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more of a electromechanical question

N

Neil

I am trying to get a small gas powered engine running, (Rockwell) and I need
some help electrically. I have the unit running on the bench, with a simple
on/off switch, and a 12 volt marine battery.
I can get it started absolutely ok, but what I'm wondering, is it possible
to have the starter motor charging the battery while its running, so it can
power lights, just like a car does?.
If I can do it, is it simply a matter of using a relay, that will take the
electrical power generated from the the starter, once the engine is running.
In other words a relay that will switch between running (starting the
motor), and generating (running from the motor).
Do I need to place a voltage regulator between the starter and the battery?.
What do I need to keep the battery from overcharging?
Thanks
Kim
 
K

KevinR

I am trying to get a small gas powered engine running, (Rockwell) and I need
some help electrically. I have the unit running on the bench, with a simple
on/off switch, and a 12 volt marine battery.
I can get it started absolutely ok, but what I'm wondering, is it possible
to have the starter motor charging the battery while its running, so it can
power lights, just like a car does?.
If I can do it, is it simply a matter of using a relay, that will take the
electrical power generated from the the starter, once the engine is running.
In other words a relay that will switch between running (starting the
motor), and generating (running from the motor).
Do I need to place a voltage regulator between the starter and the battery?.
What do I need to keep the battery from overcharging?
Thanks
Kim

Older small marine engines are often fitted with a thing called a dyno
start, which is a starter motor dynamo and regulator all in one. The
system is not terribly well liked and a lot of people remove the dyno
starter and fit separate alternator and starter motor.

The trouble with automotive starter motors is that usualy they are
very crude and inefficient, because of the abundance of power
available in a typical application where a starter motor is used,
there is no point developing a more efficient/expensive solution.

If your stater motor is not typical of automotive gear, and is of a
reasonable quality, then it may be practical but you ned to regulate
the output such that it will be suitable for your battery charging.

You might look at fitting a separate alternator, you get a known
working solution with regulator built in and they are very cheap from
the local breakers yard.

KevinR
 
A

AC/DCdude17

X-No-Archive: Yes
I am trying to get a small gas powered engine running, (Rockwell) and I need
some help electrically. I have the unit running on the bench, with a simple
on/off switch, and a 12 volt marine battery.
I can get it started absolutely ok, but what I'm wondering, is it possible
to have the starter motor charging the battery while its running, so it can
power lights, just like a car does?.
If I can do it, is it simply a matter of using a relay, that will take the
electrical power generated from the the starter, once the engine is running.
In other words a relay that will switch between running (starting the
motor), and generating (running from the motor).
Do I need to place a voltage regulator between the starter and the battery?.
What do I need to keep the battery from overcharging?
Thanks
Kim


The hybrid alternator/starter assembly used on marine engines isn't
regulated well at all. The voltage can go up as much as 16V and this is
bad for the battery.

Use a small automotive alternator. They have a regulator installed
already and it will maintain steady 13.8V to 14V even with varying RPM.
You can tweak the pulley size to change the maximum output.
 
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