Automotive electronics - Honda charging system

Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:
> Not just gadgets, many cars have electric power steering, electric
> water pumps etc. 
 
> --sp 
 
Thanks. I didn't know that. It sounds silly. To go from a pully on a power 
steering pump, to a pully on the alternator, then to an electric motor to 
drive the power steering pump or water pump, seems like a huge waste of 
energy. It has to affect gas mileage.

Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:

> On Tue, 18 Jul 2017 02:55:02 GMT, the renowned Steve Wilson
> <no@spam.com> wrote:

>>I doubt fuel economy has much to do with it. Modern cars start so
>>quickly that little energy is drawn from the battery. At 14.5V, the
>>energy is replaced in a few minutes, then the battery drain drops to
>>negligible level. Where you get the huge drain is heated seats, rear
>>window defrost, high power audio systems, and all the various electronic
>>gadgets that add to the alternator drain. Charging the battery is
>>completely negligible, if the car manufacturers would settle on the
>>correct voltage. 
 
> Not just gadgets, many cars have electric power steering, electric
> water pumps etc. 
> --sp 
 
Thanks for the info. I did some research and found some good reasons for
the switch to electric motors. 

1. Power Steering

Electric power steering has some significant advantages over any form of
conventional hydraulic steering, both for the owner of the car and its
manufacturer. The reduction in engine load of an electric power steering
system (it can be as low as 4 watts when the car is being driven in a
straight line) means that the fuel economy of a car equipped with electric
power steering is very similar to that of a car with no form of power
steering. Analyses provided by manufacturers of electric power steering
systems indicate potential fuel savings of 4-8 per cent over cars equipped
with conventional hydraulic steering, with the lighter mass of an electric
power steering also having an impact here. The independence of the system
from engine operation also means that should the engine stall, steering
assistance does not change. 

http://www.autospeed.com/cms/article.html?&title=Electric-Power-Steering&A=
110661 

2. Not all agree it's better

Electrically assisted power steering (EPS) is the latest technological
cross we bear. Replacing hydraulic assist with a computer-controlled
electric motor seemed like a reasonable idea when it first surfaced.
Someday every car control will be by-wire; today&#4294967295;s EPS looks like a step
in that direction. But in the past decade of driving EPS-equipped cars,
we&#4294967295;ve found them lacking in feel, poorly tuned, and sometimes simply weird
in comparison with the hydraulic-assist setups that have benefited from
more than half a century of development. 

http://www.caranddriver.com/features/electric-vs-hydraulic-steering-a-compr
ehensive-comparison-test-feature 

3. Water Pump

According to Davies Craig, an electric water pump has a number of
advantages over the engine-driven variety. They point out an EWP will
increase power sent to the drive wheels because the power the mechanical
pump takes from the engine increases dramatically with its speed&#4294967295;when the
pump speed doubles from idle, say 600 rpm to 1,200 rpm, the power it takes
increases by eight times, then eight times going to 2,400 rpm and so on.
This extra power and torque released by disabling the mechanical pump now
goes to the drive wheels. Additional benefits of an electric pump are
improved cooling capacity and fuel economy along with the elimination of
engine heat soak after a hot shut down. Engine cooling is improved with an
EWP thanks to a higher flow rate at idle and low engine speeds when there
is little or no ram air, and when the engine is switched off. 

http://www.hotrod.com/articles/davies-craig-reinvents-the-electric-water-pu
mp/ 

These arguments make good sense. Thanks.

On Saturday, July 15, 2017 at 5:09:06 PM UTC-7, pcdh...@gmail.com wrote:
...
> IOW large lead-acid batteries have very low impedances, which is more or less the point. The open-circuit alternator voltage will be nearly proportional to rotor speed till iron and copper loss take over. That's why I suggested a smaller alternator pulley (upthread someplace.)
> 
> Cheers
> 
> Phil Hobbs

The pulley size on car alternators is usually selected to give a maximum alternator speed of abut 12,500 RPM at the maximum engine speed - beyond that speed the slip-ring contact, bearings and structural strength of the rotor etc start to have problems.

At that speed the open circuit voltage will probably be in the 100-150v range - it is even possible to get 120V AC from a car alternator by modifying the regulator. At idle speed there should still be enough to provide power to the 12v system.

The output impedance of the alternator is highly inductive and since the impedance rises proportional to frequency the current is somewhat independent of engine speed. Most alternators do not have any specific current limiting - they just rely on this inductance.

kevin

Take a look at the first paragraph in this detailed description of the Honda Dual-Mode Charging System. The CAFE standards have resulted in charging systems doing what they can to minimize alternator load.

http://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1011&context=auto_pres

Yesterday I recharged my battery and wrote down some very interesting data. I feel much better about my voltage regulator settings at least for the initial part of the charge. My battery was discharged enough for my 2 amp charger to run for 55 minutes. The battery started at a voltage of 12.75 volts and charged at 2 amps for the full 55 minutes. I checked the voltage at the battery posts and watched the voltage rise all the way from 12.93 volts to 14.26 volts. The rise was fairly steep initially taking 1 minute to reach 13.27 volts and 8 minutes to reach 14 volts. The rise then became more gradual with the voltage rising to 14.26 volts after 55 minutes.

If an alternator had been doing the charging at a relatively constant voltage, the charge current would have been quite high initially followed by a gradual decline. Consider the factors that determine charge current.

A simple model for a lead-acid battery would be a variable ideal voltage source in series with a variable series resistance.  It's easy to see that charging current could be calculated using Ohm's Law.  The three variables would be alternator voltage, battery voltage, and the series resistance.  Current will flow whenever the alternator voltage is just slightly higher than the battery voltage which may include surface charge.

The remaining issue is what happens after surface charge builds up. It is probably not a problem if the battery is near full charge. However, if a battery is at 50% charge, it takes time and amperage to restore the charge. The voltage regulator settings might be more important for this case to achieve the required charging current.  Short trips would be an additional concern.

kt77 <kawill70@gmail.com> wrote:

> Take a look at the first paragraph in this detailed description of the
> Honda Dual-Mode Charging System. The CAFE standards have resulted in
> charging systems doing what they can to minimize alternator load. 
> 
> http://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1011&context=auto
> _pres 
> 
> Yesterday I recharged my battery and wrote down some very interesting
> data. I feel much better about my voltage regulator settings at least
> for the initial part of the charge. My battery was discharged enough for
> my 2 amp charger to run for 55 minutes. The battery started at a voltage
> of 12.75 volts and charged at 2 amps for the full 55 minutes. I checked
> the voltage at the battery posts and watched the voltage rise all the
> way from 12.93 volts to 14.26 volts. The rise was fairly steep initially
> taking 1 minute to reach 13.27 volts and 8 minutes to reach 14 volts.
> The rise then became more gradual with the voltage rising to 14.26 volts
> after 55 minutes. 

You still never made it to 14.5V

> If an alternator had been doing the charging at a relatively constant
> voltage, the charge current would have been quite high initially
> followed by a gradual decline. Consider the factors that determine
> charge current. 

> A simple model for a lead-acid battery would be a variable ideal voltage
> source in series with a variable series resistance.  It's easy to see
> that charging current could be calculated using Ohm's Law.  The three
> variables would be alternator voltage, battery voltage, and the series
> resistance.  Current will flow whenever the alternator voltage is just
> slightly higher than the battery voltage which may include surface
> charge. 

> The remaining issue is what happens after surface charge builds up. It
> is probably not a problem if the battery is near full charge. However,
> if a battery is at 50% charge, it takes time and amperage to restore the
> charge. The voltage regulator settings might be more important for this
> case to achieve the required charging current.  Short trips would be an
> additional concern. 

It looks like you need to put your battery on charge after every trip. 

Sorry if this is a dupe. Newsgroup did something wierd on the first try.

kt77 <kawill70@gmail.com> wrote:

> Take a look at the first paragraph in this detailed description of the
> Honda Dual-Mode Charging System. The CAFE standards have resulted in
> charging systems doing what they can to minimize alternator load. 
> 
> http://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1011&context=auto
> _pres 
 
> Yesterday I recharged my battery and wrote down some very interesting
> data. I feel much better about my voltage regulator settings at least
> for the initial part of the charge. My battery was discharged enough for
> my 2 amp charger to run for 55 minutes. The battery started at a voltage
> of 12.75 volts and charged at 2 amps for the full 55 minutes. I checked
> the voltage at the battery posts and watched the voltage rise all the
> way from 12.93 volts to 14.26 volts. The rise was fairly steep initially
> taking 1 minute to reach 13.27 volts and 8 minutes to reach 14 volts.
> The rise then became more gradual with the voltage rising to 14.26 volts
> after 55 minutes. 

You never made it to 14.5V
 
> If an alternator had been doing the charging at a relatively constant
> voltage, the charge current would have been quite high initially
> followed by a gradual decline. Consider the factors that determine
> charge current. 
 
> A simple model for a lead-acid battery would be a variable ideal voltage
> source in series with a variable series resistance.  It's easy to see
> that charging current could be calculated using Ohm's Law.  The three
> variables would be alternator voltage, battery voltage, and the series
> resistance.  Current will flow whenever the alternator voltage is just
> slightly higher than the battery voltage which may include surface
> charge. 

LTspice uses a large capacitor as a model for a battery.
 
> The remaining issue is what happens after surface charge builds up. It
> is probably not a problem if the battery is near full charge. However,
> if a battery is at 50% charge, it takes time and amperage to restore the
> charge. The voltage regulator settings might be more important for this
> case to achieve the required charging current.  Short trips would be an
> additional concern. 

You may need to put your battery on charge after every trip. 

On Tue, 18 Jul 2017 15:45:54 GMT, the renowned Steve Wilson
<no@spam.com> wrote:

>
>
>These arguments make good sense. Thanks.

Nice answers. I think another factor is that the accessories can run
for brief periods from the battery so more of the HP from the engine
is available to drive the wheels when passing or going up a steep
hill, thus allowing a smaller displacement IC engine to give the same
performance as a larger one (which also reduces fuel consumption). 

The servo steering can easily be made speed sensitive, which improves
the driving experience. 

--sp 


-- 
Best regards, 
Spehro Pefhany

Den onsdag den 19. juli 2017 kl. 00.48.22 UTC+2 skrev Spehro Pefhany:
> On Tue, 18 Jul 2017 15:45:54 GMT, the renowned Steve Wilson
> <no@spam.com> wrote:
> 
> >
> >
> >These arguments make good sense. Thanks.
> 
> Nice answers. I think another factor is that the accessories can run
> for brief periods from the battery so more of the HP from the engine
> is available to drive the wheels when passing or going up a steep
> hill, thus allowing a smaller displacement IC engine to give the same
> performance as a larger one (which also reduces fuel consumption). 
> 
> The servo steering can easily be made speed sensitive, which improves
> the driving experience. 
> 

and you get much more freedom on where you can place the various accessories 

Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:

> On Tue, 18 Jul 2017 15:45:54 GMT, the renowned Steve Wilson
> <no@spam.com> wrote:

>>These arguments make good sense. Thanks.
 
> Nice answers. I think another factor is that the accessories can run
> for brief periods from the battery so more of the HP from the engine
> is available to drive the wheels when passing or going up a steep
> hill, thus allowing a smaller displacement IC engine to give the same
> performance as a larger one (which also reduces fuel consumption). 
 
> The servo steering can easily be made speed sensitive, which improves
> the driving experience. 
 
> --sp 
 
I really like the idea of not losing power steering if the engine quits. If 
you have ever lost the engine in a high speed curve on the side of a 
mountain, you may agree there is probably little that is so frightening.

Steve Wilson says...

 > I think the problem is not so much measuring the battery
 > voltage as much as convincing the alternator to ignore
 > the commands from the PCM and set the charging voltage
 > to 14.5V. Then the battery will be fully charged, even
 > on short trips.

My Honda keeps the alternator at 14.4V so long as the
headlights are on.  That shouldn't be necessary, but seems
to work.