So, in making my first round of fixes to a newly acquired 84 xjs, I just read the part of the owners manual in the electrical ecu section that says:

Don't use a fast charger on battery that is connected to car
Don't run car without battery
Don't use fast charger as an aid to starting

I did all three-- multiple times.......

What is my comeuppance? So far, the only thing I notice not working that used to is the sunroof ( anyonE know where that fuse is). I was working on the climate control, so I think the a/c amp was already toast.

Perhaps these warnings are for all cars, but I have done the above three things on older cars for years. This is the most technologically advanced , or overly complicated classic I have had, rivaling my 86 and 87 Mercedes diesels.

Thanks for the help.

 

generally charging, especially fast charges, sends more power to the battery than the charging system puts out and the electrical system is designed for, this can blow fuses and damage electronic components.

If left unattended a battery can overflow and damage the car or an explosion can also occur.

It's up to you if you want to risk damaging your ECU or burning up your car because you are too lazy to simply remove a battery.

You can do whatever you want, I just don't really see any point in this post. It could possibly convince those coming here without much mechanical know-how to form uneccessary bad habits. If this is just a "I broke the speed limit 3 times and nothing happened/ I ignore torque specs and nothing is broken yet" brag post and you don't have any useful information or a question to ask, I would like to ask you to keep it to yourself on behalf of all the people that come to this forum looking for help and guidance or even just a few pointers.

I don't have any problems with you and you can, again, do whatever you like. I just see it as a problem when it can affect others

EDIT: Noticed this is your first post, don't want to scare you off or anything. You could have just made a post saying you did those things and nothing appeared to happen. Then ask WHY this is in the owner's manual if it doesn't appear to affect anything and I am sure many would've been glad to explain why.

 

sidescrollin hit on most of the issues... basically that using a charger instead of a good battery will subject the circuits to voltages and currents that they weren't designed for.

There's also the concern that the newfangled chargers will push all the smoke out of the electrics... see the last paragraph.

The mid-80s Mercedes diesels compared to the same era of Jags are friggin' tanks. Bulletproof and reliable (at least the engines... I recall the power windows were a real pain), and not much in the way of electronics. Older cars had very few electronic modules.

Electronics (and I use that term loosely) in the Jaguars are an interesting combination of component suppliers and Jaguar had a habit of making design decisions that we have trouble understanding today. There are aspects of the older fuel injected cars that can cause trouble regardless of the models... older wiring is more likely to have failed insulation, causing a short as an example.

Anyway, point is that the electrics and electronics in these cars is fragile and easily damaged. True when the cars were new, even more true now. The ECUs are especially prone to damage and having just replaced the unit in my '85 I can tell you that they're a bit pricey.

In fact, if this is your first experience with a British car then you haven't been properly introduced to the World of Lucas electrics. Just be grateful that this is not a positive ground system with a generator (those would sometimes decide to change polarity... really). Check this out for reference, paying particular attention to the discussion of proper care of the electrical system smoke:

Lucas - Prince of Darkness - Lucas Electrical Humor Jokes

I'm enjoying the puzzle that is the Jaguar XJS - quite the learning curve, but great fun.

 

I see this is you first post, welcome to the forum,
have you got a real question? as if the car is ok you must have done it right.

 

Thanks for responses. I posted for the question asked, as I was worried what gremlins I might have caused and wanted to post a general caution. Especially since it was Lucas and as noted i wasn't as familiar....given the number of views, i would think my post was constructive for at least a few, and therefore, added value to the sight. dont worry it wont happen again. Not sure what all the name calling is about for a simple honest post... I have been called a lot if things but never lazy. And the question is right before where the question mark is (?). Merry Christmas!

 

Sorry, I just can't think of any reason for not removing a battery to charge it other than not feeling like it.
As for the other one, driving without a battery. This can do basically the same thing charging with it in car can do. The battery usually absorbs voltage spikes and acts as an electric "shock absorber". Unless you HAVE to go somewhere on a jump there is no reason to drive the car without the battery.
Just because people have viewed your post does not make it highly valued. Miley cyrus has millions of views on youtube.
Since you seem to be prone to feeling the victim of name calling I'll let you know that I am not calling you miley cyrus. Unlike all the others who view this thread and chose not to say anything, I feel obligated to speak up when people are being deconstructive.
If you genuinely made the thread because you were wondering about gremlins you could've just said that. The impression you gave from you post is that the manufacturer is wrong or that you did it simply in spite of them. I am not trying to attack you, don't take it that way. I was simply trying to tell you what impression your thread gave, which is why you never really got a response before.

I answered your un-asked questions and gave you feedback on your thread, including advice on posting in the future. If you want to get upset about it or dislike me for the things I have said, you are obviously entitled to do so. Was just trying to help you, and others coming to this forum out.

 

Firstly Welcome to the forum. Guys lighten up lets not turn this into Jag Lovers.

The warning for fast chargers is based on the chargers of 20-30 years ago. These days most chargers are Processor controlled and vary the charge rate depending on the battery. I often leave my charger connected to the car on trickle, (although being a smart charger it trickles on fast when the battery is charged) There are 3 phases to charging a battery and these smart chargers read the voltage and internal resistance of the battery and switch to correct charging phase. SO if you are using a non-smart charger this MUST be done with the battery disconnected from the car. I would also charge a flat battery (with a smart charger ) disconnected from the car. Once the batter is at a reasonable state of charge (enough to start the car) then leaving it connect is ok (as long as you use a smart charger)

Running the car without a battery you risk shorting the + terminal to ground firstly, secondly a battery is capable of delivering 100's of amps an Alternator is not so the possibility of frying the alternator is high. It has nothing to do with the voltage or current in the system needing to absorbed an alternator is a variable supply and will only supply the current it is asked to.

 

If you loaded the system up to ask for the alternator to provide max power, yeah you would be running it too much. It isn't untrue that the battery absorbs voltage spikes in the system though.

 

The Battery DOES NOT absorb voltage spikes, if this were so then it would absorb ignition spikes that causes stereo interferance. Or when you connect jumper leads (Read the warning on the lead set that connecting them can damage Electronics).

If you run all of the systems in the car you can exceed the rating of the alternator especially if the car is no longer stock. The inrush current when fans ect turn on can be significant. The battery will supply this additional current draw, if the battery is not there you will fry the regulator on the alternator if you exceed its current capability.

My day job is repairing and servicing Military and Aviation electronics. So this is an area I have 30years experience in.

 

I wrote that on my lunch break for my electrical class and literally just took the test on the battery section.

The regulator doesn't fry, it regulates. If the draw exceeds what the alternator can safely put out, it normally uses the battery. Without that battery the alternator is simply going to put out its max allowable power, which means something will not get enough power and turn off altogether. The regulator won't let the alternator put out any more power than the electrical system can handle, as a result it doesn't come close to letting the alternator produce more power than it can cool either.

 

The regulator will regulate up to its rating, if you draw more current from the alternator than the regulator is capable of suppling you WILL fry the regulator. How can the regulator put out its max power if the current draw drops? Power is EI if current drops and voltage is contant power drops.

DO NOT post incorrect information. The regualator does not stop the alternator putting out more current than the system can handle. The system draws current and the regulator keeps the voltage constant. If the electical system draws more current than the regulator can supply the regulator WILL FRY. I have fixed more powersupplies than I have hot dinners.

 

Perhaps I read the way you worded that wrong, but it left me with the impression that you were saying the alternator puts out whatever it can until the regulator fries, unless the battery is there to absorb the excess.
I'm not sure how regulating the current going to the rotor and thus regulating the current produced in the stator doesn't control AC generator output, but if you say so.

 

I remember these same three things being pounding into my head many years ago by my father. That was in the '50's.

Don't, Don't, Don't. Perhaps by the time our cars came out these were taken for granted.

 

You read a lot of things incorrectly. And unless there was an election I missed on this forum, you speak on behalf of no one but your arrogant self.

 

That's an adorable smartass answer. If you missed my point that newcomers often appear and browse before asking could come to believe that it is okay to disregard manufacturer's instructions based on you uneccessary thread then I am not surprised, since you made this thread to begin with.

 

Time for the pancake bunny?