MPPT 450/200 at its limit

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1

Hello,

Today, in good weather, I noticed that my MPPT 450/200 throttles back when it reaches the 200 A limit.

I have 17 kWp on the roof, oriented north-west / south-east.

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There’s no problem voltage-wise. However, current-wise, it always throttles back to 198 A here. (The image was just a snapshot.)

Is there somewhere I can see in a graph how often the system throttles back and how much headroom there is? Then I could consider whether it might be worth splitting off a few panels and giving them their own MPPT.

2

In VRM Advanced section add a widget that shows PV Voltage and Current for your MPPT. You will see the clipping there.

3

Well, this MPPT can only handle 200 A …

You’ll have to test whether your modules would really produce more … for example, by disconnecting one string and seeing whether the others then deliver more.

How can east and west produce almost the same amount??

4

It’s a flat roof with a 10° tilt.

Therefore, the values are fairly similar.

5

Thanks, I tried that, but the resolution is pretty poor at 15 minutes.

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I’ll put something together in Home Assistant. Hopefully, I’ll be able to display more precise values there.

6

In VRM settings you can change default 15 minutes to 1 minute

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7

Thanks, it’s cloudy again now, but apparently the sun is supposed to come out again tomorrow.

I’ve created a switch in Home Assistant that turns on at 190 A and switches off again below 190 A, and I’ll use a statistics helper to track how many hours it’s on for.

That way, I have at least two areas I can check.

The only question is at what point a new MPPT would be worthwhile.

The cable won’t cost anything, just a new DC combiner box and MPPT

just for the “summer months”, when I already have too much PV power anyway.

8

Depends on how much you get paid for feeding electricity into the grid ;O)))

And how big is your battery?

9

The mppt is max 4000W per tracker, max 11500W overall - the limit determined by your battery voltage multiplied by a maximum of 200A at 25C.
Typically the recommendation is to over-panel by 30% so 15kWp.
All in the charger datasheet.

10

@HolgerBle Unfortunately, the feed-in tariff is only 8–9 cents.

My battery is still 32 kWh.

@nickdb

Yes, I hadn’t expected to go above 11 kW with my orientation, since it’s 8 kWp per direction. But apparently I can get there quite easily after all.

11

In my experience, here at least, we lose about a third of production. Cloud edge effect, not included.
Its never a good idea to run a charger above 75% for efficiency.
I would add another mppt.

12

I’ll give it a try tomorrow when the sun stays out for longer. Then I’ll disconnect two strings (east and west) and see how much more the other two produce.

And then I’ll probably order two more small MPPTs…

Once you get started :sweat_smile:

13

No need to do disconnect anything. Go to Advanced section and create a custom widget which contains PV power of all of your MPPTs. Unfortunately there has not been a clear day since I installed my system, but in this example you can see that L3 inverter (white line) starts producing later as solar panels connected to its MPPTs are pointing in South-West direction where L1 and L2 panels are facing South-East and are producing earlier in the morning.

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14

If you evaluate data via Home Assistant over MQTT: There is the topic ././solarcharger/<geräte-id>/MppOperationMode as an integer value. With “0”, the MPPT is off; with “2”, it is operating at full power; and with “1”, its output is reduced.

15

I’ve now created two helpers:

sensor:
  - platform: history_stats
    name: "MPPT Voltage Limited Dauer"
    entity_id: sensor.mppt_450_200_hq2539paxgz_mppt_betriebsmodus
    state: "voltage_current_limited"
    type: time
    start: "{{ today_at() }}"
    end: "{{ now() }}"
    state_class: total_increasing
    unique_id: mppt_vl_dauer

  - platform: history_stats
    name: "MPPT Voltage Limited Anzahl"
    entity_id: sensor.mppt_450_200_hq2539paxgz_mppt_betriebsmodus
    state: "voltage_current_limited"
    type: count
    start: "{{ today_at() }}"
    end: "{{ now() }}"
    state_class: total_increasing
    unique_id: mppt_vl_count

and I’m displaying the whole thing in Home Assistant as a statistics graph. It’s still cloudy at the moment, but I hope it works:

type: statistics-graph
title: MPPT Voltage/Current Limit
period: day
days_to_show: 30
chart_type: bar
stat_types:
  - sum
entities:
  - entity: sensor.mppt_voltage_limited_dauer
    name: Dauer (h)
  - entity: sensor.mppt_voltage_limited_anzahl
    name: Anzahl
16

With 11 kW of power achieved, you’re within the real-world range to be expected from 17 kWp (under optimal conditions, such as sunlight hitting at exactly 90 degrees). I don’t think another MPPT will be worthwhile.