Date: Sun, 14 Oct 2012 14:55:22 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Overheated wire junction on 1.9
In-Reply-To: <CAB2Rwfi+3UMCFFqSctSR6cSZfn3NmJ9vnGJikdtTit4u4B9eOQ@mail.gmail.com>
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I'm pretty sure the idea in a two battery system is to have it wired so
that starting current only comes from the starter battery.
- as in the stock Westy system. ( rather clever actually ..current to
the aux battery is not switched in until not only has the engine been
fired up, the alternator is charging. )
So ...if someone has a circuit where starting current can come from the
aux battery ..
and they didn't flip some switch to make that happen ....that is a problem.
One would not want to start off both batteries ..
as one could be quite low on charge, sucking juice from the good
battery, obviously.
my very low tech solution is two complete 'full battery cable' size
charging and starting circuits, with manual on/off battery switches for
each battery . Putting that switch in the negative cable works just fine.
I place the switches where they are reachable easily in the cockpit.
That way ...full redundancy -
can start off either battery.
Can use either battery as the house battery,
or can start off both batts. together.
and you chose whether you want to charge both at once, or just one at a
time.
plus the batt. switches I use have a 'key' that comes out ..making them
anti-theft devices too.
There is only *one* thing to be careful about - at least one of the
batteries has to be the circuit while the engine is running.
And of course, don't run down both batteries parked using 'house' circuits.
What it comes down to is ..
After you fire up the engine, you switch in charging to the aux batt.
When you park, you open that switch ..
and you wire it so house features only draw from the aux battery.
like a small older aircraft....full manual control of everything.
You have to 'think' a little ...like it's not automatic, but it's low
tech, and very versatile.
The weight and cost of the extra battery cables are about the only
downside, and that's not a very big penalty.
Scott
On 10/14/2012 11:36 AM, neil n wrote:
> Thanks for pointing that out. My apologies to all for such an inexact post!
>
> I neglected to write what I was "seeing".
>
> Right. Ok. In that incorrect scenario, if starter battery was low,
> starter would pull power from aux. battery.
>
> In past I've connected loads to the starter motor post (engine swap
> stuff). I would do same for a new aux. battery as well as include an
> isolator and fuse.
>
> Neil.
>
> On Sun, Oct 14, 2012 at 11:10 AM, mark drillock <mdrillock@cox.net> wrote:
>> There is some danger to that as a general suggestion and it should not be
>> commonly done because of this.
>>
>> Connecting another battery with heavy wire directly to the alternator runs
>> the risk that someday that battery will be called on to supply the majority
>> of the starter motor current! While the new heavy wire could support this
>> the next wire segment between the alternator and starter motor was never
>> intended for starting current! It is safer to connect the new heavy wire
>> from the new battery to the starter post, and then to beef up the wire from
>> the starter to the alternator to allow better charging of both batteries.
>> The previously linked to product from VanCafe fills the role of the beefed
>> up wire from alternator to starter.
>>
>> Mark
>>
>>
>>
>> neil n wrote:
>>> That's useful info.
>>>
>>> I can't state this as a fact, but IMO, it seems the OEM aux. battery
>>> setup was designed for low draw appliances. It works fine for that.
>>> But. If one plans to install higher draw appliances and/or lots of
>>> "bells and whistles" (i.e. digital ice cream maker), as per your
>>> comments and observations, IMO, installing a new (fused?) large gauge
>>> wire from alternator to new battery(s), is a great start.
>>> .............
>>>
>>> Neil.
>>>
>>> On Sun, Oct 14, 2012 at 8:04 AM, Rocket J Squirrel
>>> <camping.elliott@gmail.com> wrote:
>>>
>>>> I want to describe an issue I found while working on my van. Most will
>>>> probably not have this problem unless they are running an '83 or '84
>>>> digijet (1.9) camper van and draw a lot more out of the alternator than
>>>> a stock van does. But if this fits your situation, it bears inspecting
>>>> for this potential problem.
>>>
>>>
>>>
>>>> I found the second problem when poking around in the connector box
>>>> located in the engine compartment on the firewall forward of the engine
>>>> on the driver's side.
>>>>
>>>> Bentley 97.56 shows a pair of 12-gauge wires coming off the alternator's
>>>> B+ terminal and going to the plus connection** in that box.
>>>
>>>> When I opened the box I saw that the last inch or so of the wire pair
>>>> had darkened insulation, and the connector used to connect them to the
>>>> plus connection was nearly black.
>>>>
>>>> Clearly the heavy load I'd been placing on the wiring had overheated
>>>> that connection, increasing its resistance and further reducing the
>>>> charge voltage on the engine battery.
>>>>
>
>
> --
> Neil n
>
> 65 kb image Myford Ready For Assembly http://tinyurl.com/64sx4rp
>
> '88 Slate Blue Westy to be named.
>
> '81 VanaJetta 2.0 "Jaco" http://tubaneil.googlepages.com/
>
> Vanagon VAG Gas I4/VR Swap Google Group:
>
> http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
>
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