Twin 240V

[derekmercer]

I have just returned from a brief cruise through Normandy. After tying up in the marina, I normally plug my 240V shore cable to keep the batteries topped up. I have a powerful charger/inverter, and find that it draws more than the 5 amps most French marinas have as a limit - hence the circuit breaker trips. After resetting it a couple of times, the current flow will drop to "float" levels, and all remains well.

As several sockets are often unused, I thought about plugging in to two sockets at the same time to avoid this problem, but would end up with one "live" plug. Very dangerous. Does anyone know of a circuit diagram/black box which would avoid this? All hepful suggestions welcome, and all obvious comments deemed acknowledged.

LONDONCAT

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[ColinW]

Can't you turn it down a bit? It takes 1200W to blow a 5A breaker, if your charger is, say 80% efficient, you must be putting about 80A into the batteries. I'm no expert but doesn't excessive charging current reduce the life of batteries, even deep cycle ones?



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[Oldhand]

How do you intend to get 2 plugs into 2 sockets at exactly the same time?

It is usually the inductance of the charger's transformer that causes an initial current surge. When I had a similar problem I installed a "slow start" device which was available from RS Components which cured the problem. It was just a component which had high resistance at low temperature and as it heated up the resistance dropped to near zero. It was a long time ago and I can't remember the part number but this is the route you should investigate.

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[halcyon]

In days gone, and may be the same now, in the States you bought your power by the socket, and you had multiple sockets on the boat. Thus if you needed 25 amp you paid for one socket, 50 amp you paid for two sockets etc.
If you fit a relay in the second socket line, and connect the coil to the socket side, it will isolate the socket till you plug power into it.

Brian

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[Stemar]

I'm not an electrician, nor have I any direct experience of 3-phase, but, with that caveat, here's how I understand it.

"Can I plug in to more than one socket?"

Probably. 240v AC is one phase of 415v 3phase electricity. If all the sockets you use are on the same phase, you'll be fine. On any given post, I'd expect this to be the case. Adjacent posts, quite possibly not.

If not there will be a loud, and probably expensive, bang, and all the lights will go out in the marina. If the lights don't go out, LOTS of amps will flow through your cables until a fuse blows (there may well not be one in the bit you've short-circuited) or everything melts and molten copper splatters everywhere.

Your move. How lucky do you feel?

 

[derekmercer]

Many thanks for your suggestions.

I suspect that the circuit breakers are "tripping" a little before the full 5 amp, because after resetting it a couple of times, it settles down and tops up the batteries normally.

Maybe the slow start its the answer - I will peruse the relevant web site.

Fair winds


Derek

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[Oldhand]

Hi again Derek,

I found the device I used, it is a cheap and simple to install current "Inrush Supressor" component type 10R-6A (10 ohms initial resistance 6A max current), RS part number 210-746, £2.65. To install break the "live" wire between your boat's charger circuit switch, insert a "double choc block connector" connect "live-in" and "live-out" to one side of the choc-block and the 2 legs of the Inrush Suppressor to the other side such that the supprssor is in "series" with the "live" wire supply to the charger. Operate the charger from the boat switch with any switch on the charger itself left "on".

Be sure the suppressor "choc block" is securely mounted and well insulated. Also ensure the actual suppressor isn't touching anything and has plenty of air around it - it will get warm! Note the resistnace of the suppressor once stable conditions are established is only 0.142 ohms.

Your charger isn't a Victron by any chance? That was the type I had to use the inrush suppressor with.

Let us know how you get on.

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[halcyon]

If you fit one use a ceramic connector block, we used inrush surpressors on big Sealine chargers in the 90's and they get hot. Also carry a spare one, they tend to be a bit unreliable, and burn out.

Brian

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