Multiplus 3000 12V vs 24V

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johnk asked Dec 29, '21

Multiplus 3000 12V vs 24V

I'm trying to decide between setting up a 24V system or a 12V system for a new Multiplus 3000.

I often see it mentioned that 24V inverters are more efficient, but I have yet to see any solid, real world apples to apples numbers to show what the difference is.

So, in the case of the Multiplus 3000 12V vs the Multiplus 3000 24V, what is the efficiency loss of going 12V? How much energy would I be leaving on the table if I were to not go with a 24V setup?

(I understand there are other considerations, like savings for smaller cables, MPPT, etc., on 24V, but in this question I'm really just focused on the actual difference in inverter efficiency.)

battery system voltage

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Answer 1 · 2021-12-29T07:21:55Z

snoobler answered · Dec 29, 2021 at 07:21 AM

1% per the datasheet:

https://www.victronenergy.com/upload/documents/Datasheet-Multiplus-inverter-charger_2kVA-and-3kVA-120V-US-EN.pdf

It's not just about wiring savings, it's about efficiency there too. At 1/2 the voltage and 2X the current, you have 4X the losses in the conductors.

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Answer 2 · 2021-12-29T07:33:56Z

Matthias Lange - DE answered · Dec 29, 2021 at 07:33 AM

I'm not sure if there is any efficiency difference inside the MultiPlus. It is more likely outside and that means the wiring.

With the 24V MultiPlus you can use smaller and cheaper wires from the MultiPlus (and all other components) to the battery.

Or you use the same wire gauge to minimize the voltage drop and power loss in the cable.

e.g. if you use the full power of the MultiPlus 3000 which is 2400W you will have about 200A at 12V or 100A at 24V. Let's say the wires from the MultiPlus to the battery are 1.5m and 95mm². In that case at 12V you will have a voltage drop of 0.93% and 22.4W of energy is wasted in the cables. With the same wire length/gauge you will only have a voltage drop of 0.23% and 5.6W power loss. If you use half the gauge (50mm²) you will have 0.44% voltage drop and 10.6W power loss which is sill lower than with 12V/95mm², but you save money and weigh on the cable.

Edit: ok the datasheet says 1% difference inside the MultiPlus at optimal conditions, it could be more at other conditions.

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Answer 3 · 2021-12-29T07:47:50Z

seb71 answered · Dec 29, 2021 at 07:47 AM

You are focusing on the wrong target. For a 3000VA Multiplus, the best choice is 48V.

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Matthias Lange - DE ♦ commented · Dec 29, 2021 at 09:11 AM

At home for ESS yes but in my opinion it makes no sense to use 48V in a RV or on a boat.
Most camping components (fridge, pumps, light, TV, SAT, LPG/diesel heaters ...) are 12V or 24V, so you would have to use DCDC converters to supply them.
Also charging with solar would be tricky because you most likely don't have enough space on the roof to mount more than one or two small panels, so you won't get the PV voltage needed to charge a 48V battery or you get problems with shading.

Next thing is that there are not much 48V you are allowed to use in a vehicle.
BYD and Pylontech for example are only for stationary use.

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seb71 Matthias Lange - DE ♦ commented · Dec 29, 2021 at 09:35 AM

He did not said anything about an RV or a boat.

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Answer 4 · 2021-12-29T09:30:29Z

klim8skeptic answered · Dec 29, 2021 at 09:30 AM

You can get 16% more charging power using a 24/48v inverter over a 12v inverter.

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