Paul avatar image
Paul asked

Controlling the charge power of a MPPT250/100

Hi all,

Looking for many years at these nice blue boxes of Victron and finally having a good reason to buy one or two: two 4,3V European batteries 48V 16S2P LifePO4 batteries from a luxury yacht.

Since I have wired each of my solar panels seperately I am able to make a nice 3x4 configuration that can be connected to the MPPT250/100 that will charge the 48V 8,6kWh battery. BMS will probably be a Batrium.

A Multiplus 2 (FX) will run on mains power and fall back on batteries when the mains are disconnected.

Normally, the Multiplus charges the batteries at will when there is power availabe from the grid.

I, however, want to control the charge of the batteries in order to have a full charge at the end of the day. The stress on the fully charged cells will be for a shorter time before I disconnect the mains to drain the battery till 40%, where the mains is connected back again in the morning.

In this way I can harvest all my solar energy into the batteries and use the solar energy for our household too.

Is there a way to tell the MPPT250/100 or Multiplus at what speed the batteries can be charged?

battery chargingmppt charging
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2 Answers
Kevin Windrem avatar image
Kevin Windrem answered ·

Unfortunately, there is no way to prioritize solar power over grid power unless you set the system up as an Energy Storage System (ESS) via a Venus device (e.g, Cerbo). But this isn't recommended for mobile installations.

There are tools like "ignore grid assistant" but that will force the inverter to pull power from the batteries even if grid power is available, as if you switched off the breaker feeding AC into the Multi.

You can reconfigure the Multi and set the charging current to 0 but you need do this manually then reverse it manually when you want to charge from grid.

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Paul avatar image Paul commented ·
Hi Kevin,

It took me some time to realize that Victron offers ESS out of the box where I don't have to control the charging/discharging behaviour.

I bought a Multiplus 48 500/70 and a Cerbo with LCD.

Things are a bit more clear now

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Paul avatar image
Paul answered ·

Hi Kevin,

Many thanks for your quick answer and to clarify: we will be using this as a stationary setup.

Our household uses about 300-400 Watts in idle mode so a battery of 8kWh will deliver enough to get us through the night in "boat" mode until the morning charging cyclus starts or until the minimum voltage/S.O.C. of the battery has been reached. In winter, this last state will be reached earlier of course.

A simple and efficient setup will be a battery charged with a PV array that is just capable of delivering a maximum power of 0,2-0,3 C of the batteries and add a simple Skottky diode between the battery and inverter.

Then The battery can be charged until it's full and the PV array switched to a simple 1,5kW SMA or Fronius inverter in order to just feed in the net.

Can a MPPT250/100 be restricted in charging power or does it just what it gets from the panels?

Maybe there's a sort of workaround.

Any thoughts here?

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