What size fuse on solar wires to AC200P?

With four 200W 12v solar panels in series, the Immp is 9.8a and the Isc is 10.2a, while the AC200P has a maximum solar input of 12a.

What size fuse do I need on the soar panel wires?

Specs would say a 15a fuse (10.2 x 1.56 factor = 15.9a), but that would not protect the 12a input of the AC200P.

A 10a fuse might blow on sunny days when amps go higher.

I am not sure what to do here. Help?

You don’t need a fuse.

Thank you Scott-Benson. Yes, I am aware that theoretically fuses are only needed in parallel on each parallel circuit to prevent a shorted out panel from catching fire by feedback of amps from the other panels, but series connections do not increase amperage so that fire danger to the shorted panel is not present.

I am thinking more in terms of solar flares or lightning and how to protect the AC200P and our home. I will be sure to adequately ground the frame of the ground mount with a grounding rod for these and disconnect the AC200P from the panels during storms, if I am home. Lightning has a mind of its own and I am thinking that putting a 15a fuse on the + wire in the series circuit can’t hurt and might help under some circumstances. I am now choosing 15a because it follows the formula amps (10.2) x 1.56 safety factor = fuse amps needed, i.e. 15a. That might not protect the AC200P but it could help prevent our house from burning down.

That brings up another question. Are the fuses inside the AC200P user accessible or does the unit need to be shipped back to you to change a fuse?

Thank you for your help.

There are no “user” serviceable components inside the AC200P case.

Thank you Scott-Benson. That is helpful to know.

I keep reading on here that extra amps are ignored so long as 150v is not exceeded, so a 15A fuse would protect your AC200P since some over paneling solutions run 15Amps in. I’m still trying to find out what the real Amp limit is, since i’m sure it can’t be limitless.

Thanks Birvin. I went with a 16A DC breaker and 20A fuse on each wire. I like that a breaker, shuts off both wires when it trips. The fuses are an extra measure if the breaker fails to work.

It is a bit frustrating and time consuming that better specs are not provided by Bluetti regarding inputs. If you ever find out what the real amp limit is, please share it. For now, I am staying on the conservative side and ignoring the “extra amps are ignored” statement in the manual as too ambiguous and taking the 12A as a hard limit until better specs are provided.

The two 340W panels I bought have an Isc of 10.40A and a Voc of 40.70v, so running these in series keeps me within the hard specs.

I think people can get away with over paneling for a while since panels rarely provide the rated output. However, on the rare day the panels do provide near the rated output, those that over panel might damage the Bluetti, depending on what the real (unknown at this time) specs are.

I’ll monitor the solar input over time. If the winter solar output is too low, perhaps I can add a third panel just for the winter period and remove it for the summer, depending on what readings I get. In the winter, three panels (1020W) might only yield ~500 watts. But in the summer they may go over the 700W hard limit. So, adding a third just in the winter, might be a solution.

Seems Bluetti are not the only ones stating that over amperage is ignored. After digging around, I found this same conversation on several different brands of equipment. They all seem to say the same thing, but I was able to find this nugget. Hope it holds true.

“If you’re overpaneled in voltage, the charger goes poof. Quickest way to kill a charger is overvolt it, even Midnites with their “hypervoc” can get cooked if overvolted high enough.
If overamped the extra amperage is just ignored and your output is “clipped”. For longevity not a good idea to routinely run over 80% of its capacity though.”

So I’m guessing your safe under 21.6A? I hope so. Trying to overpanel my AC300 is a challenge with 12A and 150V limits. It takes in 1200Watts per MPPT but a panel array that can deliver that within limits is not working out for me so far.

One more thing. The specs for Bluetti’s step down module specifically made for the EP500 and AC300 show an output rating of 3000W, 137V and 26A. I think I’ll take that as the answer.