Smart Inverter?

Aug 26, 2018
34
3
Funster No
55,861
MH
Don't own one yet
Exp
Newbie
Just learning about inverters...

Does anybody know of an inverter that can isolate when on shore power, i.e. autosense AC power coming in from the shore (terminating on busbars) and isolates itself preventing AC power coming from both battery and shore?

Or do they all do this?
 

eddievanbitz

Trader - Funster
Oct 4, 2007
5,351
16,976
Taunton Somerset
Funster No
540
MH
RV
Exp
since 1989
Just learning about inverters...

Does anybody know of an inverter that can isolate when on shore power, i.e. autosense AC power coming in from the shore (terminating on busbars) and isolates itself preventing AC power coming from both battery and shore?

Or do they all do this?
The ones with automatic transfer do it, ones that don’t can easily be installed that way using and external purchased device or a suitable relay in series

If you buy an inverter/charger, it will monitor the incoming shore power and auto invert and short fall I.E. shore power supply 6amp and suddenly Motorhome requires 12 amp the inverter/charger will take up the slack to avoid power disruption and blowing the shore power requiring it to be reset

Don’t forget to install a RCD in series on the inverter output to the 13 amp sockets
 
OP
Red_48
Aug 26, 2018
34
3
Funster No
55,861
MH
Don't own one yet
Exp
Newbie
Thank you Eddie

Sadly I have already purchased a Victron Energy - Charger 30A 12V which is not an inverter, so I would need to buy a separate unit.

When shopping Invertors, I know I want a pure sinewave model. This model states it has "High voltage battery stop", is this the same as "automatic transfer"?
 

eddievanbitz

Trader - Funster
Oct 4, 2007
5,351
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Taunton Somerset
Funster No
540
MH
RV
Exp
since 1989
Thank you Eddie

Sadly I have already purchased a Victron Energy - Charger 30A 12V which is not an inverter, so I would need to buy a separate unit.

When shopping Invertors, I know I want a pure sinewave model. This model states it has "High voltage battery stop", is this the same as "automatic transfer"?
No, that just means it turns off I assume.
 

DBK

Jan 9, 2013
13,253
20,918
Plympton, Devon
Funster No
24,219
MH
PVC, Murvi Morocco
Exp
2013
I rigged up an automatic change over relay and wrote a thread about it on here somewhere. Others have also done it and others have fitted manual changeovers.

The one circumstance when being automated isn't perfect is if you have a very low amp supply. I've come across 3A in a few places. This isn't enough to run a hairdryer or my coffee machine so I had to unplug the EHU cable and run the inverter. You could get around this by adding a switch to force the relay to change instead but the need hasn't arisen frequently enough for me to have bothered. :)
 

eddievanbitz

Trader - Funster
Oct 4, 2007
5,351
16,976
Taunton Somerset
Funster No
540
MH
RV
Exp
since 1989
I rigged up an automatic change over relay and wrote a thread about it on here somewhere. Others have also done it and others have fitted manual changeovers.

The one circumstance when being automated isn't perfect is if you have a very low amp supply. I've come across 3A in a few places. This isn't enough to run a hairdryer or my coffee machine so I had to unplug the EHU cable and run the inverter. You could get around this by adding a switch to force the relay to change instead but the need hasn't arisen frequently enough for me to have bothered. :)
Or, simply put the AC main on the Normally Closed contacts, so the relay only being energised when the inverter is ON.

Starting from scratch an Inverter/Charger is the best bet as it would enhance your 3amp up to the capacity of the inverter to avoid any issues
 
Jul 5, 2013
7,278
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Tunbridge Wells
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26,797
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Since 2013
Starting from scratch an Inverter/Charger is the best bet as it would enhance your 3amp up to the capacity of the inverter to avoid any issues
Eddie when you fit one of those does it render the existing Electrobloc charging of the hab batteries redundant? And does it deal with solar as well?
 

eddievanbitz

Trader - Funster
Oct 4, 2007
5,351
16,976
Taunton Somerset
Funster No
540
MH
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Eddie when you fit one of those does it render the existing Electrobloc charging of the hab batteries redundant? And does it deal with solar as well?
The electrobloc charger is disabled. There are no issues with Solar. I have 2 Lithium batteries, 3 x 150w solar panels and the Victron Multiplus 2000/80 and it all works a treat. On my camper there are three very large domestic TV's run from a HDMI distribution unit, a Humax 1Tb Freesat Digi box all mains, so the inverter is rarely off.

Luckily my wife insists on having a hair dryer and tongs I get Wife approval for all of this, and cost, whilst a consideration is not too high on the list.
 
Last edited:
Jul 5, 2013
7,278
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Tunbridge Wells
Funster No
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Since 2013
The electrobloc charger is disabled. There are no issues with Solar. I have 2 Lithium batteries, x x 150w solar panels and the Victron Multiplus 2000/80 and it all works a treat. On my camper there are three very large domestic TV's run from a HDMI distribution unit, a Humax 1Tb Freesat Digi box all mains, so the inverter is rarely off.

Luckily my wife insists on having a hair dryer and tongs I get Wife approval for all of this, and cost, whilst a consideration is not too high on the list.
Thanks. Only you and Eurotunnel would ever call what you have got a "camper"!!!!!!!!!!!!!!!!
 
Nov 17, 2018
22
7
East Sussex >>> Fife
Funster No
57,251
MH
Van Conversion
Exp
6 years
Just joined and seen this today. FWIW I have just bought a complete Votronic system - kit comes well recommended. The Inverter will use the batteries but as soon as it senses 230V hook up it will switch to that. All the kit came from RoadPro - see RH column on this page for 5%. This is my system;

Votronic VBCS 60/40/430 Triple = Charger
Votronic VPC Jupiter 400 = Panel
Votronic Inverter SMI 1700 ST NVS = Inverter
Votronic Bluetooth-Connector S-BC

I am using 2 x 200W panels and 2 x 200Ah Tube Cell batteries.
 

DBK

Jan 9, 2013
13,253
20,918
Plympton, Devon
Funster No
24,219
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PVC, Murvi Morocco
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2013
I'm happy to manually switch the power source from shore to inverter and forego any "auto invert during a shortfall" but I'm concerned that the shore power charger will be energized by the inverter, creating a loop. See diagram.

https://www.dropbox.com/s/ecp2x13uqqxrm6v/Inverter.png?dl=0
The usual scheme is to connect the inverter output to the 240v sockets only. In your case through a double pole switch. I used a relay but a manual switch would be fine.

Edit. Just had a look at your wiring diagram (an annoying process as DropBox tries to get me to install their app - much better to upload the image directly to your post) and you just need to wire in the inverter to the socket side of things.
 
Last edited:
OP
Red_48
Aug 26, 2018
34
3
Funster No
55,861
MH
Don't own one yet
Exp
Newbie
Are you suggesting I need to isolate the shore charger when the inverter is in use?
 

DBK

Jan 9, 2013
13,253
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Plympton, Devon
Funster No
24,219
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PVC, Murvi Morocco
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Are you suggesting I need to isolate the shore charger when the inverter is in use?
I'm struggling a bit with your terminology but I think I understand. :)

In your diagram where you show the wires going to the sockets is where you need to break in. What you need to find is a suitable double pole changeover switch. The sockets will be connected to what I might call the centre terminals and the switch will either connect them to your "shore power" or to the output of the inverter.

If you do it this way you could stay connected to say a low amp supply (6A isn't unusual) and this would keep the battery charger running and the fridge while the inverter could be powered up to run a coffee machine or whatever from the sockets.

You also need a suitable RCD fitted where the shore power enters the vehicle and best practice these days suggests a latching RCD on the output of the inverter too.
 

DBK

Jan 9, 2013
13,253
20,918
Plympton, Devon
Funster No
24,219
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PVC, Murvi Morocco
Exp
2013
This how I wired my relay but the same idea will work with a manual switch.

240v wiring diagram.jpg

In hindsight it would have been better to connect the coil to the inverter output and I will change it to this configuration when it gets a bit warmer. :)
 
Nov 17, 2018
22
7
East Sussex >>> Fife
Funster No
57,251
MH
Van Conversion
Exp
6 years
I'm happy to manually switch the power source from shore to inverter and forego any "auto invert during a shortfall" but I'm concerned that the shore power charger will be energized by the inverter, creating a loop. See diagram.

https://www.dropbox.com/s/ecp2x13uqqxrm6v/Inverter.png?dl=0
That won’t work - you are creating a loop whereby the charger could take power from the inverter to charge the batteries that power the inverter. I suspect something would go bang.

Without something smart or a switchover your shore power sockets are exactly that and can’t be run from the inverter.

The Votronic inverter we are using is the line before the charger and any 230V sockets. It senses when on MHU and switches from battery to MHU.
 
OP
Red_48
Aug 26, 2018
34
3
Funster No
55,861
MH
Don't own one yet
Exp
Newbie
Thank you. I have amended my diagram to reflect a Single Pole Double Throw manual switch on the positive wire between the existing shore charger and the proposed inverter (see link below).

This would effectively isolate the shore charger or inverter.

The switch position would be moved from Inverter to Shore when connected to shore power. But I'm unsure whether the inverter would be damaged if the switch was left set to the inverter when connected to EHU?

https://www.dropbox.com/s/ecp2x13uqqxrm6v/Inverter.png?dl=0
 

DBK

Jan 9, 2013
13,253
20,918
Plympton, Devon
Funster No
24,219
MH
PVC, Murvi Morocco
Exp
2013
Thank you. I have amended my diagram to reflect a Single Pole Double Throw manual switch on the positive wire between the existing shore charger and the proposed inverter (see link below).

This would effectively isolate the shore charger or inverter.

The switch position would be moved from Inverter to Shore when connected to shore power. But I'm unsure whether the inverter would be damaged if the switch was left set to the inverter when connected to EHU?

https://www.dropbox.com/s/ecp2x13uqqxrm6v/Inverter.png?dl=0
If I'm reading your diagram correctly then your inverter will be damaged as the output from the inverter and the shore power are connected together. I don't know if it would be damaged if the inverter was switched off but it would certainly be damaged if it was switched on by accident as the phases would be out of sync and you could have a virtual short circuit. The sort of systems used in domestic solar installations are clever enough to sync the inverter output to the mains so that electricity can be sold back to the grid but I don't think a typical MH inverter can do this.

To avoid this risk the switch must be directly in the cables between the sockets and the busbars. I would use a double pole one but I think you could use a single pole one but I would be worried about the inverter being left switched on and a fault to earth occuring. If you can find a suitable double pole switch then for the small increase in cost I would strongly recommend you use one to eliminate this risk.
 
Last edited:
Nov 17, 2018
22
7
East Sussex >>> Fife
Funster No
57,251
MH
Van Conversion
Exp
6 years
Must agree with DBK. Far too much reliance on remembering to disconnect, unplug, switch over switch off. TBH I think you are taking too many chances just to save a few quid.

I don’t know what your 230V load is but if you don’t want to buy a smart inverter could you not just have all of your 230V outlets downstream of the inverter so that 230V is always from the batteries / charger via the inverter.
 
Reactions: DBK
Aug 6, 2013
7,498
6,101
Kendal, Cumbria
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27,352
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"Isolation" in the case of mains (or inverter) wiring means switching both L & N. You cannot always assume L/N won't be reversed from a EHU and without looking at every permutation of connection possible with your switching arrangement I'd assume that L/N reversal may cause unwanted hazards. I'm trying not to appear pedantic BUT - why use colour if it serves only to confuse? At first glance (where colour might be of use) it is impossible to separately identify L/N and 0/+12 wiring. Especially as you use DC polarity notation to refer to Live and Neutral wiring. I believe @Techno has written up a decent inverter / EHU / charger switching system that also meets low cost requirements.
 
Jan 19, 2014
2,757
6,496
Derbyshire
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29,757
MH
Elddis Accordo 105
Exp
since 2014
I wired a double pole isolator switch in to switch between ehu and inverter. I don't want a contactor buzzing away all day and if power goes off I don't want our battery flattening.
IMAG1027.jpg
Middle position is both off.
 
OP
Red_48
Aug 26, 2018
34
3
Funster No
55,861
MH
Don't own one yet
Exp
Newbie
Diagram amended with both positive and negative entering the switch.
https://www.dropbox.com/s/ecp2x13uqqxrm6v/Inverter.png?dl=0

Would this switch be suitable?
https://www.ebay.co.uk/itm/32-AMP-ROTARY-CAM-CHANGEOVER-SWITCH-3-POSITION-4-POLE-ALUMINIUM-NEW-PTA10/331117046146?epid=1088384512&hash=item4d181d2982:g:k8sAAMXQXaxRITVO#shpCntId&shqty=1#shId

Can anyone see any problems with the Inverter being innovated by 12v whilst isolated (when the switch is set to OFF or EHU)? I can always switch off the inverter locally.
 

funflair

LIFE MEMBER
Dec 11, 2013
11,573
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Guisborough
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Will the 240v ehu socket on the van be live with the inverter running? or does the RCBO isolate this.

Martin
 
Nov 17, 2018
22
7
East Sussex >>> Fife
Funster No
57,251
MH
Van Conversion
Exp
6 years
Only if it is separately switched off.

And the van MHU connection should be a plug not a socket so the pins will be live.

And there is still the risk of having both MHU and the inverter live on the same line.

All in all not safe or satisfactory.
 
OP
Red_48
Aug 26, 2018
34
3
Funster No
55,861
MH
Don't own one yet
Exp
Newbie
The switch sitting between the charger and the inverter would isolate the inverter when the EHU is use.

Similarly, the same switch would isolate the charger when the inverter is use.
 
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