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?

[pianotuna]

Almot,

Adding a panel was imo a good plan.

[BFL13]

AFAIK the LFP spec Vabs is for 25C and is not to be exceeded even if it gets colder, so they don't want any temp comp that would put the voltage above the spec Vabs.

I don't know why it would be ok to maintain the spec Vabs if it got warmer and not lower the voltage to keep it from going over the then lower equivalent voltage to the spec Vabs at 25C.

[Itinerant1]

Temp comp should be off not needed with lfp.

[Almot]

Update - decided to stay with Renogy and spend money (saved on Victron) on one more panel. Also, got a Bluetooth BT-1. Not from Renogy - they wanted $CAD 49, so I figured that BT is just a BT and got it from Aliexpress for $CAD 25: Bluetooth dongle. There were other slightly cheaper, but this one was said to work with Renogy - don't remember where, probably on Reddit. Strangely, BT arrived from China in 10 days. To modify the MPPT settings you need Admin password for BT, it was provided in the tiny BT manual that I was about to throw away.

Downloaded Renogy app, some Chinglish - not much, app works fine, set User profile for my LFP. The app has Temperature Compensation - everything I read about LFP says that Temp Comp should be zero, please correct me if I'm wrong.

Boost Duration can't be set shorter than 10 minutes - don't know whether this is the Renogy app or the Renogy controller. Will have to live with that.

Don't know whether the "demand effect" is still there, but it probably is. The battery is full so I can't tell.

Now, why you people think that 5A load is "excessive" for MPPT controller Load terminals that support 20A, I don't know. The above-mentioned "demand effect" was observed with controller current both below the 2-5A load requirement and well above, at 9A controller output. Same effect was also observed when I connected the load directly to battery posts.

[StirCrazy]

seeing as you had the same issue with two different brands of controlers, I am going to hazard to guress the issue is with something you have set up, and not the controlers for the current issue. a 100 watt pannel is going to send almost nothing to the batteries when you are using the load for your fridge, especialy if it is a 12V fridge and thats how your running it. while it is under the 20amps that load termal can handle it is more than your 100 amp panel puts out.

I went in and looked at my settings for Li and they are optimized for LFP batteries so using the gel setting isn't doing any better, in fact it probably isnt as good. try it with your sectond panel hooked up and if its a bit better I would look at getting a 24V split cell panel and letting the MPPT function realy shine. I have a 325 watt split cell 24V panel and it cranks out the power to the batteries.

Im only guessing at how you have it set up but putting a fridge on the load termanals seams excessive, mine draws 7 to 12 amps on 12v mode which is why I never use it that way.

Steve

[Almot]

Battery voltage on the controller display is 12.9, and voltmeter connected directly to battery terminals reads 12.91.
There was no difference when I dropped the load terminals on the controller and connected the load directly to the battery. Same "demand effect", same false 90% SOC at 12.9V.

Which leads me to believe that it's controller that is at fault, - its hardware or firmware or both.

[BFL13]

The probabilities in all this suggest all that various equipment and soft or firmware can't all be faulty. That suggests whatever you have set up is not right in some way. Recommend go back to square one.

First thing might be drop the whole load terminals idea. Review where and when the voltages are being read from. Something is just wrong, and remember Pogo. "We have found the enemy, and it is us!"

[Almot]

Gel mode on Renogy MPPT has Bulk ending at 14.2V and then it would go into Absorption for 2 hours.

The battery is resting now at 12.8V, goes up to 12.9 when DC supply or solar is connected, and it shows the same "demand effect" in Gel mode as it does in Li mode. It reads 86-89% in either mode. According to battery manual 12.9V under charging is only ~20% SOC: https://www.lynaclithium.com/wp-content/uploads/2020/10/12.8V-100Ah-True-Series-Quick-Sheet.pdf

[StirCrazy]

Almot wrote:

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.

ya the load is a direct draw off the panels doesnt go to the battery first so it will reduce the amount actualy being sent to the batteries. I dont use it but some people do for very small loads like lights they want to automater or something like that. its a neat feature if you have use for it. one of the solar forums I was on the general concensus was that they dont use it but the odd person did.

if I remember right the current is including the load so when you disconect it it drops. there also could be somthing to do with the different voltages being outputted and combined for the current output but when the load off it reverts to all battery charge level voltage.. I havent played with the load as I dont see the need for it as of right now, but maybe Ill have to try something.. I had a couple ideas but cant remember them now LOL


Steve

[BFL13]

Not clear, but your LFPs at 14.2 are different from "normal" LFPs at 14.4 or 14.6? So maybe the fixed LFP mode just doesn't match yours.

Some say with LFPs to use a regular converter or charger and just use its AGM mode. With your lower Vabs, use the Gel mode? Could do as well as all that fussing with settings you are driving yourself crazy with?

[Almot]

I don't think that Renogy firmware can be updated. Will know more when I get the Bluetooth dongle, but - unlikely.

[FWC]

I would agree with you that there is something not quite right with either the controller or the battery. It does appear to be operating as if the battery is fully charged and the controller is in constant voltage mode when from the battery state of charge it clearly shouldn't be. It does seem to be a shortcoming of either the charge controller voltage and current sensing (which could also explain the 0.3V offset you see) or the charge controller firmware. Can you update the firmware?

This maybe another case of false economy, the Renogy is cheaper, but is also not as well designed and supported product as the Victron. As far as I know, Victron is a real hardware development company - they have engineers in house in the Netherlands that design and test all their hardware, whereas Renogy is a branding company that primarily buys hardware designed and built in China with their brand/logo on it.

[3_tons]

Besides the programming issue, terminals provided on the EPEver controller are garbage (good luck) and factory support is nonexistent....What seems to be a good deal $$ NOT!! - buyer beware...

3 tons

[Almot]

Update with more sun and 2*100W in series.
June 1, 7.30am, battery resting 12.8V.

Clear sky, panel V=35, current 9.3A, load 2.7A.
Disconnected the load, current dropped to 8.5A, i.e. 0.8A decrease.
(Effect is similar to yesterday's single-panel conditions when current dropped by 0.7A from 1.4 to 0.7 after disconnecting 2.5A load).

Note that 9A is 60% of theoretical maximum power of 200W array post-controller, so not a bad solar day.

Haze, panel V=30, current 4.5A, load 4.2A.
Disconnected the load, current dropped to 3.2A, i.e. 1.3A decrease.
(Effect is different from yesterday's single-panel conditions but not much different: yesterday current dropped by 0.5A from 5A to 4.5A after disconnecting 4.5A load).

It should not be doing this, not with LFP battery, this is not a Float, the battery is far from being full. I am losing more than 10% of available energy.
I think this controller has a poor charging algorithm and/or poor firmware. Adding one more panel should help the bottom line but this effect of demand will likely still be there.