Max charge current is limiting PV output

[sergea]

is this restriction controlled from the inverter or from batteries? if from inverter, is it only voltronic? what about other brands?

I said on voltronic. it means the inverter. this is very inverter/brand specific. On voltronic base inverter you have zero control on battery setting once you set the battery type PYLON or on other battery with supported communication.

 

[wattmatters]

I noticed on both Growatt SPF 5000 ES and Infinisolar V IV that max charge current is limiting PV output and causing it to drop down to the set limit and this is impacting normal load output, not only battery charging.

i.e. setting max of 40ah for max charging is limiting PV output down to 40ahx56v=2240w, being total for charging and load, when load exceeds this number then it uses battery to cover the load at the time i have more than 3700w in PV on a sunny day and i could immediately see this number from PV output when raising max to 70ah.

Is this a limitation or some other parameters need tuning?

It's a limitation of the way some of these Voltronic type inverters operate.

Have a read of my suspicions, experiment and findings on the operation of my cheap clone PIP4048-HS inverter:

Backup down under

Another day, another experiment.... I wanted to test something about my AIO inverter's capabilities. As a reminder this is a clone PIP-4048HS. It was my (and others I know) suspicion that the inverter caps PV output based on the battery max current charge setting, no matter the AC load...

diysolarforum.com

I charted exactly what was going on and the behaviour of limiting PV output is just as you describe - PV output will be capped based on the max battery charge current setting irrespective of how much load is applied.

The solution to not having your PV output capped and for loads to be preferentially supplied by as much PV as is available is to have enough battery capacity so that the battery charging current setting can be higher than the PV array is capable of supplying.

 

[mnakkach]

It's a limitation of the way some of these Voltronic type inverters operate.

Have a read of my suspicions, experiment and findings on the operation of my cheap clone PIP4048-HS inverter:

Backup down under

Another day, another experiment.... I wanted to test something about my AIO inverter's capabilities. As a reminder this is a clone PIP-4048HS. It was my (and others I know) suspicion that the inverter caps PV output based on the battery max current charge setting, no matter the AC load...

diysolarforum.com

I charted exactly what was going on and the behaviour of limiting PV output is just as you describe - PV output will be capped based on the max battery charge current setting irrespective of how much load is applied.

The solution to not having your PV output capped and for loads to be preferentially supplied by as much PV as is available is to have enough battery capacity so that the battery charging current setting can be higher than the PV array is capable of supplying.

My bigger problem is these inverters are connected through BMS, max charge is determined and locked from being changed by the BMS. Therefore limiting the value as low as 30a for every inverter, i have 3 inverters in parallel, as a result i am getting my PV output to load limited as well.

The other option is to disconnect BMS and use USER type settings for the battery to release the lock of max charge.

It is a major drawback in both cases, with and without BMS.

Is this only for voltronic inverters and clones?

 

[mnakkach]

It's a limitation of the way some of these Voltronic type inverters operate.

Have a read of my suspicions, experiment and findings on the operation of my cheap clone PIP4048-HS inverter:

Backup down under

Another day, another experiment.... I wanted to test something about my AIO inverter's capabilities. As a reminder this is a clone PIP-4048HS. It was my (and others I know) suspicion that the inverter caps PV output based on the battery max current charge setting, no matter the AC load...

diysolarforum.com

I charted exactly what was going on and the behaviour of limiting PV output is just as you describe - PV output will be capped based on the max battery charge current setting irrespective of how much load is applied.

The solution to not having your PV output capped and for loads to be preferentially supplied by as much PV as is available is to have enough battery capacity so that the battery charging current setting can be higher than the PV array is capable of supplying.

I am spending days watching the inverter LCD screen trying to understand its behavior, i noticed during sunny hours, whenever battery charging reaching the limits set of 30a, and i have high load, the PV drops from 3300w down to low levels abruptly to 500w, then it goes back up to 3000w, then down to 1000w, i see this 30a limit plays with PV output like a tennis ball just to bring it down, but it is bringing it down sharply like disconnecting it instead of lowering it down, this is drastically and negatively effecting the system because i have 3 inverters in parallel, one goes charging to 30a, PV and charging drops, the other inverters will pick up to cover the shortage, then the first picks up again, I can see them keep on playing tennis ball with charging and discharging continuously.

 

[wattmatters]

Is this only for voltronic inverters and clones?

I don't know.

It is a major drawback in both cases, with and without BMS.

I guess that's part of the reason they are so much cheaper than other inverters.

 

[Vigo]

i noticed during sunny hours, whenever battery charging reaching the limits set of 30a, and i have high load, the PV drops from 3300w down to low levels abruptly to 500w,

How much solar do you actually have? Per wattmatters' statement, if your array maxes out at 3300w on a sunny day you can absolutely pump all of that into 3x 48v/100ah batteries with no restrictions. However, it would require removing the communication from bms's to inverters and go to manual settings.

As far as i know (have never used lithium bms communication before) the main downside to not letting the bms and inverter communicate is you lose the SOC% readout and just get voltage, which is much more vague in the case of lifepo4. Theoretically you also lose the ability of the bms to limit charge current to protect the batteries and the only protection the bms will offer is to fully disconnect the battery when it is threatened. However, depending on what you are doing with your system, they may have a very easy life and the odds of that ever happening would be low.

I'm all for you continuing to push the manufacturer to make their product perform in the way it is expected to based on their description of it.. but if that doesn't pan out, what are you concerned about losing if you go to manual settings?

 

[timselectric]

Well, I finally got around to testing this on my Growatt SPF-5000-ES. In SBU mode battery charging limit only affects battery charging level. I set the total charging limit for 10a. In utility mode, (solar power only used for charging) it of course only pulled 500w from the panels. But in SBU mode, it put that 500w into the battery. And the rest of the available solar power went to the loads. (2300w at the time)

But again, I'm not sure why you would want to limit the charging from solar. Limiting AC charging makes sense. Because it costs money.

 

[Vigo]

The only advantage I can see to it is limiting 'c rate' to a small battery when you have more solar than battery. I DID initially have more solar (~10kw, never seen over 7kw) than battery but im on lead acid and dont give a crap what they think about my c rate, and i've recently installed enough used deep cycles that i don't think i can technically overcurrent the actual batteries before my wiring.. does something not great. Still working on the final version of wiring.

But if you've got 3x 48v/100ah lithium batteries, it would take a pretty huge amount of solar charging to be 'inadvisable' even for 10+ yr lifespans. I think..

 

[sunshine_eggo]

Well, I finally got around to testing this on my Growatt SPF-5000-ES. In SBU mode battery charging limit only affects battery charging level. I set the total charging limit for 10a. In utility mode, (solar power only used for charging) it of course only pulled 500w from the panels. But in SBU mode, it put that 500w into the battery. And the rest of the available solar power went to the loads. (2300w at the time)

But again, I'm not sure why you would want to limit the charging from solar. Limiting AC charging makes sense. Because it costs money.

Lead acid can rarely be charged by more than 0.2C. I used the Victron feature for this. My T-1278 are limited to 0.13C, so I had to limit my charge rate to 39A, but I had up to 60A available from the array at max output.

 

[wattmatters]

Lead acid can rarely be charged by more than 0.2C. I used the Victron feature for this. My T-1278 are limited to 0.13C, so I had to limit my charge rate to 39A, but I had up to 60A available from the array at max output.

This is part of striking the balance between PV capacity and battery capacity. With enough battery capacity your PV will never exceed this limit and hence loads will get to self consume more PV and less battery.

As I mentioned in my other thread where I tested this phenomenon, yes I totally agree it would be good if the proportion of load supplied by PV was not restricted by the max charge current setting.

I can only presume it's either:
- specifically set up this way to avoid the scenario of a high load being dumped (for whatever reason) and the system suddenly having lot of PV power it needs to deal with quickly while also not exceeding the battery charge rate limit, or
- perhaps it's just a firmware bug inherent to these inverters.

Perhaps if my inverter had more robust architecture/better firmware then it would be designed to manage this situation without issue but frankly I'm not complaining when my 4 kW / 5 kVA 48 V AIO inverter cost ~$US300. It's a pretty amazing bit of kit for the money and has enabled a lot of learning. It's likely I will be replacing it with an upgraded unit at some point which hopefully won't have such a limitation, as I also hope to add more off-grid PV capacity at some stage as well.

 

[Vigo]

Agree about the price point. I’ve spelled out some crazy sounding ideas of how to hook multiple AIO’s together in unusualy ways on this forum in the last few days.. The root cause is that it seems in some cases the cheapest way to get X charger, Y inverter and Z solar controller of considerable size, is to buy THREE aio’s and only use each of them for ONE of their functions!!

I recently bought a $250 PowMr aio substantially because the next cheapest device which could do 80a 12v charging that wasnt a small stack of meanwell knockoff power supplies, was going to be $200 anyway. So i got a device with a 450v input mppt and a 1500w pure sine inverter with a built in transfer switch, with a ton of adjustability to its features, for about $50 extra.. ?

 

[timselectric]

I concede
I guess that there are situations where you would need to reduce the charging limit.