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Old 12-31-2015, 12:07 PM   #1
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Onan Generator Question

Our ( new to us ) boat came with an Onan MDKD 8 KW Generator with a dedicated starting battery. While this battery was also connected to the common AC powered charger ( I have since installed an Inverter Charger ) I am wondering if the Generator charges this battery via it's own charging system .. ? while it's running ? as I have wired the new Inverter / Charger trickle charge output to this battery as well.

I can't seem to find this info in the Gen. documentation that I have.

Hope any of the above makes sense and warrants a comment / advice.

Thanks in advance, Frank B.
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Old 12-31-2015, 12:14 PM   #2
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It probably does have a small DC alternator. But here is an easy way to tell:


Disconnect the shore power inverter charger connection to the genset starting battery. Wait a little while to let the "surface charge" to bleed down and measure the starting battery's voltage. Should be something less than 13.0 V.


Then start the generator and after it has been running for a few minutes measure the battery's voltage. If it is being charged it will read above 13.0 V.


David
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Old 12-31-2015, 12:27 PM   #3
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We have an an Onan Jurrassic Model MDJE 7.5 kw on our boat. It has its own 4D start battery. This battery is on an echo charge line from our Heart Freedom 25 inverter/charger. It is also charged by one of the engines when they're running. And the generator charges its battery when it's running. There is an adjustment on the generator to regulate the amount of charging current going to the start battery when the generator is runnng.
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Old 12-31-2015, 02:08 PM   #4
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My Onan MDKD has its own dedicated charger. It also has a small dedicated alternator to top up the battery after a start.
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Old 12-31-2015, 04:07 PM   #5
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The MDKD 8Kw does have it's own charging system.
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Old 12-31-2015, 04:14 PM   #6
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Quote:
Originally Posted by Xsbank View Post
My Onan MDKD has its own dedicated charger. It also has a small dedicated alternator to top up the battery after a start.

That's good news ! thanks ..... but I will check the battery voltage when this thing is running as was suggested, just to satisfy my curiosity ... Frank B.
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Old 12-31-2015, 05:08 PM   #7
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It has a permanent magnet dynamo and what can be best described as a "motorcycle" regulator. Rather crude voltage control compared to car type alternators, some overcharge. Many disconnect them and let the charger do the job when gennie is on.
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