I’m off grid and am struggling to charge my x12 48v AGM batteries to float, via the Victron multi I have, via a 4.5kw diesel generator.
The multi is a 48/3000/35-50 with a maximum output of 7.5A 1500W.
The volts come up, but the 7.5A output from the multi is just not getting them to float.
I’ve been thinking about a 48v charger attached to the terminals inside the multi, connected directly to the generator, will this work ? ???
What do other off griders do ??
Ideas greatly received?
If I go over 7.5A on the generator current setting, it shuts down and restarts???
Nope! 7.5A ???
If I set the generator current setting to 8A it turns itself off.
I wish I was getting 35A charge in to the batteries, alas not…… 7.5 or nothing.
How do I achieve 35A current setting and out put ??
I’ve had a similar issue with a much smaller off-grid system (gel batteries) and using a petrol generator. These charts might be of interest.
Another chart:
charging is more effective at lower temperatures.
Pass through will work, but only when multi is set to charger only.
When I set multi to on, it limits me to 7.5 A
The guys at midsummer solar have looked over my system online, they’ve done the setting for me.
Please elaborate. Does it stop? Switch off power? Or rejected by the Multi?
That’s a 240V gen, so 7.5A is 1800W. Your Multi can charge at 35A (at battery V, let’s say 50V, that’s 1750W. So really it’s maxed out for charge.
No point mucking with ‘Charge only’ and suchlike, leave it switched ON, then the gen can serve loads too at the same time.
I read your batts as being 690Ah @ 48V, is that right? A good design point for AGM’s would be a tenth of that, so ~70A. 48V chargers are fairly scarce, and another Multiplus would be competitive, Say a larger 5000/70 (the 70 means Charge Amps) or an additional one like you already have paralleled in (get the EXACT same one to parallel). The bonus is more inverter capacity.
But first work out why the genset is gagging at more than 7.5A output. Watch the power specs while it’s running for clues. If it’s getting rejected, see here… MultiPlus Generator FAQ [Victron Energy]
Hi,
It clunks inside and stops the AC from entertaining the multi.
Then, when I reduce the amps down to 7.5 it allows AC to flow again.
The guys at midsummer energy tell me that he multi will only take a max of 1600w input.
I was hoping I could leave the multi switched to on, it accepts a 35A charge, and not a pathetic 7.5A!!
Also, I’d like it to be ON, and then when my usage goes over the multi 3kw, the generator kicks in and passes through its 4.5kw.
Frustrated at I have to put it on charge only to get pass through.
So yesterday, we had the washing machine on, drawing 1900w, switched to on, it took 1500 from the generator and 400 from the batteries.
I’d like it to take all 1900 from the generators, leaving the batteries draw free.
Just trying to get advice from anyone Victron is like try to blood out of a stone !!
I’m sorry, no just a single generator.
Please be patient with me, I’m here because I’m at the end of my teather.
I’m also dyslexic
It’s a Hyundai dhy6000se.
The guys at midsummer energy have told me that the problem is a dirty waveform from the generator, that’s why it won’t go over 7.5A.
Any ideas on the pass through not working when the inverter is on ?
Thank you
All help most appreciated
a 4.5kVA generator should be good for 15A continuous at 240v. (4500 *0.8/240) this is the adjustment for power factor. (can correct this upwards if 6kVA).
this should give you a theoretical 75A at 48v - but the multi will limit this to 35A.
If you have a multiplus2: look in the grid tab of VE-configure (on a lap top connected with a Mk3) You will see a protection log - this will give the reason for the generator disconnecting under the higher load. AC input current should be set to 15A, and the battery charge current (charger tab) can be configured to 20 - 30A. This leaves plenty of power - or should do - from the generator to run the loads.
Most likely, the disconnect will be due to either an under-voltage or under frequency event. This is why it is important to look at the disconnect log. Either way, the problem probably lies with the generator.
Thank you all.
This is a pic of my devices.
Yes, the multi needs updating, I’m a bit confused about the long winded victron upgrade to the latest version?
Also, how do I get in the victron windows based page.
I’m only currently on victron connect ?
You may be better off downloading the VE-bus tools from
https://www.victronenergy.com/Executables/VEConfig/VECSetup_B.exe
This makes it easy to check the inverter configuration and access the logs.
you can update the inverter firmware from Connect, just click update device and follow the steps.
You can also use VE configure on a laptop to monitor the generator volt & frequency while it is connected, or trying to connect. The VE-configure tool also allows you to configure the max generator current and battery charge current.
Please, read this…
https://www.victronenergy.com/live/multiplus_faq
Ok great.
I’ve got the config tool on my computer.
I’ve set the config 3 to weak ac input to see if it helps.
I’m a bit nervous about the inverter update, not really that confident in I know what I’m doing?
I’m ok with the 1st stage, it’s just the last part that troubles me.
If it goes pear shaped, I’ll have no power.
Hi @TheNook ,
Coincidently, similar issues here with a recently purchased Hyundai DHY6000SE - purchased around the start of February 2025.
With a Multiplus 12/3000/120 - @2100W the generator input is relatively stable. Generally with no other AC loads, 100A@12V charging is reliable, but adding other resistive loads (e.g. 800W water heater), it becomes tends to become unreliable and intermittently disconnects, especially with variable fluctuating loads (e.g. microwave turning off) even with a higher input current limit. Sometimes I have noticed that the behaviour depends on the ambient conditions. For example, at cold temperatures recently around 3-5 degC, the stability of relay switching is more erratic until the generator has warmed up after 30 minutes. Ensure that you give the generator a 5 minute warm up-time as recommend in the manual.
WeakAC option may work to some degree, but you limit your max charge by (20%). However, after reading several reports across this forum and website, it is my suspicion the quality of the waveform is simply not good enough at higher loads (>2kW). The other recommendations people have posted is ensuring use of good wiring and connectors to the generator to prevent ‘dry-joint’.
Other recommendations are disabling (UPS) and dynamic current limiting if you don’t have sensitive equipment. See this further blog post (Understanding an AC Diesel Generator - The Sumpners Afloat)
These I will try soon at some-point soon. However, confirming the errors via the diagnositc logs in VE.Configure will be helpful identify the cause of issue.
