On 23/10/2019 10:14, charles wrote:
In article , dennis@home
wrote:
On 23/10/2019 08:30, Tim+ wrote:

About 40 years ago my mother bought a Fiat 124 which was the first car
I ever saw with a boot light. I was demonstrating this to my future
father-in-law when we discovered it had no switch but was permanently
on


Um, sounds like ******** to me. So the battery was running flat every
day?

Tim


Car batteries don't run flat every day just because there is a 5W load
on them. If yours do then buy a working one.

5W for 24 hours would be 120 watt hours; at 12v = 10 AH - quite a drain on
a small battery,


What do you think the capacity is for a car battery under a very small
load like that?
Even the cheap nasty ones you used to get would be around 80AHr for that
small a load.
An "80AHr" one in a modern car would probably be 160AHr for such a small
load.
The capacity is usually stated for a much higher drain.

Most batteries now have capacity in how many amps you can draw while
starting.