T&T: 5.9 Cummins 6BT - Large Frame Alternator installation retrofit - update

[Brian Shanafelt]

Greetings list,

Just a quick report on how the installation went on my 1992 6BT5.9M 210hp

The goal was to replace the existing small frame alternator - which in my case
was a 130A Bosch, with a large frame unit using a J-180 mounting, for an
overall more robust, and cooler charging system.

I wanted to get away from the small frame style as it is really difficult to
get charging rates above 110 amps without an enormous amount of heat being
produced at the alternator. Large frame alternators not only can be configured
for higher amp rates, but also have more cooling capacity. The J-180 mount is
commonly used in Truck/Bus applications which allows the use of a number of
alternator choices, plus lower street prices for the actual unit.

I already knew that the 6BT engine was available in certain over the road
applications with this style(J-180) of alternator and amperage ratings up to
270A, so it was a matter of finding the appropriate Cummins part for the
exchange as well as determining if there was going to be any physical
interference from the marine components.

Some suggestions from the list to this project included leaving the small
frame unit in place and mounting the large frame alternator in a different
location on the engine for redundancy and/or separation charging for
Start/House battery banks. This is a great solution if you have the space - I
don't.


My previous post on the subject led me to a discussion with the Cummins tech
in Michigan, He provided a complete parts list for the refit. I ended up using
the Cummins alternator support $35, had to buy an aftermarket alternator bar
from NAPA $11, and a new belt $30.  In my case there was no interference from
any cooling lines and the installation was very straightforward.

The upgraded alternator I used is a Penntex 200A unit - 25 lbs of copper,
diodes & assorted pieces http://www.penntexusa.com/PX-3%20Brochure.pdf .  I
now produce around 120 amps at 900 engine RPM and 170A at 1650 engine RPM -
which is my typical cruising RPM. I like the fact that at cruising speed I am
well under the max of the unit.

I did have to upgrade the connection wires to 2 AWG. I was able to re-use the
Balmar Regulator.

As an aside, after cooking a couple of battery isolators, I did away with the
isolator setup and now use a Balmar Digital Duo
http://www.balmar.net/page20-Duocharge.html for smart-charging/monitoring of
the start bank.  This allows the main regulator to only 'see' one bank.

Thanks again for all the responses both on and off list.

Brian Shanafelt
Isobel K
37' Custom Pilothouse
Seattle



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