XPost: uk.rec.driving, alt.home.repair, uk.d-i-y   
   From: rod.speed.aaa@gmail.com   
      
   "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.   
      
   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.   
      
   >>> 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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