Dead battery...

[pugboyracer]

Hi everyone,

Well the £325 XJ40 has its first issue. Battery seems to randomly discharge overnight. I had it happen last week and jump started it. All was fine until this morning when it failed to start. I use the car daily to work and back, which is a round trip of around 40 miles, so it gets decent exercise.

I've changed the battery today, as the old one looked in a right state and past its best, plus it doesn't even seem to be the right type. Looks more like one I'd use on my 205 GTI to be honest. New battery is a quality Bosch item and looks a lot more hefty.

So, hopefully the new battery will help things. However, what could have caused the old battery to discharge like that? I'm obsessive about making sure lights etc are turned off, so it has to be something remaining live when I turn the ignition off surely?

Thanks for your help!

Marc

[xj12-rob]

is it a battery in boot car??, if so it is the code battery in the radio causing the problem

[pugboyracer]

Thanks Rob,

How is this happening? Should I remove the radio and pop my aftermarket one in?

Edit - Just to add this is a 1993 Sovereign, battery in boot model.

[xj12-rob]

jag had HUGE warranty claims over this, the battery would be dead in two weeks, people came back to cars in airport carparks after holidays to find the car dead, not even a peep, v pissed off when you had forked out up to 60K for a DD6 XJ40

most cars have had a swapped radio by now, but the odd one still pops up, most of the radios out of the late cars I get that need recoding, are infact recon units, my guess is that Alpine where recoding them to match the cars, I have to have them coded back the original units code, involves a bit of soldering

Best thing is to look out for a secondhand unit, I sold my last one today!!

However, BEFORE you do this, do as you say and whack in a new battery, these cars do need to have the battery at 100%, ensure it is the correct item, I had a 4.0S that I put in an even more powerful battery in attempt to get rid of the problem and keep some life in it, 125 amps I think it was

[naki_k]

a multimeter is one of the best investments you will ever make. you can use it to read the voltage across the two terminals. this will give you some sort of warning if the battery is going down gradually, but maybe not that good if it goes over night.
fully charged good battery should be around 12.5v to 12.7v i believe. with the engine running, being charged the reading should be between 13.5v to 14.7v.
anything below 12v is considered "discharged", and the engine may struggle to start.
in addition to this there is also a way to test how much power is being drained by a single device (amps setting).(with engine off)

multimeters cost anywhere from £5-£50. for occasional use you should be ok with a cheap one. maybe go for the £10-£15 range?
i have three, one in each car and one in the house, they are that brilliant! you can also use them on household batteries like AA, to see how much power is left.

[Equinoxstudios]

OMG, I remember being told about this when I bought my March '94 Sovver . The salesman said it had the 'new stereo' to stop the dead battery problem.

I've never put it to the test but I'm off to Bulgaria for three weeks. I'll tell you if I've been bullsh***ed when I get back

Oy, give us a push...