During periods of limited or no use of the car, my battery discharges to the point it will not take a new charge without me putting a good battery between the charger and discharged battery to wake it up to the point it will accept a charge.

To avoid the hassle of an overnight charging cycle, is there a simple way (switch that can be installed) to stop the battery from discharging over time while the car is sitting.

Obviously regular use would solve the issue as would a trickle charge but aside from those options, can I just stop the draw from the battery without disconnecting the cables.

thanks, Tim

 

A battery disconnect switch is made, primarily for security purposes. You will need one rated for at least 250 amps. Your post doesn't identify the MY but there was an issue with parasitic drain a few years ago and, I believe, even a TSB on the subject (turn signal stalk?).

Since the switch would most likely be installed next to the battery there is little difference in getting to a switch and removing the ground cable from the battery.

 

I used to use one of these on a BMW 735i that suffered from parasitic drain. It's easier and cleaner than removing the connector from the post and for $9 it's hard to beat.
http://www.amazon.com/Wirthco-20308-.../dp/B000CQFWNM

 

After sitting for an extended period I had the same issues. My car has a slow drain somewhere in the system which up to this point nobody (including Jaguar) can identify. To solve the problem I wired a trickle charger directly to the battery and just leave it there permanently. Its small enough that it tucks away nicely in the back of the trunk and is unnoticeable. If the car's going to be sitting for more than a week I just plug it in and leave it. Its been almost two years now without a dead battery and zero negative affects.

 

I have also used a trickle charger and this is definitely a good solution. Mine came from Harbor Freight for less than $20. I do the same on my boat. In my case the Jag is stored outside under a cover and for convenience I have now gone to a solar charger that I built. This does the same job and the regulator I put on it prevents overcharge. I set the solar panel on the window that faces mostly south. The regulator must have a blocking diode so it doesn't discharge the battery when the sun goes down.

The drain comes from all the electronics in the Jag that are always powered even when "off". This is done to retain all the presets such as seat position, radio presets, wheel position, etc. These add up to a constant drain that over time will discharge the battery. Its like the proverbial dripping faucet.

I also have a battery disconnect on an antique car (1931 Woody) that is stored in a garage with no electricity. This works well but not sure what the current rating is. The car has an 8V battery and it holds charge well when disconnected. The switch connects directly to the battery terminal and the cable to the switch. Switches like those used on boats are also available and they definitely can handle the current as the diesels on boats draw big amps when starting.

 

I had the same problem with a 99 XK8, 3/4 days and I had window memory loss and sometimes a no start scenario. I measured the parasitic drain at 330 milli amps, I believe the normal drain to be less than 40 milliamps. I fooled around over several years looking for the culprit but never solved the problem. I kept a charger connected when it went unused for more the a couple of days. Sold the car disclosing the problem. My 2003 XKR can go weeks w/o a problem. This last statement will probably bite me.

 

Just a small point to remember, please include model and year in the title of a tech post, or at least have it in a signature such as testpoint or vagearhead. It makes it easier for everyone to give more specific replies.

I agree with the general consensus and would go with the trickle charger method.

I have previously installed battery cut out switches in a variety of my previous off roaders, that can be handy if you find yourself hanging upside down from your belts, which I hope never happens to you in the XK.

I doubt that with all the electronics and memory modules in these cars, disconnecting the battery on a regular basis is such a good idea.

From experience on other cars, I don't have an XK the last things to go out with a dying or weak battery are the passive electronic systems.

Now then, the homemade solar powered jobbie, sounds interesting, are we going to be seeing a 'how to'?

 

Thanks for the suggestions. It's a 03 XK8 Coupe. The battery tender option doesn't work because it's parked outside. I guess the best solution is "DRIVE IT"

 

Now then, the homemade solar powered jobbie, sounds interesting, are we going to be seeing a 'how to'?[/QUOTE]

I own an electronics company so put together the solar charger from parts we have in stock. I modified (by changing the feedback resistors) a small switching voltage regulator with 1A max output, to put out about 13.8V which is 13.2 plus the Schottky diode drop, plus a little more. 13.2 is the maximum charge voltage of an unloaded lead acid battery. The extra diode is to prevent reverse current when the output is less than the battery voltage.

I put this in a small box with a connector to plug in a small Solarex panel that we stock. The panel will output about 250mA and that has been OK on my 2000XKR. I just had a battery go bad (the original in the car) and this was keeping that charged up even when the battery lacked enough juice to start the car. Apparently the standby leakage in my car is less than this but I have not measured it. The battery got damaged before I used trickle charging by sitting long periods over the winter. When a lead-acid battery drops below a certain charge level (about 10V) its capacity is permanently reduced.

When I get a chance I'll put some illustrated instructions together but anyone familiar with electronics could easily make one of these from the description above. The hard part is getting a regulator that can be modified to output the correct voltage.

 

I looked on Ebay and there are several solar battery chargers listed at a low cost.

These are also available through marine suppliers (at higher cost but no Ebay ripoff risk) such as West Marine and Defender. The marine versions will be a lot more rugged.

 

Unfortunately, a solar trickle charger is not an option in the UK as you need sunshine for it to work!

 

At the risk of sounding flippant, you'd have more joy with some form of tidal charger in Birmingham at the moment!

 

I hear you on the need for sun. I'm not sure how much sun is needed with a solar cell as it also responds to UV which I am told does penetrate the clouds. I have kept a volt meter in the trunk since going to the solar cell so I can keep track of how it is doing but this time of year we have sun. I think in your case a solar cell would work but you would have to use a bigger panel. This is always the challenge with solar systems, getting things sized right. The one I'm using we had in stock to use for remotely located telemetry systems so there was no science. It is what was handy.

The solar approach is a good one if line power isn't readily available and has the added feature that you can take it with you. I took the charger on vacation to Maine, where we had no electrical power on an island in a lake, and used it to keep my cell phone charged.