On Thu, 18 Aug 2005 20:29:49 -0400, Jeff wrote:

I have a similar setup on my cat. It came with twin Yanmars which
have simple alternators with internal regulators. I replaced one
alternator with a high output, regulated by a 2000R regulator. It
would, on occasion run the output voltage up to 17 V until I figured
out what was happening.

The high output alternator was still connected directly to the
starting battery. When the battery combiner latched everything
together, it worked fine. But if the connection parameters weren't
met, the regulator sense was seeing the house bank, but the output was
going to the starter battery. This mismatch could permit overcharging.

The solution was to reroute the output only to the house bank, and
feed the starter battery only through the combiner. Recently, I added
an EchoCharge, and had to reroute the other alternator output. All
charge sources are now directly (more or less) to the house bank,
while the starter batteries are isolated by the EchoCharge, and the
normal connection between the starters and their alternators is severed.



This issue is from a cruiser 1/2 way around the world and via sailmail

From some research here are some Ideas and the message I sent.

Which of the following 3 do you have? I am assuming the parallel
solenoid one?

#1 Parallel Solenoid #SOLxx-100, #SOLxx-200
Recommended Application
- R/V cross charging from the main coach battery bank to a second
house battery bank
Other Notes
- Secondary battery bank may be overcharged, suggest using
Lead-calcium type battery that can tolerate higher voltages for
prolonged periods
- Add-on option to the #NEXT or #SARV3

#2 AutoSwitch #ASxx-100, #ASxx-200
Recommended Application
- Cross charging from a house battery bank to a second battery bank
that has large duration loads or conditions that exceed the
limitations of the EL512

#3 Eliminator #EL5xx
Recommended Application
- Sailing vessel with one house battery bank and a seperate, dedicated
starting battery bank.

Other Notes
- Limited to 5A nominal (12A peak) charge current... Absolutely no
loads can be attached to the starting battery except the electric
starting motor
- Recharges the starting battery with little or no intervention; only
a few Amp-hours are depleted during a normal starting sequence
- Starter battery can be undercharged if engine is started and stopped
multiple times per hour (or charge cycle)
But this is uncommon practice for most sailing vessels.

XXXXXXXXXXXXXXXXXXXXXX

Table 1. Comparison of Ample Cross Charging Products.
#EL5xx #ASxx-aaa #SOLxx-aaa #1029
Amperage Rating (Continuous) 5 100 or 200 100 or 200
200
Solid-State x x
Precision Multi-stage Regulation x
Temperature Compensated x Note 1
Primary Bat.V Sensing x x x
Secondary Bat.V Sensing x x
May Overcharge Secondary Battery x x
May Discharge Primary Battery x
Stand-alone operation x x x
Low-cost Alternative x
Simplest Design and Installation x x

^^^^^^^^^^^^^^^^^^^^^^^^^
Not sure how the above table will render out for you via email.\
^^^^^^^^^^^^^^^^^
From Ample Power

Modifying Internally Regulated Alternators

In Theory ...

All alternators can be converted to external regulation. Sometimes,
however, regulator replacement spacers need to be fabricated. If
required, some spacers may need to be conductors, and other spacers
will need to be insulators.

Temperature is the Real Issue

More importantly, however, is the alternator cooling issue.
Alternators designed with internal regulators use temperature of the
alternator to cut back charging Amps to prevent alternator burn-out.
An external regulator doesn't pay attention to alternator temperature,
only the batteries, so the alternator will run at full output as long
as the batteries will accept the charge rate. Many stock alternators
will burn up if used in this manner.

ZZZZZZZZZZZZZ
The alternator system consists of the alternator, the alternator
regulator, the ignition switch, batteries, distribution wiring, and in
older boats, a battery selector switch. Each of the parts may cause
the alternator system to charge improperly, or not at all.

The Battery Selector Switch

In boats that don't follow the Ample Power way of wiring an
alternator, a selector switch is used to enable charging either or
both batteries banks.

A running alternator has energy stored in its field winding, and
suddenly interrupting the alternator output by disconnecting the
batteries results in hundreds of Volts appearing at the alternator
output. Since this same circuit is powering other devices, such as
electronic gear, the high voltage spike can immediately destroy lots
of equipment ...not the least of which is the alternator regulator.
ZZZZZZZZZZZZZ

One thing that might be an issue is that it is likely one alternator
was modified for an external reg. (the one that is working OK) and the
other still has its internal reg.I think this could be a real
possiblility, given the issues you have already had.

Do you have THIS ITEM?
http://www.amplepower.com/wire/autosw/index.html
Determining the Mode of Operation
The AutoSwitch operates in one of four modes described below.

Solar/Charge Control Mode
This mode is used to control a charge source, Device 2, such as a
solar panel. In this mode, the solenoid opens and closes at desired
voltage setpoints. This mode can be used with some unregulated battery
chargers, but should never be used with an alternator because
alternators can not tolerate being open circuited while producing
current.

Load/Continuous Cross Charge Mode
This mode is used to continuously deliver energy to Device 2 whenever
the voltage on Battery 1 is within the voltage setpoints. In this
mode, Device 2 can be a load, such as a water pump, or it can be a
second battery. The second battery can be another house battery, or a
starter battery.

Voltage Limited Cross Charge Mode
This mode is used to provide power to Device 2 whenever Battery 1
voltage is greater than a set voltage, but also less than a limiting
voltage. In this mode, Device 2 is typically a starter battery where
it's desired to limit the maximum applied voltage. Device 2 could also
be a voltage sensitive load that could be damaged by sustained high
voltages. The solenoid will disconnect if the Battery 1 voltage ever
falls below 13.0 Volts.

Time Limited Cross Charge Mode
This mode is used to time limit an applied voltage to Device 2. The
countdown time begins when Battery 1 voltage exceeds a set voltage.
This mode is another good way to cross charge a starter battery. For
example, the connect setpoint could be set for 13.8 Volts with a time
limit of 20 minutes. The solenoid will reconnect when the voltage
falls below the 13.8 setpoint voltage, floating the starter battery
with the house. The solenoid will disconnect if the Battery 1 voltage
ever falls below 13.0 Volts.

Configuring the AutoSwitch
The AutoSwitch is configured by setting switches on the DIP switch and
adjusting a potentiometer, as explained below.