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yeoman-24 avatar image
yeoman-24 asked

MPPT sizing and MC4 connectors

I have used the Victron MPPT calculator tool but the different PV connections setting has made a big difference and I don’t know why.

Example 1,

When I put in, 2 Longhi 435w panels (I have a Fiat Ducato lwb so plenty of room for solar) in series on a 12v system with 4mm2 cable over 10m with pv terminal connectors, the calculator recommends a 100/50 MPPT. Hurrah, that’s what I have bought.

Example 2,

However, if I change just the connectors to MC4 and everything else stays the same, the calculator changes the recommendation to 150/60. I note that this recommendation has a MPPT with actual MC4 connections as part of the MPPT

I intend to use MC4 connectors to connect the panels together and run the cables to a 100/50 terminal connection unit. Will I be ok to use example 1 and use my 100/50 MPPT? (Screenshots below).

Thanks

Example 1

d6a5f689-d335-45b1-a9f6-fd6d494b78a9.png

Example 2

4d3429c5-9667-4430-aba0-d5200c1ffbbd.png

MPPT Controllersmppt calculator
d6a5f689-d335-45b1-a9f6-fd6d494b78a9.png (325.9 KiB)
4d3429c5-9667-4430-aba0-d5200c1ffbbd.png (340.3 KiB)
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2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Yeoman_24,

The type of connector you use between the panels doesn't make any difference to the design (most are MC4 or some other similar variant).

The MC4 setting in the Victron MPPT Calculator refers to the way those panels are connected to the MPPT itself (not how the panels are connected to each other, and/or the connection at the panel end). Victron has limited models that have an MC4 connector directly on the MPPT. Some situations require it, or prefer it, but many do not.

It is also usually fine to use the terminal connection models, there is a larger range of those (especially in the smaller models) so you can get a closer fit to your requirements.

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yeoman-24 avatar image yeoman-24 commented ·

Hi Guy. That’s great. Thanks for your answer

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rikhf avatar image
rikhf answered ·

You're panels are able to do 435x2=870W. Take 2% loss that makes 870x0,98=853W on the battery side of the MPPT. Assuming you charge LFP batteries we divide 853 by 12,8V. That makes 66A. So the 100/50 loses 16 Amps and the 150/60 only 6 on full power. The two different outcomes of the calculator is weird.

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ejrossouw avatar image ejrossouw commented ·

@rikhf Not at all. If you specify MC4, the 150/60 is currently the smallest MPPT with MC4 connectors that will meet his requirements. For TR it will be the 100/50 as mentioned given the wider range of options.

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