Battery drain mystery

[WhyTwo]

I've had no problems with my car starting during the winter and have had it on trickle charge the whole time. After cleaning it yesterday with my 3 year old sat inside fiddling with the controls as usual - better that than him 'helping' it wouldn't start - had been sat for about 3 hours after cleaning.

Battery was reading 12.6 v then dropped to 6 when I turned the key. I jumped it off my other car and went for a spin to charge the battery. I did about 30 miles. When I got home I switched it off and on again. It started a couple of times no problem, problem solved I thought.

Anyway when I came to put it in the garage a couple of hours later it wouldn't start again - same readings as before. So I just pushed it into the garage. I then noticed a dim light coming from inside the car - turned out to be the drivers side window control led. Why would this be on? I fiddled with it, locked and unlocked the car and it went off.

2 questions - why was the led on when the car ignition was off (car unlocked)?

Could this have drained the battery if left for a few hours?

[330p4]

Led would not drain battery in a couple of hours they only draw approx 20mA i would suggest you charge battery fully then watch the voltage reading on the pod when starting the car if it drops to 6 Volts then suspect a battery cell has gone down if OK check for interior lights,boot light etc been switched on permanent or they switches that turn them off when closed. Ideally if you have a meter you can check the current draw switched off & locked if more than 100/200mA then something is wrong
Ian

[WhyTwo]

Thanks Ian. I didn't expect the LED to be the cause of the problem as like you say the current it draws is negligible. However it's the reason for the LED being on when parked that I was concerned about.

I'll take your advice and check to make sure no other lights/switches etc are on. I did actually disconnect the boot light a long time ago as I never needed it and would occasionaly leve the boot open while the trickle charger was plugged in

[Mark A S]

It sounds to me like your Battery is Kaput! how old is your battery?, has it gone flat and stayed flat for some time?
With your engine running voltage should be in the 13's, and on start up should not really drop below 9v, well this is what mine does anyway

[WhyTwo]

I thinking the same myself TBH. Dont know how old the battery is, I've had the car about 18 months. It went flat once last year but I charged it after about a week. This is only the second time but it's strange it was fine then suddenly in the space of 2 - 3 hours it was not charged enough to start the car.

I had it on trickle for 24 hours and when I got home last night it started no problem. It was showing 14V, dropped to around 9 when starting but was then at 14,4V whilst idling. I'm going to disconnect the trickle charger today and then try and start it after a few hours.

If it starts it's OK and I'll put it down tho typical TVR unexplained issues, if not I'll buy a new battery

[Laser Sag]

It could be worth checking the 100amp fuses in the footwell and under the airbox as they can crack after time and do some weird things to battery connection.

[WhyTwo]

Bugger! Left it for 3 hours and when I went back it was showing 12v, when I cranked it the reading dropped to 7.8v and of course it wouldn't start.

Going to check the 100 amp fuse under the air box but need to charge the battery to get it out of the garage as not enough room to get the bonnet off! Got a spare fuse if the other one is cracked. If not I'll get a new battery. Really annoyed as I wanted to use the car on Friday and don't have time before hand to sort it out

[so called]

Your little one didnt turn the interior light on did he ?
Sorry if its a stupid question