In article ,
Fredxx wrote:
On 24/04/2021 00:27, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
On 23/04/2021 13:44, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
At 50mA that would be less than the self discharge rate of a lead acid
battery.

Not so. A lead acid in good condition has a very low self discharge
rate.

More than a 1,000 hours?

Yes.

A pal has a place in Spain. In better days goes there for at least 2
months at a time, leaving a car here. With the battery left connected,
totally flat on return. And toast. Disconnected, it will start the car
after re-connecting.

I thought the self-discharge rate was quite high but you're spot on, as
per usual.

Just experience of them.

This gives a self-discharge rate of 40% per year, I did see another
article that said 5% per month, but give or take they're both in the
same ball-park.

https://batteryuniversity.com/learn/...n_modern_times

At one time new batteries were dry stored. When you bought one, they'd add
the acid. Not so now. Yet most would expect a new battery from Halfords
etc to start their car right away, without charging. So they must have low
self discharge. As not even Halfords will turn over their stock every
couple of weeks.

Apart from a remote locking receiver being active I really don't see the
need for a current draw from anything else.

Immobiliser? Radio memory? I'm sure the makers of expensive cars would do
everything they could to reduce quiescent load. It's not a good advert if
the car won't start after being left at an airport carpark while on
holiday.

I would propose it would be cheaper to fix the current drain issues than
the cost of a second battery.

I really don't see an answer to it with modern cars. And I'm sure many
very clever engineers have given it much thought.

--
*He's not dead - he's electroencephalographically challenged

Dave Plowman London SW
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