How long (roughly) should you expect a good condition, charged battery to last with the engine off and the ignition / radio on? I ask because after working on the car yesterday for about 3 hours and another 20 mins yesterday, the battery is flat. Voltage down to 9.4.

 

The only other time I've had similar is when at Beaulieu a few years ago, was sitting in the car, radio on for a couple of hours, car wouldn't start then either. It's only a normal unit, not ICE with amps and stuff. I've not had this problem with any other car than Zs!

Do you mean accessory or ignition on, if the later the engine sensors are all powered and with the coil packs will eat power... also interior lights can be hard on the battery especially if it is not 100% charged, even in accessory position many of the modules power up ready for the start, typically maybe 0.5 to 3.0 amps depending is just radio or cd player etc. with the interior lights and modules, with an 80 amp battery at say 75% charge then not as long as you would thing.

 

Most modern cars have a 20 minute cut off for the radio if the engine is not running for just this reason.

 

Jeff

Edited February 15, 20196 yr by JeffTT

Most modern cars have a 20 minute cut off for the radio if the engine is not running for just this reason.

 

Jeff

 

Yeah mine does that, tells me to start the vehicle and if I ignore it shuts down, clever knowing how many volts it needs to preserve for another crank.

It also depends on how often and far the car is driven to replace the start up draw....

 

How old the battery is also has an impact how well it holds a charge and discharges.

 

Also the batteries CCA (Cold cranking Amps), Ah rating, alternator output voltage, condition of all earthing and wiring, etc.

 

A website with some basic explanations.....https://www.autobatteries.com/en-us/how-to-choose-your-car-battery-replacement/overview

Do you mean accessory or ignition on, if the later the engine sensors are all powered and with the coil packs will eat power...

Jeff

 

Ah, that makes sense. I had ignition on because I was trying to get my PC connection to the Consult interface working. Will remember that in future. Thanks Jeff.

Battery tested - had one bad cell. So not entirely my fault!

Might be an idea to hook up a battery charger to these cars while working on them with accessories switched on?

Might be an idea to hook up a battery charger to these cars while working on them with accessories switched on?

 

Perfect this is the normal procedure on even brand new cars whilst been serviced at dealers.