Date:         Fri, 4 Sep 2009 13:17:43 -0700
Reply-To:     Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject:      Re: Only 13V from Alternator
In-Reply-To:  <2f18aa9f0909041016w6605ecarb9d60c34feb87d8e@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I know what Jeff is saying here, but I have to respectfully disagree.

As I understand it, the voltage regulator in the alternator does not know
the battery state of charge. State of charge cannot be determined by
measuring battery terminal voltage under charge.

It can be determined with a hydrometer, or it can be derived pretty well
by measuring how much current flows into the battery when a charging
voltage is applied. But the regulator in our Vanagons has no hydrometer to
use, nor any way to measure the current flowing into the battery. All the
regulator does for a living is keep the voltage at the output of the
alternator set to a pre-determined voltage.

13V seems low.

Steve, you said you measured the output of the alternator and got 13V. Was
that right at the B+ terminal on the alternator, or somewhere downstream?

--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
Bend, OR
KG6RCR



On 9/4/2009 10:16 AM VW Doka wrote:

> Steve,
>
> Depending on the charge state of your battery, 13V is perfectly fine.
> If you're recharging at night, your battery will require very little
> "topping off" after starting the engine.
>
> Cheers,
>
> Jeff
>
>
>
> On Fri, Sep 4, 2009 at 12:37 PM, Steve Williams<sbw@sbw.org> wrote:
>> I've known for awhile that the batteries aren't getting charged while
>> I drive.  The ProMariner has been saving me: It charges the batteries
>> each night while I'm parked.
>>
>> But I just measured the alternator output at idle and at 2,000 rpm:
>> 13 volts.  My understanding is that it should be 14.2-14.4 volts.
>>
>> So, is it pretty easy to replace just the regulator on the
>> road?  Somebody point me to a how-to?  (It's mounted on the alternator,
>> right?)
>>
>> Or should I bite the bullet and just get a whole alternator with the
>> integrated regulator?
>>
>> I'm planning to drive some remote stretches on the way back to
>> California, and I don't want to get stuck.
>>
>> http://twitter.com/sbwsty
>>
>> Thanks.
>>
>