On Wednesday, 23 October 2019 13:48:43 UTC+1, Tim+ wrote:
dennis@home wrote:
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.



How about between 1966 and 74? Batteries have changed a lot over the years.
Its by no means uncommon for a boot light to flatten a battery, how long
itll take will obviously depend of the state/quality/capacity of he
battery.

All this is beside the point that no manufacturer would design a boot light
to be €œpermanently on€�. As TNP suggested, it was probably just linked to
the door switches instead of having its own boot light switch (as an
economy measure), or the OP is just wrong about it having no switch.

Tim

On a 1960s Fiat 124 I'd expect about 30Ah. It could be less.


NT