I am not 100% sure, but I am pretty sure it will work. If the EB3A is in the cycling mode, it will likely pause for at least 0.2s, during which the cap will charge up.
The overload issue is a completely separate problem. I have 3 of these and 2 of them overloaded in a few days powering a 20W modem and switch. A significant portion of EB3A seems to have this issue. My 3rd one however, doesn’t have this issue and has been in operation for 2 months without issue powering the same 20W load.
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Meanwhile I tested the “overnight use case”, i.e. the one where the solar panel stays connected to the EB3A over the 2200uF-cable, starting from complete darkness.
I measured the real battery charge/discharge currents with a DC current clamp directly on the cable to the battery’s BMS. Basic result: When EB3A is on (only display, no output), it will draw 0.16A (~3.6W) from the battery.
Here are the stages of EB3A wake-up:
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Panel in the dark: EB3A switched off, no battery drain
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Very low light: EB3A switches on, INPUT is flashing, App says “PV undervoltage”, battery drain = 0.16A
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Bit more light: INPUT is on now (no flashing), App shows an active PV input (0W), battery drain = 0.16A
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Even more light: INPUT = 000, App shows 4W, battery drain ~ 0A (break even point)
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Sufficient light: INPUT = 000, App shows 10W, battery charging ~0.2A
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Good light: INPUT e.g. 12W, App shows 12W, battery charging >~0.2A
Result: You do not need to precharge the cap. The system will auto-start from a permanently connected panel, but will drain the battery until the break-even light level is reached.
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Thanks, thats good measurements. So I guess you can permanently solder the 2200uF cap inside the EB3A without any issues.
I have measured with latest firmware - It starts up (on the display) at 11W. I can’t say if it will charge below that, but I have not seen it start with less that 11W.
I guess, it will start even below 11W, but you would realize that via Bluetti app only - as the display refuses to show values up to 10W.
Your suggestion to place the 2200uF cap inside the EB3A itself sounds feasible. Would be a good enhancement request for Bluetti. But they will probably decline - as this may swallow their margin … ;-)
Thank you for testing! My plan was indeed to solder the capacitor inside the unit, so good to know it will at least not make things worse. Of course it still remains to be seen whether the charging is going to be a net positive on cloudy days if left plugged in overnight, but hopefully this will at least shorten the period when the battery is being drained…
Another idea that I was considering would be to add a physical switch to cut off power to the display, i.e., if it turns out that the majority of the power drain is due to the display being on, the switch would allow turning it off when the unit is unattended and no-one is looking at the display anyway.
You should sell these. You would probably make a good profit.
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Caution! may cause overheating, and damage to your EB3A.
This is a great idea to compensate for a flaw with the EB3A charging function. My EB3A refused to start charging with my Solar Panels. Thank you to the person that let us all know how to get the charging function started.
When I did connect a capacitor across the Solar Panel wires it did not work with a 100 Micro Farad (probably too small) capacitor … so I used a 2 Farad capacitor instead (probably much to big) … it took several minutes to reach 15V … then I connected the EB3A … and it started charging. I removed the Capacitor … and it was too hot to touch with a bare hand. There is always some heat generated when electricity flows through any component, the amount of heat is related to the electrical characteristics of the specific circuit … it is not possible to predict what the characteristics of your unique combination of components will be … you should actually test it and find out before you decide what size of capacitor to use, and the place you will use it … you should avoid putting anything that generates a significant amount of heat inside your EB3A.
Before you consider putting a capacitor inside the case of your EB3A … I suggest that you test it outside with all of the different solar panels that you might want to connect to your EB3A, and make sure it does not get too hot.
Better yet make it removable … connect the capacitor across the wires from the Solar Panel(s) and monitor the voltage across the capacitor, allow it to exceed 15 Volts, then connect it to your charging port … when the display shows it is charging properly … disconnect the capacitor.
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Sorry for my late information.
For that warm up problem you should use LOW-ESR electrolytic capacitor(s).
And it would be better to use many smaller caps in parallel instead of one cap.
You know electrolytic capacitors are no long live parts.
If your grandpa’s radio is no more working it would be an old cap that stops that.
Sigi
@sgreenshot
Wow, i am impressed by your solution. I think that your analyse of the charging problem in low light conditions is correct. Before Bluetti, i had a Goal Zero Yeti200X (equivalent powerstation). This one was able to charge early in the morning (7am). With Bluetti EB3A, i have to wait 8am or 8:30am, when it stops blinking INPUT.
Maybe i will test this solution. Could you give us the exact model of Capacitor ? Thank you
Hello, I bought 1 capacitor and it seems to work !
I can keep on charging my EB3A when very low light (now dark cloudy sky and 5W PV only)
Thank you
It worked for me as well. Thank you!
Good to hear - I bought one too and will try it soon. Will report back here with the results.
Finally got round to testing this. And it works for me too. So the EB3A is charging from solar even in low light. The display shows 0W input, but the app shows from 1W input. Not sure how much this will do in practise for me, because in the morning if I wait an hour, the sun is strong enough to charge normally anyway (on a sunny day), but I suspect it may make a difference when it’s cloudy.
One watt will not even keep up with the energy consumed by the unit being turned on even with no load.
Yes, that’s what I thought. So there might not be much point. What’s the minimum again @Scott-Benson that the unit consumes? Was it 4W?
Thank you 
Not sure, but I think it is more like 12 to 15. In any case, connecting a solar panel of less than 100 watts will most likely not produce much in the way of positive results.
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Hey, I also got the same issues as thomas has. Please help me.
I have the same problem with mr Thomas need help
Great “cap-hack”! #like [!] ;)
So i build this too with two old 1000uF/40V Caps a friend found in an old amplifier! (s.pics)
They are not new but working and my question is, if this is a good and right setup for my Bluetti EB3A or if i just have to buy a little new cap of 2200uF/50V like in this thread shown!?
First tests under really bad light conditions were running good. it works! :)
i think this low-voltage-mptt-trigger-problem is not a bug - it’s a “feature”!? ;)
Maybe some other powerstations or diy projects are able to load (and showing this) if there is less power, but this box needs >11W to start and i think this is something i can deal with it.
Makes sense, because the MPTT and other stuff needs > 4W and if somebody just loading some things, while charging the bluetti over solar it needs maybe some more reserves!?
And it would be a lie than, if the display showing input, but in fact it is NOT charging, like you can find in this thread above!
So it’s just the specification of this special box and i think no firmware update could fix this, because than it would be done in the past, because this “problem” is well known since month.
Short term: The bluetti EB3A needs enough power to start and load.
And this great “cap-hack” is just to trigger the mptt under bad light conditions (<11-18W), stabilizing the signal and helping loading all between 4-11W!
Other Option is a bigger solarmodul with more watts and/or a more lightly place.
C’est ca! Merci.