On my way home my wipers and windows where moving very slow, the battery gauge was between the 12 O'Clock and the 9 O'Clock position. Once I got home I turned the car off and started it back up but now everything was fine, wipers and windows where working fine and the needle was at the 12 O'Clock position. I assume everything was fine and it's just a hickup? The cold weather has probably killed my battery long term though maybe. My battery is only a year or two old and I drive the car almost every day.

 

Is the car on a battery tender when not being driven overnight or longer ?

The stock charging system, even when working as designed, will not keep a battery of any age up to 100%.

In these 20+ year old cars, any battery voltage / strength under 100% is going to open the door to various electrical gremlins.


Z

 

will not keep a battery of any age up to 100%.
You need to define what you mean by 100% ..ultimate capacity 100% would require a charge to 15.5v
the alternator does 14.4 v so 80% of ultimate but that is in 2023 fully charged. It charges it a point just before it gasses so you can have it sealed and no maintenance.

 

You’ve got me there.

my 100% is a subjective 100%, not a mathematical 100%.

whatever the voltage difference is between what a fully functional X-100 charging system can deliver and what a good battery tender can increase, that’s the missing link to
my subjective 100%.

so many people on the forum, myself included, have had electrical gremlins vanish once the
“battery tender factor” is added in, that it’s a little more than anecdotal information at this point that a tender does something good for these old cars.

how to measure that something good is some measure above my intelligence.

Z

 

No it's not on a battery tender but I drive it pretty much every day so I figured that should be enough. It would be enough for any car, I do know these cars are very voltage dependant but I'm alredy doing everything reasonable? I don't think having a battery tender on whenever it's parked even overnight is reasonable. I would understand if I left it for a week or a month but overnight and then to drive it again shouldn't be a problem. The car seems fine though now, I assume it was just a hiccup in the system? I will start it up this morning and see what it's like though once light is out.

 

on the face of it, it certainly is reasonable that driving a car daily should keep the battery up to a level that would preclude any battery related issues.

For reasons I admittedly don’t fully understand these cars are far from reasonable.

Whether it’s the age of the wiring, electrical connections, components, or simple voodoo, there’s more than anecdotal evidence that having and using a battery tender makes a difference in the car’s reliability.

It’s aggravating to have to deal with unreasonable things. But the XK’s idiosyncrasies are about the most insignificant of all the unreasonable things on my personal list of life’s unreasonableness.

Far easier for me to hook up the battery tender than have the gremlins come back.

Z

 

I will look into getting a tender then I think if it keeps these problems away.

 

Our old jags have two differences from "modern" cars.
The standby current is higher than the 50 mA you would expect on a modern car .this runs the battery down when standing.
On a modern car the systems/sensors are all running on 5v. This gives the electronics some headroom when the voltage drops. I dont see evidence of this on our old design electronics.
No alternator will charge a discharged battery to 100% on any car despite what the roadside assistance moron says .
The power used to start the car is replaced in about 1 min of running.
If you measure the battery voltage and then again at the front "live Bolt" you will get less . The cable joining the two is not copper or even aluminium looks like steel to me .Hence the references to old wiring.
Hence for reliability we use a tender

 

Keep in mind that "driving a car every day" will not necessarily keep your battery sufficiently charged. Short trips at low speeds is simply not enough to do it. You must get the car out on the highway for a good 20-mile romp on a regular basis....

 

Considering the alternator runs at 3x engine speed and produces sufficient output from 2000rpm to charge the battery what you say above is an old wife's tale. The charge used to start the engine is replenished in about 1 minute.
The max battery charge you will get is 15-20A at any speed and the voltage wont go above 14.2 v

 

On my way home when it seemed low I did use the J-Gate to keep the revs high, took it down a country lane to blast it down the road breifly. It didn't make any difference during the drive though. I should think it was just a hiccup on that run of the systems because it has been fine since I restarted the car.

 

Reasonable expectations aside, both of my jags are much easier to live with since I employed battery maintainers. If not driven for three days they may/maynot start to display upsetting messages. Battery tender maintained they only display actual issues.
Life is better, less stressful!
WJ

 

This one look OK? Röhr Intelligent Car Battery Charger for AGM / GEL / WET Batteries - DFX-15 5060569763278 | eBay

Or this one? Röhr Intelligent Car Battery Charger for AGM / GEL / WET Batteries - DFX-40 5060569763285 | eBay

 

The brands I’ve used / am using are the NOCO Genius 5 and the Delran Battery Tender +. Others on the forum swear by the CTEK brand.



I used the Delran for years with no complaints, but a recent Amazon sale on the NOCO’s convinced me to buy one. One nice feature the Delrans have is the metal case. I ran over mine 2 or 3 times in the last 8 years without doing any more damage than a few cosmetic scratches. I don’t think the NOCO or CTEK could stand that kind of abuse. But I do really like the NOCO, so a little more care is worth it.



Z

 

Thanks.