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

[Divertrev]

I think general conclusion is, why take the risk when there could be a risk of expensive damage. There are other safer, more efficient ways with less risk to systems.

 

[dawsey]

Running the absorption fridge from the invertor is possible at least part of the time Spring to Autumn if you have loads of solar and at least 200ah of battery capacity. I’m assuming the engine/B2B isn’t used to recharge much. In fact we are doing it right now.

When the batteries are back up to 100% by around midday or soon after, the solar power available would otherwise be wasted where it exists - so flicking over to 240V and running the fridge off the batteries/solar is OK for the rest of the afternoon and even a little into the evening. The draw from the 12V battery is about 10A, it becomes continuous as the weather gets warmer and the fridge works harder.

The problem comes when one forgets to switch back to gas when the sun has gone. We typically use 30-50% of our 200ah capacity evenings (lights TV, amp, air fryer, air con etc) and morning (making coffee, microwave, hairdryer etc) before the batteries then quickly recharge from the 600W of panels.

10A continuous, from when the sun stops supplying it (around 6-8pm) until it starts again (9am) is an additional 120-140ah, or 60-70% (ie all) our reserve battery capacity.

We have woken up to dead batteries a couple of times, so I tend not to forget to switch back to gas around 7- 9pm nowadays.

 

[autorouter]

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.

I don't see why that would happen. The inverter output will be 230V, no more, no less, and stabilised at that voltage. Any battery voltage increase or decrease will have no effect at all on that voltage.

So the charger will be powered by a stabilised 230V, it will see a battery that has a reduced voltage because it is powering loads, and will turn on its maximum output current, as it always does in these circumstances. That's what the 'bulk charge' stage always does.

The charger will boost the voltage of the battery a bit, and the inverter will notice this, but it will have no effect on the 230V output voltage. If the charger is pushing out 20A, then it will probably be drawing about 25A from the battery to do this, so it is wasting 5A for absolutely no benefit. But no reason to think any damage will be caused.

 

[autorouter]

So what happens if you switch off the mains switch on the Reich Ebox, labelled 3 in your picture (post #87)? Sorry if you've already said this, maybe I missed it. Doesn't that switch off the charger?

 

[Divertrev]

So what happens if you switch off the mains switch on the Reich Ebox, labelled 3 in your picture (post #87)? Sorry if you've already said this, maybe I missed it. Doesn't that switch off the charger?

That shuts all services down. I think I read somewhere that even on a shutdown but connected to an EHU the batteries will still be charging. Not sure but whatever, no lights, pump fridge etc. Moreover the Truma HW tankI think is dumped as well. Not been an issue as the MH is tucked up in a garage with a mains connection all nice and warm when not in use!

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[autorouter]

The next thing to ask is, what happens when you take out the fuse for the charger 12V output. I think it's fuse number 2, maybe 20A or 25A. That should stop the charging, and with any luck won't affect anything else.

If that doesn't work, you can remove the mains input fuse to the charger. It's on the back of the Ebox, a round black plastic thing. It contains a glass tube fuse. It can be removed by one of two methods, I don't know which one applies to that particular fuse. Some are bayonet type, you turn it through 90 degrees and then pull it out to extract the fuse. The other type is a simple screw type, just keep unscrewing until the fuse comes out. With any luck that will stop the charger working but won't cut off anything else like that cutoff switch does. Look at picture 3 of this set from the Apuljack website:

Reich E-Box 2 Fuseboard with Integrated Charger | Apuljack Electronics

Description - The E-Box 2 is 12V distribution system with an integrated 20A battery charger. It is one half of the habitation systems, as it is paired with a E-

www.apuljackelectronics.co.uk

 

[Divertrev]

The next thing to ask is, what happens when you take out the fuse for the charger 12V output. I think it's fuse number 2, maybe 20A or 25A. That should stop the charging, and with any luck won't affect anything else.

If that doesn't work, you can remove the mains input fuse to the charger. It's on the back of the Ebox, a round black plastic thing. It contains a glass tube fuse. It can be removed by one of two methods, I don't know which one applies to that particular fuse. Some are bayonet type, you turn it through 90 degrees and then pull it out to extract the fuse. The other type is a simple screw type, just keep unscrewing until the fuse comes out. With any luck that will stop the charger working but won't cut off anything else like that cutoff switch does. Look at picture 3 of this set from the Apuljack website:

Reich E-Box 2 Fuseboard with Integrated Charger | Apuljack Electronics

Description - The E-Box 2 is 12V distribution system with an integrated 20A battery charger. It is one half of the habitation systems, as it is paired with a E-

www.apuljackelectronics.co.uk

Thanks Autorouter, I'll have another try at removing the fuse to check whether that stops the charging function. When I tried it the other day I couldn't readily ascertain that it was isolating the charger but I'll have another go. Your second paragraph presupposes the back of the unit is accessible. It's situated under the front passenger seat and the rear is not easily accessed at all. Presumably it should be if there was a service necessity but certainly not for an ad hoc temporary purpose. The E-Box you have illustrated is I would say a later model to mine.

 

[Divertrev]

Thanks Autorouter, I'll have another try at removing the fuse to check whether that stops the charging function. When I tried it the other day I couldn't readily ascertain that it was isolating the charger but I'll have another go. Your second paragraph presupposes the back of the unit is accessible. It's situated under the front passenger seat and the rear is not easily accessed at all. Presumably it should be if there was a service necessity but certainly not for an ad hoc temporary purpose. The E-Box you have illustrated is I would say a later model to mine.

Just had another scoot around the Applejack website and I can see that my Box is a Series 1. At least I now know where to go if I ever have an issue with the E-Box itself.

 

[autorouter]

Yet another possibility is to add another trip switch to the mains consumer unit, and swap the wire to the charger from its existing trip switch to the separate one. Then you can switch it off from there when you plug the inverter into the EHU inlet.

Your consumer unit should have one RCD, and one or more MCBs. The RCD has a 'Test' button, the MCBs don't. Everything goes through the RCD, it's for shock protection/earth leakage. Then to one or more MCBs, which are for overcurrent protection. You can add an MCB, if there is space. There's a metal rail (DIN rail) at the back that the MCBs clip on to. If there's no space you could get a bigger box, or add a second box nearby.

Make sure you get a double pole MCB - those available in DIY stores are all single pole, and are not suitable. You can get double-pole MCBs from a specialist electrical supplier like CEF, or maybe a caravan accessories shop. They are used in motorhomes, caravans and campsite hookup posts.

 

[Divertrev]

Yet another possibility is to add another trip switch to the mains consumer unit, and swap the wire to the charger from its existing trip switch to the separate one. Then you can switch it off from there when you plug the inverter into the EHU inlet.

Your consumer unit should have one RCD, and one or more MCBs. The RCD has a 'Test' button, the MCBs don't. Everything goes through the RCD, it's for shock protection/earth leakage. Then to one or more MCBs, which are for overcurrent protection. You can add an MCB, if there is space. There's a metal rail (DIN rail) at the back that the MCBs clip on to. If there's no space you could get a bigger box, or add a second box nearby.

Make sure you get a double pole MCB - those available in DIY stores are all single pole, and are not suitable. You can get double-pole MCBs from a specialist electrical supplier like CEF, or maybe a caravan accessories shop. They are used in motorhomes, caravans and campsite hookup posts.

Thanks Autorouter, I think all the extra work does not justify the benefits. I’ll have another look at pulling a fuse as that’s the simplest way to protect the system. Although it could be a bit of a fag to so to do it’s only going to be if I really need to resort to that source of energy.

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[Petroleumblownapart]

Why don’t you just connect the inverter straight to your consumer unit, which is what it is designed to do? That’s what I did with mine, turning off the battery charger and running the fridge on gas.

Connecting to the EHU input IS direct to the consumer unit!

 

[stevewagner]

Connecting to the EHU input IS direct to the consumer unit!

Obviously I meant hard wiring it in. No exclamation mark required. But thank you for your contribution.