Bugout4x4

I'm glad mine doesn't have it! If it did, I would try and find a cheat even if temporary because If I had to walk out from the boonies 20 miles just because this stupid thing stopped my system from charging I would be pissed! Where I go out wheeling it could actually result in loss of life!


Truly unneeded and a breakdown in the middle of nowhere just waiting to happen! It's a JEEP!, and the last thing they need to add are more systems that can fail out in the sticks where even a towtruck can't get to you.


If this keeps up we are going to need a trailer just to carry the spare parts needed to get ourselves back out of the boonies alive. lol

SteveMongr

^ Guess that's another reason to use a dual purpose battery, deep cycle/starting.
But, of the number of pre-97 XJ's I have owned, never had an issue with the charging system. Even here in the salty ocean air, so salty that when the wind is onshore I have to rinse off the house windows just to see out clearly.

Bugout4x4

And that's the point, All makes and models have had simple but dependable and reliable charging systems for decades and decades. If it ain't broke don't fix it! Then they go and design this type of complicated mess without any real need, reason or justification for it except maybe their own job security.


It's like trying to redesign a revolver pistol frame. no need, leave it alone, It has been refined and improved on as far as it can be and any redesigning now will only make it worse. Better materials maybe, but not the basic design.


I would like to once again reiterate how much I hate Automotive Engineers...I wish the general public would wake up to these design scams!

SteveMongr

Allow me to clarify. All my XJ's did have the battery temp sensor, including my current one.

dave1123

This is a little off topic, but you brought up a point about breaking down in the boonies. I think that for decades, environmentalists don't want us in the wilderness and will do everything in their power to keep us off public lands. There was a picture posted recently of a stretch of rocks in MOAB that were painted with rubber from tires. I don't have a problem with that, but I can see where others might. I've always used the "buddy" method when hunting. I don't go into the woods alone. I also wouldn't go wheeling alone either. Every time my brother and I went hunting, he brought alone an FAA emergency transponder. He said we could get in trouble using it, but at least they'd find us.

'90Cherokee

The alternator can't put extra amps into the battery without extra volts. The short theory wouldn't work either, the power would pass through the cables and not the battery.

I think it's undercharge damage. 13.5 and never over 13.7 is low. A battery that never sees a full charge will die early. If it had been over charging you'd usually see signs of boiling; spilled acid or at least low acid level, as well as possible case bulging from the cells being destroyed. Had they given it a good charge and retested it it may have come up in power some. Have you noticed what the standing voltage of it is after the engine is off for a couple hours?

Bugout4x4

You raise another possible issue, but I do have to share some interesting history. Before cars had Voltmeters as standard issue they had Amp Gauges. Regulated Amperage output control from the charging source, depending on demand, could be monitored with exact precision.

dave1123

Okay, I agree, so why not install an ammeter? You'll also remember that was with generators, not alternators. Generator output was dependent on rpm more so than alternators. They also had external regulators that you could fine tune to demand. Generators also required maintenance more often than alternators. Commutator brushes wore out frequently. Alternators have brushes that ride on "slip rings" that are not segmented and last a long time. One of the reasons the industry went to alternators is they'll put out 10 amps or more at idle. They also run cooler than generators.

Alternators produce around 110 VAC that is rectified to DC by a diode bridge. The frequency of the AC changes, but the voltage doesn't. The output is controlled by modifying the field voltage input. You electrical gurus correct me if I'm wrong, okay?

Bugout4x4

Honestly Dave...I would much rather have an Amp Gauge And they did continue to use Amp Gauges for many years after the Alternator became standard. Only recently in "Yours and my days" Dave did they change to new fangled Voltmeters.


I liked being able to instantly read a "- or +" discharge or charge in Amps.

dave1123

So, like I said, why not install your own ammeter? I believe it goes into the wire from the battery to the PDC. You'll need a heavy duty one, like from a truck or construction equipment. Today's vehicles need a lot more amperage than the 30 or 40 amps of the older cars. You'll probably need 8 or 4 ga. wire to and from the PDC.

'90Cherokee

An ammeter shows how hard the alternator is working, a voltmeter shows what it's achieving. They give you different information that can be used to guestimate the info it doesn't give you. For me, if I only get one, I'll take volts. Having both gives you more info, and you could diagnose some problems on the fly if you know what to do with the information. I assume the reason for the switch from amp to volt was cost, or might be for simplification for the driver. Gauges pretty much went away for a long time and are now back, altho some 'gauges' are basically idiot lights with a needle in place of a bulb. Automakers know that most drivers don't care what the car is doing as long as it's working. Of the few that do care most don't know what to do with the information. In dash meters, whether volt or amp, are never directly connected to the battery so the information they give can be more or less useful depending on what you're looking for.

'90Cherokee

Just know that if any part of the installation, including the gauge itself, fails you'll have a dead circuit. If your wiring gets damaged the short circuit of that fat wire would be detrimental. Most of the information it would give you can be deduced from a voltmeter so I see little use for the ammeter. The average high power ammeter's resolution won't show an obvious change if your alt. dies where voltage will swing a lot.

'90Cherokee

It isn't good at 13.5 so they're wrong. Assuming you're measuring your voltage at the battery.(?) If you're measuring anywhere else it's somewhat useless for diagnostics and 13.5 might be ok. You should have around 14 at the battery with no accessory loads on. Even with proper voltage it's possible that a fault in the alt. can be putting A/C into the battery. Using your meter set to A/C check the battery with the engine on. I think the limit to see is around .02, but you may be able to confirm that number with some googleing.

Bugout4x4

Not sure but we may have gotten off track in this debate. I only mentioned ammeters because this is how output and demand were once monitored. The point was that regulated amperage output and amperage demand are just as important from a charging source as the voltage.


The voltage regulator controls the field current applied to the spinning rotor inside the alternator. When there is no current applied to the field, there is no voltage produced from the alternator. When voltage drops below 13.5 volts, the regulator will apply current to the field and the alternator will start charging. When the voltage exceeds 14.5 volts, the regulator will stop supplying voltage to the field and the alternator will stop charging. This is how voltage output from the alternator is regulated.


Amperage or current is regulated by the state of charge of the battery. When the battery is weak, the electromotive force (voltage) is not strong enough to hold back the current from the alternator trying to recharge the battery. As the battery reaches a state of full charge, the electromotive force becomes strong enough to oppose the current flow from the alternator, the amperage output from the alternator will drop to close to zero, while the voltage will remain at 13.5 to 14.5. When more electrical power is used, the electromotive force will reduce and alternator amperage will increase.


This includes a direct high amperage draw short and the battery will indeed get cooked from the extreme alternator amperage output as collateral damage in a situation like this. Done it many times


It is extremely important that when alternator efficiency is checked, both voltage and amperage outputs are checked. Each alternator has a rated amperage output depending on the electrical requirements of the vehicle.

dave1123

you are right about ammeters when you said in later years, they are NOT directly in the circuit. On the old 6 volt circuits, they were and if they failed, would cause NOTHING to work. Later circuits had some sort of a sensory circuit that wasn't directly hooked up through the main accessory wire, therefore not really accurate. Voltmeters, on the other hand, just need to be connected to the battery supply somewhere to show the status of system voltage. When you turn on the key, they will show battery voltage. After the engine starts, they show SYSTEM voltage. A fully charged battery should show between 13.5 and 13.7 volts. When the alternator comes on-line, the voltage should be 13.75 to 14 volts.