On 09/04/2024 21:03, Harry Bloomfield Esq wrote:
> On 07/04/2024 18:00, Grumps wrote:
>> I have a current clamp meter that I stuck on the negative lead to the
>> battery and measured the current. It idles at about 4-5A, and after
>> half an hour it is down to about 0.08A (80mA), after various items go
>> into power down states.
>> How long would a battery hold a decent charge at a discharge rate of
>> 80mA? Is 80mA reasonable?
>
> 80mA means the battery should be discharged to around half it's
> capacity, after around 300 hours, if not run to recharge, or four weeks.
> Short runs, after cranking over, do not really help - how frequently
> does it do the 200mile run?

On average every 3 weeks. Sometimes she'll sit idle for 4 weeks.

> The garages, might have had it sat a while, with thing left on,
> flattening the battery even more.
>
> I had a discharge of around that level, eventually traced to my voltage
> sensing relay, clicking on and off, which would flatten my battery if
> parked for an extended period. After resolving it, parked up, it drops
> to 18mA.

On 4/9/2024 4:16 PM, Harry Bloomfield Esq wrote:
> On 07/04/2024 18:00, Grumps wrote:
>> Oh, and I just remembered, there are other wires going to the battery terminals other than the chunky red and black ones. Maybe there is something else that takes power that I'm not measuring. I can't get ALL of the wires into the clamp meter.
>
> You can measure them individually, and add the amounts together.

Usually, you just select the ground strap, which has all the return current in it.

Paul

Grumps <not@here.com> wrote:
> On 09/04/2024 17:07, Chris Green wrote:
> > Grumps <not@here.com> wrote:
> >>>
> >>> Nothing is as "Off" as an older car was. The current on those
> >>> only needed to be enough to run the car clock, which is 10uA
> >>> (with the display dark).
> >>>
> >>
> >> I'll probably have to wait until next year when it has its service. Then
> >> I can measure the battery current with my clamp. See if it holds at a
> >> high reading when it's supposed to be asleep.
> >>
> > I wouldn't have thought a clamp meter is going to tell you much down
> > at the amp or so that you're concerned about.
> >
>
> The clamp meter has a resolution of 10mA in the 60A range setting.
> Testing the accuracy with my current-limiting bench PSU and a normal DMM
> seems reasonably promising.
> With the PSU set to 100mA, the DMM reads 100mA and the clamp (mostly)
> says 0.11A.
> (mostly = the reading is not stable, so I took the most common reading)
>
That's often the problem with clamp meters down at that sort of
current, as I was saying. :-)

--
Chris Green
·

On 10/04/2024 12:57, Grumps wrote:
> On average every 3 weeks. Sometimes she'll sit idle for 4 weeks.

The deeper the discharge, the more the wear and tear on the battery,
which reduces it's capacity and life.

On 4/10/2024 9:18 AM, Chris Green wrote:
> Grumps <not@here.com> wrote:
>> On 09/04/2024 17:07, Chris Green wrote:
>>> Grumps <not@here.com> wrote:
>>>>>
>>>>> Nothing is as "Off" as an older car was. The current on those
>>>>> only needed to be enough to run the car clock, which is 10uA
>>>>> (with the display dark).
>>>>>
>>>>
>>>> I'll probably have to wait until next year when it has its service. Then
>>>> I can measure the battery current with my clamp. See if it holds at a
>>>> high reading when it's supposed to be asleep.
>>>>
>>> I wouldn't have thought a clamp meter is going to tell you much down
>>> at the amp or so that you're concerned about.
>>>
>>
>> The clamp meter has a resolution of 10mA in the 60A range setting.
>> Testing the accuracy with my current-limiting bench PSU and a normal DMM
>> seems reasonably promising.
>> With the PSU set to 100mA, the DMM reads 100mA and the clamp (mostly)
>> says 0.11A.
>> (mostly = the reading is not stable, so I took the most common reading)
>>
> That's often the problem with clamp meters down at that sort of
> current, as I was saying. :-)
>

But they can be made more sensitive. By turning
up the Hall (cc) current in the sensor.

On portable instruments, there isn't the power
available to do that. If the instrument was
lithium powered, you would have more room for
cranking it up.

All I know is, the one I had in the lab, the
sensor current was "constant current 350mA" and
the current came from a bench supply (the gray HP
bench supplies that put out up to 50 volts @ 500mA
and they run CC or CV).

It doesn't matter what sense current level you run
a Hall Probe, it's going to drift and it needs
to be zeroed before you make a measurement.
(Zeroed with the conductor out of the jaws.)

Paul