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Battery Isolator Switch


pearley

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When new Joanie M had what looked like a cheap isolator switch for the Victron 3000/12/120 Combi and if happily sat there without being touched for 5 or 6 years passing charge current in one direction and running our 1600 watt washer in the other direction. One day it melted and I replaced it with one from a Chandlers that was rated as 300 amp continuous. This lasted about 4 years before it took melted. This coincided with a change of washer, same power consumption but washer, Zanussi, wouldn't work from inverter. Never the less I replaced the isolater again, this time with a Blue Sea one rated at 500 amp continuous, 1000amp  on overload. This is now 18 months old. 

 

Now we had a small bit of welding  done and turned all the isolators off. First time for 4 years. When turned back on all the LEDs on the inverter lit up as they should and the LCD reading on the remote display lit up. However, after a while it became apparent that the batteries were not being charged from mains. Panicking, I thought that the welding had damaged the charger despite the isolator being turned off. Checking voltages and fuses I found that it was charging, just wasn't getting to the batteries and traced the fault / high resistance to the isolator. Whacking the knob back and forward and the fault cleared. I removed the switch from its mounting and checked the connections behind. So assumption was that contacts were tarnished and now cleared. 

 

Came back from a day away and started the generator and all was well and the batteries charged from 88% to 96% before the gennie was switched off. Switched the gennie on again an hour ago to bring the batteries up to 100% and no charge again. Whack the switch back and forth again and now charging. 

 

So, any recommendations for an isolator that will last more that 4 years in continuous use, but rarely more than 150 amps. 

 

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25 minutes ago, pearley said:

When new Joanie M had what looked like a cheap isolator switch for the Victron 3000/12/120 Combi and if happily sat there without being touched for 5 or 6 years passing charge current in one direction and running our 1600 watt washer in the other direction. One day it melted and I replaced it with one from a Chandlers that was rated as 300 amp continuous. This lasted about 4 years before it took melted. This coincided with a change of washer, same power consumption but washer, Zanussi, wouldn't work from inverter. Never the less I replaced the isolater again, this time with a Blue Sea one rated at 500 amp continuous, 1000amp  on overload. This is now 18 months old. 

 

Now we had a small bit of welding  done and turned all the isolators off. First time for 4 years. When turned back on all the LEDs on the inverter lit up as they should and the LCD reading on the remote display lit up. However, after a while it became apparent that the batteries were not being charged from mains. Panicking, I thought that the welding had damaged the charger despite the isolator being turned off. Checking voltages and fuses I found that it was charging, just wasn't getting to the batteries and traced the fault / high resistance to the isolator. Whacking the knob back and forward and the fault cleared. I removed the switch from its mounting and checked the connections behind. So assumption was that contacts were tarnished and now cleared. 

 

Came back from a day away and started the generator and all was well and the batteries charged from 88% to 96% before the gennie was switched off. Switched the gennie on again an hour ago to bring the batteries up to 100% and no charge again. Whack the switch back and forth again and now charging. 

 

So, any recommendations for an isolator that will last more that 4 years in continuous use, but rarely more than 150 amps. 

 

I doubt if you will better Blue Sea. 

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Blue seas is one of the best makes. Perhaps the environment is particularly damp or subject to acidic battery fumes?

 

Anyway, I would suggest not having an isolator for the Combi. We don’t. Just have a fuse which, on the very rare occasions you need to switch it off, can be removed. In the 7 years we’ve had out boat, I have de-powered the Combi only twice - once when I added a Mastershunt into the system and once when I replaced the ordinary leisure batteries with Trojan 6v ones and had to redo the wiring.

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Its almost as if there's something other than the quality/cost of the isolator switch affecting the electrical path. Like, the fact that its a high humidity environment because its on a boat, or something, making the contacts corrode.

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38 minutes ago, Paul C said:

Its almost as if there's something other than the quality/cost of the isolator switch affecting the electrical path. Like, the fact that its a high humidity environment because its on a boat, or something, making the contacts corrode.

Highly unlikely as Blue Sea are waterproof  & IP66 rated (they are pressure jet rated according to Blue Sea). Also they have tin plated copper threaded terminals.

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13 hours ago, Paul C said:

Its almost as if there's something other than the quality/cost of the isolator switch affecting the electrical path. Like, the fact that its a high humidity environment because its on a boat, or something, making the contacts corrode.

It sits in the engine bay alongside the isolators for the engine and the generator. Those  two are now 12 years old and have never given any problems. 

 

13 hours ago, nicknorman said:

Blue seas is one of the best makes. Perhaps the environment is particularly damp or subject to acidic battery fumes?

 

Anyway, I would suggest not having an isolator for the Combi. We don’t. Just have a fuse which, on the very rare occasions you need to switch it off, can be removed. In the 7 years we’ve had out boat, I have de-powered the Combi only twice - once when I added a Mastershunt into the system and once when I replaced the ordinary leisure batteries with Trojan 6v ones and had to redo the wiring.

When built there was no isolator for the Combi, just a fuse in the feed and the internal one. It was only a few months later when having some work done on the generator that we were told BSS required it so one was fitted. 

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2 minutes ago, pearley said:

we were told BSS required it

As it’s a Combi and therefore a battery charger the above is incorrect. 

 

See 3.6.2 of the Guide:

https://www.boatsafetyscheme.org/media/268789/ecp-private-boats-ed3_rev2_apr2015_public_final.pdf

 

”All d.c. electrical circuits must pass through a battery isolator, except those which feed equipment requiring a continuous supply which must be protected by a suitable fuse or circuit‐ breaker.”

 

The third from last exclusion listed on the left is ‘battery charger’

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7 minutes ago, WotEver said:

As it’s a Combi and therefore a battery charger the above is incorrect. 

 

See 3.6.2 of the Guide:

https://www.boatsafetyscheme.org/media/268789/ecp-private-boats-ed3_rev2_apr2015_public_final.pdf

 

”All d.c. electrical circuits must pass through a battery isolator, except those which feed equipment requiring a continuous supply which must be protected by a suitable fuse or circuit‐ breaker.”

 

The third from last exclusion listed on the left is ‘battery charger’

I'll put it back to as built then, without isolator, when my arthritic knee let's me bend it again. 

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12 minutes ago, pearley said:

I'll put it back to as built then, without isolator, when my arthritic knee let's me bend it again. 

There’s never a double jointed midget around when you need one...

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1 hour ago, pearley said:

It sits in the engine bay alongside the isolators for the engine and the generator. Those  two are now 12 years old and have never given any problems. 

 

When built there was no isolator for the Combi, just a fuse in the feed and the internal one. It was only a few months later when having some work done on the generator that we were told BSS required it so one was fitted. 

Always best to check the “horse’s mouth” rather than what someone said to someone in the pub according to their mate’s aged mother! As said, according to BSS certain devices don’t need an isolator including things designed to be permanently connected and battery chargers. They just need to be fused. If you look at the installation instructions there is no isolator mentioned.

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15 hours ago, Paul C said:

Its almost as if there's something other than the quality/cost of the isolator switch affecting the electrical path. Like, the fact that its a high humidity environment because its on a boat, or something, making the contacts corrode.

It's likely that this particular isolator is prone to failure because the Victron contains some big capacitors. The high inrush current causes severe arcing and burning of the contacts when switching on. If you want to keep an isolator in this circuit, a fix is to wire a 470 ohm resistor and push button switch in parallel with the isolator. Pressing the button for 15 seconds or so before switching on will gently pre-charge the capacitors and prevent the arc.

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Cute idea,

1 hour ago, Rick-n-Jo said:

It's likely that this particular isolator is prone to failure because the Victron contains some big capacitors. The high inrush current causes severe arcing and burning of the contacts when switching on. If you want to keep an isolator in this circuit, a fix is to wire a 470 ohm resistor and push button switch in parallel with the isolator. Pressing the button for 15 seconds or so before switching on will gently pre-charge the capacitors and prevent the arc.

 but not a good idea with current day SMPS inverters or chargers.

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8 minutes ago, Boater Sam said:

Cute idea,

 but not a good idea with current day SMPS inverters or chargers.

Care to elaborate on why? Genuine question, always keen to learn. It's worked for us for ten years, two Victron combi 48/3500/35s, but they are left on pretty much 24/7.

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SMPS don't take kindly to being slow run up. they are basically oscillators switching mosfets and dependant on frequency to achieve correct currents in mosfet gates. I don't know if this applies to Victron units but its worth mentioning, everything is going more and more electronically sophisticated.  

Edited by Boater Sam
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1 hour ago, Rick-n-Jo said:

It's likely that this particular isolator is prone to failure because the Victron contains some big capacitors. The high inrush current causes severe arcing and burning of the contacts when switching on. If you want to keep an isolator in this circuit, a fix is to wire a 470 ohm resistor and push button switch in parallel with the isolator. Pressing the button for 15 seconds or so before switching on will gently pre-charge the capacitors and prevent the arc.

Except that the 2 previous, much cheaper, switches lasted much longer, with much higher use of the inverter. 

 

2 minutes ago, Boater Sam said:

SMPS don't take kindly to being slow run up. they are basically oscillators switching mosfets and dependant on frequency to achieve correct currents in mosfet gates. I don't know if this applies Victron units but its worth mentioning, everything is going more and more electronically sophisticated.  

Certainly too sophisticated to run our Zanussi, or is it that the Zanussi is too sophisticated to run from the Victron. 

Edited by pearley
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14 minutes ago, Boater Sam said:

SMPS don't take kindly to being slow run up. they are basically oscillators switching mosfets and dependant on frequency to achieve correct currents in mosfet gates. I don't know if this applies to Victron units but its worth mentioning, everything is going more and more electronically sophisticated.  

OK thanks. I do connect mine to the battery before switching the Victrons on.

16 minutes ago, pearley said:

Certainly too sophisticated to run our Zanussi, or is it that the Zanussi is too sophisticated to run from the Victron. 

Don't know but we have the same issue, even with twin inverters. When it gets stuck just switched off and on again at the mains plug gets it going again.

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It seems to be caused by the transient spike when a high load like the water heater switches off. If that happens when the machine motor is about to start, it will twitch/ stick. OK if the drum is already turning. I think this is a separate problem to just not working at all, which as said is more likely the mains sense feature.

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43 minutes ago, Rick-n-Jo said:

It seems to be caused by the transient spike when a high load like the water heater switches off. If that happens when the machine motor is about to start, it will twitch/ stick. OK if the drum is already turning. I think this is a separate problem to just not working at all, which as said is more likely the mains sense feature.

That's sort of what happens with ours. Will start off ok but at every change of programme the drum will just sit there twitching away. Sometime switching off on the front panel and restarting at the next big of programme, ie rinse or spin, will get it going but it often seems as if the programme takes much longer. Have hot into the habit of just using the washer when our Onan gennie is running. 

 

It was whilst trying the washer with a resistance load that the previous isolator packed up. 

Edited by pearley
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2 hours ago, Boater Sam said:

SMPS don't take kindly to being slow run up. they are basically oscillators switching mosfets and dependant on frequency to achieve correct currents in mosfet gates. I don't know if this applies to Victron units but its worth mentioning, everything is going more and more electronically sophisticated.  

Not really relevant, provided the Combi is switched off. The capacitors are still presented across the 12v connections but the SMPS circuitry isn’t.

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19 hours ago, Flyboy said:

Highly unlikely as Blue Sea are waterproof  & IP66 rated (they are pressure jet rated according to Blue Sea). Also they have tin plated copper threaded terminals.

 

6 hours ago, pearley said:

It sits in the engine bay alongside the isolators for the engine and the generator. Those  two are now 12 years old and have never given any problems. 

 

 

4 hours ago, Rick-n-Jo said:

It's likely that this particular isolator is prone to failure because the Victron contains some big capacitors. The high inrush current causes severe arcing and burning of the contacts when switching on. If you want to keep an isolator in this circuit, a fix is to wire a 470 ohm resistor and push button switch in parallel with the isolator. Pressing the button for 15 seconds or so before switching on will gently pre-charge the capacitors and prevent the arc.

 

This is why I was reluctant to firmly point the finger at corrosion on the Blue Sea isolator; because, in theory, it shouldn't be the issue. But then corrosion is a funny thing, its driven by a differential in electrical potential at each end of a conductor, so "world's best" waterproofing would be inadequate if there was a potential in the circuit which led to deposits from something else building up at a point on the circuit. I never did fully understand corrosion at university, so I'll leave it to others who might suggest a definite cause; or everyone else to make suggestions on this one.

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5 hours ago, Rick-n-Jo said:

The high inrush current causes severe arcing and burning of the contacts when switching on

Except it’s not been turned off for four years, so therefore not been switched on either. 

 

I wonder if the contact springs have become a bit lazy just sitting there doing nothing for years. 

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15 minutes ago, WotEver said:

Except it’s not been turned off for four years, so therefore not been switched on either. 

 

I wonder if the contact springs have become a bit lazy just sitting there doing nothing for years. 

How many liveaboards ever turn their isolators off? 

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40 minutes ago, pearley said:

How many liveaboards ever turn their isolators off? 

Exactly. So it’s not arcing from a high inrush switch-on current that’s corroding the contacts. 

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