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walter-widmore asked

Solar Panels 4S with 1 charge controller or 5S with 2 charge controllers?

Hi all,

I'm deciding on a solar setup. I already have:

- 395W 20 solar panels (Voc 46,3 / Isc 10,74 / Vmpp 38 / Impp 10,39)

- Victron MPPT 250/85 (but could probably exchange this for a 250/100 if needed)


I've read that it's better to connect as much panels in series as possible. My panel dealer told me to put the panels in 10S2P but I think that's not possible with a Victron system?


So question is do I put my panels in a 4S5P system and would that work with a single MPPT 250/100 controller?

Or is there a better setup where I can put more panels in series with multiple MPPT controllers?


This will be connected to a 24V battery. Victron MPPT calculator form link: https://mppt.victronenergy.com#djE7Y3VzdG9tLDQsNSw1NCwtMTAsNzAsMjQsMTAuMzksMC4wNCwxMC43NCwzOTUsMzgsLTAuMjcsNDYuMywxMiw2


Many thanks!

MPPT Controllers
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2 Answers
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wkirby answered ·

You have 7900W of PV and a 24V battery. This is 330A of charging current when it is nice and sunny outside.

A good fit for you would be 5x 250/70 controllers each with 4S1P (4x 385W modules). This means each controller will be making 65A in good conditions.
Also 5x 150/70 controllers with 2S2P would work.

The 24V battery system is very much a limiting factor for such a large system.
For example, in a 48V battery system you would be able to use 1x 250/100 with 12 modules and a 250/70 with 8 modules.

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walter-widmore answered ·

Thanks for the quick reply.

Am I correct that in that case I can connect the 5 charge controllers in parallel to the battery and connect them all together using RJ45 cable to the Cerbo GX?

Would be an expensive solution tough, might be worth upgrading the inverter to 48V instead.

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wkirby avatar image wkirby ♦♦ commented ·
Make sure you get the VE.Can model of MPPT, these MPPTs and the CerboGX all connect in a string using RJ45 cables. Terminators are supplied.

You are right, things get very expensive at high power levels when a "low Voltage" battery system is use. 48V systems allow for smaller battery cables too.
There is also a much wider choice of 48V lithium batteries on offer, often at better cost than 12V or 24V batteries.

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walter-widmore avatar image walter-widmore wkirby ♦♦ commented ·

Thanks. Would this setup also be feasible?

Using an MPPT 250/100 and an MPPT 250/85.

solar-setup-18-panels.jpg

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