48V Charger

[Andy]

I have a small p2500i generator which I want to hook up to my house. With it having a floating neutral ie no earth-neutral link there doesn't appear to be a safe easy way of incorporating it. Therefore what I want to do is charge the US5000 directly on the DC side. On the victron forums they mention that you can 'just' use another multiplus. That seems like quite an expensive solution. The other charging inputs are the DC MPPT and victron quattro. I don't envisage using the generator unless the battery stack gets discharged so in that case it will not be possible to over charge as I'll probably only get 10% SOC if I'm lucky from a tank of gas.

I was wondering what issues I might have if connecting a charger to the DC side. Are there any cheaper solutions than the Multiplus? It seems a bit excessive paying for all the extra features when all I want to do is some dumb charging. If I get another brand would they all get 'confused' or as they provide power does the voltage cumulatively rise correspondingly?

[Andy]

I've just seen Resybaby's post which I guess is asking similar questions. I was going to plug whatever solution in to my busbar. I haven't seen the solarlock anywhere else but it seems a good price for what I need to achieve. only 900W but then my generator would probably not be happy running constantly at a higher output.

[sharpener]

I have a small p2500i generator which I want to hook up to my house. With it having a floating neutral ie no earth-neutral link there doesn't appear to be a safe easy way of incorporating it.

Don't see the problem, if grid is connected you have earth-neutral link from that, and if grid down since you have a quattro does that not provide a link in this situation? At most you would need an external contactor driven from ?AC2-Out.

[Andy]

Well, that was my initial plan but as I've read more I'm not sure.

I wanted to install on AC IN 1 but as the ground relay opens the generator needs to provide the MEN which it doesn't in my case. Can I just bridge the earth to neutral at the connection point in the Quattro to achieve this? I can't do it in the plug as then all my cabling to the generator would need to take 9kW worst case. From what I can tell my house hold RCDS would work in this scenario.

The other problem is that I haven't managed to achieve a stable current draw from the generator yet. I had the quattro disconnected from grid/house to experiment in charging the battery. The generator was hunting like crazy. I still have to try disabling LOM to see if that makes a difference.

[Andy]

Trying to clarify my thoughts. It is essentially an IT system. From various reading around the web you can't just use normal RCDs in an IT system and expect them to work. Other protections are required. So if I just charge the DC directly from the generator, accepting the inherent loss, then I don't have to worry about all these problems. I probably gain in efficiency just have the generator charge constantly. It's a bit annoying as I didn't really need to buy a Quattro, or I should have bought a more expensive generator.

EDIT:
But... if I consider bridging the ac in N -> earth which is connected to earth stakes then it is equivalent to figure 3. here https://electrical.theiet.org/wiring-ma ... busters-6/

[sharpener]

Will need to study that link at greater length! But I think you are right in that you need an N-E link somwhere for the genny if your grid is TNCS. Perhaps not essentlal if you are TT, maybe converting to TT would be simpler?

Presumably you are connecting the genny to the ACIn 2 as that is what the distinguishes the Quattro from the Multiplus. As I only have the latter I don't know what happens with your internal N-E link relay when the grid fails but the genny input is active. Or whether the ACOut 2 is enabled in this scenario but I think it can be using Assistants. My thinking upthread was that if ACOut 2 is connected to the coil of a n/c contactor this could make an external N-E link whenever it switches off.

Have you looked to see what Victron Wiring Unlimited has to say?

[Andy]

Cheers sharpener .

Perhaps not essentlal if you are TT, maybe converting to TT would be simpler?

It is something I have thought of. The house is on 3m deep soil with granite below. It isn't terribly conductive especially when dry. We had 3x2m copper stakes put in for the Quattro but only achieved about 120 Ω. I was wondering if those discs with conductive concrete might be a way to go.

Presumably you are connecting the genny to the ACIn 2 as that is what the distinguishes the Quattro from the Multiplus. As I only have the latter I don't know what happens with your internal N-E link relay when the grid fails but the genny input is active. Or whether the ACOut 2 is enabled in this scenario but I think it can be using Assistants. My thinking upthread was that if ACOut 2 is connected to the coil of a n/c contactor this could make an external N-E link whenever it switches off.

The gen is on AC1 as that is the logic used in the system operation. If either AC input is live then the default behaviour is top open the ground relay. The assumption is that a neutral to earth connection is provided elsewhere. So in normal operations if I lose the grid then the neutral earth connection is made in the unit. However one is still required if I connect the generator. There is a way to override this behaviour

Have you looked to see what Victron Wiring Unlimited has to say?

This post on the Victron community has the following

Another downside with generators operating at the AC-input is, that the network type plays an important role. Most smaller gensets are isolated IT type gensets. It is not legally allowed to use them at a house installation by most local laws. You have to use a genset equipped with RCD, those are not the entry level price ones.

I had a house changeover in the past done by an electrician and never got told about which type of generator I could use. Presumably as the victron disconnects from the grid it is ok to use? If the N-E is combined then all the RCDs are downstream of that connection so should presumably function. Further down Markus then mentions that the easiest solution is just to add a DC charger and then all issues go away. I am still tempted to do this as I am not intending to have the generator sit there waiting for a load. It's incredibly inefficient doing that.

[AGT]

You can add bentonite or marconite to improve soil conditions for the earth electrode

[Andy]

You can add bentonite or marconite to improve soil conditions for the earth electrode

Ah cool, thanks. I think I had that round my water borehole. Do I dig round the existing electrodes and back fill? We put cat litter in some of them as that was supposed to work as well.

EDIT: just been looking at post hole borers. I'm not sure they will work in our ground but I could keep trying until I find a route down without rocks in it.

[AGT]

Yes, you kind of make a mortar with it.

You could also get bare copper tape, and bury this in a trench, tie it to the rod too and run a 16mm2 earth to the equipment.