Date:         Fri, 28 Jan 2000 14:47:51 -0800
Reply-To:     andrew swingler <andys@ECE.UBC.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         andrew swingler <andys@ECE.UBC.CA>
Subject:      Re: more ???? Re: Diesel alternator
In-Reply-To:  <01BF69A0.2258EC00.m.radtke@elm.az05.bull.com>
Content-Type: TEXT/PLAIN; charset=US-ASCII

> Andy et al,
>
> Some charge current notes:
>
> 1) Alternators naturally current limit at their rated current.

Only if the 'internal' regulator is designed to do so. THis is not always
the case, especially for the external regulators that don't know what the
current is.

> 2) If 13.8 volts is applied (room temp) to a good battery, the
>    battery limits itself to a safe charging current.

Possibly for a starting battery that is not discharged completely. Try
maintaining 13.8V while charging a completely discharged deep cycle
battery, you'll be surprised at what the charge current is. I have test
results for various batteries if you really want to know.

> 3) VW does it wrong.  The VW alternator regulator voltage senses
>    at the alternator terminal.  The correct place to voltage
>    sense is at the battery, and many cars do.  Please see #2.

Agreed, this is necessary for 'properly' controlling charging. But the VW
method works just fine for practical purposes.
>
> 4) The heavier the charging cable the better since the reduced
>    voltage drop reduces the error introduced by #3.

.....resulting in increased charge current. Gotta be careful here because
it is sometimes good to limit the charge current. Don't want to fill our
vans full of hydrogen gas do we ??


I'm not sure if the VW alternators have a current linit in their
regulators. If so does anyone know how it works?