I will test voltage at the posts tomorrow in daylight and see what I get.
Looking forward to possible battery purchase, I found a 35% coupon code for Advance where I can get a group 65 850cca battery for less than $100 with tax. Seems like a good deal? Anyone have any opinions on Advance Auto batteries?
I wouldn't be "looking forward" to any battery purchases, unless money is no object, lol! Run the charger on it till it's fully charged, and then run the tests mentioned before you buy a new battery. If it passes, then you have a problem elsewhere.
That doesn't sound like a bad price, but again if your charging system has a problem or there is a parasitic draw then you're throwing good money after bad. The thing about batteries, even with conductance testers in use these days, can't always tell if you need a new one until it has been fully charged. And if it's been rode hard and put away wet, it can take a while to charge up at a low rate.
Slow charging is best because this fully penetrates the plates. But - the newer type batteries like to have some current run through them. Most small home chargers are not capable of this. Buying the biggest, baddest specialty battery won't really help if it isn't charged right or sized for the application. Every car manufacturer has a different idea of the ideal charging voltage too!
Sometimes I think battery cases should be clear plastic. I bet sulfation shows up and would be a visual indication something isn't right. Have to monitor the voltage on the old school chargers, partly because it's temperature dependent. A couple days or more at a moderate rate may bring a sulfated battery back in the green. But - and this is easy to do - they will eventually boil a battery dry if you were to forget about it.
It sounds like you have a drain somewhere in your electrical system, if your battery and charging system is otherwise OK.
That's good for an OCV, or open circuit voltage. A maintenance free battery at 66F would measure 12.7ish so it's about 100 percent charged or thereabouts. It's that last 10 percent that takes a while. Put it on a low rate charger and measure the current in series with with the battery post and charger clamp, and the voltage across the posts' voltage over time, it should taper down to less than a tenth of an amp and reach a nice absorption charge level for the temperature you're at, probably over 15 volts , that might seem a little high but use the chart. It should start moderately gassing and bubbling around 14 or so. This is good. Let it "cook" for a couple hours or so. Done! Don't forget it!!
Then measure the voltage across the posts when cranking for 15 seconds, and record the lowest voltage. A good battery will not drop below 9.6 but it should be higher than that. Kind of a "poor man's load test". A battery that passes these tests is likely OK. It's not just the ability to crank an engine over, but reserve capacity. A marginal battery or sulfated batt will not have any endurance. Charge it back up again. Then put it on a tender for long term storage
Clean all grounds, posts, alternator connections, etc. start looking for excessive current draw when shutoff, voltage drop at cables, cables getting warm (loose connections). I'm always amazed at the diagnostics that can be determined with a voltmeter and a test light, and smart guys (not me!) . Today ya need an uplink w/ a satellite but not with the vintage stuff.
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