Solar charging experience with EP500

Hi all EP500 owners,

I’ve recently borrowed some spare panels from a friend.

I noticed that the PV to aviation plug cable has two sets of positive and negative MC4 plugs…

Do I need to use both? Or can leave one set unplugged?

See the screenshots to see how I’ve plugged them in; can anyone explain why I only see Volts and no current?


do you have PV chosen in the settings page?

Yes, here are settings.

PV mode is selected. Does the whole EP500 need to be restarted or something for the settings to take effect?

Hi @Aduviel,

Can you show me the spec of the solar panel and how do you connect them ?

They are attached in series (to my best knowledge) and all 3 panels share the same specifications.

I also sent a video of my setup via email to per instructions from the bluetti associate.

Your panels are not out in the sun, they appear to be behind a glass window or several panes. The panels need to be placed them out in the sunlight and aim them directly towards the sun (angled and aligned so that the sun casts a shadow directly behind each panel) and insure that no part of any panel in the series has anything shading it.

You can receive voltage but almost no amperage (watts) if the panels are not exposed correctly.

When I used my multimeter yesterday. The panels, in series, showed 3 amps positioned where they are.

Does the EP500 round to 0 Watts when the total amps are below a certain amount? Shouldn’t the EP500 show ~180 W at ~60V with 3 amps if the panels are getting 3 amps behind the windows?

If you were getting three ams, you should have seen 180 watts of charging. Again though, solar panels need to have direct sunlight to operate. The position you have the panels in will not operate effectively.

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I’ve moved the panels into the full sun (per your suggestions), they are no longer behind windows. Little to no shade. Im getting 8.50amps via the multimeter. Still no amps on the bluetti display.

Im starting to suspect that my EP500 is faulty or that somehow the mc4-to-aviation cable is bad. What are suggested next steps?

Not sure how you are reading 8.5 amps on your meter when no energy is flowing. You are showing 60 volts so if your cable was bad you would be seeing the voltage. Are you possibly not having the correct polarity on your panel connections vs the Bluetti cable? May want to check the panel polarity vs the polarity of the Bluetti input to make sure the - and + is correct. It does take about 30 seconds or so for the wattage to appear.

Note: I edited my previous response if the wording caused confusion.

What do you need to be convinced? A picture? Or are my words trustworthy enough?

You take a multimeter that can measure current and you apply the leads of the multimeter to the interior of the positive and negative leads of the mc4 cables leading to the in-series solar panels… In full sun, with the panels repositioned outside (i.e. Not as shown in the previous pictures) the 3 panels, in series, output 8.5 amps…

Now if I take the same mc4 +/- ends from the solar panels, remove the multimeter leads from them and plug them into the mc4-to-aviation cable, then take said mc4-to-aviation cable and plug it into the EP500, I only see voltage and no amps…

Ill send you updated pictures if you don’t trust me.

Finally the mc4-to-aviation cable cannot be plugged in wrong, the leads on the mc4 side of that cable only allow for one direction, so no, I cannot accidently reverse the polarity: there is only one way to connect the panels to the mc4-to-aviation cable and then to the EP500.

Hope this clears everything up.

Not at all. The MC4 connectors on your panels (different brand than Bluetti) can be wired with opposite polarity compared with the MC4 solar cables with the Bluetti. That is why I asked. I was trying to get some more detail or clarity because your initial post showed your solar panels positioned inside of a building behind double paned glass and not directed perpendicular to the sun. This would hint to me that your understanding of how to connect or position the solar panels was not at an experienced level. Since you are posting about why you are not receiving charging watts and considering my above statement, I think more detail would be a good idea. It has nothing to do with trust, it is simply understanding your issue and being able to offer assistance which requires complete understanding of your setup and configurations.

If my solar panels are wired in the opposite polarity, I’m not sure how to verify that; the mc4 cables have a distinct male and female head which makes it physically impossible to connect the panels to the bluetti EP500 in any way other than in one polarity “direction” or “way”.

Meanwhile, the bluetti’s mc4 to aviation plug cable has four mc4 ports; I’ve tried connecting all possible one positive/one-negative combinations; none of them seem to make the bluetti EP500 display any amps.

In any case, testing the 3 panels connected in series with nothing connected to their mc4 “ends” other than my multimeter produces the correct amount of amps.

If i take the same mc4 “ends” from the solar panels, remove my multimeter, and plug them into bluetti’s mc4 cable, then take that cable, and plug it into the EP500, then the EP500 shows no amps/watts only volts.

So I need bluetti to send me a replacement, known-to-be working mc4-to-aviation cable, so that i can see if it is the cable that is not working or the EP500 that is not working.

You are getting voltage to the Bluetti because it appears on the screen of the Bluetti and that demonstrates cable is fine or you would not be seeing the voltage. The wiring polarity must be correct for charging or operation to function.

The way to determine polarity is to take your multimeter and test each of the solar panel MC4 connectors and determine which connector is positive and which connector is negative. The fitting together of the connectors has nothing to do with correct polarity as some mfg. place connectors in different configurations. The positivity or negativity of the electricity in the wire determines if the connector is positive or negative. Both the wires coming from your solar panel appear to be black and have a white tag which I suppose contains the polarity info for each wire. It looks like you then have those two black wires connected to extension MC4 cables which may or may not be the correct polarity.

Let me know what the bluetti’s EP500 aviation-to-mc4 cable positive end is supposed to connect to (solar neg or solar positive). Let me know what the EP500 aviation-to-mc4 cable negative end is supposed to connect to (solar neg or solar positive). I would imagine our answers will not be different.

Hi guys. When i hooked up my 1st bluett with my panels, i was getting strange numbers. I can’t remember if the wattage or the volts was wonky. I played with different combination of connecting the mc4 cables with the panels.

Have you tried different combinations? Meaning keeping the positive from the ep500 connected and connecting the other negative?

Crazy thought but thats how i hooked it up with different results.

Hi Aduviel,

Back to your original question of the 2 input on the aviation-to-mc4 cables. My assumption is that they are parallel inputs, to allow you to attach two different PV panel strings coming in on separate extension cables. But this is a guess, I couldn’t find a description of that in the EP500 manual.

To check if that cable is meant for two parallel inputs and good, disconnect it from everything. Use an ohm meter to see that the 2 red inputs are a short circuit (zero ohms) between them and one of the aviation connector pins (it might be 2 of the 4 pins), and also that they are open (infinite ohms) with the 2 black inputs. Then repeat to make sure the 2 black inputs are a short ciruit between them and one (or two) of the aviation connector pins, and open with the red inputs. If that checks out, then you would just use 2 of the cables (one “+” and one “-”) and leave the other pair unused.

If you find that each of the 4 PV cables go to one of the 4 aviation connector pins, then follow the suggestion from Felton, and shame on bluetti for not labeling or indicating which +/- PV cables are paired with each other.

I use Renogy panels with my Bluetti AC200P, so a similar setup as yours. In your photo, I can clearly see the “+” on the panel output wire going to your “+” extension cable, which then plugs into the “+” aviation-to-mc4 cable, which is all correct. I also doubt that your EP500 would show 60v if it was receiving -60v. So I’m pretty confident that your setup is okay. Like you said, the MC4 connectors won’t let you plug it up wrong.

The MC4 connectors have a red-ring on the male end to indicate “+” and the female end is “-”. That designation is looking into the cable towards the PV panel. So your extension cable has a positive (male) side on one end and negative (female) on the other end. I can see that your aviation-to-MC4 cable has the negative end of the PV panels (female) plug into a male end (with the red-ring), which is correct, because the other end of that cable will be the negative end going into your Bluetti. And vice-versa for the positive. If that’s confusing, don’t worry, you can’t hook it up wrong.

Your open voltage and short circuit measurements on the panels in series is also the correct way to check your panels. Your Renogy RSP200D panels have a built-in bypass diode, so that if one of the panels in the series is completely shaded, it will be bypassed and the power from the other panels will still be delivered. But with your 3 panel setup, you need all 3 to be in the sun to exceed the 55 volt minimum of the EP500.

I use four 100W panels in series, so around 80v. It will still show a charge on my AC200P in the most dismal conditions. Full overcast with the sun setting in the evening and the panels looking straight up can still show 30 or 40 watts of charging. Power(W) = Voltage(E) x Current(I), so 40W at 80v is 0.5A; I figure 1/2 amp of power seems to be around the minimum current needed for my AC200P. Perfectly clear skies and the panels aimed directly at the sun will maximize charging, but certainly not a requirement to get some charging.

Bluetti doesn’t specify the minimum current needed to start charging, but only the maximum current it can accept. I also wonder if their current specs might be dependent on the voltage input, but who knows. Your 60V input is near the bottom of the EP500 minimum voltage input. This article will explain that PV panels maintain a near constant voltage in differing sun conditions, but it’s the current output that suffers. So I agree that your 3 panel measured @ 60v input with 3.5 amps or 8 amps of current should provide some charging even in less than perfect sunlight.

My AC200P will accept a PV charge at 99%. I’ve seen some comments indicate some models throttle back the charge rate as it nears 100%, but I can’t find any documentation about that. At any rate, you might let your EP500 run down under 50% to see if it will start charging on PV. From your setup, I agree with you that it should show a charge with your setup. “Plug-and-Play” means plug and play, you shouldn’t have to screw around with it to make it work.

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Yes, I have tried all viable combinations of positive/neg or “pos/neg” pairs on the bluetti mc4-to-aviation cable to my three in-series renogy panels; no amps only volts on the bluetti display.

Both ends of both cables and connectors have a positive and a negative contact. Your issue seems to be that you are assuming a connector is positive or negative without actually using your meter to determine if the electrical current is positive or negative from a given connector. The connector does not determine positive or negative, the wire does. VERY IMPORTANT

After a long chain of emails, Bluetti support claims that they are connecting my case to an engineer.

For anyone else who has gone through Bluetti support, do you know how long it took for them to resolve either an aviation cable or EP500 replacement?