XPost: uk.rec.driving, alt.home.repair, uk.d-i-y
From: CFKinsey@military.org.jp
On Sun, 23 Jun 2019 03:59:55 +0100, Rod Speed wrote:
>
>
> "Xeno" wrote in message
> news:gn84kjF24gkU1@mid.individual.net...
>> On 23/6/19 1:30 am, Rod Speed wrote:
>>>
>>>
>>> "Xeno" wrote in message
>>> news:gn6eudFlh2sU1@mid.individual.net...
>>>> On 22/6/19 7:58 pm, Rod Speed wrote:
>>>>>
>>>>>
>>>>> "Xeno" wrote in message
>>>>> news:gn6a5eFkg1fU1@mid.individual.net...
>>>>>> On 22/6/19 9:57 am, Rod Speed wrote:
>>>>>>>
>>>>>>>
>>>>>>> "Commander Kinsey" wrote in message
>>>>>>> news:op.z3rc17q7wdg98l@desktop-ga2mpl8.lan...
>>>>>>>> On Fri, 21 Jun 2019 23:57:52 +0100, Rod Speed
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> "Commander Kinsey" wrote in message
>>>>>>>>> news:op.z3q9fvpjwdg98l@desktop-ga2mpl8.lan...
>>>>>>>>>> On Fri, 21 Jun 2019 22:57:44 +0100, Max Demian
>>>>>>>>>>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> On 21/06/2019 21:19, Commander Kinsey wrote:
>>>>>>>>>>>> How does a lead acid battery charger (or car alternator) know
>>>>>>>>>>>> when to
>>>>>>>>>>>> switch to trickle charge? 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?
>>>>>>>>>>>
>>>>>>>>>>> The voltage perhaps.
>>>>>>>>>
>>>>>>>>>> Why would the voltage change?
>>>>>>>>>
>>>>>>>>> That's the way batterys work, the battery voltage does change as
>>>>>>>>> its
>>>>>>>>> charged.
>>>>>>>>>
>>>>>>>>>> That's determined by the alternator or charger.
>>>>>>>>>
>>>>>>>>> Nope.
>>>>>>>>
>>>>>>>> Yip.
>>>>>>>
>>>>>>> Nope.
>>>>>>>
>>>>>>>> I can put any voltage I like across a battery's terminals.
>>>>>>>
>>>>>>> Nope.
>>>>>>>
>>>>>>>> The battery then chooses how much current is drawn.
>>>>>>>
>>>>>>> And that current changes depending on the how charged the battery is.
>>>>>>>
>>>>>>>>>> Let's say the charger/alternator gives out 14.4V initially, to
>>>>>>>>>> charge the
>>>>>>>>>> battery quickly. It'll just sit at 14.4V forever, providing the
>>>>>>>>>> charger
>>>>>>>>>> can give out enough current to charge the slightly flat battery
>>>>>>>>>> and power
>>>>>>>>>> any connected loads.
>>>>>>>>>
>>>>>>>>> Its more complicated than that with the current going to the
>>>>>>>>> battery and the
>>>>>>>>> battery is charged.
>>>>>>>>>
>>>>>>>>>> If the battery had no loads connected, it would take a lot less
>>>>>>>>>> current
>>>>>>>>>> when it became full, but the voltage would stay the same.
>>>>>>>>>
>>>>>>>>> No it doesn't even with a very crude battery charger.
>>>>>>>
>>>>>>>> For example, I'm currently keeping my car's battery topped up with a
>>>>>>>> bench supply overnight. It's set to 13.8V, with a current limiter
>>>>>>>> only to prevent overloading the supply.
>>>>>>>
>>>>>>> It actually specify the current being supplied.
>>>>>>>
>>>>>>>> The voltage stays at 13.8V all the time, sometimes 100mA is drawn,
>>>>>>>> sometimes up to 4A. The only way I or the supply can tell the
>>>>>>>> battery is full, is by the current dropping to 100mA. But it's
>>>>>>>> actually always full, as when 4A is drawn, that's going to a load.
>>>>>>>
>>>>>>> What load ? There no load with a battery being charged with a bench
>>>>>>> supply.
>>>>>
>>>>>> Correction
>>>>>
>>>>> Nope.
>>>>>
>>>>>> the *battery* is the *load*.
>>>>>
>>>>> Not when the battery is fully charged and is being charged
>>>>> with a bench supply that is delivering 4A to the battery.
>>>>
>>>> Take the case of an alternator charging a battery at ~4 amps.
>>>
>>> That isnt what was being discussed there. What was being discussed
>>> there was charging the battery out of the car with a bench supply.
>>>
>>>> The battery is the load and it also provides, as part of that function,
>>>> the reference *voltage* that the alternator *must have* in order to
>>>> control the output.
>>>
>>> None of that is relevant to what was being discussed there,
>>> charging the battery out of the car with a bench supply.
>>>
>>>>>> In the process of being charged it is using electric current. That
>>>>>> makes it the load.
>>>
>>>>> See above.
>>>
>>>> What happens to the charger when you disconnect the power with the
>>>> battery connected?
>>>
>>> With a BENCH SUPPLY, it continues to provide the
>>> same voltage as it did with the battery connected.
>>>
>>>> It should, if designed correctly, shut down since it no longer sees a
>>>> load. Otherwise it may destroy itself.
>>>
>>> That is just plain wrong with a BENCH SUPPLY.
>>> None of those destroy themselves with no load.
>>>
>>>>>> Even when it is fully charged it will still take a trickle charge
>>>
>>>>> 4A isnt a trickle charge.
>>>
>>>> That depends entirely on the amp hour rating of the battery.
>>>
>>> We're discussing a normal car battery in a steaming turd with
>>> wheels frog car.
>>>
>>>> Also, my bench charger
>>>
>>> We arent discussing a bench charger, we are discussing a bench SUPPLY.
>>>
>>>> will start off at 4 amps, its maximum capacity. As the battery becomes
>>>> charged, that current will drop down to *1 amp* and, from that point, it
>>>> will maintain a *trickle charge*.
>>>
>>> So that is nothing like the situation being discussed
>>> with a BENCH SUPPLY which is still delivering 4A to
>>> a battery that has been removed from the car.
>>>
>>>> From Wikipedia;
>>>> For lead-acid batteries under no load float charging (such as
>>>> in SLI batteries), trickle charging happens naturally at the
>>>> end-of-charge, when the lead-acid battery internal resistance
>>>> to the charging current increases enough to reduce additional
>>>> charging current to a trickle, hence the name. In such cases,
>>>> the trickle charging equals the energy expended by the
>>>> lead-acid battery splitting the water in the electrolyte into
>>>> hydrogen and oxygen gases
>>>
>>> Irrelevant to what is being discussed, 4A isnt a trickle charge.
>>>
>>>> The car alternator regulator is no different.
>>>
>>> We arent discussing that there.
>>>
>>>> It sees the battery as a load, determines the voltage reference and
>>>> pumps up its output. When the regulator sees the battery voltage at the
>>>> peak setpoint, it too will drop the current to a trickle. If you add a
>>>> load, say by turning headlights on, that is in *parallel* to the battery
>>>> and it will drop the system voltage down a tad. The regulator will see
>>>> that and pump up the output current appropriately. The current will
>>>> apportion itself to the *two* loads as appropriate to their individual
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