Date:         Tue, 20 Apr 2010 21:03:46 -0400
Reply-To:     Ian Allan <ian.allan@BMTS.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Ian Allan <ian.allan@BMTS.COM>
Subject:      charging aux battery: too much of a good thing?
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Mark:

Congrats on the Bostig.  Very intelligent:-)

I think that the Ford alternator is 105 amp. Much more than that needs
a serious drive pulley. I think that there should be an ID tag on the
alternator with that info.

So far as the batteries are concerned I think you are good to go.
Don't change a thing unless you find that the batteries are quite hot
to the touch or you have to add water on a regular basis. To get a
lead acid battery to full charge you need voltage in the high thirteen
to low fourteen volt range/ 13.6 won't cut it but will never hurt the
batteries. The real test is to apply a digital voltmeter across the
battery terminals after the engine has been running for at least 10
minutes.

Hey, here is a little caution with the Surepower. Be aware that after
shutdown and pulling the neg. terminal on your main battery, the
batteries remain banked for some time. I think from 2 to 5 minutes
before the Surepower switch isolates the batteries from each other.

> Today I was able to fire up my 3 battery system for the first time. A
> dedicated 125 amp hour deep cycle was added for the Vitrifrigo fridge
> only. With the Zetec it fits easily in the engine compartment and is a
> foot from the alternator. I used short #6 wires with a Surepower 1314
> between the alternator and the battery, and ran #6 between the neg
> post
> and the engine block.
>
> As part of this setup I added an amp meter for the fridge battery so I
> could see how fast it was charging and then know how long I needed to
> run the engine to get another night of camping. I was surprised to see
> the meter reading over 60 amps going into the battery when I first
> started the engine even though the battery was fairly full. This
> quickly
> tapered down over a few minutes to a steady 25 amps. I wonder if
> maybe I
> have too much charging?
>
> I have not been able to pin down the capacity of this Ford
> alternator. I
> have seen it listed as 105 amp, 115 amp, and 130 amp. I don't care
> much
> either way as 105 would be plenty but it would be good to know. I am
> measuring 14.5+ volts at the alternator which I believe is pretty
> common
> with modern vehicles but I wonder how good it will be for the battery
> long term.  I could slow down the charging rate by switching to longer
> and thinner battery cables but this would not drop the voltage much
> after the battery was full. That seems too high for a "float charge"
> but
> I don't know how it will be in practice. Anybody know? Suggestions?
>
>
> Mark
>

Ian Allan

94 Eurovan Westfalia
86 Syncro
85 Westfalia/Bostig
84 Westfalia
02 Jetta 1.8t