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Victron BMV 712 - Does it have a memory?


jetzi

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57 minutes ago, Keith M said:

Most if not PV installation standards required a form of isolation so that any require maintenance can be undertaken safely.

Some PV installation voltages within marine applications are in excess of  200-volts

Obviously I’d agree with having an isolator if the voltages presents a hazard, but it makes no sense to extrapolate from that to saying all PV installations must have an isolator even if just a couple of 12v panels.

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2 minutes ago, Keith M said:

Surely in a situation, if the panels needed to be disconnected quickly I would rather turn a switch than have to look for a screwdriver, then undo the two screws. 

Or pull the plug.

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15 minutes ago, Keith M said:

Surely in a situation, if the panels needed to be disconnected quickly I would rather turn a switch than have to look for a screwdriver, then undo the two screws. 

But why would the panels need to be disconnected quickly? How often does that actually happen in reality? And if such an emergency situation can arise, what happens when there is no person on board to open the isolator? (Which is a roundabout way of saying that the installation must be such that a catastrophe requiring immediate disconnection of the panels must be unfeasible).

Edited by nicknorman
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I had three occasion last year when the the panels required disconnecting when the regulator was putting around 20-volts into a 12-volt battery system.

This situation caused damage to both a Mastervolt and Victron equipment.

Both unit required replacement.

 

A significant number of installers do not use the correct type of solar plug meaning that a screwdriver is required to disconnect the panels.

The cost of a switch is around £ 25.00

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3 minutes ago, Keith M said:

I had three occasion last year when the the panels required disconnecting when the regulator was putting around 20-volts into a 12-volt battery system.

This situation caused damage to both a Mastervolt and Victron equipment.

Both unit required replacement.

 

A significant number of installers do not use the correct type of solar plug meaning that a screwdriver is required to disconnect the panels.

The cost of a switch is around £ 25.00

Ok well we’ve had a thread recently about a regulator putting out much too high a voltage so obviously it can happen. But it can happen when there is no-one on the boat, which for many people is the majority of the time. Or even when the owner is on the boat but isn’t aware that there is an issue. So having a rapid means of disconnecting the panels doesn’t really fix that problem. Yes I appreciate it’s only £25 but it also introduces the potential for operator error (turning it off by accident) and more importantly introduces another source of potential failure and voltage drop.

 

So clearly there are pros and cons (both the pros and the cons being pretty minor). There is nothing wrong with having an isolator, but I question your original point that it is “bad practice” to not have one on a system where the panel voltage isn’t dangerous.

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2 minutes ago, Keith M said:

With any mircogenerating system  it is always good practise to have a means of isolating the DC output as is checked during a BSS inspection.

I think you should check the BSS inspection procedure. Solar power installations and the like are specifically not required to have any sort of isolator. They have to have a fuse at the battery end, that is to protect against excessive battery discharge into a short circuit.

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5 minutes ago, Keith M said:

With any mircogenerating system  it is always good practise to have a means of isolating the DC output as is checked during a BSS inspection.

???

 

What BSS check are you saying requires disconnecting the panels?

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To all who have question my statement that it is good practise to have the means to quickly isolate and electrical system.

I Ref to page 21 of the BSS check list dated April 2015  general requirements box at the top of the page item 9.

 

I have been a BSS examiner but not for a number years. 

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9 minutes ago, Keith M said:

To all who have question my statement that it is good practise to have the means to quickly isolate and electrical system.

I Ref to page 21 of the BSS check list dated April 2015  general requirements box at the top of the page item 9.

 

I have been a BSS examiner but not for a number years. 

And in turn I would refer you to section 3.6.2 which states that they can be directly connected to the batteries.  

 

There is no specific check that covers what you state it does.

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12 minutes ago, Keith M said:

To all who have question my statement that it is good practise to have the means to quickly isolate and electrical system.

I Ref to page 21 of the BSS check list dated April 2015  general requirements box at the top of the page item 9.

 

I have been a BSS examiner but not for a number years. 

 

And I will refer you to section 3:6:2 which says :

 

 

 

Screenshot (141).png

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3 minutes ago, WotEver said:

And in turn I would refer you to section 3.6.2 which states that they can be directly connected to the batteries.  

 

 

Just now, Alan de Enfield said:

And I will refer you to section 3:6:2 which says :

 

Great minds think alike.

 

Typical BSS examiner, doesn't read the rules and prefers to make things up depending on which way the wind is blowing.

 

Of no practical use whatsoever, just 'jobs for the boys'

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8 minutes ago, Keith M said:

To all who have question my statement that it is good practise to have the means to quickly isolate and electrical system.

I Ref to page 21 of the BSS check list dated April 2015  general requirements box at the top of the page item 9.

 

I have been a BSS examiner but not for a number years. 

It is a general requirement and all these are expanded upon in the detailed inspection list. It is not possible to fail a BSS based on someone’s interpretation of a general requirement (although I expect that happens with some rogue BSS examiners). That is what the subsequent paragraphs detailing specific points to inspect are for. I refer you to item 3.6.2 which is categoric:

 

Do all electrical circuits pass through a battery isolator, or are those requiring a continuous supply otherwise protected?
  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.
   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.

 

(my bold)

And of course this demonstrates one of the many flaws in the BSS - having made that general requirement, they then go on to specifically violate it in certain circumstances (which by the way is the right thing to do in this case, IMO).

 

Anyway you are now falling back on bureaucracy for your argument. I would still like to know why, in practical terms, you think there is a need for overcurrent protection between panels and the controller, and what in practical benefit arises from having an isolator between panels and controller for systems where the panel voltage isn’t dangerous, bearing in mind that human intervention is required to operate it and it is quite likely that a human won’t be around when the problem arises, and even if one is, most people don’t have over-voltage alarms so are unlikely to notice in the short term.

13 minutes ago, Keith M said:

I am referring to the panels and the regulator

 

Not the regulator and the batteries which requires protection in the form of fuse or a circuit breaker 

Ok but a BSS examiner is not empowered to take a general requirement and use it to make up a new pass/fail rule. If the BSS wanted the examiner to check that solar installations had an isolator between panels and controller, it would have a specific sub-para for that item. It would be an easy thing to add but clearly, the BSS don’t think such a rule has any merit.

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52 minutes ago, nicknorman said:

Most solar installations use MC4 plugs and sockets, like this:

 

https://www.sunstore.co.uk/product/mc4-solar-connectors-male-female/

Yes... that's what mine uses...... on my boat, there is one pair hidden in the ceiling behind the Mushroom vent gauze, and the others are on the roof outside, near the panels..... so a real PIA to get to, whether in a hurry, or not. In fact, when you get to them, mine are really stiff and difficult to "pull".

 

Therefore, without a switch, or a breaker switch, the easiest and quickest way to cut the power from panel to controller is to undo a screw or two.

 

Of course, because the cable between panel and controller is current limited, there is no need for the protection of a fuse/breaker. However, in practical terms, I find a breaker switch between panels and controller, in a convenient location, has been handy on more than a few occasions.

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1 hour ago, Richard10002 said:

I find a breaker switch between panels and controller, in a convenient location, has been handy on more than a few occasions.

No doubt. But that’s a world away from an (ex) BSS examiner asserting that it’s mandatory. 

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I have four 400W panels in series so they produce up to 10A at 160V. I'm not sure what the threshold of danger is but that seems like enough to cause a pretty big spark if I disconnect them abruptly on a sunny day - possibly even a shock if I touch the wrong things?

 

Seems to me like a breaker is a good idea, I don't care much whether it is a BSS requirement - it just feels like it would make maintenance tasks (like switching the polarity of shunts) a lot easier. Ideally I'd like to have breakers everywhere really but the low voltages on most of the system make that non cost effective. Since you can get a 10A DC breaker fairly affordably it seems like a no brainer to add one to the solar input!

 

No one answered my other question so I assume that it's not a problem to have solar panels in series in the sun not connected to anything, i.e. if you have the breaker turned off`? What happens to the energy - would they simply get hot if they didn't have any load on them?

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