Date:         Fri, 4 Aug 2000 22:07:38 -0400
Reply-To:     David Beierl <dbeierl@attglobal.net>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@attglobal.net>
Subject:      Re: Alternator regulator voltage tolerances #
Comments: To: d t <tinkerman@usa.net>
In-Reply-To:  <20000803223926.28126.qmail@nwcst312.netaddress.usa.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 18:39 8/3/2000, d t wrote:
>  (a battery should be charged to 14.4V and
>then charging stopped (cycle mode),

Right.

>  or left constantly charged to 13.8V (float
>mode),

Right

>  or a combination of both (smart algorithms).

Even better.

>  A battery should NOT be
>constantly charged to 14.4V because it will overcharge and dry out).

Right.  Even possibly go into thermal runaway and burst...

>The problem is that due to charging circuit resistances between the alternator
>and the battery, the voltage reaching the battery varies, depending on the
>load on the battery (because they're connected at the battery, NOT at the
>alternator and the alternator doesn't have remote sense as it should).

So...you can run a sense wire from the regulator to the battery instead of
picking up the internal contact, or you can beef up the wiring between, or
both.  I'd start by finding out exactly where that 0.6v is being dropped,
fix the bad crimp or whatever, then think about whether you need heavier
wires or remote sensing, or neither.


>What compromise would you recommend (I can install either a 14.4V or 15V
>regulator with about 0.6V voltage drop on the wiring)?

Fix the wiring...that melted insulation is such a nuisance.  Half a volt at
90 amps is 50 watts... :)

>The best would of course an adjustable regulator, preferably 2-step (13.8V and
>14.4V).

Next Step regulator, http://www.amplepower.com/ -- does bulk charge to
setpoint voltage (temperature compensated, it measures battery temp), then
absorption charge for a set time (adjustable), then shifts to float.  Has
an input to lock it in float mode so you don't burn out your halogen lights.

Of course there are a couple little issues: 1) it costs $300 and 2) you'll
find out whether a Bosch alternator can sustain full output without smoking
(in which case a hot-rated alternator will run another $300 or so).

david
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"