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Battery & Charging System Question

11K views 42 replies 8 participants last post by  maxillius 
#1 ·
My battery quit for good yesterday and I found something I thought was interesting along the way. After I got a jump to make it home, I noticed that the alternator alone was hardly sufficient to keep everything running. This was at night, with lights on and everything. The radio went in and out, and the headlights even blacked out on occasion during the trip. I was always under the impression that the alternator could power everything on its own and charge the battery as well, or I am misinformed. Is this how the charging system operates?

No sooner than I powered the van off and attempted to restart, it was totally dead. I know the battery is gone and plan to replace it of course.

Anyone know of any Battery deals by chance? :nut: Thanks!
 
#2 ·
Current to the electronic modules (power control module, body control module, etc.) goes through the battery and the electronics don't like dirty/unsteady current. The battery, if working properly, steadies the supply. Engines won't run off the alternator like they use to. All the various relays can go wacko with weak current. Ever see wipers operating without the switch being on or the dash gages doing a break dance? Many, including me, have experienced that with a run down battery. It's quite a show, unbelievable at first. :)

WalMart batteries are likely as good as any considering price and warranty. Johnson Controls supplies them and it may actually say that on the battery. It did on some I looked at.

Walmart selects Johnson Controls as sole source provider for automotive batteries - http://www.johnsoncontrols.com/cont...trols.mediaroom.com/index.php?s=113&item=2182
 
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#3 · (Edited)
I always thought that the charging system was designed to meet all of the demands of the electrical system of a vehicle. Not quite so, I found out. If the engine RPM is above idle, say 2k, then yes. But at idle, the alt will not keep up with max. demands (lights, brakes, heated seats, defroster, etc). This is not peculiar to Chrysler, its is pretty much true across the board.

That being said, it sure sounds like your battery is shot (if the alt is ok and a diode is not shorted). I used to buy my batteries at Sams club(basically Walmart) because it seemed like the best deal($75). Then I found "Rural King" stores and Exide batteries for around $50. Just bought one for my van a month ago and it is working fine. Should be a Rural King close to you in Michigan...depending upon your location. http://www.ruralking.com/store-locator/

[edit] just looked. There is only one in Niles, Mi. Probably not close to you.
 
#4 ·
I bet the battery was sucking juice due to an internal short. The alternator is more than enough to handle all factory equipment at idle. You could let it st idling all day with all the accessories on with a good battery and it will never die.
 
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#13 ·
The alternator is more than enough to handle all factory equipment at idle. You could let it st idling all day with all the accessories on with a good battery and it will never die.
Thats what I used to think, andy. However, on most cars this is just not the case. And some owner's manuals actually warn against using all available electrical accessories while idling for long periods of time. Of course, some vehicles contain more options(electrical loads) than others. The charging design is a compromise between alternator size, average RPM and expected loads. It makes sense that the engineers would have some trade-offs. They can use a pulley ratio to get a lot of alternator spin at idle or a beefier alternator or both...but at a cost. And they are trying to squeeze every dime out of the design.

I tried a little test on my van. I started it up and with no appreciable loads other than the computers, fuel pump, etc, the charge voltage was 14.10 VDC at idle (800 RPM). Then I started turning on accessories. Headlights, brake lights, blower, defroster, heated seats, radio, and watched the voltage fall below 12 VDC. It hit about 11.8 VDC at idle and slowly fell but was stabilizing. Goose the throttle a little and it comes back above 12V. Turning off the defroster netted the largest uptick. The seats made some difference. The headlights and brake lights were a significant draw as well. Even though the alternator was not able to keep up with the maximum accessory load at idle, the engine was not in any immediate danger of stalling due to lack of voltage. It would take a fairly long time to lose significant voltage and at some point the voltage would stabilize but the battery would not be charging. If one were stuck in traffic on a cold day with all of these accessories running, you might think about shutting a few down and that is what some owners manuals recommend.
 
#5 ·
Let's not assume the alternator is 100% good.
 
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#7 ·
You need to exercise caution but yes, you can remove the battery post and battery. First, I would attempt to neutralize the sulfuric acid with some baking soda. Sprinkle it on and about the leaky area. Take the negative post off first so that there is no spark produced at the positive when you remove it. Just don't get any sulphuric acid on your clothes or paint and use disposable gloves. It can cause some pretty severe corrosion. Again, use baking soda and water to neutralize if it gets spilled on something you want to keep. If you don't feel comfortable DIY, have it done by a shop.
 
#8 ·
Let it air out first, then baking soda it, then remove cautiously. If there is a concentration of hydrogen gas in the area, a small spark can literally blow the battery up. It has happened to people and it is not pretty.
 
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#9 ·
Thanks much for the quick help, got it out safely and got rid of that. Just curious, what causes that to happen? The internal short or something else?

Found this gem for $30 at a used parts store with 1 year warranty. Hopefully it lasts, just got it off a caravan that came in they said.
 
#10 ·
:thumb: Those numbers on top should tell you when it went into service.
 
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#14 ·
There are two alternator sizes (140A vs 160A) for my 2002 GC depending on whether the vehicle has rear heat or not.
 
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#16 ·
The 90 amp vehicle might have a smaller gauge wire in the harness to alternator or a smaller fusible link in which case it might not be a good idea to go higher. I would just stick with the original size but a good quality brand.
 
#17 ·
Partly on topic, but is there a reasonable explanation as to why my new (last year) serpentine belt that has proper tension on it (tensioner same age) stops spinning the alternator if the belt's wet below 2500ish RPM? I have to drive on the freeway if it's raining or else the load on the alternator causes the belt to lose its grip below freeway cruising revs. That means sitting at lights the lights go dim and the wipers slow down like it's running off battery only. Goose it and everything comes back to life. The belt doesn't make any noise (chirping, squeaking), so is my alternator going bad?
 
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#20 ·
Water getting on your belt from a disconnected wiper tray drain hose maybe? Happens on the 4th Generations.
 
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#18 ·
I'm not sure which alt I have (guessing the bigger one) but when its not enough at 600rpm, the computer wisely raises the idle speed up to 900 if it needs more juice. The voltage never drops under 13.2 at full load on mine. My GTO wouldn't be smart enough to do that, but its only electrical load is the radio (never on) and the lights.
 
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#23 ·
I'm not sure which alt I have (guessing the bigger one) but when its not enough at 600rpm, the computer wisely raises the idle speed up to 900 if it needs more juice
I thought my computer would also have been 'smart' enough to raise the RPMs to get to a charging level with heavy load but no such luck. My idle runs at around 800 RPM when in Drive and under severe electrical load.
 
#19 ·
I always thought the big draw is the ignition system. You need a lot of power to make a spark. I was always of the understanding that you couldn't even turn the alternator with your hand when that much is being drawn from it. So there is a big draw when the engine is running, even with no radio, headlights, etc.
 
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#26 ·
Boneyard?
 
#29 ·
I'm the offspring of an electrical engineer and have been playing with it since age 6. We all have flowing electrons in common haha. But it is true, the alternator may get harder to turn, but not much compared to other accessories. The rpm increase is to increase output at idle through a faster rpm, not due to the load.
 
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#30 ·
99 I wasn't offended, you told me P+IXE so what, we all tell peoplr things they know on forums because we don't know they know it.
I was googling around and with other mechanical losses and efficiency losses, say 4 hp for 100A, So now I wonder if my hand can do 4 hp?
That's 4 hp at the alternator. With different pulley ratios, what the engine needs to do to put 4 hp at the alternator will vary.
If you had a smaller crank pulley and a larger alternator pulley, you wouldn't need as much effort from the motor but it would have to turn faster.
 
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#33 ·
So now I wonder if my hand can do 4 hp?
That's 4 hp at the alternator. With different pulley ratios, what the engine needs to do to put 4 hp at the alternator will vary.
If you had a smaller crank pulley and a larger alternator pulley, you wouldn't need as much effort from the motor but it would have to turn faster.
Actually, there would be no way to even come close to turning an alternator with 4 hp worth of effort by hand. If you have never cranked a generator by hand, you should do so if you get the chance. It is quite humbling. I hand cranked a 120V generator made in WWII for powering radios. To produce 100 watts is a struggle, although it can certainly be done. To keep it up for any length of time is very tiring. Let's look at the world of cycling(bicycles). An amateur can produce a steady pace(20 MPH on flat land) that requires about 200 watts of continuous power. And that is "leg" power... considerably higher than "hand" power. Elite Tour-de-France riders generate up to twice that amount(400W) on a steady basis with burst much higher(though not sustainable). Suffice it to say that turning an alternator to produce 1200 watts of power is a very tall order for any human and would be virtually impossible for anyone but an elite athlete with leg power(and then only for a very short burst).

As regards the pulley ratio, you are right. The designers have determined what speed the alternator needs to spin WRT the engine. It all comes down to size and economics.
 
#31 ·
My approach to the common battery/charging issues in all my cars:

When I suspect a problem, put charger on battery at 10A. If it goes from showing little charge to fully charged real quick (~10 min), I suspect a bad battery (sulfated plates) that no longer holds a charge. Stop at Autozone or others that do a free battery load test in their parking lot. If it shows bad, I buy their ~$90 gold top battery on the spot and they will even install it. That has fixed 90% of my problems.

If they say the battery is good (once), I suspect the alternator. I have a neat Black & Decker charger with "alternator test" function, bought for $40 at Big Lots. It is electronic, small and light. It just looks for any activity from the alternator, like a sinusoidal voltage output, more of an "anybody home" test. I recently got a clamp-on DC probe (F.W. Bell) cheap off ebay to easily measure alternator output. Before that, I used a 100A dial gage ammeter you had to wire in series. My three 60's Chryslers have a dash ammeter, which is great for foretelling upcoming problems when driving. In my old cars, it is easy to test the alternator since you can get at the connectors for the altenator field easily. New cars have sealed connectors making probing and inputting difficult. I don't think there is much warning in the new cars when on the road. My 2002 T&C ran down on the highway after I lost the serpentine belt (cracked pwr steering pump plastic pulley). I had done a field repair of a nylon rope around the alternator and water pump to try limping to the next town. Right at the freeway exit, everything died, since the rope must have been slipping on the alt pulley. Quite a show. The transmission shift display showed all gears, the windshield wipers actuated on their own, lights were flashing on the dash. I don't recall any dash warning of "low battery" before that, and I was certainly watching everything closely.
 
#32 ·
Oops I meant 98 as in 98t&c, not 99.
 
#37 ·
It was rhetorical and for laughs. I assumed you were male, but now that I think about it I had no reason to. Anyway had I thought I was asking a girl if she were half as pretty as 99 it would have been very sexist and objecificating.
 
#40 ·
C'mon there must be a pic out there showing the legs.
 
#41 ·
I thought the new battery was a turd, but the terminals aren't fitting snug anymore and have to be replaced. Wiggle the ground a bit and off to the races.

Would it be possible to convert to a side post setup? This battery has side posts as well, but I wonder if the wire lengths will be enough without adding to them.

This has turned into quite the discussion!


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