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cj1 avatar image
cj1 asked

Multiplus II 48V/5000: Absolute maximum charging voltage that can be set?

The Multplus II 48V/5000 datasheet states a maximum charging voltage of 64 volts, and a maximum "inverter input voltage range" up to 66 volts.

The https://www.victronenergy.com/media/pg/MultiPlus-II_GX/en/configuration.html page at section 9.2.1 (Equilisation) states that it is possible to charge up to 68 volts (for flooded/OPzS) batteries.

What is the maximum charging voltage that can be configured?

Community member langer75 states 69.56 volts for an MPPT device. Does this upper limit apply to the Multiplus too?

Stretching the 48V MultiPlus to its upper voltage limits

Would setting such a high charge voltage make it possible to create a DIY 20s LiFePo4 battery? 20 times 3.45 = 69 volts. Usually the LFP cells fall back to 3.3-ish voltage levels after a few hours. Would this mean I have to wait a little while before the MultiPlus before it is able to take energy out of a 20s LFP battery?

Is the 66V limit a hard limit, and is it 66.0V, or 66.5V. Is there some wiggle room on that front?

Multiplus-IIbattery charging
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3 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

IMO it's not a good idea to run the system at the upper voltage level all the time.

There are already a few questions about that topic.

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cj1 avatar image cj1 commented ·

I can't find the few question regarding this topic.

Can you add a little more detail, why you think that it is not a good idea to run the Multiplus battery bus at the upper voltage level?
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Duivert NL avatar image
Duivert NL answered ·

Bad idea, system is designed for 48V with room for higher voltages for charging, and margin for safety

why would you want do this? I dont see any usefull scenario…

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cj1 avatar image cj1 commented ·

To increasy capacity (kWh) and reduce LiFePo4 battery building costs and because Victron's advise is to run LiFePo4 cells at 3.45 volts maximum. The same BMS can monitor both 16s as well as 20s. The balancer can be set to kick in at lower levels, f.e. 3.40 volts. The same box can house both 16s as well as 20s. Higher voltage at the same power = less current => less heat (exponential are the ohmic losses).

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Duivert NL avatar image Duivert NL cj1 commented ·
i understand your reason why, but the multiplus 2 datasheet says maximum input voltage is 66V, victron put that in there for a reason..


as sean in the next answer states he is running his system at 64V charging, thats already the maximum you can set the multiplus to


running your system higher can cause isseu's and or malfunctioning of your multiplus beyond warranty...
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cj1 avatar image cj1 Duivert NL commented ·
When the internal charger can charge up to 69,54 volts, I don't expect the inverter, at the same DC bus, to become damaged at that 69,54 voltage level. Or are my expectation wrong?
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sean avatar image sean cj1 commented ·
Have you confirmed that the "69.56 volts for an MPPT device" is factually correct via a datasheet ?

I'm looking and don't seem to be able to find any mention of this 69.56 voltage.

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sean avatar image sean sean commented ·
... found it.
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sean avatar image
sean answered ·

I run a fair number of 16s system (including my homes), max charge of 64v using single/parallel/multiple parallel MP - without issue for many many years with zero issues.

These units are specified as per the documentation, and they definitely are capable of running to the limits, but straying outside of them would be at your own risk.

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