Problem with Victron MPPT in parallel with wind controller

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lightbox asked Dec 17, '20

Problem with Victron MPPT in parallel with wind controller

We have the following 48V Victron setup:

Multiplus II
150/35 MPPT
CCGX
48V, 260Ah SLA array

As an experiment we are trying to add some wind power to keep the batteries topped up at night and in bad weather etc. The wind controller unit is setup to have a higher cutoff than the Victron and during testing we are putting about 4-5A into the battery array. The unit is simply wired in parallel with the DC bus.

The Victron MPPT seems to behave as expected as it approached the set-point (current backs off to less than 1A) until it switches to float mode.

What appears to happen when the Victron switches to float is that it gets confused by the other charging source and switches back to bulk charge mode. This is then dumping the full 35A into the battery and taking the bus voltage up to ~55V, until we pull the plug to stop it.

So we are wondering if there is something in the MPPT configuration options that would enable us to stop the Victron from behaving like this

Hydro and Wind Power

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Guy Stewart (Victron Community Manager) ♦♦ commented · Dec 17, 2020 at 03:55 AM

Can you do a screen recording of the Trends screen in VictronConnect of the battery voltage and battery current when this occurs?

Have you tried setting the wind controller to slightly lower target voltage than the Victron MPPT?

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Answer 1 · 2021-02-09T21:22:02Z

48v-on-56north answered · Feb 09, 2021 at 09:22 PM

2nding Guy's comments.

I have circa 4KW 12 panels across two Victron Smart MPPT's They are linked for charge control (with feedback from Pylontech BMS). The Victron/Pylontech loop controls High Voltage Discharge to just over 52V. Solar takes it to 90-97% SOC.

In parallel, a 3KW Winturbine where the (tristar)MPPT HVD s set just below 52V. This way the Windturbine is 'bulk charging' but stops before the Victron solar MMPTs. Wind will take the battery to 80-85% SOC, then stop.

Key is to prevent the Turbine taking SOC above 85-90% where most damage can be done to the battery bank either by too high current or by confusing the Solar MPPT's. Its helpful if the windturbine turbine MPPT battery voltage sense is directly on the battery terminals to avoid HV Disconnects in gusts.

HVR (high voltage reconnect) happens battery when battery voltage has dropped 1-2V to 50-51V which is equal to loosing 15-20% SOC. Hence without sun and with amble wind the batteries will cycle between 65/70 and 85/90 % SOC which is a safe operating zone for LiFePo.

You may consider some way of braking / load dumping, when the HVD occurs. I switch over the turbine to a set of dump load resistors that moves the turbine out of the power zone and its left turning slowly until the In my case a 5KW 1 ohm resistor across the turbine hence able to absorb 50-60V 50-60A which is quite a lot of braking but its acting smoothly to slow down the turbine.

In a fully operational system like an off grid house, there is plenty of ways to use excess energy so load dumping or braking should be rare.

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