Hi,

I installed this backup system. I need some feedback on the installation to ensure everything is OK. I used:

• KODAK Solar Off-Grid Inverter King with UPS 5kW 48V (Axpert)
• 4 x 240Ah omnipower batteries.
• 50mm2 Battery Cable
• 80A Fuse on + battery cable

Inverter Settings (Axpert):

Program 1 : Utility first (default)

Program 2 : 20A 

Program 5 : User 

Program 11 : 20A 

Program 26 : 56.4V

Program 27 : 54.8V

Program 29 : 44.60V

On 2020/02/18 at 6:57 PM, solarman said:

• 80A Fuse on + battery cable

That fuse is too light, unless you intend limiting your inverter to 3500 W maximum (70% of rated power). I'd use 100 A or 125 A. However, limiting the power will be kinder to your battery.

Quote

 

Program 2 : 20A 

Program 11 : 20A 

 

Those are a bit light. Your battery is rated at 200 Ah (at the 10 hour rate), so that's 0.1 C. That's cautious, but the battery seems to be an AGM type, which I believe can take a bit more current. I note that the datasheet states that the maximum charge current is 50 A. I'll leave it to lead acid experts to say what these maximum charge current settings should be set to.

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Program 26 : 56.4V

I calculate 57.0 for 30°C as follows: 14.4 V per module or 57.6 total. But for 30°C take off 5 mV/°C x 5°C x 24 cells = 600 mV = 0.6 V; 57.6 - 0.6 = 57.0. I'm assuming that 30°C is a not-uncommon temperature in summer. You can increase the voltage in winter.

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Program 27 : 54.8V

I calculate as follows: 13.65 V @ 25°C x 4 modules = 54.6 V. But for 30°C take off 3 mV/°C x 5°C x 24 cells = 360 mV = 0.36 V. So 54.6 - 0.36 = 54.24 V, closest allowable value would be 54.2 V [ edit: was 52.2 V ].

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Program 29 : 44.60V

That would let you run your loads for the longest time, but would murder your batteries quickly. Unless you have something else to save the battery from such a large discharge, I'd put this at 48.0 V (possibly the highest that the inverter will allow). If you want a different balance between surviving load shedding and battery life, choose a value in between.

Edited February 22, 20205 yr by Coulomb

Thank you sir!

I appreciate you helping me out here. 

Do you have a link or previous post explaining settings 26 & 27 in more details? 

18 hours ago, solarman said:

Do you have a link or previous post explaining settings 26 & 27 in more details? 

No, but perhaps I should have stated where the numbers originated from. From the bottom left corner of this datasheet:

I note that a 48 V battery (4 nominally 12 V modules in series) has 24 cells; each lead acid cell is nominally 2.0 V.

On 2020/02/18 at 2:19 PM, Coulomb said:

That fuse is too light, unless you intend limiting your inverter to 3500 W maximum (70% of rated power). I'd use 100 A or 125 A. However, limiting the power will be kinder to your battery.

Those are a bit light. Your battery is rated at 200 Ah (at the 10 hour rate), so that's 0.1 C. That's cautious, but the battery seems to be an AGM type, which I believe can take a bit more current. I note that the datasheet states that the maximum charge current is 50 A. I'll leave it to lead acid experts to say what these maximum charge current settings should be set to.

I calculate 57.0 for 30°C as follows: 14.4 V per module or 57.6 total. But for 30°C take off 5 mV/°C x 5°C x 24 cells = 600 mV = 0.6 V; 57.6 - 0.6 = 57.0. I'm assuming that 30°C is a not-uncommon temperature in summer. You can increase the voltage in winter.

I calculate as follows: 13.65 V @ 25°C x 4 modules = 54.6 V. But for 30°C take off 3 mV/°C x 5°C x 24 cells = 360 mV = 0.36 V. So 54.6 - 0.36 = 54.24 V, closest allowable value would be 52.2 V.

That would let you run your loads for the longest time, but would murder your batteries quickly. Unless you have something else to save the battery from such a large discharge, I'd put this at 48.0 V (possibly the highest that the inverter will allow). If you want a different balance between surviving load shedding and battery life, choose a value in between.

 

 

 

 

 

I have changed my setting accordingly. My system batteries measures 52.5V with a multimeter. So all seems to be in order?

Edited February 21, 20205 yr by solarman

1 hour ago, solarman said:

My system batteries measures 52.5V with a multimeter. So all seems to be in order?

That's an average of 13.1 V per 12 V module. That's quite high if the battery isn't being charged, and astounding if it's supplying a load.

If it's supposed to be float charging, it's quite low. If it's supposed to be bulk charging, it's OK only if it's just started bulk charging.

In short: one reading without knowing more about the system state doesn't tell much.

45 minutes ago, Coulomb said:

That's an average of 13.1 V per 12 V module. That's quite high if the battery isn't being charged, and astounding if it's supplying a load.

If it's supposed to be float charging, it's quite low. If it's supposed to be bulk charging, it's OK only if it's just started bulk charging.

In short: one reading without knowing more about the system state doesn't tell much.

This is after charging for 10 hours since use, pure backup system, no solar. so I assume float charging then. 

11 hours ago, solarman said:

This is after charging for 10 hours since use, pure backup system, no solar. so I assume float charging then. 

Arrgh! My bad. I made a typo in my response to your setting 27, float battery voltage. It should be 54.2 V, not 52.2 V. So change setting 27 to 54.2 V, and the battery voltage reading at the same stage should be close to 54.2 V.

Then everything should be in order. Sorry for the stuff up.