[T3] I don't know why yet for some reason my 73 T3 chargingsystem seems off.

Thu Jun 29 16:45:08 PDT 2017

 Thanks for the info Jim.

 The only reason I use the charger is lets say I drive 3 miles twice a week 
and all of this is stop and go street traffic and I start the car 2 to 4 
times and most of the time I'm sitting at a light or traffic . I have found 
if I do this twice a week by the third time I can tell the engine cranks a 
bit slower, and checking the battery voltage instead of 12.72 volts it's at 
12.4 even though the battery is 14 months old . I really noticed it when we 
had a garage fire Sept 30  2015 and I had no power in my garage for  3 
months . If you get down to 12 volts an Battery is getting near damage point 
. It was different when I drove 6 days a week 14 mile round trips to work it 
have time to charge fully. If I let is sit and didn't start it at all and 
have no draw I would just check and maintain as needed. I realize the 
starter does not draw much to start the car yet it's enough drain plus the 
sitting at idle for the battery to drop voltage . The 2 amp charge for 2 
hours each night I feel just keeps the battery from going down in voltage . 
I checked how much voltage at the 2 amp setting is and it's 13.5 and I don't 
see the amp gauge on the charger move . Made the mistake of setting it on 
the 12 amp setting three years ago and saw a 3 amp charge and 15 volts , 
well that didn't take long to ruin that 5 year old autozone battery life.

 I haven't attempted to figure out even it I could how much each start draws 
down a 45 AH battery ,think that's what a interstate MT-42 is, or how much 
it charges in this stop and go sitting . Today I drove it after is sat for 3 
days with the 2 amp 2 hour charge , started it twice and drove it about 4 
miles I'd say 50% of the time it was at 14.1 volts and the rest was 13.5 and 
then 12,45 and shut it down and saw 13.4 volts as the surface charge which 
is fine . Other times if I drive the same distance yet start it 4 times and 
sit I've seen it at 12 volts when started the 4th time yet it comes back to 
14.1 to 14.2 .

 I probably don't need to keep it on the charger every day with the 2 amp 2 
hour deal and when the power was out I couldn't yet after a few of these 
same 3 to 4 miles trips after 4 of these trips the battery was sitting at 
12.4 volts so I'd run extension cords out there and charge it for 3 to 4 
hours on 2 amp which would bring it back to 12.65 volts after the surface 
charge drain off over night. When I did that I could see 1 1/2 amp yet this 
charger tapers off as the battery charges so after 2 hours it was 1/2 amp.

 Perhaps i'll set it for 2 amp for 1 hour for 2 APH  instead of 4 as it is 
now.
----- Original Message ----- 
From: "Jim Adney" <jadney at vwtype3.org>
To: <type3 at vwtype3.org>
Sent: Thursday, June 29, 2017 2:37 PM
Subject: Re: [T3] I don't know why yet for some reason my 73 T3 
chargingsystem seems off.

> On 29 Jun 2017 at 13:17, William J wrote:
>
>>  Why at 1000 engine RPM I read 14.2 VDC and at 800 engine RPM I read
>> 14.1 and as I idle at a stop the voltage drops to 13.5 and the longer
>> I sit and idle it will drop to 12.34 Volts ? As soon as I step on the
>> gas to drive off it jumps back to 14.2 volts. 14,2 volts is the
>> highest reading I will get even at 2500 rpm. Once I shut it off with
>> DVOM still connected the battery read 13.45 volts which is surface
>> charge. It settles to 12.72 Volts over night. To add I don't drive
>> much or very far so I keep a charger connected on the 12 volt 2 amp
>> setting on a timer set for 2 hours each day it sits and after short
>> drives with no less than 4 starts just to keep the battery topped off.
>
> Everything here is perfectly normal. Think of it this way. If not for the 
> voltage
> regulator the generator output voltage would be proportional to generator
> rpm. It starts with zero output at zero rpm and rise in a straight line as 
> the
> rpm rises.
>
> We can divide the generator operation into 3 regions:
>
> 1) Low RPM, when the generator field windings are fully energized, but the
> output voltage is still less than the battery voltage. Under these 
> conditions
> the battery would normally push current backwards thru the generator. The
> voltage regulator prevents this. (It's not perfect, but it's close enough 
> to
> ignore the difference.) In this RPM range, no current comes out of the
> generator.
>
> 2) Medium RPM, when the generator output voltage is between the stable
> overnight voltage and the regulating voltage (14.1-14.4 V.) In this range, 
> the
> voltage regulator is still fully energizing the generator field windings,
> allowing the generator to put out whatever voltage it's capable of. In 
> this
> range, the generator will put out whatever current the car needs, plus any
> current the battery needs to bring it up to that voltage. (The voltage 
> regulator
> may cut back on the output current if it approaches the current limit, but 
> this
> seldom happens in normal operation.)
>
> 3) Higher RPM, when the generator has reached the RPM where it is
> capable of generating voltages higher than the regulating voltage 
> (14.1-14.4
> V.) At this point, the voltage regulator reduces the amount of current
> supplied to the field coils, limiting the output voltage to the regulating
> voltage. At this point, the generator and the output voltage are "in 
> control."
> This is where the charging system spends most of its time when you're
> driving. In this range, the generator provides all the current that the 
> car
> needs, plus perhaps a bit more to bring the battery up to charge. Most of 
> this
> time, there's NO current coming in or out of the battery under these
> conditions.
>
> At idle, theres no output from the generator. When you run the engine 
> above
> idle it charges the battery. The voltage regulator limits the generator 
> output
> voltage to something between 14.1 and 14.4 V. When you come back to idle
> the generator is no longer doing any charging, so the full battery voltage
> slowly drops back down, as the car draws power from the battery.
>
> The battery discharge curve is not linear, so as it discharges, the 
> voltage
> falls rather quickly from 14+ to the mid 12s. This is normal.
>
> Unless you don't drive the car for a month or more, it's really 
> unnecessary to
> use the charger. I finally bought a solar charger to keep my Square 
> charged
> in the winter, when it seldom gets driven, but I had to modify the circuit
> inside it to prevent reverse discharge at night and to provide a 
> reasonable
> indicator LED output. All it takes is 20-50 mA during the day to maintain
> itself.
>
> -- 
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
> _______________________________________________
> VWType3.Org mailing list - type3 at vwtype3.org
> To unsubscribe or change subscription options, visit:
> http://lists.vwtype3.org/listinfo.cgi/type3-vwtype3.org
> If you need more help, contact: gregm at vwtype3.org
> 

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus