AlanC
MD
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I have an electrical problem that is driving me bonkers
Our 1992 Monaco Dynasty has a two battery (house-4D, Chassis- 8D) system. The chassis battery is charged only by the engine alternator, and is not connected to the inverter/charger or converter.
Our EMS Heart Interface 1200 watt inverter/charger (with remote panel) works properly as a charger when hooked up to shore power and works properly as an inverter (showing 126 volts measured on an analog voltmeter at an outlet) when turned on after disconnecting from shore power and the coach engine is not running. When the coach engine is started though, the inverter will shutdown shortly after being turned on, apparently due to too much DC voltage being input (voltmeter shows 131 AC volts at idle and is pegged at 134 AC volts at cruise rpm). The voltmeter is one of those plug in types that Camping World sells. I understand that accurate voltage readings my be difficult to get from an inverter and in fact, my digital voltmeter showed 109.5 volts with the engine not running and the reading decreased when the engine was started and rpms increased.
At rest, with no shore power, and the engine not running, my 12 volt system shows 12.79 volts. While driving, our 12 volt outlet in the coach shows up to 16.44 volts. Sometimes, after driving for 3-4 hours the voltage will drop to 14.6 and the inverter will function.
I have had the 190 amp alternator checked out and had the brushes and bearings replaced, had the voltage regulator tested, cleaned off all the connections, and also tried another voltage regulator. I have replaced the 12v house battery (4 D) which was just under 4 years old, and tested the diodes in the battery isolator. The engine battery (8D), which is 3 years old, seems to be working fine. I have tried putting the chassis battery on an external charger to top it off before driving, but this has not made a difference. I have also tried two of the small (cigarette lighter plug in type inverters) in our 12v outlet and they seem to shut down due to over voltage as well, but when the engine is turned off, they work fine.
The only thing that I can remember happening that may be somehow connected to this problem is that the main (80 amp) 12 volt circuit breaker that is connected to the house battery failed while the motorhome was plugged in to shore power. During the time the battery was not connected, the converter was still providing 12 volts to the system.
Any suggestions as to what the problem may be would be greatly appreciated.
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wilpower
Punta Gorda, Fl
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Sounds like the alternator is putting out too much voltage. I know you said you had it and the regulator checked, BUT I don't think 16+ volts is normal. JMHO
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wa8yxm
Wherever I happen to park
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The first thing I'd do is hang a DC volt meter on the house (inverter) batteries and see what is happening on that side of the inverter.
Nothin adds excitment like something that is none of your business
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beemerphile1
NE Ohio
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AlanC wrote: ...While driving, our 12 volt outlet in the coach shows up to 16.44 volts...
Way too much voltage if your meter is correct. I think you need to revisit the alternator output. 14.6 is a high charging rate but possible, 16.4 is bad.
Tim
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MELM
GA
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You have a problem between the alternator input to the diode isolator and the voltage at the chassis battery. It may be the diode, or it might be the wire or terminals that connect the isolator to the chassis battery.
The alternator regulator "senses" the chassis battery voltage - you report one reading of 12.79 volts. The regulator will increase the alternator output to bring that voltage to something over 13 volts. But that isn't happening.
But the regulator voltage is increasing, as you report for the house battery voltages.
Check the alternator input to the isolator with the engine running. Then check the isolator outputs to the two batteries - they should be roughly 0.7 volts lower than the input and about equal. The diodes may have passed the resistance checks, but one may be breaking down under load.
If they are correct, then check the voltage at the two batteries. They should be roughly equal (which they weren't in the data you provided). Check the wire terminals and connections - there can be hidden corrosion in the terminal.
Let us know what you find.
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YC 1
Yuba City Calif.
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MELM wrote:You have a problem between the alternator input to the diode isolator and the voltage at the chassis battery. It may be the diode, or it might be the wire or terminals that connect the isolator to the chassis battery.
The alternator regulator "senses" the chassis battery voltage - you report one reading of 12.79 volts. The regulator will increase the alternator output to bring that voltage to something over 13 volts. But that isn't happening.
But the regulator voltage is increasing, as you report for the house battery voltages.
Check the alternator input to the isolator with the engine running. Then check the isolator outputs to the two batteries - they should be roughly 0.7 volts lower than the input and about equal. The diodes may have passed the resistance checks, but one may be breaking down under load.
If they are correct, then check the voltage at the two batteries. They should be roughly equal (which they weren't in the data you provided). Check the wire terminals and connections - there can be hidden corrosion in the terminal.
Let us know what you find.
Just for a quick test take all the wires on the isolator and stack them together. Make your voltmeter test then. This will eliminate any issues with that.
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MELM
GA
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To be on the cautious side, use the Emergency Start switch when you start the engine if you do as YC 1 suggests. You'll actually be using the wires from the isolator to the two batteries as a "jumper" cable, and there should be a pretty big load on both batteries when starting the diesel. The Emergency Start wiring and relay will carry that current - as designed.
If you have a diode failure in the isolator, doing as YC 1 said is a good way to keep all the voltages under control until you can get a replacement. Just watch the current when starting and disconnect the chassis battery if camping without power hookup.
A couple of links that may be useful:
SurePower Isolator Guide
SurePower Instructions There are testing instructions on the last page.
Mel
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AlanC
MD
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Thanks for the responses. I'll do some more checking in the morning.
Now that I think about it, even though the diodes checked out fine, I seem to recall evidence that the isolator got hot at some time.
AlanC
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AlanC
MD
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Thanks a lot for the isolator suggestion. I checked the voltage with the engine running and got 16.4 VDC at the alternator connection, 15.7 VDC at one of the battery connections, and 13.5 VDC at the other battery connection. I then stacked the wires on the alternator connection and used the emergency start switch to bridge the batteries when I started it. I then got 14.36 VDC at the output and the inverter worked fine. I revved the engine up just to make sure and it did not cut off.
Now for the next question, concerning replacing the isolator. I have a HEHR Powerline 190 amp alternator and the isolator is a HEHR Powerline 190 amp Model 22-31 PL5 190-2. Am I better off trying to track down a HEHR unit to replace it or should I just go to a truck supply place and get any 1-in-2-out, 190 amp unit??
Thanks again for all the suggestions.
AlanC
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YC 1
Yuba City Calif.
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AlanC wrote:Thanks a lot for the isolator suggestion. I checked the voltage with the engine running and got 16.4 VDC at the alternator connection, 15.7 VDC at one of the battery connections, and 13.5 VDC at the other battery connection. I then stacked the wires on the alternator connection and used the emergency start switch to bridge the batteries when I started it. I then got 14.36 VDC at the output and the inverter worked fine. I revved the engine up just to make sure and it did not cut off.
Now for the next question, concerning replacing the isolator. I have a HEHR Powerline 190 amp alternator and the isolator is a HEHR Powerline 190 amp Model 22-31 PL5 190-2. Am I better off trying to track down a HEHR unit to replace it or should I just go to a truck supply place and get any 1-in-2-out, 190 amp unit??
Any isolator rated for that current should work fine. Clean the wire terminals with sandpaper and make them shine when you put it back together.
Thanks again for all the suggestions.
AlanC
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