Charger/ inverter circuits

[Broughton 2]

Is there an AC changeover switch available (shoreline/ off/ inverter) that will isolate the battery charger circuit when the inverter is selected? Such a switch could easily be made but does any manufacture actually offer one?

 

When we have a battery charger and inverter in the electrical system it is necessary to prevent the batteries trying to charge themselves through the inverter (yes?). One way is to have an on/off switch to the battery charger but some of us will forget to use it and the result may not be too good. A fail-safe method is to wire the battery charger in parallel with the main circuit (from the shoreline socket as shown on the excellent ‘Smartgauge’ web site) but this means we have an extra circuit with it’s own consumer unit (RCD and fuse/breaker) dedicated to the charger.

 

If we had a changeover switch of the type suggested we could have a fail-safe system, simplified electrics and save the cost of an additional consumer unit.

 

Or have I got it all wrong?

 

Alan

[steelaway]

Is there an AC changeover switch available (shoreline/ off/ inverter) that will isolate the battery charger circuit when the inverter is selected? Such a switch could easily be made but does any manufacture actually offer one?

 

When we have a battery charger and inverter in the electrical system it is necessary to prevent the batteries trying to charge themselves through the inverter (yes?). One way is to have an on/off switch to the battery charger but some of us will forget to use it and the result may not be too good. A fail-safe method is to wire the battery charger in parallel with the main circuit (from the shoreline socket as shown on the excellent ‘Smartgauge’ web site) but this means we have an extra circuit with it’s own consumer unit (RCD and fuse/breaker) dedicated to the charger.

 

If we had a changeover switch of the type suggested we could have a fail-safe system, simplified electrics and save the cost of an additional consumer unit.

 

Or have I got it all wrong?

 

Alan

 

Hi Alan

I have been thinking about how I would do this for 10 minutes.

I imagine all the sockets are on one 240v fuse. The only way, as you suggest is to have a seperate socket/fuse wired to the land line side. Sorry

Alex

[Yoda]

Hi Alan

I have been thinking about how I would do this for 10 minutes.

I imagine all the sockets are on one 240v fuse. The only way, as you suggest is to have a seperate socket/fuse wired to the land line side. Sorry

Alex

 

You should be able to do it by putting a break before make switch on the inboard side of the external power connector. That way you have to switch over to get external power and that would disconnect the onboard power.

[Chris Pink]

The simple way is to get an inverter/charger combination unit.

[steelaway]

The simple way is to get an inverter/charger combination unit.

 

Very pricey!!

[blackrose]

The simple way is to get an inverter/charger combination unit.

 

If you have separate inverter & charger, another simple way is to put a small notice next to your inverter switch (or the inverter setting on your mains selector switch), reminding you to switch the battery charger off. That's what I did and it seems to work! It's not totally foolproof but it's a lot easier than a rewiring job.

Edited January 28, 2008 by blackrose

[john4647]

I just connected my battery charger to the live side (shore line input) of the switch. In this way the charger only works if the shore line is connected. Doesn't make any difference where the off/mains/inverter/generator switch is and the inverter can't power the charger.

 

No doubt someone will tell me it's immoral or illegal.

 

John

[Dylan]

I just connected my battery charger to the live side (shore line input) of the switch. In this way the charger only works if the shore line is connected. Doesn't make any difference where the off/mains/inverter/generator switch is and the inverter can't power the charger.

 

No doubt someone will tell me it's immoral or illegal.

 

John

Or makes you fat........

Trouble is you won't be connected to the boat RCD. You could of course fit one in the supply to the charger. That is how mine is done.

[MikeV]

Sterling do an Auto Power selector Switch AC32A which includes a relay contact which is only activated if the switch is on shore or generator power. This can then be used to release a power relay which can control devices you do not want on the inverter such as washing machine/immersion heater/battery charger/etc.

 

Note: I found the operation of the relay was the opposite of what their instructions said - i.e. they said it was a normally open contact, I found it to be normally closed (or maybe visa versa - I can't remember! )

[Broughton 2]

You should be able to do it by putting a break before make switch on the inboard side of the external power connector. That way you have to switch over to get external power and that would disconnect the onboard power.

 

Thanks Yoda but I can't vizulise your suggestion. Do you mean to incorporate an additional switch ("break before make switch") in the input wiring to the changeover switch? Would your scheme mean onboard power (DC 12V say to lights) would be denied when switched to Inverter? I wouldn't want to loose DC circuits simply because I'm plugged into the shore.

 

There must be several ways to arrange a suitable change-over switch. Imagine for example a switch having two elements stacked one behind the other and operated by a common spindle through both elements. The first element could be the standard arrangement for a change-over switch but the second, additional, element would have only two connections (Live and Neutral) connected in series with the output from the battery charger fuse/breaker of the AC panel. Contacts in the second element would be aligned so that when 'shoreline' is selected they would make a circuit to the charger but, when 'inverter' is selected the contacts would move to open and the charger would be isolated. Job done?

 

Probably I've not described my switch very well, let's call it a two element stacked switch, but if anyone does recognise either it or something like then please shout now because my simple mechanical mind tells me it would greatly simplify the charger-inverter circuitry.

 

Alan

[john4647]

Or makes you fat........

Trouble is you won't be connected to the boat RCD. You could of course fit one in the supply to the charger. That is how mine is done.

 

Sorry, forgot to mention, the charger is wired through a B&Q RCD socket.

 

John

[Broughton 2]

Or makes you fat........

Trouble is you won't be connected to the boat RCD. You could of course fit one in the supply to the charger. That is how mine is done.

And that takes me back to where I started. I want to simplify, whilst maintaining all safety, through a single (better) change-over switch.

[Keeping Up]

I just love fixing up unconventional switches and things like this - but after much thinking I ended up powering the charger from its own supply & RCB by using a 13 Amp socket with a built-in RCB, like this, because it was just the simplest and cheapest way

[Dylan]

I just love fixing up unconventional switches and things like this - but after much thinking I ended up powering the charger from its own supply & RCB by using a 13 Amp socket with a built-in RCB, like this, because it was just the simplest and cheapest way

Great minds think alike, I was about to reply with the same solution.

[blackrose]

Great minds think alike, I was about to reply with the same solution.

 

Yeah, me too...

[Dylan]

Yeah, me too...

I've seen a good few done this way, and can't see a problem TBH.

[Broughton 2]

Great minds think alike, I was about to reply with the same solution.

 

If I understand you diagram correctly it seems an excellent scheme where we have two AC circuits, (inverter powering the auxilliary AC circuit only and the charger being run from shoreline main). However my boat is a deal more basic than yours, having only a single AC circuit and therein lies the problem.

 

Alan

[Keeping Up]

If I understand you diagram correctly it seems an excellent scheme where we have two AC circuits, (inverter powering the auxilliary AC circuit only and the charger being run from shoreline main). However my boat is a deal more basic than yours, having only a single AC circuit and therein lies the problem.

 

Alan

Well, yes and no. I should have taken the time to add some explanation, sorry.

 

If you ignore the small inverter on the right-hand-side which powers the "Auxiliary mains circuit" (this is used only for the TV and for powering phone chargers etc), and concentrate instead on the left hand side of the diagram, you will see that there is a Rediline Generator. This can be regarded as an inverter (in case you haven't come across this item, it takes 12v dc in and puts 240v ac out, exactly like an inverter. The difference is that it is not electronic, it is actually a battery-powered generator consisting of a 12-volt dc motor which drives a 240v ac alternator).

 

So I have the choice of whether the shore-line or the big inverter (Rediline) powers the ring main circuit, by plugging a 13-Amp plug into the appropriate socket, but the charger can only be be driven by the shoreline because it plugs into a separate socket which incorporates its own RCD. The 13-Amp plug is on the end of a short length of flex, the other end of which is connected to the main RCD that is permanently mounted and connected to the cables of the ring main.

 

I hope this makes it a bit clearer

 

Allan

[Broughton 2]

Well, yes and no. I should have taken the time to add some explanation, sorry.

 

If you ignore the small inverter on the right-hand-side which powers the "Auxiliary mains circuit" (this is used only for the TV and for powering phone chargers etc), and concentrate instead on the left hand side of the diagram, you will see that there is a Rediline Generator. This can be regarded as an inverter (in case you haven't come across this item, it takes 12v dc in and puts 240v ac out, exactly like an inverter. The difference is that it is not electronic, it is actually a battery-powered generator consisting of a 12-volt dc motor which drives a 240v ac alternator).

 

So I have the choice of whether the shore-line or the big inverter (Rediline) powers the ring main circuit, by plugging a 13-Amp plug into the appropriate socket, but the charger can only be be driven by the shoreline because it plugs into a separate socket which incorporates its own RCD. The 13-Amp plug is on the end of a short length of flex, the other end of which is connected to the main RCD that is permanently mounted and connected to the cables of the ring main.

 

I hope this makes it a bit clearer

 

Allan

 

Thanks Allan, I had no idea what a Redline was and I think now I understand what you are about.

 

Nonetheless, to avoid additional plugs, sockets and dedicated RCD I would still like to know if there is a changeover switch that would connect the charger through the AC panel RCD/ Breakers when shoreline is selected, then disconnect when inverter is selected. If such switch exists it would(?) simplify things.

 

I think I'm asking for something that doesn't exist but it's interesting to hear what you guys have to say. As a newcomer and fitting out my first boat I find this site very informative. Nice folks who give up their knowledge so freely are to be cherished.

[DHutch]

Im just reading this up myself having bought a small inverter and wondering how im going to wire it.

 

One option, partiularly as its a fairly small inverter, would be to simply have it running one or two indipendant sockets which are the 'inverter sockets' like allans small inverter and his auxillary mains circuit.

 

The other option is to pipe it round the existing 240vac ring main, in which case there becomes a need to have a changeover switch to select whether the ring main is conected to the inverter, or to the incoming shoreline socket.

And as the OP has highlighted, a way to prevent the battery charger running from the inveter. Partiularly as our inverter isnt big enough to power said charger.

 

Following a link on another thread to the smartgauge website they show the two ways of doing it i had come up with while thinking about it myself.

- Eather two RCD/MCB's for the two sources (shoreline & inveter), and a change over switch after that for the main ring main, with the battery charger going in before the change over swtich. Needs two RCD/MCB's and a DPDTswitch. See first image.

- Or else as the OP has suggested, have the changeover switch before the RCD and MCB's but have that swtich also disconect you battery charger and or other non-inverter loads at the same time, Only needs one RCD/MCB but needs a 4pole doublethrow switch. See second image.

 

 

 

Obvously eather way you effectively need the charger on a dedicated circuit, or atleast its feed needs to go via the control pannel with all the switches, rcd, and mcb(s).

 

Currently our charger and ring main are already fed separately from there own MCB, inside the same consumer unit, with a shared RCD so eather way could easly be done in our case.

 

It seams not uncommon to go for the first of the two options, and use a plug-in RCD in the inverters outlet as sufficient (?) protection (presumably with a suitabe fuse in the plug, plus the inveters overcurrent device) so that might well be an option for us. It seams silly to have two consumer units (RCD/MCB) but the little plug in RCDs are quite cheap i guess. Otherwise its a case of finding a purveyor of such a 4pole switch, as per the OP first posting?

 

Anythoughts on which is the better? Or if a plugin RCD is suitable protection?

- That then proberbly leads onto what to do for earthing regaurding the inveter and what its internat contections are.

 

 

 

Daniel