XPost: uk.rec.driving, alt.home.repair, uk.d-i-y
From: rod.speed.aaa@gmail.com
"Commander Kinsey" wrote in message
news:op.z3rc8ux1wdg98l@desktop-ga2mpl8.lan...
> On Sat, 22 Jun 2019 00:26:13 +0100, Rod Speed
> wrote:
>
>>
>>
>> "Commander Kinsey" wrote in message
>> news:op.z3rauixewdg98l@desktop-ga2mpl8.lan...
>>> On Fri, 21 Jun 2019 23:39:34 +0100, Rod Speed
>>> wrote:
>>>
>>>>
>>>>
>>>> "Commander Kinsey" wrote in message
>>>> news:op.z3q6mue3wdg98l@desktop-ga2mpl8.lan...
>>>>> On Fri, 21 Jun 2019 21:54:38 +0100, Rod Speed
>>>>>
>>>>> wrote:
>>>>>
>>>>>> Commander Kinsey wrote
>>>>>>
>>>>>>> How does a lead acid battery charger (or car alternator) know when
>>>>>>> to
>>>>>>> switch to trickle charge?
>>>>>>
>>>>>> From the current the battery takes.
>>>>>>
>>>>>>> I can understand it noticing a drop in charging current if the
>>>>>>> battery
>>>>>>> is
>>>>>>> on its own, but what if a random changing load is connected, as
>>>>>>> there
>>>>>>> is
>>>>>>> in a running car?
>>>>>>
>>>>>> You just look at the current going to the battery. The variably
>>>>>> loads like with lights isnt supplied by the battery when the
>>>>>> engine is running, its supplied by the alternator.
>>>>
>>>>> But how can the regulator on the alternator possibly know the current
>>>>> it's
>>>>> passing to the battery is going into the battery and not going
>>>>> straight
>>>>> across to the lights?
>>
>>>> The computer knows whats going to the battery and you can see that with
>>>> an ODB2 dongle.
>>>
>>> My dongle only lists faults.
>>
>> Because it's a steaming turd with wheels frog car.
>
> Which should adhere to the fucking OBD standards according to the frog's
> own EU regs!!
Steaming turd with wheels frog cars don't. And that isnt an EU reg anyway.
> And a very basic OBD reader I bought to determine why a warning light was
> on.
That will still show more than just faults.
>> Most show all sorts of things.
>>
>>>>> If you look at the battery in your car, there are two or three thick
>>>>> wires
>>>>> coming off each terminal. One will go to the alternator, another to
>>>>> the
>>>>> fusebox for all the lights etc.
>>>>
>>>> And it's the voltage across the one going from the alternator to the
>>>> battery that allows the computer to know how much current is going to
>>>> the
>>>> battery.
>>
>>> Bullshit.
>>
>> We'll see...
>>
>>> How could it possibly know if the current flows into the battery or goes
>>> to the other wire leading to the fusebox?
>>
>> By measuring the voltage drop across those cables, stupid.
>>
>>>>> Unless there's some clever circuitry monitoring each
>>>> battery wire individually and subtracting the currents,
>>
>>>> Yes there is, its called the computer.
>>
>>> So what happened with older cars before they did that?
>>
>> The voltage across the battery changes as the battery is charged.
>
> Wrong.
Nope.
> Say the alternator can produce 14V at up to 50 amps. When the battery has
> been used to start the car and perhaps run some lights when the engine was
> off, it takes maybe 25A, and the voltage is 14V,
Yep.
> regulated by the alternator's circuitry.
Nope, by the battery.
> When the battery becomes full, it takes only a fraction of an amp,
Yep, because the battery voltage is now higher.
> but the voltage is still 14V.
The battery voltage isnt.
> What needs to be measured is the current going into the battery,
Nope, the current drops automatically.
> and that cannot be done by just measuring the current coming from the
> alternator, as that could also be going to lights, heaters, spark plugs,
> etc, etc.
That's why there is more than one wire to the battery positive terminal.
>>>>> the alternator can't tell the difference between a battery taking 12
>>>>> amps,
>>>>> and a battery taking 2 amps plus lights taking 10 amps.
>>>>
>>>> But the computer can. And knows if the lights are on too.
>>>>
>>>>> The second one requires switching to trickle charge, the first
>>>>> doesn't.
--- SoupGate-Win32 v1.05
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