# What are the max limits for my charge controller?

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Registered Users Posts: 18 ✭✭
I have the blue sky 24 amp 12 volt charge controller.

Right now I have a 6 x 55 watt panels that produce 17 volts each and 3.2 amps each. They run in parallel. My calculations follow:

6 panels * 3.2amps = 19.2amps
add 2 more panels and I'll be at 25.6 amps.

So does that mean my theoretical max for this charge controller is only 440 WATTS? That sounds really low! Someone grade my math and tell me where I'm going wrong please. Thanks.

• Registered Users Posts: 21
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Re: What are the max limits for my charge controller?

Well, let me take a stab at this one. I'm totally new, and maybe will get my hand slapped by a solar panda. But here goes.

That is an MPPT controller, and with 25.6 amps of power @ the MPPT voltage, and if it that is actually 17 V (?!?), your calculation is right. Slightly beyond spec, as you know. If it wasn't MPPT, you'd have to consider only the battery charging voltage times the current.

400 Watts off that little controller seems pretty good.
• Solar Expert Posts: 10,300 ✭✭✭✭
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Re: What are the max limits for my charge controller?

unless your insolation is really bad, i'd think twice about adding more pvs. it is an mppt controller and as such it will often recover some power that would otherwise be wasted. being it's output current is limited to 25a then it's a good idea to allow it room to be efficient by having it around 20a maximally. now to add more won't hurt it, but you may lose some of the mppt action and efficiency. if your pvs are not outputting because of low insolations then it may be ok, but you'd need to get an idea of the max current you have been getting to the cc. you may find in such a case that 1 more pv may suffice.
now i do have to mention that the nec does not allow the cc to be fed more than 80% of its rating which happens to be 20a with that cc. in spite of this requirement and if you're being ok with violating that requirement then you can add more pvs and not hurt the cc as it would be current limited.