Sharp drop in PV production in the afternoon

[Lt.Dan]

I don't think so unless 82F or is considered hot

Solar Assistant should be showing in Celsius, are you sure its 82* F? 82*C would definitely be shutting it down.

 

[Lt.Dan]

I don't think the batteries are charging fully, they get to 99% then the inverters reduce charge amps to around 6-10. This included chart shows the battery voltage and current

I see a normal charge curve here. The battery gets up to peak charging voltage (looks like 57v), and then voltage drops to float. That battery is fully charged.

 

[labeeman]

I think that is what's going on here. Your chart looks very similar. Does your system run on both solar and battery at the same timw?

I am in the testing stage this system has 50 kWh of battery and runs a separate inverter 24/7 powering a constant load the inverter is only 2.7 kW and 2 kW of PV. It uses a Growatt charge controller.

 

[Billybob16]

Solar Assistant should be showing in Celsius, are you sure its 82* F? 82*C would definitely be shutting it down.

Yes, I did the conversion

 

[Billybob16]

I see a normal charge curve here. The battery gets up to peak charging voltage (looks like 57v), and then voltage drops to float. That battery is fully charged.

Thanks for the info. It's my first time messing with solar so learning this new system, only been running for 6 weeks. Currently I have 4 48V 100ah batteries in the rack, I will be adding 2 more as soon as I can.

 

[Lt.Dan]

Thanks for the info. It's my first time messing with solar so learning this new system, only been running for 6 weeks. Currently I have 4 48V 100ah batteries in the rack, I will be adding 2 more as soon as I can.

Look into raising your float voltage to something higher too.

 

[TorC]

Sounds like you're more or less using the battery capacity you're willing to/can safely use at night. In that case, you probably will take in more of your PV power by adding batteries, as you'll be able to use more from them each night.

 

[Billybob16]

Look into raising your float voltage to something higher too.

I don't think I can do that in LI mode. I can set all parameters in another mode though. Do you think that is a better way to go and what would you suggest the settings should be?

 

[Billybob16]

Sounds like you're more or less using the battery capacity you're willing to/can safely use at night. In that case, you probably will take in more of your PV power by adding batteries, as you'll be able to use more from them each night.

You are correct, I figure 2 more batteries for a total of 600 AH is what I really need. It's on my buy list. Thanks for your help.

 

[Hedges]

What else do you want the system to do? Maybe it is working perfectly right now. You could consume more power in the daytime if you wanted.

Oh, do you want to be able to draw more at night? The more batteries you're considering would be one way. Turning off some unnecessary load at night could be another. For instance, do you have an electric water heater? If so, switch it off by timer or photocell (manually the first time for an experiment, just turn thermostat down.)

 

[GXMnow]

Billybob16,

Looking at the graphs from post #18 and reading the thread, I agree it looks like once the batteries are full, the charge controller is just turning off. If you want the solar to keep powering the inverter, you need to have it go to a float cycle. A lot of people say to use "No Float" on lithium batteries, and I think that is what is going on here. There is no float current coming from the charge controller. A properly set float voltage is what forces the solar charge controller to provide the current to run the inverter while the battery "floats" fully charged. It looks like setting a float voltage a bit above 53 volts will do what you want. When the batteries get that low, the charge controller will then supply the current needed to hold the voltage from dropping below the desired float voltage, until there is no longer enough sun on the panels. You should have the float voltage set at your maximum safe resting voltage of your batteries. With 16S LFP batteries, I think that works out to something like 3.40 volts per cell x 16 cells = 54.4 volts. How high do you have your absorb and boost voltages set? You want the float a bit below your absorb. Looking back at the solar assistant graphs, it looks like the charge controller is going from Bulk to Absorb at just over 55 volts. That is where the current drops, then the voltage dips a bit, then climbs a little slower until it hits the upper knee and takes off. At that point the current drops to zero. That is where the charge controller stays off until the battery voltage falls to the resting voltage plateau. You obviously still have decent sun still, because at 16:15 or so, it looks like the voltage drops enough, that the charge controller goes back into a bulk charge cycle again. With the float set correctly, it should not need to do that. That may also be where the float voltage is set now, and it is just taking that long to fall far enough. Does your charge controller report what mode it is in? Check it at this time if possible.