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Old 26-05-2019, 12:48   #1
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Genset cranks up at 14.5v but not at 13v

I have a Mastervolt Whisper 3.5. When the boat is on shore power then batteries charge up to 14.5v and the genset starts fine. But when batteries are charger only up to 13v then it doesn't even cranks. Just one loud click.

Yanmar engine starts up just fine on this voltage.

The boat has 3 battery banks, the genset seems to use it's own battery. I've tried to connect it to the engine start bank and it didn't help. Batteries themselves probably old but again Yanmar is fine with it. When the genset is cranking up the voltage on the starter drops to almost zero and wires near the genset heat up. Voltage on battery itself drops to 10-11v.

What could be the problem?
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Old 26-05-2019, 13:06   #2
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Re: Genset cranks up at 14.5v but not at 13v

Too small wire and or a loose / corroded connection.
Iím betting connection as I assume it hasnít always down this.
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Old 26-05-2019, 16:19   #3
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Re: Genset cranks up at 14.5v but not at 13v

Maybe a LVC cutout. Could be battery aging / degradation, do not expect the two motors to act the same.

But yes likely degraded connections - remove, inspect for corrosion, rewire if needed or at least resurface, then reconnect, they may even spec torque.

Can check resistance before and after with a DMM to be scientific about it.
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Old 26-05-2019, 16:38   #4
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Re: Genset cranks up at 14.5v but not at 13v

If it were a cut out, then the wires wouldnít be getting hot.
Never heard of a low volt cutout on an engine starting circuit, not saying there isnít one, just never heard of one, and I wouldnít want one myself
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Old 26-05-2019, 16:54   #5
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Re: Genset cranks up at 14.5v but not at 13v

Quote:
Originally Posted by colonel View Post
I have a Mastervolt Whisper 3.5. When the boat is on shore power then batteries charge up to 14.5v and the genset starts fine. But when batteries are charger only up to 13v then it doesn't even cranks. Just one loud click.

>>>>>>>>>>>>>>>>>>>>>>>>>>

The boat has 3 battery banks, the genset seems to use it's own battery. I've tried to connect it to the engine start bank and it didn't help. Batteries themselves probably old but again Yanmar is fine with it. When the genset is cranking up the voltage on the starter drops to almost zero and wires near the genset heat up. Voltage on battery itself drops to 10-11v.

What could be the problem?

We'd love to help, but perhaps you would consider editing the paragraphs to better explain your issue.


I don't understand the bold material.



For example, which bank(s) is/are engaged when this happens? Why 3 banks? What is the basic design.


Of course, hot wires mean bad connections and/or undersized wiring.


Help us to help you.
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Old 26-05-2019, 18:22   #6
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Re: Genset cranks up at 14.5v but not at 13v

I think the gist of it is, the boat has multiple banks, and even when switched to another bank, the issue is the same.
However the main engine starts fine, assumption is on the same bank that was tried to start the generator.
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Old 26-05-2019, 21:15   #7
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Re: Genset cranks up at 14.5v but not at 13v

If the starter is dropping to 0v and the battery is at 10v The your issue is in the Cables or connections. . I’m amazed it starts at 14v. Because yiu’d Still have near 0 at starter . Unless the charger connects after the problem. Which is my guess.
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Old 26-05-2019, 23:11   #8
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Re: Genset cranks up at 14.5v but not at 13v

Quote:
Originally Posted by colonel View Post
I have a Mastervolt Whisper 3.5. When the boat is on shore power then batteries charge up to 14.5v and the genset starts fine. But when batteries are charger only up to 13v then it doesn't even cranks. Just one loud click.

Yanmar engine starts up just fine on this voltage.

The boat has 3 battery banks, the genset seems to use it's own battery. I've tried to connect it to the engine start bank and it didn't help. Batteries themselves probably old but again Yanmar is fine with it. When the genset is cranking up the voltage on the starter drops to almost zero and wires near the genset heat up. Voltage on battery itself drops to 10-11v.

What could be the problem?
I once had an electrian tell me that if things were getting g hot it is never a power problem. This only leave por wires or bad starter.

Jump the start er with a set of cables. From a different battery that you know is good after disconnecting the existing supply. If it starts well you have a wiring problem, if it doesn't you have a problem with your starter. Remember poor grounds cause more problems than poor supplies.
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Old 27-05-2019, 04:32   #9
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Re: Genset cranks up at 14.5v but not at 13v

Have a similar issue with ours that I have been tracking down for 3 years.
Big solar so genset not a priority.
Solution thus far has been a permanently connected charger and a timer to kick it on from 8:30am to 9:30am to get it over 13v for glowplug and start if required.
Not the answer but it is for now.

Have shot the wires today with laser thermometer and found one warmer than the others so will attempt to solder that joint tomorrow.
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Old 27-05-2019, 05:02   #10
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Re: Genset cranks up at 14.5v but not at 13v

I'm going to go against the grain a bit here.

My vote is for a bad starter. 0 volts read at the starter means that either the voltage has been lost due to resistance of the cable, or there is more current flowing than the cable can handle and the starter is acting like a dead short to ground. If the battery starts at 13 volts, the cable gets hot, and the battery voltage is dropping to 10v, then the battery is supplying lots of current. If there's a high resistance problem, current flow is slowed, and there's nothing to draw down the battery voltage. Ohms and Watts laws tell us that even a 10 ohm resistance at 13v would result in only 1.3 amps and 1.69 Watts. Hardly a hot battery cable.

The cable is heating up from high current flow caused by the starter.
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Old 27-05-2019, 05:16   #11
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Re: Genset cranks up at 14.5v but not at 13v

Even a dead short to ground wonít take a battery all the way to 0 volts, I donít believe, although Iíve not done that to measure the results
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Old 27-05-2019, 05:37   #12
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Re: Genset cranks up at 14.5v but not at 13v

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Even a dead short to ground wonít take a battery all the way to 0 volts, I donít believe, although Iíve not done that to measure the results
But that's not what's happening. He's reading 0 volts at the starter, and 10 volts at the battery. This means the battery is putting out just about as much current as it can, and the voltage is being consumed along the way. The question is by what. If the voltage was being consumed by high resistance, then Ohms law tells us there won't be much current flow, and therefore nothing to draw down the battery voltage and nothing to heat up the cable. However, if the voltage is being consumed because the wire is being overloaded, then we have to find what's causing the extra high current.

This is not to say he shouldn't very carefully inspect his cables and clean his connections. He absolutely should. But I would be shocked if the starter wasn't the problem.
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Old 27-05-2019, 06:01   #13
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Re: Genset cranks up at 14.5v but not at 13v

If you have a high resistance connection, you will have a serious voltage drop and it will get hot. That is what is happening
High resistance is often a dirty connection.

In my experience this is most often a loose or dirty connection, it seems as often as not to be a ground for some reason, I have no idea why grounds would become loose and or dirty more often
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Old 27-05-2019, 06:11   #14
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Re: Genset cranks up at 14.5v but not at 13v

Have you checked the starter solenoid?
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Old 27-05-2019, 06:17   #15
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Re: Genset cranks up at 14.5v but not at 13v

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Originally Posted by Tornadosailing View Post
But that's not what's happening. He's reading 0 volts at the starter, and 10 volts at the battery. This means the battery is putting out just about as much current as it can, and the voltage is being consumed along the way. The question is by what. If the voltage was being consumed by high resistance, then Ohms law tells us there won't be much current flow, and therefore nothing to draw down the battery voltage and nothing to heat up the cable. However, if the voltage is being consumed because the wire is being overloaded, then we have to find what's causing the extra high current.

This is not to say he shouldn't very carefully inspect his cables and clean his connections. He absolutely should. But I would be shocked if the starter wasn't the problem.

Me too.
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