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diy solar

Solar system "surges" when I'm fully charged, in sunlight while drawing power.

ForestTheBoy

ForestTheBoy

New Member
Joined
Oct 17, 2020
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28
I'm not sure the best section to post this in, I'm just hoping to get any input.

I've noticed that while I'm in sunlight nearing a full charge, and I'm drawing power there's a moment when the battery become fully charged where something in the brain of my system hiccups or "surges". Most of my appliances will reset, such as a monitor having to turn back on again.
I haven't seen any damage to electronics from it, so I guess it's not really a surge.

I'm not sure the right terminology for this issue, otherwise I'd Google for some answers.

I'd appreciate any info you guys could share, I'll list my components below.

-420w solar
-280ah 12v battery using Overkill Solar 120a BMS
-Epever 40a mppt charge controller.
 
My money is on the Epever. You should search for your SCC model on this site. Failing that, start a thread with your SCC in the title with "surge?"
 
I should also ask about your batteries and where your loads are connected. Are your loads connected to the battery and NOT the Epever? Any other things in your load path like a battery protect before your inverter? And what inverter?
 
Are you talking about AC loads powered by an inverter being reset?
If so, what inverter?

With a battery charger and a BMS, it is possible for battery to be charged until BMS disconnects due to a cell having too high voltage.
Is that history available from BMS?
Check battery voltage and BMS report of cell voltages. When fully charged, are they imbalanced?
Are battery charger settings appropriately lower than BMS settings?
 
All of your loads should be connected to the batteries, and not 'through' the EpEver. As MisterSandals requested: please describe your loads in detail, including wire sizes from the battery to the Inverter. Your Inverter could be blasting through the BMS limits if you turn it on with 120-VAC load connected and turned on (always turn on the Inverter first, without AC load, so that it can stabilize its internal capacitor loading). The EpEver WILL 'blink' if the battery appears to die, and the BMS might be doing that.

Even if the EpEver is flipping back and forth (between "Boost" and "Float"), that should not have a fatal effect on the Inverter or other appliances. As Hedges asked - are you sure about this Inverter?

Anyway, you've got 3 experts listening (the other two are definitely big-shots around here). We need to know WHAT appliances, WHICH Inverter, and WHICH specific model of 'Epever' (they make about 20 different kinds of SCCs). If your EPEver is programmable, we need to know your charging parameters too. Thanks in advance!
 
Hey, thanks all for your replies. I'll get some more specific details when I can, but I'll say what I know off the top of my head.

I run everything off 12v dc through my busbars hooked straight to my battery. All that is connected to that busbar includes; DC block, 1500w inverter/charger (I almost never use it, nothing is connected), Battery, and the SCC. I don't remember the specific gauge wiring, but I know I oversized them all. I have adequately sized circuit breakers in place strategically throughout the wiring to prevent damage as a further precaution.

I suppose the only appliance I notice truly "resetting" is the monitor which is hooked into a cheap 150w cigarette lighter inverter. (Should have tested that before asking, duh)
I do notice my 12v DC lights and fan ramp up for a second or two when things get to full charge though, so it's not entirely the crummy inverters fault.

I believe this happens every time the BMS either turns on or off charging, because it happens every 5 minutes or so when I'm pulling a load in the sun at full charge.

I do recall checking voltages at full charge earlier, and while 3 were around 3.35v, the fourth cell was around 3.5v
 
Sounds like the (still unidentified) EpEver is pushing too hard, running "Boost Mode" the whole way through the BMS test cycles which lead to BMS suppressing the charge current. If you set a lower "Boost Return" Voltage, and shorter "Boost Duration", then the problem might become less frequent. (This was all SWAG, of course.)
 
ForestTheBoy said:
I believe this happens every time the BMS either turns on or off charging, because it happens every 5 minutes or so when I'm pulling a load in the sun at full charge.

I do recall checking voltages at full charge earlier, and while 3 were around 3.35v, the fourth cell was around 3.5v
Click to expand...

If BMS turns charging on and off, good chance that is the problem. It is only supposed to be a safety net, and one you never use.
The charge controller should limit voltage so something enough below BMS max cell voltage x 4 to tolerate some imbalance between cells.

Sounds like you could improve voltage margin by up to 0.15V if cells were perfectly balanced and stayed that way. Which might not be possible.
3.35V x 4 = 13.4V; would that be a high enough charge controller setting to get the battery pretty much charged, and to get BMS to balance, while avoiding over-voltage disconnect?
 
So there are a few parameters I would need to change. It's currently set at a 14.4 disconnect. But I can't just adjust overvoltage, I also need to adjust these other settings I'm not so sure about. Here's a page from the manual stating some info regarding priority. 2B612D0B-955E-4241-B29F-AD69350BA51F.jpeg
 
I'd like each cell to Max out at 3.4v even though it's rated to 3.65 or so just to save some of its longevity. So what should my parameters be set to for these other settings if I want a Max 13.6v battery?
 
hopefully you can turn off all the "fancy" settings like equalize and boost...
set the overvoltage disconnect at 3.6*4 = 14.4 .... overvoltage reconnect at 13.6 (these settings should never be reached if all goes well)
set the charging limit voltage to 3.4*4 = 13.6 ... max charging voltage
set float charging to 3.4*4 = 13.6 ...float voltage, so this is where it will sit most of the time

low voltage disconnect 2.9*4 = 11.6 (you can go right down to the limits for the bold and daring of 2.5v/cell)
low voltage reconnect 3.0*4 = 12

fyi I have not used a tracer, so fair warning...
 
Diysolar123 said:
hopefully you can turn off all the "fancy" settings like equalize and boost...
set the overvoltage disconnect at 3.6*4 = 14.4 .... overvoltage reconnect at 13.6 (these settings should never be reached if all goes well)
set the charging limit voltage to 3.4*4 = 13.6 ... max charging voltage
set float charging to 3.4*4 = 13.6 ...float voltage, so this is where it will sit most of the time

low voltage disconnect 2.9*4 = 11.6 (you can go right down to the limits for the bold and daring of 2.5v/cell)
low voltage reconnect 3.0*4 = 12

fyi I have not used a tracer, so fair warning...
Click to expand...
Sweet, I'll try this out. I couldn't turn off the fancy settings so I just set them at 13.6 as well.
I'll check out tomorrow how I'm doing in the same conditions again.
 
ForestTheBoy said:
I couldn't turn off the fancy settings so I just set them at 13.6 as well.
Click to expand...
You NEED to turn off equalization, its a battery killer. Either set the equalization voltage to zero or equalization time to zero (i am not sure exactly how to do your unit but these are good things to try).
 
MisterSandals said:
You NEED to turn off equalization, its a battery killer. Either set the equalization voltage to zero or equalization time to zero (i am not sure exactly how to do your unit but these are good things to try).
Click to expand...
I can set the equalize time to 0, but can't set the equalize voltage to zero.

I can also set the boost time, it's set to 120 minutes by default.
 
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