Over the past few years I've needed to jumpstart my 1996 XJS a couple of times due to leaving a light on, or something silly like that. I even managed to do this at my local garage once.

I have found that none of the portable chargers work. The ones that plug into the lighter, nor the mini suitcases that connect with jumper cables. I've even tried connecting the suitcase directly to the starter, without any luck. The only thing that works is a jump from another car. Even then, it seems to take a while for the car to work up the charge to finally turn the car over.

Is this normal, and do I have another option? The suitcase thing I have claims 750 peak amps. I forgot what the lighter plug in jump starter was rated at.

Does anyone here carry along so wing to get them out of a jam, other than jumper cables?

Thanks.

 

Hi Vee

Trying to Jump Start your XJS is not a good idea, especially as you seem to be doing so on a regular basis, as it it only a matter of time until you blow the diodes on

your Alternator, in which case it is going to cost you a Fortune $$$$$

Not to mention the problem of taking off the old one, to put a new one on, which can be more of a PIA, than you could ever imagine.

Maybe your Boot/Trunk light is not switching off, or it could be your Alarm/Immobilizer

Which is a problem that I used to have, before I fitted a Gadget called the Dis-carnect, so when I put my Car in the Garage, all I do is turn the switch to disconnect the battery.

And using it during the Winter has kept my battery fully charged even after 6 months of No Use, although I did start her up a few times just to keep the Engine and the Battery Fresh.

It only costs a few dollars and has to be one of the best things, that I have ever bought and one more hoop for any potential thief to jump over.

 

I'd say it's happened to me about four times over the past six years of ownership, one of them was the result of a battery that was old.

This car is my daily driver, so it gets a lot of action, so I don't think that's too frequently. As I mentioned, I was the culprit each time, so there's no strange power leak going on.

I was just wondering if there was a better tool out there than jumper cables.

 

A new Heavy duty battery, might be worth considering?

 

I use a battery disconnect switch on my car. The electical on the XJS is self draining. Lol

 

I have never had an XJS that a good quality jumper box (not the cheapo models from Walmart and such) booster would not start.

I use a JNC660 which has 1700 peak amps and nice long heavy duty cables. It cost a bit more but believe me a professional quality model jumper pays for itself in how well it works, the cranking speed it gives, the reserve time it offers, and how many years it will provide reliable service.

Like one of the reviews on Amazon says; "If you can't start your car or truck with this thing, you have bigger problems than a dead battery! This unit is one of the most powerful portable battery jumpers out there at 1700 peak amps. That's twice as powerful as many other lower quality competitors.".


The same company also makes a JNC990 that's 2000 peak amps/950 cranking amps, and a Jump-N-Air model that's also 1700 and includes an air compressor, a friend has that one and it works great. The JNC990 is nice but a bit on the pricey side. They all can be charged via AC or comes with a 12V cigarette lighter plug to charge it while driving (great for tow vehicles, just plug it in and leave it in your tow rig). They all also have a 12V outlet for powering 12V devices if you need to (and it will run them for HOURS AND HOURS too). They also all serve as a battery charger, so if you want you can hook it to your battery for awhile and it will charge your battery (recommended to plug the unit into AC when using it as a battery charger), the only caveat about using it as a charger is that it will not automatically shut off when your battery is fully charged, so you have to monitor the charge progress yourself.


The companies website page is;
Jump-N-Carry for Vehicle Jump Starting Applications - Clore Automotive | Call us at 1-800-328-2921 | Clore Automotive

But you can also find them at , eBay, or from an actual auto parts store. Many auto parts stores usually only carry the cheap'o models in stock, but can order one of these if you ask if they have anything bigger and more reliable made for professional shops.


They have made these models for years (over a decade) and are still one of the most popular professional-grade models out there and their battery's last for years and years through many many recharge cycles.

 

Yep, a great point as well. I always find the biggest possible battery with the most Amps, CCA, and RESERVE CAPACITY (an important rating that many people overlook) that will fit into all of my vehicles.

 

Nope, although jumper cables vary in quality.

As you have learned from past experience, it is a good practice to let the
'dead' battery soak up some charge from the donor before trying to start.

This is because even the best quality jumper cables will not transfer as much
instantaneous current as the positive and negative leads at the battery itself.

So, some patience lets the 'dead' battery soak up some charge and the donor
battery helps during cranking.

The battery boxes do not work as well because their output voltage is not as
high as a running donor vehicle.

The advantage of jumper cables is that they can be stored indefinitely in the
spare wheel well without maintenance. Not so with a booster box.

 

Actually that statement but is not totally correct (though is a very common misconception); Good quality jumper cables making a good clean connection at both ends transfer just as much power just as fast as the regular connector does from a battery. The actual problem is that if the main battery is low on power, that battery is "soaking up" the new energy coming in and so keeping all of the power from getting to the car. When a battery is dead or very low and you connect power from any source that battery will soak up the energy like a sponge and the more dead it was the faster the rate it absorbs in-coming power, it's an exponential formula... This is going to be WAAAY overly simplistic, but for the sake of easy and simple explanation you can think of it like this; A 12V battery drained down to 6V will absorb new incoming power at a rate almost 8x the speed that a 12V battery only drained down to 9V will absorb it, and by the time the battery gets back to 11V the absorption speed may drop to to only 10% of the speed it was when the battery only had 6V. That's why when you hook up a battery charger with a digital % display and hook it to a battery drained to say 50% you may notice that it only takes half an hour to get from 50% to 90% but then still takes another half hour to get from 90% to 100%

But there is nothing degrading about the connection on the jumpers themselves so long as they are good quality cables with good clamps and you have a positive bite on the lead on both ends.

An easy way to see this in action is if you try to jump a car with a dead battery without letting it charge up a little first the car may not start, yet on the same car if you disconnect one of the terminals from the dead battery totally and connect the jumpers to the dead cars connector, the car will start because now it's getting the full power from the jump vehicle via the cables, without any energy being wasted pouring into the dead battery.

That's also why if you don't disconnect one of the cars leads from the dead battery you do need to (as you correctly said) leave the cables from the jump vehicle connected for a bit with the jump vehicle running before trying to actually start the dead vehicle, your giving it time to bring up the power level in the dead battery so it's not absorbing so much of the energy so fast and if it builds up enough, as you said it may even begin to aid in the starting process as opposed to just being a power sponge.

You start the jump vehicle (after the connection has been made, never leave it running while making the connection) to keep the dead battery from just absorbing energy of the battery on the jump vehicle without anything to replenish it. If you don't start the jump vehicle after making the connection and you left the cables between the battery's connected long enough, eventually they would equal each other out. Again, overly simplistic, but if the low battery had 6V left in it, and you connected the battery from the jump vehicle that had 12V, and left them connected long enough without starting either vehicle, eventually both batteries would end up with 9V, or actually a little less due to the energy loss during the connection as they equalized which can be felt in the cables and batteries in the form of being slightly warm to the touch. Which by the way, the reason your cars regular battery cables from the battery do not get warm while the car is running (assuming everything is functioning correctly) is because batteries do not RUN cars, they START them, once the car is running it actually RUNS mainly on what comes from the alternator, with a little extra going back to maintain the batteries charge for the next time it's needed to start the car. The battery only helps if the alternator has a drop in power or fails. But feel of the cable from a battery on a car that has a bad alternator and is then running on the battery, and you will notice the battery cable will get slightly warm just the way jumper cables do when jumping a car and charging it's dead battery.

 

I always connect a battery trickle charger/tender to my car when l don't use it for a while. Works well and very simple to use.

 

This is the best advice there is. Like you, I have a battery tender/conditioner thingy that charges and then maintains the battery, and I always connect it and have done so for over 15 years. The car always has a good battery performance and if the hype is to be believed, the battery lasts much longer for some reason or other about anti-sulphating or somesuch that I do not understand!
Greg

 

Four adventures with jump boxes.


1. Jaguar failed to crank at a local mall. AAA came with a "pro quality" box. It fired almost immediately. Service guy, "that isn't a Jaguar engine!!! true.


2. Local shop, owner and tech, friendly. helped resolve Lump issues.
Impressed. left interior lights on. Embarrassed, battery down. Pro jump box fire it.


3. I bought a couple. Why two? I forgot. Bummers. Dead and I never used. Garage thief stole one and my bolt cutters!!! I hope he got stranded and found no help from the dead one he stole!! I demolished the other. Some neat parts saved...


4. I was in the Jaguar and neighbor flagged me down. His RAV
failed to crank. He late for dental. He with jumpers at the ready.
The big 140 amp alternator with the LT1 at idle cranked his Toyota easily.


Carl

 

Wow, that is a ton of useful and interesting information posted here!


When I clamped the battery pack that I did have (750 peak amps advertised), I did not leave it connected for an extended period of time. I basically clamped it on, and tried to fire her up. Should I have left that pack clamped on for a few minutes before attempting to start her up? As soon as I made the connection the charge went from 100% to somewhere in the 60s before I could turn the key.


I did mention that I connected the battery pack directly to the starter and the result was no different from when I connected it to the battery. This is the point at which I figured the battery pack was useless.


I was checking out that JNC660, however, does anyone have any experience with one of these smaller battery packs, such as this one:

 

Absolutely, totally true. With the trickle charger connected you're guaranteed a good-ready battery no matter what. It is a $30 one time expense for insurance that never runs out.

Cheers,

 

A boxed jump starter is .... a battery with leads. When you connect it to the car battery you have two batteries connected in paralel, where their current capacities are added, with the voltage remaining in the vicinity of 12 volts. The car continues to see a 12 volt source connected to it, only now with a rather higher current delivery capacity. WHat part of this action is that burns the diodes, provided that the polarity hasn't been reveresd?

 

There is a small possibility that it can cause an electrical spike or so I have heard, if the leads from the box are not on tight and spark

 

At the levels of current involved and the typical clamp
involved, no.

I'll leave it at that.

 

Precisely, as you pointed out with the current levels involved, not liked we're talking about clamping onto a 250,000k power station here. Yet people still tend to think jumper cables don't transfer the energy as well when good ones actually do ...as long as the connection is good and one thing that I didn't mention was by good ones I mean quality all copper core ones in a heavy gauge (like mine are 2 gauge) that is usually heavier than the cars actual battery cables, often twice as heavy. That also assumes good pure copper coated stainless clamps with strong springs and nice double-rowed teeth making connection on a good clean bite, not on top of corrosion, etc.

So indeed not talking about a cheap $7 pair from some place that's only made of 10 gauge tin stranded wire with cheesy stamped steel clamps with flimsy teeth, a spring so weak it couldn't squeeze two wet noodles together, and a center pin that often twist sideways the first time they are used.

 

Wow, I wouldn't know why nothing works in your car, except for another car. In my case, I'm always charging, not only my XJS battery, but my XJR's too with no problem. We do not drive a whole lot anymore and we have three cars, so it is hard to keep them all "happy". One device I have is a Schumacher, 1.5 amp charger/maintainer (trickle charge) that I use mainly to keep the battery charged after some four days of not driving the car. The charging port here typically is the cigar lighter receptacle, which I have rewired to always hot.

Sometimes I wait too long and then I need a jump start, which I do with my Harbor Freight portable jump starter (aka "mini suitcase"..). It has a 400 "cold cranking amps" capacity, not that I know the most powerful portable device out there, but it certainly does the job. It has an internal battery that's supposed to be kept fully charged (but, not necessarily, as I have learned) and I have started both Jags with it, the XJS (from the firewall's right battery post and not from the battery post in the trunk!!) and also the bigger V8 XJR, both cranking fast right away. However, this is just a portable jump starter and not a battery charger.

Another device that has worked beautiful on both my Jags is this other Harbor Freight combo charger-jump starter. It is not portable, as it must be plugged in to the wall 110 v outlet for charging or for jump starting. It's a relatively small box (approx. 8"x 7"x 6") which I've successfully used to start both of my Jags, as well. It can charge a battery at 2a, 10a and 50a rates, including the ON-OFF switch maintainer mode when used at the 2 amp charging range. The only thing it cannot do is to jump start a car at a car show where there are no a/c outlets... so I keep it at home and rather carry the portable unit.

All of these devices seem to be "Jaguar-friendly" and work just fine on my XJS. Again, for your XJS not to accept a charger, or a portable jump starter, there must be something borderline wrong somewhere with the electrical system. Make sure that the jump starter is fully charged and also remember that "the ones that plug into the lighter" are not going to work right on your XJS unless your cigar lighter receptacle gets power from a hot wire source (i.e. not via the ignition switch, but direct from the battery). You certainly don't want to be charging your car battery with the ignition switch ON, meaning with all the electrical loads ON and, therefore, connected to the charging source, as well. My '94 was not like that until I rewired it; I don't know about the '96 XJS, but I don't see Jaguar changing this just for the '95 and '96 models.

Good luck.

Cheers,

 

Do you still think it's a good idea to keep a Portable Jump Start Power Pack in the

Boot/Trunk of your XJS or Your Home or Garage/Shop?

This is what happened to me yesterday.

I was charging the Battery of my Hedge Cutter in the Kitchen and the Charger that comes with it, has a Safety Cut Out to prevent Over Charging.

Now while I am not professing to be an electrical expert and no doubt someone will correct me if I am wrong, it probably had a Lithium or a Nimh Battery inside it.

And I wouldn't be at all surprised, if some of those Start/Chargers, use the same Technology.

It had been on charge for a couple of hours in the Kitchen, while I was watching the News in another room.

When all of a sudden, I heard a mighty explosion!

And when I went into the Kitchen, I couldn't believe what I saw, as there was flaming shrapnel, all over the Floor and things that looked like Shotgun Cartridges.

At first I had no idea at all what had happened, until I went to the Kitchen Sink to get a Bucket of Water to put the Fire out.

Which was when I realised that the Battery had exploded, with enough force to throw a Stainless Steel Kettle, from one side of the Kitchen to the other as well as flinging burning plastic all over the Kitchen.

Had I gone out and left the Battery on Charge, it would have burnt the House down, that's for sure.

And had I been standing in front of it, I have no doubt I would have been badly injured.

Take a good look at the photo, as its only a very Small Battery compared to a Jump Start Power Pack, which may or may not use the same Technology.

So after that experience, there is no way that I would keep one of those things anywhere in the Car or in the House.

As for using a Power Pack to Jump Start a Car, I certainly wouldn't want to ever make a habit of it, especially on an XJS because with many Power Packs, you are connecting 'Hot Leads' to an already discharged battery.

And there is a possibility, where a power spike can take out the diodes in an alternator and don't forget the fuseable links on one of the battery leads.

Personally I would not want to risk any stray current, interfering with any of that stuff and as for myself, I would rather know that my electrical system is running properly and spend the money on a Brand New Heavy Duty Battery.

As for having the Dis-carnect, I wouldn't be without it, as it is so easy to use it to turn the battery off, every time I finish using the Car.

And best of all, I know the Car is going to start every time without any problems.



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