Can I safely connect my Inverter to my EHU input socket? (1 Viewer)

[autorouter]

There's another option, if you have no gas, and you don't want to go on a campsite, run a generator or run an Efoy fuel cell. You could get a special cable that will connect the motorhome round blue mains inlet to an EV charger with a Type2 connector. There's a couple of threads on this, if you want further info:

Has anyone here?

Made up an EV lead to top up batteries etc,is there any reason or rule not to? The plugs are about£30 and probably some 4mm flex, 10 mtrs. I like carrying spare things and this is a “just in case”thing.

www.motorhomefun.co.uk

The cable is here:

Juicy Brucie EV-Cable — Bruce Lauderdale

www.brucelauderdale.com

There's several chargers listed in the Outer Hebrides, not many, but you only need one.
Or just do a barbecue on one of those wonderful Outer Hebrides beaches.

 

[Divertrev]

There's another option, if you have no gas, and you don't want to go on a campsite, run a generator or run an Efoy fuel cell. You could get a special cable that will connect the motorhome round blue mains inlet to an EV charger with a Type2 connector. There's a couple of threads on this, if you want further info:

Has anyone here?

Made up an EV lead to top up batteries etc,is there any reason or rule not to? The plugs are about£30 and probably some 4mm flex, 10 mtrs. I like carrying spare things and this is a “just in case”thing.

www.motorhomefun.co.uk

The cable is here:

Juicy Brucie EV-Cable — Bruce Lauderdale

www.brucelauderdale.com

There's several chargers listed in the Outer Hebrides, not many, but you only need one.
Or just do a barbecue on one of those wonderful Outer Hebrides beaches.

Thanks Autorouter, but I can't see me hooking up to an EV charge point to charge my battery and heat my water up! I have a 30A B2B charger to supplement the PV Panels.

 

[Shortap]

Yes I suppose it would be. Not sure what the consequences to that are. I'll be interested to receive some feedback on that one.

I will caveat this by saying that your original power set could be different to mine but on an Elddis base they use a BCA consumer distribution unit/system which has a mains (EHU) battery charger coupled to a 12v transformer that powers the 12v ccts when shore (EHU) power is detected. I naively tried to run a Victron multiplus2 inverter with ups function and everything went a bit crazy. Basically the battery was trying to charge/power itself and there seems to be no way around this, as a number of power people have advised me. I’ve since connected the Multiplus to some dedicated 240v sockets to run kettle, toaster, chargers etc.. As I said earlier your system may not be set up this way but thought it was worth mentioning. Good luck with your mods.

 

[Divertrev]

I will caveat this by saying that your original power set could be different to mine but on an Elddis base they use a BCA consumer distribution unit/system which has a mains (EHU) battery charger coupled to a 12v transformer that powers the 12v ccts when shore (EHU) power is detected. I naively tried to run a Victron multiplus2 inverter with ups function and everything went a bit crazy. Basically the battery was trying to charge/power itself and there seems to be no way around this, as a number of power people have advised me. I’ve since connected the Multiplus to some dedicated 240v sockets to run kettle, toaster, chargers etc.. As I said earlier your system may not be set up this way but thought it was worth mentioning. Good luck with your mods.

thanks for that, your Ellis system seems to have the same functionality as my Burstner E-Box. The Renogy

 

[Divertrev]

thanks for that, your Ellis system seems to have the same functionality as my Burstner E-Box. The Renogy

Thanks for that, your Eldis system seems to have the same functionality as my Burstner E-Box. The Renogy inverter switchover (UPS) is not built in as an Auto function, it needs to be plugged in from the Camp/Shore mains so I don’t think I have a conflict in that regard. As I mentioned in an earlier post, it is not plugged in and is therefore a redundant function. When I have done a”test” connection of the inverter to the EHU I haven’t had any “crazy” effect other than the apparent 70-80 amps that was being drawn if I turned the Truma water heater on but Meanders and others have already explained that and it’s nothing untoward except an inefficient use of battery resource! The inverter is connected to its own separately dedicated wall sockets as I think you have now done yourself.

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[Divertrev]

Short answer - yes you can if sensible safely precautions are taken -
and you understand that the invertor will not power some of those heavy load devices for very long.

If using Invertor direct to the vans sub main (240V distribution board) - you need to remember to isolate either the 240V feed to the main control block (ie electroblok) to isolate the inbuilt 12V battery charger, or isolate the 12V circuit from the control unit connecting the leisure batteries to prevent the circular circuit as described in previous posts. You seriously risk damaging your charger or your main control block if you don’t do this. While these units do usually have some sort of crude charge current limiters, older ones were designed in the era before lithium batteries with very low internal resistance. They thus rely to a large extent on the much higher and ever increasing internal resistance of a lead acid battery as it charges, which limits charge current. The extremely high sustained currents possible with lithium batteries were not considered. It’s why charge current controllers are needed whem lithium batteries are used (aka B2B chargers). They are designed to safely and rapidly charge your lithiums while protecting all parts of the original charging circuits and the alternator by limiting and controlling the otherwise extreme charge currents possible with lithium batteries - and of course using a charge profile suitable for lithium batteries. Incorrect charging/cheap chargers are one of the principle cause of all these lithium battery fires we now hear so much about. The risk with the larger/higher end lithium batteries used in marine/MoHo is however greatly reduced due to the commonly specified inbuilt Battery Management Systems (BMS) - but it’s probably only a matter of time before the real nasties start to creep in
as they have done with all those electric bikes and scooters.

I did it by connecting the outlet of the invertor (exact same one as yours) to the main consumer unit via a 3 way industrial selector switch where there are two inputs - but only one can be selected. So one is the feed from the external EHU input socket and the other is the output from the invertor. I can thus select one or the other, but not both.

Then I put a 50A ideal diode in the 12V link between leisure batteries and the Schaudt Electroblok in my old Hymer - so the inbuilt mains charger can not charge the lithium leisure batteries, but the batteries can discharge to power all the normal 12V circuits as normal via the original 50A fuse. The leisure batteries will still charge from solar, or from the engine via B2B, (an integrated Renogy 50A MPPT/B2B unit) and they even trickle charge via the B2B when the starter battery is fully charged and the van is undercover but on EHU in winter (via voltage rise). It’s a bit belt and braces, but it is safe, robust, foolproof and all bases are covered.

We have used the system for 18months of living in the van. We use (alternatively) air fryer, microwave, hair dryer, TV, roof air con and all manner of other 240V stuff every day. Our 240V circuits are permanently live, only switched off when driving. The 200Ah of lithiums are kept topped up by 600W of roof solar via the MPPT/B2B. It has worked flawlessly for the whole time. We almost never need to plug in, and virtually never do, even when we can. There’s lots of free EHU in france if you know where to look.

Strangely - the only time we have ever needed to plug in EHU is full summer in south of france, where ambient temperatures are so high and the sun is so strong you have to park under a tree, then with mimimal solar (because of the shade) you need EHU for the A/C.

Alternatively you can run the ehu input to the socket at the rear of your invertor - this is neater and deletes the need for a changeover switch. You still need to disconnect/isolate your charger or use an ideal diode to protect your main 12V distribution block.

You’ve lost me a bit Dawsey but I think you are explaining the issues if the inverter is connected directly into the MH consumer unit and therefore livens up the original sockets. I’m not doing that but connecting via the external EHU socket. I suppose that in turn would liven up the MH’s original wall sockets but I can’t see there is a dangerous conflict there. The key thing with how I’m doing it is that it’s impossible for both 240v AC inputs to occur. It can only be one or the other through the EHU socket. Am I understanding you correctly?

 

[Divertrev]

You’ve lost me a bit Dawsey but I think you are explaining the issues if the inverter is connected directly into the MH consumer unit and therefore livens up the original sockets. I’m not doing that but connecting via the external EHU socket. I suppose that in turn would liven up the MH’s original wall sockets but I can’t see there is a dangerous conflict there. The key thing with how I’m doing it is that it’s impossible for both 240v AC inputs to occur. It can only be one or the other through the EHU socket. Am I understanding you correctly?

Just reread your post. Seemingly you are alerting me to a potential problem with the inbuilt charger. I am unable to turn the inbuilt charger off so I think you are saying I should use an Ideal Diode. Looked it up and understand what one is but not clear which one specifically and how/where I install it!

 

[Divertrev]

Just reread your post. Seemingly you are alerting me to a potential problem with the inbuilt charger. I am unable to turn the inbuilt charger off so I think you are saying I should use an Ideal Diode. Looked it up and understand what one is but not clear which one specifically and how/where I install it!

Hi Dawsey again about this Ideal Diode. Never heard of one until now but apparently it’s a one way electrcal valve. So if it’s to stop the current flowing the wrong way and damaging my E-Box, how will such a situation arise? Current out from battery to inverter then to E-Box via external EHU socket and then back into battery via the E-Box Charger. Where’s the potential reverse current that I need to protect against?

 

[Jeffr3y]

This is something I've considered just to keep the fridge running on a long ferry trip, but I'd have to make sure the everything else was off and figure out how to stop my charger trying to operate in a loop.
If I knew where the fridges 240 v supply was routed I could solve it easily by fitting a trailing socket to it then a 3 pin plug to the original supply leaving that connected for normal use, then switching to an extension cable from the inverter for the ferry journey, no need to switch off other things that way.

 

[Tombola]

Yes, the Renogy has the switchover facility and is therefore a built in UPS. Explained and demonstrated on the Youtube.

And it works very well too.

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[Tombola]

I am unable to turn the inbuilt charger off

A simple switch on the charger positive cable ?

 

[Divertrev]

A simple switch on the charger positive cable ?

The charger is within the E-Box so has no seperately identifiable cable to insert a switch into.

 

[Tombola]

The charger is within the E-Box so has no seperately identifiable cable to insert a switch into.

At the battery end ?
Just hate to see you wasting all that juice..

 

[Divertrev]

A simple switch on the charger positive cable ?

The charger is within the E-Box so has no seperately identifiable cable to insert a switch into.

At the battery end ?
Just hate to see you wasting all that juice..

I just can’t see a separate identifiable cable relating exclusively to the charging circuit coming into the buttery for me to put a switch into. At the moment I’m puzzled by Dawsey’s thought that I may have a potential reverse current that I need to protect against with an Ideal Diode. This could be going on the “too difficult” pile!

 

[autorouter]

At the moment I’m puzzled by Dawsey’s thought that I may have a potential reverse current that I need to protect against with an Ideal Diode.

The current between the E-box and the leisure battery can go both ways. The battery supplies current to the Ebox to run the habitation appliances. When on EHU, the charger in the E-box supplies current to the leisure battery to charge it up. That's how the E-box normally operates.

If you want to stop the charger sending current to the battery, but still allow the battery to send current to the E-box when required, then you can put an Ideal Diode in the wire. That would have a similar effect to turning the charger off. If it was wired the right way round, it would stop current from the Ebox to the battery, but allow current from the battery to the E-box

You could put a standard diode in the wire , but that would cause a voltage drop of maybe 0.5V. An 'Ideal Diode' is a little box of electronics that only allows current to flow one way, like a standard diode, but has almost zero voltage drop.

I still can't believe there is no way to disable the mains charger. Is it a Reich E-box? Does it have any number/label on it?

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[LithiumConvert]

How about an inline switch in the live wire in the mains input to to the charger.

Should be more easily identifiable.

 

[pat100]

The charger is within the E-Box so has no seperately identifiable cable to insert a switch into.I

I replaced my BCA charger with an Apuljack lithium specific one which has a ( difficult to reach - maybe I’ll try extending it one day …) on/off switch. Expensive drop in replacement.

 

[headlight]

The charger is within the E-Box so has no seperately identifiable cable to insert a switch into.

I just can’t see a separate identifiable cable relating exclusively to the charging circuit coming into the buttery for me to put a switch into. At the moment I’m puzzled by Dawsey’s thought that I may have a potential reverse current that I need to protect against with an Ideal Diode. This could be going on the “too difficult” pile!

Surely all that will happen with your proposed set up is as the van would think it was on EHU then your charger will charge your battery from the inverter using power from the battery.
All this will do is that you will end up using a few more amps than you would if your charger wasn't powered due to inefficiencies.
Inefficient use of electric but not dangerous as far as I can see ?

 

[dawsey]

How about an inline switch in the live wire in the mains input to to the charger.

Should be more easily identifiable.

The issue with such a solution, or unplugging the 240V input to the e-box or electroblok, or pulling the charging fuse, etc etc is that you have to always remember to do it. I wanted a solution that was fool proof, to know I could one day sell on the van happy in the knowledge that one wrong move, or one thing forgotten would not result in fried electrics.

Apologies to those who struggle to understand my description, and thanks to others for explaining well what an ideal diode is and how it works. They are a great solution, about £7 from ebay for a continuous 25A or peak 50A unit. Typical fuse from leisure battery to E-box is around 40-50A. Of course depends on how much 12V power you use, but these days with invertors usually powering the heavier power items it isn’t usually very much, just lights, fans, water pump. Highest load is usually the electric step but of course it’s very intermittent. More modern/cool stuff than we can afford may have higher power stuff like levellers etc.

50A Ideal Diode Controller Solar/Battery Anti-backflow 9-80V Protection Module F | eBay

1x DC9-80V 50A Ideal Diode Solar Anti-backflow Protection Module 2 mΩ (Ri). Continuous working current 25A (with no heat sink) within 60 â, backing large area heat sink forced air cooling 50A. 80V50A high power ideal diode.

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There are just two things to make sure that you don’t do, one is to ensure you can’t inadvertently connect both an external supply and the output of your invertor to the busbar of your 240V sub main at the same time. The second is to avoid circular circuits where a lithium battery is trying to charge itself via the invertor and the e-box. Of course you must also ensure that the invertor is chassis-earthed, you use correct fusing and you respect the maximum continuous discharge amp and power ratings of batteries and invertor respectively.

 

[headlight]

The issue with such a solution, or unplugging the 240V input to the e-box or electroblok, or pulling the charging fuse, etc etc is that you have to always remember to do it. I wanted a solution that was fool proof, to know I could one day sell on the van happy in the knowledge that one wrong move, or one thing forgotten would not result in fried electrics.

Apologies to those who struggle to understand my description, and thanks to others for explaining well what an ideal diode is and how it works.

There are just two things to make sure that you don’t do, one is to ensure you can’t inadvertently connect both an external supply and the output of your invertor to the busbar of your 240V sub main at the same time. The second is to avoid circular circuits where a lithium battery is trying to charge itself via the invertor and the e-box. Of course you must also ensure that the invertor is chassis-earthed, you use correct fusing and you respect the maximum continuous discharge amp and power ratings of batteries and invertor respectively.

The way the OP intends to use this, ie plugging the outlet of his inverter into the EHU input socket on the side of his van means that he can't connect an external supply without unplugging his inverter supply.
What is the issue with charging the battery from the charger powered by the inverter from the battery other than being inefficient and wasting power ?

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[dawsey]

The way the OP intends to use this, ie plugging the outlet of his inverter into the EHU input socket on the side of his van means that he can't connect an external supply without unplugging his inverter supply.
What is the issue with charging the battery from the charger powered by the inverter from the battery other than being inefficient and wasting power ?

You seriously risk blowing your ebox charger, especially with lithium batteries. Losses mean the circulating current will quickly go to the maximum until something goes bang. The circuit you create becomes completely reliant on the current limiter in your ebox, a piece of protection unlikely designed to permanently control/limit what will be possible with a lithium battery with very low internal resistance and enormous possible charge current (and enormous possible discharge current). All parts of the circuit will be at risk.

 

[Richard n Ann]

My charger is wired via a switched fused spur directly to the EHU socket. So when the van is switched over to INVERTER it's automatically disconnected

 

[headlight]

You seriously risk blowing your ebox charger, especially with lithium batteries. Losses mean the circulating current will quickly go to the maximum until something goes bang. The circuit you create becomes completely reliant on the current limiter in your ebox, a piece of protection unlikely designed to permanently control/limit what will be possible with a lithium battery with very low internal resistance and enormous possible charge current (and enormous possible discharge current). All parts of the circuit will be at risk. Hopefully it would be just an internal/external fuse that will keep popping.

The OP's 300AH lithium battery will have a BMS of probably 200-250 amps continuous draw.
His inverter is rated at 2,000 watts continuous.
His mains charger is say 30 amps.
If say he is running his hot water taking 80AH and his charger is taking 30AH then his inverter is supplying 110AH, ignoring inefficiencies.
That is well within both his battery discharge rating and his inverter continuous power rating.
I would have thought that all that would happen is he would end up with a flat battery ?
The battery BMS won't let the battery discharge at above its max discharge rating and likewise won't let it charge at above it's max charge rating.
This is not something I would do myself but I would have thought that the BMS would protect the battery which would in turn stop any damage being done to his charger ?

 

[dawsey]

My charger is wired via a switched fused spur directly to the EHU socket. So when the van is switched over to INVERTER it's automatically disconnected

View attachment 888463

Yep - another great solution. There’s lots of different ways to skin this particular cat.

 

[Revolvor]

I am surprised that in some MHs, the built in charger does not have an on/off switch.

My Sargent EC325 has an illuminated red switch on it, which I very rarely switch on, as I rely on Solar and B2B charging.

This does not affect any other functions or the control panel over the hab door.

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[MisterB]

The OP was asking about powering their fridge and water heater by connecting their inverter into their EHU connection, yet they have an inverter with a pass through facility so all they need to do is put the fridge and water heater on the output side of his inverter. When on EHU they will function as per normal and when on battery power will also function as per normal.
The only issues I see are that whilst on battery power the water heater and fridge will quickly drain down the battery after a few hours, BUT both the fridge and water heater can be switched to gas if there's a danger of doing that. There seems to be an advantage in that the fridge and water heater can be running on 240v via the inverter whilst driving if the B2B can keep up with supplying enough power to the inverter ....
I think a bigger inverter than 2000w might be an option and potentially a bigger B2B and a larger battery bank will also help, but at that sort of cost, would it be just as cost effective to get a compressor fridge ....?

 

[Divertrev]

Well guys, I really don't know what to do, other than not risk it and not plug my inverter into the EHU! It was after all not the reason I installed an external socket to the inverter and I thought it was a neat idea as a fall back if I was getting low on gas in the Outer Hebrides. None the less it certainly has been a fascinating discussion with some really useful feedback except perhaps plugging the inverter into a wall socket! It would have been a perfect and safe solution if I could switch the charging function off on my Reich E-Box but alas not to be. In answer to Autorouter's and others query that they find it difficult to understand I can't turn the charger off, attached is a photo of the opening pages of the Manual from which you should gather there is no charger switch as such. The cover page does have the numbers 226-10001 visible which may be a model number for those who are familiar with Reich products, does anyone who has a similar E-Box have a switch?

 

[dawsey]

Well guys, I really don't know what to do, other than not risk it and not plug my inverter into the EHU! It was after all not the reason I installed an external socket to the inverter and I thought it was a neat idea as a fall back if I was getting low on gas in the Outer Hebrides. None the less it certainly has been a fascinating discussion with some really useful feedback except perhaps plugging the inverter into a wall socket! It would have been a perfect and safe solution if I could switch the charging function off on my Reich E-Box but alas not to be. In answer to Autorouter's and others query that they find it difficult to understand I can't turn the charger off, attached is a photo of the opening pages of the Manual from which you should gather there is no charger switch as such. The cover page does have the numbers 226-10001 visible which may be a model number for those who are familiar with Reich products, does anyone who has a similar E-Box have a switch?
View attachment 888487

There will be a fuse you can remove. But, as stated, you would have to remember to remove it every time you plugged in.

As with all else, but especially in a camper, electrical power, especially the stored kind (energy in a battery) is precious. Using it to cook (unless microwave or air fryer) or power an absorption fridge isn’t the best use for it. Using it to heat water is very wasteful use of a (precious and slow-to-recharge) resource, especially where LPG or diesel water heaters are available. It’s because heat is relatively easy to generate, electricity isn’t. Even a pump circulating water through a metal pipe on the roof will generate hot water in summer.

Others have stated the basic physics which shows how quickly you will eat through the precious charge in any 12V battery if using it to cook or heat water.

In terms of heating water continuously (ie for a shower), Power (choose any units you want) is equal to mass flow rate multiplied by specific heat capacity multiplied by the temperature rise required - P=mdot.Cp.deltaT
It means that the, say, the roughly 1kWhr of energy in a 12V 100Ah battery will give you a normal dribbly camper (5ltr/min) shower at a balmy 40-45C (if the water is in the tank at ~ 10-15C) for an absolute maximum of 6 minutes.

Of course - this is assuming you have the required 10kW invertor and your battery can discharge that fast (even a lithium can’t btw). So you’d be heating the water more slowly in a tank where thermal losses would increase, the result would be even worse. You would get ~ one 5 min shower if lucky from your 100Ah lithium battery before it’s fully discharged and less from a lead acid which would rapidly reduce further if you continued. You’d very quickly kill a lead acid battery discharging it that much, that rapidly.

 

[VXman]

Presumably if you connect it to your ehu it's going to try charging your battery as well.

Yes - when I did this I just unplugged the mains power (240v) plug out of the EBL.

 

[VXman]

I've followed this thread and although what the OP suggests will work I can't see the point.
Electric hot water and heating are to power hungry to run off a battery and inverter.
Far better to run these on gas.
Also by 'fooling' the van into thinking it's on EHU then the battery/inverter will be powering the onboard mains battery charger to replace the current being taken by the battery with power from the battery, so the mains charger would need to be disabled/disconnected.
I can't see the point ?

I did this temporairly when my fridge wouldn't run on gas but was fine on EHU. It worked and made me think why don't i do this more often when I have plenty of charged as solar is working well filling up my batteries and I am not making used of the excess power stored. Benefit is saving on LPG.

I tend not to do it very often as we have electric bikes now so I use most of my stored energy on charging them but it's still an option should I choose to.

Wouldn't do it for my hot water as that would soon deplete batteries.

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