Date: Fri, 10 Jan 2014 00:06:08 -0800
Reply-To: "SDF ( Scott Daniel Foss )" <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "SDF ( Scott Daniel Foss )" <scottdaniel@TURBOVANS.COM>
Organization: Cosmic Reminders
Subject: Re: Battery Voltage under cold starting load?
In-Reply-To: <CAO+YcsL1wre31he_S=DsX+SmGcDMxqjO0WyU=t0SfemZ9m7R7g@mail.gmail.com>
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I'd say about 10.5 volts is 'minimum acceptable' at the ecu.
Battery voltage during starter cranking..
starting out with a battery at a resting voltage of 12.6 volts say ..
I wouldn't want to see that voltage drop below 11 volts maybe .
I also like having a Battery Load Tester.
$ 52 at HF I think I paid..
totally worth it for checking batts.
you clip it on , read the resting voltage, flip the switch to load ..
then see where the needle points .
like green area, yellow, or red.
if a battery drops to say ....8 volts and sinking, with load applied..
it's no good.
A good battery will maintain 11.5 volts for ...I never load them for
more than maybe 10 seconds..a
weak battery is immediately apparent .
'exalted members' ..I just know what works and what is about right. No
need to get all exotic and complicated about it.
12 volt DC car systems have not changed fundamentally , the basic
principles, in 70 years since cars started having 12 volt DC batteries.
The systems have evolved sure, ..
and a lead-acid cell still produces 2 volts when it's healthy ..the
basics of that have not changed .
That's like chemical ..and that doesn't change . Still the same
electrons moving from annode to the other node ...or vice versa, like
it's been all along.
I've had poor starting situations that were lack of enough voltage where
you wanted it ..
and I had several starters to try, several batteries ..great charging
voltage and had it take a long time to get enough of the little suckers
to the right places at the right times..
matter of battery cable sizes, good connections etc. That can be
nebulous to fix sometimes. It's not always just a clear case of weak
charging, bad starter, tired battery etc. Sometimes it' s far more
subtle than that.
Scott
On 1/9/2014 10:32 AM, Al Knoll wrote:
> Yah, I know, I should know all about this, but I live under my sunny rock.
>
> With cold weather, the ability of the Lead Acid flooded cell battery to
> deliver starting current to the vanagon starter is diminished. Yup.
>
> How low can the voltage go before the ECU decides to not produce FI
> pulses? 9V? 8V? or?
>
> The internal resistance of the battery is a function of temperature and
> with the ideal battery that resistance is zero. ( No, Ben, Ideal batteries
> are not available so we have to make do with what is available. ) As
> batteries age, the internal resistance rises, much like mineself.
>
> IFF you measure the voltage at the ECU under starting loads what should you
> read. IF you measure the voltage at the battery terminals under the
> starting loads what should you read?
>
> What are the boundary conditions for these voltages and what is the no-go
> threshold? Surely one of the exalted members has done extensive research
> in this matter and would be pleased to offer data. (We already have lots
> of opinions, mostly divergent) .
>
> I no longer own a WBX nor it's FI system so I can't do the experiment.
> FWIW establishing these boundary conditions is neither simple nor easy.
>
> Pensionerd.
>
