Passive Car Battery Trickle Charger

On 2/28/2021 7:11 AM, Cursitor Doom wrote:


Just turn it over and let it run for 10 min once a week which is better  
for the powertrain, also

Just chiming in for a second on something just mentioned.

If you can, avoid the 10 minute every week or two thing.  Automobile
engines produce quite a bit of H20 in their exhausts and that water
will accumulate in the exhaust system, especially the muffler, and
contribute towards rusting out the muffler pretty quickly.

An answer is to run it more like 20-25 minutes every 2 or 3 weeks, so
that the entire exhaust system gets up to full temperature and drives
out the moisture that has condensed in the system.

Better yet, and since automobiles don't charge all that efficiently at
idle anyway, drive it down the road to the store back or similar every
so often.

Or just have a trickle charger as the thread is about.  Modern engines
sit just fine for a couple of months as long as a charger is on.

Ray

On 2/28/2021 6:26 PM, Ray Otwell wrote:


I think people got odd ideas about how long it takes an exhaust system  
to get up to "full operating temperature."



A 4 cylinder engine will draw maybe 250 amps for 3 - 5 seconds to start,  
even a crappy alternator at idle can restore that in like 1 minute. Then  
you have another 9 minutes to top off the battery

On 3/1/2021 6:34 AM, bitrex wrote:


















3 - 5 seconds is a pretty pessimistic estimate too, like you gotta run  
the starter for 5 seconds to start this car:

<
https://www.youtube.com/watch?v=5RH-TvUDmXI

That is *incredibly* optimistic!
 --  

"Andrey Semyonovitch really was rather stupid; he attached himself to the
 progressive cause and 'our younger generation' from enthusiasm. He was one
 of the numerous and varied legion of dullards, of half-animate abortions,
 conceited, half-educated coxcombs who attach themselves to the idea most
 in fashion, only to vulgarise it and who caricature every cause they serve,
 however sincerely."

     - Fyodor Dostoevsky

On 3/1/2021 9:36 AM, Cursitor Doom wrote:


Nah it isn't. The e.g. Honda Civic starter motor is only rated for 1kW.  
The worst-case upper bound on a starter energy consumption is the max  
rated cold cranking amps times 12 volts times the cranking time; even  
pessimistically you're only talking couple 10s of kilojoules to put back.

Here's a paper, mathematical model of a single piston 150 cc engine  
(you'd have to extrapolate for a 4 cylinder 1.5L or something)

<https://www.jstor.org/stable/44611429

Peak current draw tops out at 80 amps and it's down to about 15 in under  
half a second.

On 3/1/2021 4:53 PM, bitrex wrote:


















Modern cars can also detect if the 12 volt battery SoC is running a bit  
low and preferentially direct power to top it back up it's not entirely  
at the mercy of whatever the idling engine and free-running alternator  
feel like doing.

You need to define what you mean by "modern cars". To me a modern car
is anything manufactured post-1960. And I have no idea what "SoC"
refers to.
 --  

"Andrey Semyonovitch really was rather stupid; he attached himself to the
 progressive cause and 'our younger generation' from enthusiasm. He was one
 of the numerous and varied legion of dullards, of half-animate abortions,
 conceited, half-educated coxcombs who attach themselves to the idea most
 in fashion, only to vulgarise it and who caricature every cause they serve,
 however sincerely."

     - Fyodor Dostoevsky

On Tuesday, March 2, 2021 at 6:30:36 AM UTC+11, Cursitor Doom wrote:



State of Charge. Wikipedia lists it as one of about a dozen meaning for the acronym - it should have been obvious from the context, but it wasn't for me.  
Authors always imagine that their favourite acronyms are obvious from the context, and their readers are rarely as deeply immersed in the subject as they are.

[Editor's hat on.]

The rule is to print the expression in full the first time you use it,
then abbreviate it, if necessary, after that.  Also, abbreviations
should have full stops between the words to indicate that they are
abbreviations.

[Editor's hat off.]

On Tuesday, March 2, 2021 at 8:56:10 PM UTC+11, Liz Tuddenham wrote:

  

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wrote:  

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Agreed. I'm putting together the March issue of the newsletter of rhe NSW b
ranch of the IEEE at the moment - not that I've got many of the promised ar
ticles yet - and my editors hat is near to hand. It will be my nineteenth i
f it ever gets out, and with any luck one of the contributors will get cros
s enough with me to volunteer to take over the job.

[...]  


With a deadline approaching, I've been known to write the contributor's
article myself and e-mail it to him with a note asking if this is what
he would have said, if he had ever got around to it.

On Tuesday, March 2, 2021 at 9:39:44 PM UTC+11, Liz Tuddenham wrote:

 for  

wasn't  

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Not an option with my contributors. It's mostly about what their particular
 chapter did. The only article I've got so far by a relatively young profes
sor reporting a presentation about adding in-band signalling to low voltage
 DC distribution set-ups, and included the usual references to the Internet
 of Things.

On Monday, 1 March 2021 at 08:57:29 UTC-8, bitrex wrote:
...


Often it is more the other way round that the system detects the battery is above about 80% charged and reduces the output voltage of the alternator (Honda reduces it to ~12.5V). If the battery is below 80% SOC the voltage will be ~13.8-14.5v.

Older cars used the same voltage (13.8-15V) independent of battery state-of-charge.

Modern maintenance-free batteries use a lower max voltage to avoid excessive gassing.

On 3/1/2021 6:24 PM, snipped-for-privacy@kjwdesigns.com wrote:


I wonder if it detects somehow whether there's a regular flooded  
lead-acid or an AGM battery in there. AGMs are sensitive to overcharging  
so maybe just assumes it. I see that all Hondas (and maybe all cars)  
that do auto-stop have AGM batteries stock.

On 3/1/2021 8:10 PM, bitrex wrote:


Particularly sensitive I should say

On Monday, March 1, 2021 at 6:24:19 PM UTC-5, snipped-for-privacy@kjwdesigns.com wrote:

  

  

  

is above about 80% charged and reduces the output voltage of the alternator
 (Honda reduces it to ~12.5V). If the battery is below 80% SOC the voltage  
will be ~13.8-14.5v.  

of-charge.  

ive gassing.

That doesn't make much sense.  I think you mean when the voltage rises they
 reduce the current.  When a battery is low the voltage is low and you aren
't going to raise it much unless you pump a huge current into it.  As it ch
arges the voltage rises.  When it is getting near topped off they limit the
 voltage and let the current drop off.  Once reaching nearly a full charge  
the voltage can be dropped back to a "float" charge level, but I don't thin
k cars do that.  It would make the headlights dim and such.  I think the al
ternator puts out a max current at whatever voltage the battery takes, then
 cuts back the current at the max voltage.  

On 3/3/2021 2:00 AM, Rick C wrote:


Headlight aren't just dumb bulbs connected straight to the supply bus no  
more.

On 03/03/2021 12:45, bitrex wrote:











The internal resistance of a lead acid battery is so low that headlamps  
would not be much dimmer with the alternator backed off maximum output.  
I'd guess filament headlamp provide quite a nice ballast load.

Even when they were it would be a puny alternator that couldn't power  
headlights and still charge the battery a little. Dynamos in old cars  
tended to struggle in British long dark winters with push starts needed  
back in the good old days when batteries often went flat in mid winter.