Inverter feeding inverter

Inverters
1

Hey everyone,
I’d really appreciate some comments regarding my plans.
I have an inverter (LuxPower) with battery and panels. This works very well 99% of the time. With the recent weather I’ve discovered that I’m not as bulletproof as I’d hoped. I’m off grid so I can’t use Eskom as backup. I have a small generator but I now realise I need to feed my system properly. I’m looking at connecting a generator permanently to my genny connection on the inverter. I’m looking at an inverter generator as they are a lot quieter. My question is, feeding my inverter with another inverter could cause problems and I would prefer not to create a problem. The reason I’m asking is I had an experience with an inverter feeding a soft start and they did not play nicely together resulting in a fried soft start. I want to avoid any problems so if anyone has experience or suggestions I would be very grateful. Sorry for my rambling :grinning:
Thanks

2

In the other place there has been some discussion about this. The consensus is that it won’t work, because the generator hunts as the load changes, and so voltage and frequency are variable, and so there will be a cycle of

  1. Load on the generator increases
  2. Voltage and maybe frequency drop
  3. Inverter disconnects
  4. Load on the generator decreases
  5. Voltage comes up
  6. Inverter reconnects
  7. See 1.

It may depend on how good the generator is. Perhaps if you hugely overspec then it will do the job.

3

Im running a Microcare in offgrid, i have a 1kw inverter genny I sometimes need to use, i bypass the inverter but go via ac to dc battery chargers, the units have a wide input so they dont mind the genny variables. 47 to 63hz and 180 to 264 vac(even dc to dc capable)
Its an added cost, but solves a few issues for me.

4

Is this all permanently connected, or is there some manual changeover required?

And what batteries? Lithium? SLA?

5

Thanks Bobster,

This is what I was thinking. I was thinking of limiting the input from the generator to say 3/4 of maximum load. There is a setting available in the inverter to do this. My thinking is that the inverter will take this available power and divide it between the household load and the rest will go to the battery. I would be glad to hear your thoughts.

Thanks

Kevin

6

Hi Gh3kko,

Thanks, now that is a solution I hadn’t thought of :grinning:. I will have to check if it is possible to connect separately to the battery. The battery is a 10kw Deyness and I will research the best way to do this.

Cheers

Kevin

7

Hi again Bobster,

The system consists of 4kw peak panels, a 10 kw LuxPower hybrid inverter and a10.24 Deyness lithium battery. This is all permanently connected. When I lose power I shut off the inverter and make an illegal connection to my 1000watt generator. This is OK for emergencies but doesn’t really help solve the problem. The solution I was thinking of was make a fixed connection to the inverter genny input via a breaker. This would be to allow me to charge the battery via the inverter. This is why my question arose concerning inverter to inverter. The other possibility is to buy a non inverter generator. I know there are other problems associated with that, namely voltage and frequency variations creating problems. Gh3kko had a good suggestion that I use a battery charger in between the generator and the battery. Not sure about availability of ac to 48vdc chargers though. Any further thoughts or suggestions would be appreciated.

Thanks again

Kevin

8

My question was really meant for @Gh3kko. AIUI he is directly charging the batteries. I am wondering what happens when the genny is running and connected to the batteries and SOC = 100%. Do the chargers take control of that? And is there some manual work to be done to connect everything together when needed?

9

I too am interested in this :grinning:

10

The thing that caught my attention is Victron’s introduction generator start and stop functionality in the Venus/Cerbo software.

That interfacing opens up a whole new level of automated control IF one has Victron.

Or even if one takes a Rpi, install the Venus OS on that, to control the gennie start/stop using a BMV or whatnot, for the SOC.

Just a idea I thought to share

11

The thing that caught my attention is Victron’s introduction generator start and stop functionality in the Venus/Cerbo software.

We are doing that to my genny in coming month.

12

The chargers i use taper off as the voltage you manually set on them is reached, so they will try and do CC then CV after that with minimal amps just to maintain float, as its an inverter genny it runs slower and slower(and quieter), but the days i need it there is no whay i fully charge, just enough to make it to the next day. My chargers are small 360w each( 3 of them but only 2 on genny)

But depending on your genny you can get bigger ones, on FB there is one installer that installs 2kw chargers although he does not want to give me the model no, i know its a meanwell one.
Again its not cheap but it does bypass some currect coct regs aswell :wink:

There is also a automatic change over switch for those that want to use a genny to inverter, put that where your eskom source is and let it change over to generator input, think they even have a generaror start relay, around 500 to 600 bucks on takealot.

I’d love to oneday do a dc to dc generator to stepup/charger and cut out the middleman.

1 Like
13

Thanks for the explanation Gh3kko,
I started to look for a 48v charger and nearly died when I saw the prices. Insane. Couple that with the fact that I can see no sensible way to connect the charger either, means this will not work for me. I’m beginning to think Bobster idea of overspeccing the generator could work. I’m also still wondering if my idea of limiting the input into the inverter might actually work. I might try this with my small genny and limit the input to say 500w and see what happens. If it works I’ll have my answer. Just hope nothing gets damaged :pray:. I’ll report back once I’ve tried it. So unless anyone has another suggestion this will have to do. I’m just wondering how many people are running a genny into their inverter. Rather than do that are they using a changeover switch and bypassing the inverter altogether. I guess I’ll never know.
Cheers

14

I am running a genny into my Victron.

First genny was petrol 4kW. Now a 7kw diesel genny. Settings set to accept 2kw max

15

Thanks Robert,
That’s exactly what I wanted to hear. Can I ask if the genny is an inverter model and have you ever experienced any problems with this setup. Limiting the input to the inverter was what I was thinking of doing. Not pushing the generator should allow it to be stable while feeding the inverter.
Cheers
Kevin

16

My 2 cents on this subject.

What I’ve deduced from all I’ve read for if I’m forced to get a gennie:

  1. Smaller diesel inverter generator with auto start/stop.
  2. Will be interfaced with Cerbo/Venus as it will control the gennie based on SOC and time of charge.
  3. Match the gennie to the charger, probably an MPPT, that is connected to the battery bank.
  4. Recharge the batteries at the gennies optimal setting, its most effective setting.

End Result:

  1. The inverter does its thing and runs from the battery, the battery powers the inverter.
  2. Gennie supplements the battery, so load control will be critical at the time.
  3. Need the gennie to be quiet and installed in the right spot with sound reduction, as it would probably run at night when loads are the lowest, using all the sun can give the next day.

The tricky part for me:
The weather, as it is only x times per year that I cannot do it all with sun, like this past Cpt winter with rain the same as back in 1976.

17

Normal genny’s. Straight connection to inverter
The 4kW was old and voltages, Hz all over the place, just set parameters on Inverter to a wide variance. Worked quite well for me.
The diesel genny is more stable with constant voltage and Hz hovering between 49 & 50.

We gonna do auto start via wifi in coming month

18

Thank you Robert,
I think I will try to connect my small genny first setting the input to the inverter really low and increase little by little. If that works I’ll invest in a larger genny. I just need enough power to get me through the night. My system works well. It is just the multiple days of rain/cloud cover that get me :grinning:. This is my first year off grid so I’m learning and adjusting as I go.
Cheers
Kevin
PS. 48v charger more than R30k so won’t be doing that.

19

https://www.mouser.co.za/ProductDetail/MEAN-WELL/NPP-1700-48?qs=Rp5uXu7WBW8spzPEszsQ0g%3D%3D

There is also the EG4 chargeverter.

20

So I was thinking … Victron inverters can take a whole lot of bad “shore power” and make it clean power. The settings are there.

What if one was to take like a 2nd hand Multiplus, connect it to one’s battery bank, connecting the Multiplus to a generator as its AC_in 1, as a dedicated generator charger?

No NRS settings nothing involved, use the bad input power settings … just take whatever power comes in, and charge the battery.

The equipment is built for it.

And then one has a “backup” if the main inverter develops an issue.