Date: Sat, 5 Sep 2009 12:31:14 -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: <BAY132-DS524A771AA5F51ADCA9FEAA0ED0@phx.gbl>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
And Dennis is absolutely right, too. There are states of operation where
one cannot expect the alternator to get enough voltage to the battery to
put much into it. Low rpms -- like idle -- may not let the regulator
achieve regulation, you can check this with a voltmeter at the B terminal
on the alternator. Heavy loads downstream -- lights and suchlike -- can
create significant enough resistance losses ("wire losses") that the
battery just isn't seeing enough voltage to push current into it.
--
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 9/5/2009 7:27 AM Dennis Haynes wrote:
> You're absolutely right. However, depending on system load and a battery at
> a low state of charge, the alternator may not produce enough current at idle
> to reach or maintain the set voltage. In fact, with enough accessories and
> lights, fans, etc, the alternator and especially the VW wiring will not
> maintain voltage with the alternator at any speed.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Rocket J Squirrel
> Sent: Friday, September 04, 2009 4:18 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Only 13V from Alternator
>
> 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.
>>>
>
>
| 
