Hello. The datasheet for Multi RS Solar states that the PV start-up voltage is 120 V. In 1.16 firmware update I’ve noticed that the lower voltage limit of MPPT was decreased from 85 to 65 V. Is there any chance that the start-up voltage will be decreased too in future updates?
I would appreciate if the start-up voltage would be decreased to battery voltage + 5 V like it is in standalone MPPT controllers. That would make it possible to use the Multi RS Solar with small solar arrays.
It would be great if someone from the engineering team could tell if such change can theoretically be done via a software update or is MPPT designed in such a way that it will not be able to start at a much lower voltage.
They are saying that the startup voltage is 120V, but in fact is around 90V. You can see by looking at the graphs on VRM.
Once the MPPT is started, it can go as low as 65V, indeed.
But because the maximum short circuit of each MPPT is about 16A, with an operational limit of about 13A, it will mean that you can’t parallelize PV strings like in the case of SmartSolar range of solar chargers.
That 13A limit will mean that you can only have one PV string at most per MPPT, because most panels have such short circuit current.
And a 13A limit at such low start voltage like you want (approx. 55V) will mean a very low generated power which will be just inefficient.
Different approach, by just making a long string rather than parallelizing multiple short strings.
Lower current of long strings will mean smaller cables.
Thank you for the information. The system that you’ve described is exactly the kind of solar array that I have - just two panels in series and BlueSolar 150/35. Not much, but better than nothing.
There may be an option in the future to install additional two panels facing a different direction, so I was wondering if I’ll have to buy another MPPT for them or will manage to somehow make Multi RS work with them.
Regarding the max current. What’s interesting is that the logs of BlueSolar tell that on some days (cold air, plenty of solar and a bit of clouds) the max current was up to 17A even though the panels have short circuit current of 14A max per datasheet, so I’m curious how Multi RS would behave in such case. Is it drawing all the amperage it can get until it will overload and shut down or is there a safety mechanism that would cap the current to 13 or 16A?
It was charging the batteries at 17A, but the PV side was carrying 12.9A (869W divided by 67.11V, assuming Pmax and Vmax were happening at the same time) so no, your panels did most likely not exceed their nameplate Isc
You should use a second MPPT if the panels are facing a different direction. Connecting them into one string would lead to the shaded panels to impede current flow trough the whole string
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Alex, are you sure 13A per MPPT?
Or 13A per 2 MPPT (whole system)?
Later hardware revision Multi RS has 2 distinct MPPTs, each having an 13A limit.
The old Multi RS has only one MPPT with a slight higher short circuit current.
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I asked because I never saw on my systems 1MPPT + 2MPPT more than 16A
(7A+9A for example)
Do you saw something like 20A or more at the same moment in sum?
- May be I have specific arrays, which never can reach more than 9A…
Yes, I saw about 18A, 9A on each MPPT channel.
I have 2 strings of 5 x 460W pannels.
A few days ago they decreased the current limit to 12 A per string for the Multi RS Solar (down from 13 A) in the datasheet.
Can someone using a Multi RS Solar confirm this change? I was about to buy the Multi RS Solar, but my solar panel current is 13.44 A…
You should worry about the short circuit current, because that current is the one that will cause damage IF the panel is mounted in reverse polarity.
The operational current limit will mean that the MPPT will not draw more than the specified figure, even if the panel can supply more than that.
Look at the panel and it’s max current as a power supply. You can always connect to it a load that is drawing less.
The short circuit current of my panels is 14.18A, which is below the allowed maximum of 16A.
I’m more worried about potential yield losses because of this operational current limit.
12A limit with a 13.44A panel means a loss of 10.7% just because of the operational current limit.
You’ll rarely get to those 13.44A… In much less than 10% of the cases… 
The Multi RS share a lot the hardware design with MPPT RS and there the operational/short currents are 16/20.
Don’t know if lower capable components are used in Multi RS or is a marketing thing in order to buy MPPT RS. Or both.
Truth is that people started to acquire a taste for AlO devices like Multi RS and the competitors offer AIO devices with much bigger current and voltage per channel. If it’s a marketing thing, it will be a loss for Victron. And if not, they better come close to the MPPT RS figures, because the market will choose…
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But why is it changed from 13A to 12A? Victron doesn’t want to annoy customers I guess, so there must be a story behind this change.
The MPPTs side and the inverter side of the Multi RS are sharing the same heatsink.
And that heat sink is pretty small for such job, even if it’s force ventilated.
See below… 2 x 3kW MPPTs and the 6kW inverter on the same, pretty small, heatsink… Not so wise…
I’ve once tested the Multi RS with 3 panels in series array (the datasheet specifies the current at maximum power as 14.53 A) for a week and indeed I never saw current drawn from panel higher than 12.9 A. I’ve since switched that array to BlueSolar 150/35 primarily because of the fan noise, that ~1.6 A difference was not significant to me as that max power would only be achievable during summer days when there is an abundance of solar anyway.
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But does it still run at a current of 12.9A?
I wonder if they just changed the datasheet, because some people complained that it is capped at 12.9A (or a little bit below 13A in general) instead of 13A.
Or did Victron actually update the firmware to limit the current at 12.0A (or 11.9A)?
You can do such thing like limiting the current in firmware, alright…
I can’t test it as I don’t have the panels that could supply such high figure and I am still on a 1.16 firmware.
I’m running v1.26 firmware which is AFAIK the latest version, so they probably didn’t decrease the current to 12 A in firmware yet.
Well I was taking a look in the firmware changelog, the latest firmware version 1.26 is from september 1st and there is nothing mentioned about the current limit.