diy solar

diy solar

Battery not charging effectively from Panels

ABarbarian

New Member
Joined
Mar 13, 2022
Messages
30
Panels:
- 455W MONO Genius GS-455WM/HC
- Open Circuit Voltage: 55.25 V
- Voltage at Pmax: 44.61 V
- 4 panels: s2p2

Inverter:
- MPP 4kW PIP-MS4048
- Max PV Input / Output: 3000 W
- Max Charging Current MPPT 60A
- Max PV Input Voc, MPPT Range: 145V, 60~115V

BMS:
- Jikong Smart BMS

Batteries:
- BYD LiFePO4 1P8S 24V 200Ah x2 wired serial to be 48V
- Voltage when fully charged: ~54V


I have the inverter setup to only charge batteries from solar as I feel the panels should supply enough power to both support my load and the batteries, but the batteries seems to charge very slowly, even on days when I have very little load (~100-200W) and full sunlight the battery voltage only rises by about 1V.

When charging I see about 2-7A being sent to the battery (at least I think that is the value, the dashboard and inverter display are not clear).

Can anyone see any errors in my configuration that would cause this slow charging?

BMS values when fully charged:
when_fully charged.jpg

BMS configuration:
2022-06-19a.jpg
2022-06-19b.jpg
2022-06-19c.jpg

Inverter settings I think are important:

01 - Output Source Priority
Sbu: Solar first (then battery until setting 12)

02 - Maximum Charge Current
60A

05 - Battery Type
USE: User configured, see settings 26/27/29

11 - Maximum Utility Charging Current
30A

12 - Setting voltage point back to utility source
50V

13 - Setting voltage point back to battery
53V

16 - Charger Source Priority
OSO: Only Solar will charge batteries

26 - Bulk Charging Voltage (C.V voltage)
57V

27 - Floating Charging Voltage
54V

29 - Low DC cut-off voltage
41V

31 - Solar Power Balance
SbE: enable


All Inverter settings:

01 - Output Source Priority
Sbu: Solar first (then battery until setting 12)

02 - Maximum Charge Current
60A

03 - AC Input Voltage Range
UPS: 170-280VAC

04 - Power Saving Mode
SdS: inverter will not turn off when load low

05 - Battery Type
USE: User configured, see settings 26/27/29

06 - Auto Restart After Overload
Lfd: disabled

07 - Auto Restart After Temperature Cutoff
tfd: disabled

09 - Output Frequency
50: Thailand standard

11 - Maximum Utility Charging Current
30A

12 - Setting voltage point back to utility source
50V

13 - Setting voltage point back to battery
53V

16 - Charger Source Priority
OSO: Only Solar will charge batteries

18 - Alarm Control
bON: On

19 - Auto return to default display screen
ESP: return to default

20 - Backlight Control
LON: On

22 - Beeps when Primary Source Interupted
AON: On

23 - Overload Bypass
byd: disable bypass

25 - Record Fault code
FdS: disable

26 - Bulk Charging Voltage (C.V voltage)
57V

27 - Floating Charging Voltage
54V

29 - Low DC cut-off voltage
41V

31 - Solar Power Balance
SbE: enable

--- Parallel (inverter has parallel board but I do not use)

28 - AC Output Mode
SIG: Single

30 - PV Judge Condition
ONE
 
p.s. my assumption is I have set Bulk Charging Voltage and Floating Charging Voltage too high and it is only trickling in charge, but want to double check before adjusting them.
 
p.s. my assumption is I have set Bulk Charging Voltage and Floating Charging Voltage too high and it is only trickling in charge, but want to double check before adjusting them.

Those are fine. If the BMS is triggering over voltage protection, lower bulk by 0.1V until it stops. Raise float to 55.2V to force the BMS to balance the cells. Once you can achieve your desired bulk voltage drop float to 3.40V/cell.

Are you ever seeing 57V?

If so, you're in absorption phase, and it can only charge as fast as the battery needs to maintain the voltage.

Recommend you hit the system with a very large load that is far greater than your array power at high noon under max sun.

It's always worth checking each and every connection in the circuit between the inverter and battery including cell interconnects.

Your #10 cell resistance is about 50% higher than the others I can see.
 
Those are fine. If the BMS is triggering over voltage protection, lower bulk by 0.1V until it stops. Raise float to 55.2V to force the BMS to balance the cells. Once you can achieve your desired bulk voltage drop float to 3.40V/cell.
Thanks for the reply, I have not seen the BMS show over voltage protection. Only an error about inconsistent current, which is apparently common and unimportant when charging from AC
Are you ever seeing 57V?
Not on the batteries, max was about 54.2V, goes down to about 48V when discharged. I found it interesting that the Remaining Battery % did not seem to correlate with the battery voltage, eg it would bump up to 51/52V but only show ~10% remaining battery
Recommend you hit the system with a very large load that is far greater than your array power at high noon under max sun.
Why? It would switch to battery but that would be the same as the evening when the array runs out of sun..?
Your #10 cell resistance is about 50% higher than the others I can see.
I think I mistook this for the BMS testing wire resistance, but I guess it is the resistance across the LifePO2 cell, is this an issue?
 
Thanks for the reply, I have not seen the BMS show over voltage protection. Only an error about inconsistent current, which is apparently common and unimportant when charging from AC

Not on the batteries, max was about 54.2V, goes down to about 48V when discharged. I found it interesting that the Remaining Battery % did not seem to correlate with the battery voltage, eg it would bump up to 51/52V but only show ~10% remaining battery

Voltage and SoC are only semi-accurate for batteries at complete rest - no charge or discharge for about 30 minutes.

Why? It would switch to battery but that would be the same as the evening when the array runs out of sun..?

It's a means of testing the array output.

I think I mistook this for the BMS testing wire resistance, but I guess it is the resistance across the LifePO2 cell, is this an issue?

Possibly. Hence the recommendation to check that all connections are secure.

Is it possible you're just using too much power for your array? If you're pulling the battery down to 48V regularly, it sound like you're using the system at the ragged edge.
 
s it possible you're just using too much power for your array? If you're pulling the battery down to 48V regularly, it sound like you're using the system at the ragged edge.
Maybe I am, I thought I was way under and running over the weekend with not a heavy load but not really charging the batteries seemed strange, however I did add a refrigerator which might be the cause for draining energy down. I will play with it some more -- mainly concerned I had the settings wrong but I thought I had them right and you looked over them and said they look ok....
 
Back
Top