In article ,
wrote:
On Friday, 4 May 2018 14:25:02 UTC+1, Dave Plowman (News) wrote:
In article ,
Graeme wrote:
The battery takes a charge, but it must be the battery not holding a
charge. New battery time :-(

I've got a very posh ACT battery tester. It gives you an instant
readout of the battery's actual capacity in amp.hr. Left over from
when I was working. I'd expect any decent battery place to have
similar.

Basically, if that capacity is something like 20% (or more) less than
the figure on the case, it's scrap.

I hear figures like that often. I've run car batteries to way lower than
that before they became problematic. I doubt the last one had 10% of its
capacity left before it began to struggle.

It does depend on the type of failure. I've had some which were OK one
day, and dead the next. And how much 'reserve' the battery has which is
going to depend on the individual make.

But this tester does show if your battery is good too. Plenty fit a new
battery when the fault is elsewhere.

So like all test gear you do nee to know how to interpret the results.

FWIW, I've yet to find any lead acid which is vastly down on capacity but
can still deliver its original peak current for starting a car on a cold
day. That's not to say such a battery might not have some other uses.

--
*It's a thankless job, but I've got a lot of Karma to burn off

Dave Plowman London SW
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