question

martin24 avatar image
martin24 asked

Additional Generator at Multigrid?

I have a Multigrid with a Byd B-Box and AC coupled SMA PV inverters. This works well as ESS and can also switch to island mode, using the Battery and PV inverters as power supply.

Is there a reasonable way to charge the battery with a diesel or gasoline generator in case of a longer power outage (and bad weather)?.

I guess I cannot connect the generator instead of the mains supply because it is not stable enough. Or can this be done?

Or can I connect an additional charger (powered by the generator), in parallel to the multigrid to the battery?

Regards,

Martin

Generator
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

A three way transfer switch would allow you to connect a generator to the AC-input of the Multigrid / Multiplus-II while safely isolating the grid. This would require a licensed electrician.

However this configuration is not recommended, as the programming of ESS seeks to minimise import from the AC-input, when running a generator you wish to minimise generator run time. There is also the possibility of back feeding to the generator, which is never recommended.


Depending on your backup requirements, perhaps the safest way would be to put the three way transfer switch between the Multi and the loads. This way once the battery in the ESS system is exhausted, the multi is disconnected safely, and the generator runs the loads until the grid / solar supply returns. Not optimal for generator run time.


Perhaps others users have some better design options?


One other note, I would HIGHLY recommend a Victron MPPT DC solar supply of some sort, so that your system can automatically wake up if you discharge your batteries to the point when the multi shuts down (and with it your AC solar).

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

martin24 avatar image
martin24 answered ·

Hi Guy,

thanks for your answer.

My main question was: what happens if I supply the Multigrid with a generator instead of mains supply. Will that work at all or is a generator output too unstable so that the Multigrid shuts off?


An additional problem: when generator frequency is not absolutely stable the AC-coupled PV-inverters will switch off.


I agree, DC coupled chargers would be much better (not only for the issue that the system cannot start with empty battery), but the AC-coupled invertes are already there.


Regards,

Martin


2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.