# Odd number of panels and MPPT: parallel -then- series?

**URL:** <https://community.victronenergy.com/t/odd-number-of-panels-and-mppt-parallel-then-series/43467>\
**Category:** DIY\
**Tags:** parallel, mppt\_controllers, diy\
**Created:** [16 August 2025 20:21 UTC](https://community.victronenergy.com/t/odd-number-of-panels-and-mppt-parallel-then-series/43467 "2025-08-16T20:21:40Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![VEuser](https://avatars.discourse-cdn.com/v4/letter/v/5fc32e/32.png) [@VEuser](https://community.victronenergy.com/u/VEuser)\
**Post date:** [16 August 2025 20:21 UTC](https://community.victronenergy.com/t/odd-number-of-panels-and-mppt-parallel-then-series/43467/1 "2025-08-16T20:21:40Z")

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Let’s say you have five identical panels, 40V, 10A for argument’s sake.

Will an MPPT function correctly if you put two sets of parallel panels (2P and 3P) in series, where one “string” is just higher current than the other?

I realize this is the reverse of the way panels are normally configured, but just curious about how it might work (if at all!)

If not, is there any practical way to use a “prime” number of panels, other than having another MPPT?

Thanks!

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**Author:** ![DuivertNL](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/duivertnl/32/279_2.png) [@DuivertNL](https://community.victronenergy.com/u/DuivertNL)\
**Post date:** [16 August 2025 20:47 UTC](https://community.victronenergy.com/t/odd-number-of-panels-and-mppt-parallel-then-series/43467/2 "2025-08-16T20:47:53Z")

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Hi, It will work, but the low power panels will make the higher ones produce less energy

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**Author:** ![VEuser](https://avatars.discourse-cdn.com/v4/letter/v/5fc32e/32.png) [@VEuser](https://community.victronenergy.com/u/VEuser)\
**Post date:** [16 August 2025 20:56 UTC](https://community.victronenergy.com/t/odd-number-of-panels-and-mppt-parallel-then-series/43467/3 "2025-08-16T20:56:00Z")

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Like, “less energy” in that it’s pointless, or just not optimal? 😉

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**Author:** ![chrigu](https://avatars.discourse-cdn.com/v4/letter/c/ba9def/32.png) [@chrigu](https://community.victronenergy.com/u/chrigu)\
**Post date:** [16 August 2025 21:02 UTC](https://community.victronenergy.com/t/odd-number-of-panels-and-mppt-parallel-then-series/43467/4 "2025-08-16T21:02:13Z")

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Most likely only using four, 4S, 4P or 2S2P, would yield more energy than using five because of the weird config you would need to use. But ive never tried to be honest

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**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\
**Post date:** [16 August 2025 22:38 UTC](https://community.victronenergy.com/t/odd-number-of-panels-and-mppt-parallel-then-series/43467/5 "2025-08-16T22:38:59Z")

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as a first approximation, panels of different ratings in series will be limited to the current of the panels with the lowest Imp. In your case you have 30A of panel in series with 20A of panel, it will only produce up to 20A at 80V. In other words, no more power than 4 panels. The same is true if you tried to connect a 3S string in parallel with a 2S string, a first order approximation is the 120V string would be reduced to 80V.

The rule for series is all panels have similar Imp. The rule for parallel is all panels have similar Vmp.

You either use 4 panels or 2 MPPTs.

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**Author:** ![VEuser](https://avatars.discourse-cdn.com/v4/letter/v/5fc32e/32.png) [@VEuser](https://community.victronenergy.com/u/VEuser)\
**Post date:** [16 August 2025 23:31 UTC](https://community.victronenergy.com/t/odd-number-of-panels-and-mppt-parallel-then-series/43467/6 "2025-08-16T23:31:34Z")

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Thanks!

This also demonstrates how a “weak” panel could drag-down an entire array. Although disparity between panels of the same age/type is rare, I have found some that tested a fair bit lower under identical conditions (same Sharp panel)