Thanks again Dennis.

Though the solar panel was intended solely for charging the 2nd larger
group 27 house battery and running a TruckFridge, I later installed a
fused switch between the group 27 positive post and the group 41
battery so the panel could charge both batteries. In hindsight, even
though the group 27 has a fused/isolated dedicated feed from
alternator, when the engine is running, power from alternator to group
41 could feed back into the ground 27 battery; the system could be
imbalanced. ?? I should double check but I recall part of the engine
swap process included changing out the OEM 1981 Vanagon alternator
wires to a single larger gauge wire from the Jetta alternator to
starter 30.

On 8/8/17, Dennis Haynes <d23haynes57@hotmail.com> wrote:
> For house battery charging I like to use a home run all the way back to the
> alternator. Also, the wire from the alternator to the battery cable should
> also be upgraded, especially if it also has to charge a 2nd battery. If
> planning an inverter that will be used while driving that charge line and
> relay also has to handle that. Since you have solar, a bi-directional
> automatic charge control relay (ACR) can really simplify things. Solar
> charging the house battery can also charge the chassis battery.
>
> Dennis.
>
> -----Original Message-----
> From: Neil N [mailto:musomuso@gmail.com]
> Sent: Tuesday, August 8, 2017 2:00 PM
> To: Dennis Haynes <d23haynes57@hotmail.com>
> Cc: vanagon@GERRY.VANAGON.COM
> Subject: Re: Fuse Size: Aux battery to fuse block
>
>> Out of curiosity, why would you be connecting "fog" lights to the
>> house battery?
>
> I'd read your earlier post about the fog lights. Though somewhat misguided,
> my intent was to have no extra loads on the starter battery that might drain
> it should I leave that load on too long. But then of late, I've been
> carrying a small "jumper" battery pack. I'll be moving the fog lights to the
> starter battery.
>
>> For the lights, especially for DC circuits and lighting wattage
>> ratings are nominal. For incandescent bulbs, especially halogens
>> actual current can be over a wide range affected by delivered voltage
>> and lamp tolerance. 110 watts at 12 volts is 9.16 amps.
>
> Ok. So if my alternator puts out 13.8 Volts, in paper, I assumed the fog
> lights were drawing 7.97 Amps but then in practice, I see how circuit
> resistance and bulb design affect actual current draw.
>
>> It is counter intuitive but as system
>> voltage drop increases (less voltage at lamp) the bulb will run cooler
>> and current draw can actually increase. A fuse in its simplest form is
>> a resister. It will also introduce a voltage drop. Operation a fuse
>> near its full rating will cause it to heat up and can cause nuisance
>> failures. As the fuse heats up some of that heat goes to the socket
>> and over time does damage there.
>
> Yes. Right. So this might've have been a factor behind the melted terminal
> insulator I saw at the OME 30 wire from starter battery to fuse panel.
>
>>..... For the house battery, the charge line circuit however you  did
>>that needs to support charging the battery (20-25 amp) and all those
>>connected loads.
>
> Last night I thought more about the charge wire gauge between starter and
> aux battery. That battery has 3 potential charge sources (alternator, house
> battery charger, solar panel) but in certain conditions it could be drawn
> down and pulling all its charge through the (8 or 10?) wire from starter
> batter via isolator and "Max" fuse.
>
> On 8/8/17, Dennis Haynes <d23haynes57@hotmail.com> wrote:
>> Out of curiosity, why would you be connecting "fog" lights to the
>> house battery? They should be wired so that they operate with the low
>> beam headlights. While driving the alternator, not battery should be
>> the power source and for lighting especially you want that path to be
>> as resistance free as practice. For the house battery, the charge line
>> circuit however you did that needs to support charging the battery
>> (20-25 amp) and all those connected loads.
>> For the lights, especially for DC circuits and lighting wattage
>> ratings are nominal. For incandescent bulbs, especially halogens
>> actual current can be over a wide range affected by delivered voltage
>> and lamp tolerance. 110 watts at 12 volts is 9.16 amps. It is counter
>> intuitive but as system voltage drop increases (less voltage at lamp)
>> the bulb will run cooler and current draw can actually increase. A
>> fuse in its simplest form is a resister. It will also introduce a
>> voltage drop. Operation a fuse near its full rating will cause it to
>> heat up and can cause nuisance failures. As the fuse heats up some of
>> that heat goes to the socket and over time does damage there. For the
>> wire from battery to the fuse distribution block an ATO may not be the
>> right choice, too much available fault current. Consider a Max or as
>> American cars like to use a fuse link. Generally you choose fuse link wire
>> one gauge smaller than the wire being protected.
>>
>> Dennis
>>
>>
>
>
> --
> Neil n
>
> Blog: Vanagons, Westfalia, general <http://tubaneil.blogspot.ca>
>
> 1988 Westy Images <https://picasaweb.google.com/musomuso/New1988Westy>
>
> 1981 Westfalia "Jaco" Images, technical <http://tubaneil.googlepages.com/>
>
> Vanagon-Bus VAG Gas Engine Swap Group <http://tinyurl.com/khalbay>
>

--
Neil n

Blog: Vanagons, Westfalia, general <http://tubaneil.blogspot.ca>

1988 Westy Images <https://picasaweb.google.com/musomuso/New1988Westy>

1981 Westfalia "Jaco" Images, technical <http://tubaneil.googlepages.com/>

Vanagon-Bus VAG Gas Engine Swap Group <http://tinyurl.com/khalbay>