[Vwdiesel] Cold WX Starting, VW Diesel

[kayser at sympatico.ca]

Greetings!

A chap on this list, Sandy Cameron, suggesting this idea and I tried it three times this past winter when the
temperature dropped below –20C here.

My car is a ’91 Jetta, NA, manual approaching 300K kms, probably best described as a “bit tired”.

I bought a standard and amazingly cheap 300W inverter, package rated by Canadian Tire at 400W (but they
only lied a little bit) and took a well-charged 12V battery over the ice to the mainland.  There I plugged the
block heater in the VW into the Inverter and quickly gave a nasty discharge to the 12V battery.  In 12 to 15
minutes the VW block was plenty warm enough and the car started easily.

This technique has some problems however.  The 12V battery is normally very cold and the internal
resistance is appreciable and the terminal voltage drops rather quickly.  The internal low voltage alarm on
the Inverter kicks in at about the 10 minute mark.  To get by this little problem I put three Gates Gell cells,
the 25AH type, in parallel and put them on the end of the 12V battery.  This is in similar fashion to what
the telephone company has been doing for many many years and is called an “End Cell” operation, adding
an extra cell on the end of the string to keep the voltage up.  This gets me past the 15 minute mark.  This
solution is not elegant but it does beat hauling the generator over to the mainland to warm up the VW block
heater.

I will make two short observations on some previous posts.

First, putting TWO or more auto batteries in parallel on one alternator is a sure-fire way undercharge one
and overcharge the other eventually destroying one or both of the batteries.  There absolutely must be an
equalizing series resistance to each of the batteries.  I have over the years studied carefully a number of
dual battery designs in vehicles, GM and Ford mainly.  In most cases I find that the designer has made use
of the internal resistance, I^2R loss for those inclined, of the cables was used as the equalizing source
resistance.    Normally in these cases the Alternator put out an extra .3 to .5 V when it was doing the heavy
lifting of recharging the batteries.  This extra voltage makes a mess out of regular batteries over a period of
many months when there is no equalizing resistance present.

Not for discussion here but if you absolutely must destroy lead acid batteries use one of those diode block
isolators to parallel batteries for charging.  If you can not adjust the alternator operating voltage up .6V DC
over normal floating voltage you will eventually destroy the batteries.

Second, there was some rather negative comments about the Cruise Control on the Auddi/VW series with
regard to what my wife and I call  “take off” when the cruise control grabs the throttle and tries to take
over.  She had a ‘91 Passat automatic with cruise control from 1991 until late in 2000 (350+K Kms).  This
car could be easily provoked to “take off” at any time – we learned quickly to keep the Cruise Control OFF
at all times unless it was being used.  If you had the Cruise Control ON and not being used, waited about 5
minutes in that condition and then pushed “Resume” you had instant “take off”.   It would frequently do
this if you started the engine with Cruise Control ON and pumped the brakes a few times as you  backed
out of the garage.  We learned to keep the Cruise Control OFF, and checked it was OFF frequently.

I am not a VW specialist, just a happy owner of the Jetta and someday owner of a Jetta TDI Wagon if I live
long enough.  I do know a fair amount about batteries, I built a NiCd battery back in 1984 that has lasted
through some 100,000 charge / discharge cycles, yes every 90 plus minutes for over 19 years.  The battery
still works perfectly and is powering the longest lived amateur radio spacecraft in history that is not a
derelict polluter of the radio spectrum.

Larry
VA3LK  / WA3ZIA