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adding third solar panel

h4ckberry

Member
Joined
Sep 18, 2025
Messages
8
I'm a total newbie, trying to get my head around solar panel sizing. I already have a Victron MPPT 150 | 45 charge controller for my 12V, 280Ah battery bank.
I'm looking at getting a couple of 250 watt panels and wiring them in parallel. I've been trying to figure out the math, and I think that would give me about 26.6A of current.

Is my thinking correct, and will my 45A controller be oversized for just two panels?
Is a third panel okay, since that would get me pretty close to the 45A limit?
Also, would it be better to wire the panels in a series parallel configuration if I decide to add more down the line? Any thoughts would be a huge help!
 
Your math checks out, two 250W panels in parallel on a 12V system would give around 21 to 26A depending on conditions, so your 45A controller is fine, just not fully utilized. Now, a third panel would push you close to the limit, which is okay as long as you don't exceed it
 
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