Fun with solar and Renogy MPPT 30 Li (kind of)

[Almot]

Battery 100AH LFP nominal 12.8V, suggested max Bulk 14.2V.

In another post I reported my experience with Epever MPPT 30. To configure custom profile for LFP it required downloading a proprietary software that was difficult to install, then software crashed and I returned it to the seller.

Got Renogy MPPT 30 with a pre-configured Li profile: Boost 14.4V, Boost Return 13.2V, Float duration 0, HVD 16V, LVD 11V.
Li profile can be configured via Bluetooth dongle (not included, ordered from another store, but I doubt that changing parameters will change my findings).

Renogy MPPT opens at 15.2V - there isn't much current to be had with panel below 15V, but Epever MPPT opened at 14.2V so some energy is lost.

Battery resting 12.8V, SOC ~50%, controller reads 90% but I doubt. It also reads 0.3V with no solar panel which number I also ignore.

100W solar, mono - I have 2 of them but testing only 100W for now. Voc 22.3, Vmp 18.6, Imp 5.38A, Ioc 5.86A.

Lat 49, May 31, 8.30am, little haze.

Load 0, panel input 18V, current 0.7A.
Turned on the load 2.5A, current went up to 1.4A.
(What the heck? I need those amps even when the load is off, I have a battery half empty).

Sky cleared a bit, panel 20V:
Load 4.5A, current 5A.
Load 0, current is still 4.5-5A.
(The only time when MPPT worked as it should).

Haze, panel 18V:
Load 4.5A, current 1.8A.
Load 3A, current 1.4A
Load 0, current 0.7A.
(Same effect again, current drops when load drops).

Clouds, panel 17V:
Load 0, current 0.4A
Load 2.5A, current 1.2A
(same effect again).

I don't think I saw anything like this with Rogue MPPT, though I used it with 450W 48V array.
Maybe I should bite the bullet and get that Victron MPPT.

Q: There will be 2*100W in series or parallel (MPPT doesn't care). But I could also run 2*100 in parallel with PWM. Are PWM free of such quirks - dropped current when there is no load and battery is half empty?

[Almot]

BFL13, this is another controller - Renogy (not Epever that I tested last week). Unlike Epever, this one has pre-configured settings for Li as shown in post #1. I didn't change settings and couldn't, this would require Bluetooth dongle which I don't have yet :).

Yes, it seems like the controller thinks the battery is near full and is in Float - despite being in Li setting where there is no Float and no Absorption, it disconnects when reaching 14.4V. Display reads 80-90% SOC depending on whether there is a load or not, though battery voltage sags very little under load - from 12.9 to 12.8. Poor firmware, IMO.

[BFL13]

Responding to "demand" and then amps drop with less demand is normal while in Float. Seems like the controller thinks batt is nearly full and that is how it is acting.

With the high voltages of an LFP, maybe it is confused about the battery SOC, although it is supposed to be in LFP mode?

IMO you are doing something funny with the settings or set-up and confusing yourself (and us!)

[Almot]

StirCrazy wrote:
what load are you talking about? if it is the termanals on the renogy dont hook your batteries to that and realy I dont use it at all as it is kinda useless unless you want to hook a outside light to it but you can use the batteries for that.....

Steve

LFP battery is connected to "Battery" terminals on Renogy.

The load is a 12V fridge connected to "Load" terminals, to monitor the draw on the Renogy display. This is how I obtained all these numbers - controller current increases and decreases depending on the load draw.

When I connected the load directly to the LFP, this didn't make any difference - there was still same current drop when the load dropped, while the sun was still shining as before.

[StirCrazy]

what load are you talking about? if it is the termanals on the renogy dont hook your batteries to that and realy I dont use it at all as it is kinda useless unless you want to hook a outside light to it but you can use the batteries for that.....

Steve

[Lwiddis]

Bad solar days can be mitigated with additional panels. 200 watts is light IMO.

[Almot]

Time2roll, bad solar days is what we mostly have in coastal BC and PNW :). Will try two panels tomorrow.

This controller has some sluggishness in low light conditions - there is no output below 15.2V. Epever MPPT worked off a small 15V DC supply, at 15.2V input to controller it was sending 3-10A to battery. This one at 15.2V sends only 0.2A.

[time2roll]

Sounds like a bad solar day more than trouble with the Renogy controller. Get the second panel connected for best results.

[pianotuna]

Consider Blue Sky as well as Victron. Both are excellent, but I'd give the edge to Victron. Another brand is Morningstar.

What you are posting is valuable imo. Thank you for doing so.