I see some situations described overhere that resemble ours. But not completely and not with a clear solution that could work in ours
Situation: We live on a ship with a 5k MultiPlus II, a Cerbo GX, 10kWh LFP batteries and this set operating without shorepower for 90% of the year.
We use PV during the summer season to keep our batteries charged with some MPPTs and run everything through the inverter of the MultiPlus.
In the early spring and autumn the PV doesnât deliver all the power we need, so the additional power is brought in through a small generator.
The problem in this situation is when sudden larger loads are switched on during the time that the generator runs to fill the batteries. Loads like pumps for our watersuppy etc.
Then, the MultiPlus âswitches offâ the charger, tries to get enough power to the loads from the batteries and then slowly goes on with charging from the generator again.
The moment of âswitching offâ the charger âconfusesâ the small generator. Itâs capable of providing 1600W of power continuously, so I have the input limited to 7.5A and so the generator provides around 1500W, charging the batteries, which is perfectly ok for our needs.
But when the charger of the MultiPlus is switched off in this abrupt way, the generator has no way of adapting as fast and sometimes stops alltogether like it was in overload (probably because the load goes from around 1500W to 0W at an instance).
I tried fiddling with PA (Power Assist) on and off, but that didnât help. In both settings (PA on or off), the charger stops completely when accomodating the sudden loads thus confusing the small generator.
Maybe thereâs another setting in VEConfig I could try? Some setting that does âseperateâ the inverterfunction and the chargerfunction of the MultiPlus completely? So the the inverter covers the loads onboard (like it also does when operating on PV) and the charger just converting anything coming in from the AC-in to flow into the batteries. And this WITHOUT stopping this charging when a sudden load appears at the inverterâŠ
Hope there is a way
Not really you are basically asking for two direction of electron flow (charge and convert) over one path both over cables and through electronics. It would physically cancel out itself i guess for lack of a better way of explaining it simply.
A more suitable (stable load) way is a separate charger that does not carry AC loads.
I donât think the charger switches off⊠quite the opposite⊠the load from the pumps probably causes the input parameters to be ignored briefly and the 7.5A to be exceeded.
To test this, simply reduce the input current value to 2A or similar and observe what happens. I assume that the generator briefly sags when the pumps are switched onâŠ
If necessary, post the message in the German section⊠Some of the content and meaning always gets lost in translation.
Have you ever thought about a soft start for the pumps?
If that is an AC Genset, adding a so called âchargeverterâ to your system might provide an alternative solution. Technically these are based on industrial telecom PSUâs that combine a very forgiving wide range AC input stage with a high efficiency programmable DC output. There is at least one commercial product from EG4 and and they are not too difficult to build yourself either and quite popular in the diy and open source scene. We build our own based on the Huawei R4850Gx and R4875Gx PSU series in combination with a dedicated BMV Smartshunt.
You could get a used PSU Eltek FlatPack 2 from eBay at around 150 EUR. You can get CAN-bus control board to define the output voltage to match your battery or use open-source projects.
Both Eltek as well as Huawei will work and both are well supported with open source projects for settings and control. As I only have experience with Huawei Iâd recommend an newer models such as the R4850G5 (3kW continuous) or even an R4875G1(or G5?) (4kW continuous and AC & DC input ready) for having the functionality of setting a fixed maximum (AC) input power limit (on top of having programmable default CC-CV DC output settings (active when an external can-bus control signal is absent for longer then 60 seconds). When used at half or less of their rated power these are extremely efficient too, 96% or higher. You would only need can-bus to set the default values correct once. Pretty handy stuff. R4875G5.Rectifier.User.Manual.V2.3.pdf (563.5 KB)
Thanks for all the reactions and suggestions.
As I read them, thereâs no real solution in the settings to âsplitâ the inverter and charge-functions of the Multiâs.
It would be a nice to have feature, for these kinds of situations, but I can understand the choices of Victron in this.
The suggestion, of a separate charger like suggested, looks like the most feasible path to follow.
It would be nice to have such a seperate charger appear as a supported device and have it managed by the allready available Cerbo
Like just connect it to the batteries and the VE-Can and go
We added a BMV Smartshunt to incorporate the DC power values and itâs relay (remote, via Node-RED) to switch it on and off. Not much else to do with the chargeverter pre set to correct CC-CV and max AC power. But there is an open source esp dev board available that integrates with home assistant, if not also with Victron already. Not sure what else you could need really, generator to AC in, DC out to battery.
what do you want to manage? the gasoline engine canĂt be started by the Victron system - he additional charger is nothing else as an AC-coupled PV System
I use such a charger to get my batteries faster charged with PV Power
Rule is simple: as long as the MP2 pushes more than 1700W in the Batterie, charger starts
I think the right solution (sugested by multiple people) is an external âchargerâ that gives a steady load on the generator.
The MP2 simply is not able to switch slowly from a large load to a (temporary) lower load.
