So a jump starter like this with higher amp rating will do the job with (if done correctly) no adverse effects?

 

Yes. there is an off/on switch to allow you to connect first.

 

Actually, the unit I referred to does not have the isolation switch, clamps are hot all the time. The JNC-660 is a powerful, no nonsense booster intended for just that. Some people don't care for it because it doesn't have the idiot-proof features, or it doesn't incorporate a compressor or other bells & whistles. That's why I like it. I want one thing, the most boost for the buck. That's why I started my post with, "lots of opinions.......... here's mine."

It has a gel battery, so it can lay over without having to worry about the battery, it has a float charger, so it can be left plugged in without worrying about overcharging, and it works.

And looks like there are some better prices out there than I thought:

Edit: Oh, if you are not in California or Oregon, avoid the JNC-660C. It is required in those states, but it has "green" features that gut the power of the internal charger.

Happy motoring!

 

I don't think a Jaguar is any different to any modern car stuffed with electronics. It's all too easy to be thinking about older tech cars which had no or almost no electronics.

I think the reasons for connecting to a body negative rather than the battery include:
1. wanting to get power to the starter more than wanting it to get to the already-flat battery (which will just suck the power you need to start the engine and also may cause damage to the flat or non-flat battery if the voltage difference is big, which causes a big current due to the very low internal resistance of batteries - that's behind Thermo's 100:1 rule of thumb)
2. as posted before, reduced chance of sparks near gas (emitted as the flat battery charges) when you disconnect the cables
3. as already posted, slightly reduced risk of voltage spikes at the battery posts when disconnecting, upsetting any battery monitoring devices

The several reasons not to have the donor car's engine running have been covered and are what I'd have posted.

Ideally you'd make sure the flat battery hasn't gone open circuit (a quite rare failure I believe) as that would mean, when you disconnect the donor after starting the Jag, that the Jag then effectively has no battery - very bad and liable to cause electronic damage. Checking the Jag voltage being non-zero before connecting a donor should be enough.

(Anyone who's liable to connect the donor the wrong way around - please don't attempt a jump start as the costs and risks are potentially horrific.)

 

Those "booster" packs are just that, a booster. They are meant to take a battery that is discharged and provide a second means of power to give the vehicle just enough power to get the starter to roll. They are not meant to take 100% of the starting surge. They may provide say 50% of the starting current, but it is still relying on the installed battery to provide the other 50%.

Now, you get the ones that plug into your cigarette lighter, now you are looking at something that is really meant to only be a helper. Keep in mind that at best the kits like this can provide is 20 amps. When a starter will put over 100 amps, how much is it really helping? Yes, it may be just enough if you are at the ticking stage or if you simply plug it in and let it set for say 30 minutes so you can transfer the charge from the booster into the main battery.

If you want a booster that is worth anything (atleast in my opinion), the test that I would use is to completely disconnect a battery, put this booster in its place and see if you can start the car that way. If you can, then that is a booster worth the money. Granted, this is also just one more thing that you would need to do "monthly maintenance" on if you are keeping it in the trunk of your car as any battery will loose its charge over time. So, you would need to say once a month to put it on a charger to keep it near 100% capacity.

 

I still like the idea of the booster device if only we can find one of the proper load.

As for connecting the ground what is the difference in attaching it to the battery or the bolt for the tire. They are both in the trunk only one is less than 2 feet from the battery. Also looking at my tire bolt it is painted and would need to be cleaned and what if it is lose it does little for a good connection. I am still thinking this out.

 

There is always SOME resistance in a metal path. You want the smallest from good battery to starter instead of to the bad battery. At 100A 0.01 ohm is dropping 1V that you don't want to drop. Well, you don't want to drop it to the starter but do want to drop it to the bad battery so any metal path is good in one place but bad to the other...

Ideally you'd connect the good power source direct to starter but it's awkward to do that on many cars!

 

1. take control of all booster cables yourself, do not allow anyone to "help"

2. stop both vehicles (and pocket keys if someone is likely to try to "help")

3. carefully identify positive and negative post locations on each vehicle

4. attach positive cable to dead battery positive post - no spark here

5. attach positive cable to live battery positive post - no spark here

6. attach negative cable to dead battery negative post - no spark here

7. swiftly and firmly attach negative cable to live battery negative post - small spark when done right (swiftly and firmly)

8. start donor vehicle and fast idle for at least 10 minutes to bring up float voltage of dead battery

9. attempt to start dead vehicle

10. if vehicles starts, disconnect the cables in a reasonable time in the reverse order of connection.



To avoid accidental connections, when working with the first clamp of either cable, keep the other clamp under your foot on the ground.

With the help of step #8, a start is almost guaranteed if there are no other problems aside from a dead battery.

If the first attempt does not work, wiggle the clamps to get through possible corrosion, wait another 10 minutes and try again.

If unsuccessful after the third attempt, give up and thank the driver who was kind enough to offer help.

There is nothing to be afraid of, as there is nothing at the end of the cables other than electrical current at 13-15 VDC ... no magic computer destroying pulses. The trick is not arsing around on that last connection of step #7 which completes the circuit.

BTW, the trick with booster packs is similar to step #8. Connect and wait for the booster pack to boost the capacity of
the vehicle battery before attempting to start.


++

 

These are instructions from the operators manual of the Diehard portable power unit I use.

 

Do Jaguar themselves recommend a jump starter? Or one for a Varta RC 150 950amp 90Ah battery?

 

Again there's nothing unique about Jags that make them different for jump starting.

 

There sort of is - Jaguar say NOT to have the jump starting car's engine running. That's the exact opposite of many other recommendations I've met over the years.

I suspect Jaguar are right for a modern, electronics-stuffed car. But that is still a bit of a novelty, or was when Jaguar were writing up their handbooks.

 

Well today we had an opportunity to try an InstaBoost. After a week and a half of temperatures below 40 and not being started for about 3 to 4 weeks I went out to my truck “93 350 Silverado” and found that the battery was flat. We took a fully charged InstaBoost and connected it to the BATTERY pressed the button on the InstaBoost and gave it a try. Much to my surprise it turned that 350 engine over and it started right up. I thought it was going to take a few tries but to it started on the first try and it did not sound like it was laboring to start. I was impressed! Not a bad device to have I think I might get one.

 

One item to consider, if a battery is Dead/Dying why? This could be caused by defective charging circuits within the car, or internal problems with the battery. Regardless of 'sealed' batteries they all contain fluid and chemicals, often the case is a reduction of fluid which can be due to a number of reasons, ie boil-off if overcharged in some cases, other is chemical dilution over time/reaction stages. Connecting higher amps to a unknown battery could cause unknown results ;-). I've never been too concerned with hydrogen fumes since these will be generated under charging mostly and be it some residual from a previous drive, Keeping in mind the battery internals are vented. Using a frame ground will help suppress any spikes that may occur (alot of metal to absorb) before it's returned to the neg battery terminal.

 

I am good with why it was dead but it came unexpected. It is old and it sits for weeks without being driven.

 

Like someone telling me "thats a British car, so it has a positive ground". .......

 

It's funny when people say things like that, often with some air of certainty, despite being completely wrong.

 

I think I can prove everybody wrong! I didn't know there was a 'procedure', so I've started both my Jags (XK & Sov) by -

Start donor car.
Connect jump leads (any order and direct to battery).
Wait 2-3 mins.
Start crippled car.
Disconnect leads (in any order)

This winter I must have done that 10 times. However, a caveat - I open the boot and uncover the battery for a few mins before connecting up.

When I got my XK I didn't realise there was a manual lock hole in the bootlid (it's hidden!) So I connected to the fusebox supply under the bonnet and, once, managed to connect it back to front! The only damage was it blew the radio (or to be more precise, the radio hasn't worked since).

 

Please don't do that to start an S-Type unless you like the risk of damage.

 

Two points......... and this is no attempt to be a smarta**

One. That was truly spoken like a guy that has never had a battery explode in his face; I've seen it, it ain't pretty.

Two. Had you brought your car to someone for service and they connected up to the car as you did, I'm sure you would have jumped down their throat when you found the radio no longer worked.

Please don't "prove everybody wrong" by advocating what can be dangerous procedures, as noted by many others.

My two cents.......