Jesper

Thanks for your explanation. Hopefully this is resolved on the units I will receive.
A different between the 7200 and the 8000 model is not just the AC output but also the MPPT charger. It goes from 80A to 120A.
I have 30kw pv, so I am going to max out the inverters pv power input capacity. So I was thinking that the 8000 model is good for me to utilize my PV power to the charging of the battery bank.
 I am also considering to double up the battery capacity in a year of two, when I have made enough savings on our electricity bill.
There is something I don;t understand, maybe you can explain. The 7200 model has a max pv power input on 8kw, the same for 8000 model, but the inverter output is bigger and the charging is bigger on the 8000 model. Why is it that the rated pv power input are the same on the two? To my logic it should be bigger on the 8000 model.
Jesper
 
 

How to charge your Pylontech US3000 and why
From time to time, there's a discussion on Pylontech US2000/US3000 batteries and what is the best charging voltage for them. So, here's the answer based on my personal experience:
C.C. = 52.5V
C.V. = 52.0V
 
Why:
First of all, it's important to clarify what the term "charging voltage", sometimes referred as C.C. aka constant current, means. It's NOT the voltage that's being created by the charger and then applied to the battery terminals. In reality, the charger just pushes current into the battery, while constinuously measuring the voltage on the terminals. Once the voltage reading on the terminals is equal to the value that's set as charging voltage, the charger stops pushing current. Then, based on the selected charging profile, the charger goes in the next stage, like C.V. aka constant voltage, for example.
If the C.C. voltage is set too high, the charger will continue to push the current in the batteries for too long. The voltage will rise above the safe level for that given battery chemistry and the cells will overcharge, swell and take damage.
In order to protect the cells, US3000 has a balancer for each individual cell and a MOSFET for each brick. Once the voltage of the individual cell goes above 3.480V, the balancer will kick-in and start to burn the excessive current, turning the electric energy into heat. That's the way how US3000 ensures that at the end of charging all the cells have equal voltage, in other words "are balanced". Of course, cell balancers are not powerfull enough to burn all the energy that might be potentially pushed by the charger. That's the reason why there's a MOSFET in the battery pack. If all the balancers are already burning energy and the charger is still pushing energy, then the MOSFET will limit the current in order to protect the pack.
 
In the specsheet, Pylontech recommend to set the charging voltage somewhere between the 52.5V to 53.5V:
 

There's 15 LFP cells in each US3000 pack and balancers are starting at voltage 3.480V per cell: 15 x 3.480V = 52.2V
So, the setting C.C. to 52.5V (52.2V + 0.3V) ensures that all the balancers will operate correctly and at the same time, they won't be overloaded.
If your solar charger is actively communicating with the US3000 via CAN bus or RS485, then he can read the battery voltage via this digital communication. Therefore, it does not matter how long the battery-to-charger cables are and whether the charger itself is measuring accurate or not. The voltage is measured by the BMS and communicated digitally. In that case, the best is to set C.C. to 52.5V.
If your solar charger does NOT utilize BMS comunication, then he has to rely on his own voltage measurements. In that case, one has to take into account the length of the battery-to-charger cables, all the joints resistance and the associated voltage drop. Therefore, it might be necessary to adjust C.C. to a higher value, like 52.6V or 52.7V for example. There's nothing you can break if you will experiment and raise the C.C. slowly in order to find the best value for your setup. Just be sure to stay away from the maximum allowed voltage as described in the specsheet.
While the specsheet allows charging voltage up to 53.5V, it's not a good idea:
The higher voltage puts a higher load the balancers, mosfet and on the cells too. All the excessive energy is wasted and turned into heat. And the heat is generally not good for the cells, of course. Second reason, why setting the C.C. to the maximum is not a good choice is the fact, that during the charging there might be occasional spikes of power that will go to the battery. Sometimes these spikes are caused by the charger algorithm itself, sometimes they are caused by a changing light conditions or by turning ON/OFF bigger loads. Once this happens during the charging, and the battery is already at it's 53.5V maximum, the BMS will sense the overvoltage and throws an error. If not corrected immediatelly, it will shutdown the battery.
 
How to set C.V. voltage:
The LFP cells used in US3000 have a resting voltage 3.2V per cell. Technically, there's no "float" voltage that you need to apply to LFP, like is common in the Lead-Acid world. LFP cells are best to be charged and then disconnected. This is based on the fact that you can overcharge and damage a LFP cell even with 100mA of current, if applied for a long time.
On the other hand, in solar applications it's impossible to disconnect the batteries from inverter once fully charged, since the batteries are acting as an energy buffer 24x7. Therefore, it's good to set C.V. to a value that will supply just a tiny amount of current into the batteries in order to keep them topped, and live with the fact that balancers will kick-in from time to time and will waste some energy by turning it into heat. With some other types of batteries, where balancers are visible, you can see this state - LED on each balancer blinks randomly, once per second or two. It's like a heartbeat. For a shame, Pylons don't have this direct visibility and you have to go into CLI, if you want to see what's going on inside the battery.
Based on that, I'm personally using C.V. = 52V,  so the balancers are not wasting excessive amounts of energy, and operate only when really needed.
 
US3000 battery:
 

Phantom BMS sitting inside a Pylontech battery:

 
CLI info for a stack of 8xUS3000:
pylon_debug>pwrsys Power System Information --------------------------------- System is discharging Total Num : 8 Present Num : 8 Sleep Num : 0 System Volt : 49756 mV System Curr : -17724 mA System RC : 558692 mAH System FCC : 588892 mAH System SOC : 94 % System SOH : 100 % Highest voltage : 3319 mV Average voltage : 3317 mV Lowest voltage : 3315 mV Highest temperature : 22000 mC Average temperature : 21500 mC Lowest temperature : 20000 mC Recommend chg voltage : 53250 mV Recommend dsg voltage : 47000 mV Recommend chg current : 118400 mA Recommend dsg current : -296000 mA Command completed successfully Note one interesting information:
The stack has 592Ah of nominal capacity, but the recommended charging current, advertised by the BMS, is 118A = C/5.
Recommended discharging current, advertised by the BMS, is 296A = C/2.
No matter what values (much bigger) are being promoted in the specsheet, I would say that the battery designer had a very good reason why he hardcoded C/5 and C/2 into the BMS as recommended Amps.
 
CLI info on the 1st brick:
pylon_debug>info Device address : 1 Manufacturer : Pylon Device name : US3000A Board version : PHANTOMSAV10R03 Main Soft version : B65.6 Soft version : V1.3 Boot version : V1.4 Comm version : V2.0 Release Date : 18-09-12 Barcode : PPTAH02 Specification : 48V/74AH Cell Number : 15 Max Dischg Curr : -100000mA Max Charge Curr : 102000mA EPONPort rate : 1200 Console Port rate : 115200 Command completed successfully  
State of Health for 15 cells in the 1st brick:
pylon_debug>soh Power 1 Battery Voltage SOHCount SOHStatus 0 3317 0 Normal 1 3317 0 Normal 2 3318 0 Normal 3 3317 0 Normal 4 3317 0 Normal 5 3318 0 Normal 6 3318 0 Normal 7 3319 0 Normal 8 3316 0 Normal 9 3316 0 Normal 10 3317 0 Normal 11 3318 0 Normal 12 3319 0 Normal 13 3317 0 Normal 14 3318 0 Normal Command completed successfully  
Statistics for the oldest brick in a stack of 8:
pylon_debug>stat 8 Device address 8 Data Items : 0 HisData Items : 2048 MiscData Items : 122 Charge Cnt. : 0 Discharge Cnt. : 3180 Charge Times : 31004 Status Cnt. : 3179 Idle Times : 41151 COC Times : 0 DOC Times : 0 COCA Times : 0 DOCA Times : 0 SC Times : 0 Bat OV Times : 0 Bat HV Times : 0 Bat LV Times : 0 Bat UV Times : 0 Bat SLP Times : 0 Pwr OV Times : 0 Pwr HV Times : 0 Pwr LV Times : 0 Pwr UV Times : 0 Pwr SLP Times : 0 COT Times : 0 CUT Times : 0 DOT Times : 0 DUT Times : 0 CHT Times : 0 CLT Times : 0 DHT Times : 0 DLT Times : 0 Shut Times : 1 Reset Times : 14 RV Times : 0 Input OV Times : 0 SOH Times : 0 BMICERR Times : 0 CYCLE Times : 62 Pwr Percent : 95 Pwr Coulomb : 254001600 Dsg Cap : 4614627 [email protected] Cnt : 0 [email protected] Cnt : 0 HT Cnt : 0 LT Cnt : 0 LV Cnt : 0 LifeWarn Times : 0 LifeAlarm Times : 0 Command completed successfully Note the Cycle Times, this brick has 62 full cycles on it's meter. One full cycle is accounted whenever you discharge a full nominal capacity from the pack.
 
Hope the above info will help someone to understand how to treat these batteries.
Youda