What somebody electronically minded did on a battery where you can actually
get at the cell interconnects, few these days, sadly, he put a monitor so it
looked at every cell on its own and then he could tell the weak cell or
cells, but as to what to do with such info, who knows? I'm surprised modern
car electronics do not already allow this like they tend to do on Lithium
cells these days.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Steve Walker" wrote in message
...
On 20/04/2021 20:17, Chris Green wrote:
Cliff Topp wrote:
All modern cars will have an amount of quiescent current draw to power
things like the alarm, the clock, the radio presets and so on when the
car is parked up and switched off. I've seen it written somewhere that
around 50mA can be considered 'normal'.

My question is - if the quiescent current draw is 50mA (0.05A), how do
I calculate voltage drop per hour?

For instance, if I park the car up at 10pm and the battery is showing
12.5V, with a 50mA draw overnight what will the voltage be at, say,
9am?

At that sort of current it depends more on the battery's self discharge
characteristics than anything else.

In other words there's no simple answer, it depends on so many things:-

Ambient temperature
Battery condition (part or fully charged)
Battery capacity
Type of battery (wet cell, calcium, etc.)

And quite commonly (from experience of my own and neighbours), it'll still
be high enough to start after a fortnight, but likely not after 3 weeks.