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Sterling Inverter Query


tommytelford

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At the weekend I had to do a few jobs in preparation for a holiday cruise in a couple of weeks, including some small electrical jobs.

 

When I had finished I decided to check the operation of the inverter so I unplugged the shoreline and let the it do it's job.

 

After about 20 minutes I was surprised when the low voltage alarm started going off as the batteries were all fully charged. I let it continue until it cut out and then switched the inverter off and back on.

It started working for about 2 minutes and the alarm started again, on a whim I turned on the microwave, thinking that it would switch the inverter off and I could then check the voltage. Much to my surprise the alarm stopped, the green light came on and the inverter continued working for the next 4 hours without a problem until I was ready to leave and re-connect the shoreline.

 

In the past I have had problems with the invereter cutting out too early and I returned it to have it upgraded to Full Sinewave operation and checked out by Sterling because I wanted to use my laptop onboard.

 

 Any ideas why it should have started again in this way?

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Unfortunately this reads to me as yet another “Why does my Sterling...?” thread. I have no suggestions other than to say check the battery voltage at the inverter the next time it happens and if it looks normal then a phone call to Sterling I guess. 

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Check every connection from the battery to the inverter for terminals that have "relaxed" their grip due to copper creep.

 

Is the inverter wired through one of those horrible red key isolator switches? They frequently go intermittent due to lousy contacts. Replace with a decent one.

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No it doesn't go through a switch as I was advised to wire it direct through a suitable fuse. Maybe when I go to the boat next it may be worth checking the fuse connection. 

 

It just seemed that switching on the microwave woke it up so maybe a bad connection somewhere

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14 minutes ago, Boater Sam said:

So you have no isolator on your cabin batteries? BSS fail.

No, he has no isolator on his inverter.

 

Maybe it is you who is 'wired up incorrectly'

 

In accordance with 3.6.2 of the BSS.

 

Identify any d.c. electrical circuits bypassing the battery isolator.
Check that any electrical circuits bypassing the battery isolator supply the
following equipment:
• automatic bilge pumps;
• security alarms (including marine radios);
• fire pumps;
• electronic navigation equipment with memories;
• any other equipment where the manufacturer’s instructions indicate or
specifically require direct connection to a battery, such as diesel‐fired
central heating boilers;
• battery charger outputs;
inverters or combination inverter/chargers;
• solar panels and wind turbines.
Check electrical circuits supplying any equipment on the specified list, and
which bypass a battery isolator, for the presence of a fuse or circuit‐breaker,
where the circuit can be seen.

Edited by Alan de Enfield
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9 minutes ago, Boater Sam said:

So you have no isolator on your cabin batteries? BSS fail.

Maybe not-if its a combi and therefore a battery charger it is allowed to be wired direct (fuse fitted so all good) and not via the isolator.

But I know you already know that..

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10 minutes ago, Boater Sam said:

 

Confused me with the reference to being converted to pure sine wave.

Think if memory serves me correctly (Tommy will confirm) that if you send a quasi off to Sterling for repair they will replace the innards with a Sinewave board. Or something like that ☺

Edited by PaulJ
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48 minutes ago, tommytelford said:

I assume the voltage must have been ok as it continued working. You are probably right but just wondered ..........................

Certainly safe to assume it was good when it was working but what was it when it was cutting out?

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bad connection causing low voltage, when you demanded a lot of power the connection probably arced slightly and effectively welded itself connected.

 

go through every high current connection (batteries to inverter) and check them for tightness and signs of having been hot.

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It is a combi sorry I should have said. It is very difficult to monitor voltage at the actual time it cuts out as once the load is removed the voltage goes up. 

 

When I had problems originally, a couple of years back I actually tried running a video camera to monitor it but the battery ran out on the recorder first.

 

I also tried putting the wife in charge of monitoring but the gin got to her and she went to sleep.

 

I think the most likely cause is a loose connection somewhere which as the previous poster said , has welded itself together 

 

I will have a thorough check when I go to the boat. Thanks for the suggestions

Edited by tommytelford
  • Haha 3
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Long shot, but what type of battery (wet cell, sealed, AGM etc) and how long since your batteries were last exercised? How long have they have been on float?

There is a phenomena called "Coup Dr Fouet" which affects AGM and gel type valve regulated sealed lead acid batteries if they are not used to support a load often enough.

 

When a little used VRSLA is asked to support a load, its voltsge collapses. After a couple of attempts it will recover and perform normally.

 

If, and only if you can find no other fault, and everything now seems to be OK with your inverter, this could explain it.

Edited by cuthound
To unmangle the effects of autocorrect
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26 minutes ago, cuthound said:

There is a phenomena called "Coup Dr Fouet" which affects AGM and gel type valve regulated sealed lead acid batteries if they are not used to support a load often enough.

I believe it’s a phenomenon also associated with wet batteries too, isn’t it?

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29 minutes ago, WotEver said:

I believe it’s a phenomenon also associated with wet batteries too, isn’t it?

 

Yes, insomuch as the battery voltage drops a little and then recovers what and load is connected. 

 

Howwever with VRSLA's, the voltage can dip below the low voltage threshold of equipment before recovering.

 

This caused many service failure in the early 80's, until the cause was understood. Modern critical dc power systems incorporate "exercise timers" to periodically lower charger output voltage to periodically work the batteries a bit. This method allows the charger voltage to be quickly ramped back up if the battery shows any signs of not being anyone to support the load.

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