Help to connect Axpert Mks3-24v to Pylontech UP2500

[Jaco Kotze]

I received some pamphlets, printed pages and whatnot to setup this two devices to work but cannot get them to communicate. The Axpert goes all crazy. Is there a nice step by step guide from any of you who did this before in getting this two entities to work as everything in the book promised?

The inverter has a RJ45 underneath, not like the old a USB or printer jack.

Do I need a RS485 cable between the inverter and battery? or anything else.

Trying to help a fiend here with his setup and I am totally lost getting this to work.

[Coulomb]

11 hours ago, Jaco Kotze said:

this two devices to work but cannot get them to communicate.

There is no automatic connection between them possible. The 24V models don't have the computer horsepower required to do this.

You can still use the 24V Pylontech, just that the battery's BMS won't automatically control the charging. So just treat it as an ordinary battery. It will be 8S LFP, so you should use settings with 8/15th of the voltage for 48 V Pylontechs. For example, bulk/absorb setting should be about 8/15*52.5 = 28.0V. When the result isn't exactly a value you can set on the inverter, use the nearest value. For example, the float voltage should be 8/15*51.8 = 27.63V, just use 27.6V.

[mangetalife]

Hi All

I have been running 2x Pylontech UP2500 on an Axpert VP-3000 24VDC off Grid System. Using MultiSIBControl I am able to monitor the Inverter, Panels and the 2 Batteries. My findings are that the BMS systems work very well and have experimented with the Bulk and Floating charge settings to optimize the battery SOC.

The UP2500 Charge Voltage is 28.2-28.5VDC and discharge at 23.3-28.5VDC. When the BMS reaches the set Floating Voltage the charge is stopped by Inverter and the BMS puts the Batteries go into Idle mode. The problem is, when do the UP2500 reach 100% SOC? If one sets the Floating charge to 27.2VDC the batteries hover at about 94-96% and this is because the individual cells are not charged to their full capacity. Thus I gently set the Floating charge to a point where 100% SOC was achieved.

Here is a breakdown of the system and setting that I used to achieve the results.

6x 300w panels with the potential on 50A charge split in 3, 1 the Inverter load and the balance split between the 2 Batteries. The batteries also balance each other when connected as Master-Slave. The recommended Charge rate for the Batteries are 55A but at an average of 18A each the charge to 100% within about 4H

My Inverter settings.

02 = 60A - (15A Grid)

05 = USE

16 = OSO

26 = 28.4VDC

27 = 28VDC (Individual Cells at about 3.4VDC) Please also Note the the BMS will shut the Charge down if the Battery capacity exceeds 28.5VDC

With the logging capabilities of MultiSIBControl and SOC settings I am able to control the low SOC to Grid and reconnect SOC levels with timers based on the SOC.

The Batteries are able to carry my appliances through the night with the a SOC at about 40% the next morning. I have set the minimum SOC to Grid at 35% giving enough space for charging to commence before going to grid. Of course, these results depend on the load during the night and my average is at between 2-3kWh.

Thus, Contrary to Fears on using Axpert with Pylontech, if one stays in the ranges of the Battery Charge and Discharge ratings the system should for one never undercharge the Batteries and keep the batteries happy and healthy as LiPo batteries like to be charger to the correct voltage up to 3.6VDC/Cell.

Please note my finding have been an exhaustive project for the last 6 months and I am sharing my findings with your and am in no way recommending these settings and will not be held liable for any damage you may incur with your own experimentation. However the math's should speak for itself.

[Coulomb]

On 2021/09/07 at 1:42 AM, mangetalife said:

27 = 28VDC (Individual Cells at about 3.4VDC)

? 28.0 / 8 = 3.5 VPC, average. 3.4 VPC would be 3.4 × 8 = 27.2 V. Is there a typo?

I suspect that you need such a high float voltage because of the premature float bug that affects all Voltronic Power inverters without patched firmware. That voltage is actually higher than I use on my 48 V system for the bulk/absorb voltage. I use bulk/absorb = 55.2 V (16S LFP, equivalent to 27.6 V for your 24 V 8S system), and 53.7 V float (equivalent to 26.85 V).

Edited September 8, 2021 by Coulomb

[Freddals]

On 2021/09/06 at 5:42 PM, mangetalife said:

Hi All

I have been running 2x Pylontech UP2500 on an Axpert VP-3000 24VDC off Grid System. Using MultiSIBControl I am able to monitor the Inverter, Panels and the 2 Batteries. My findings are that the BMS systems work very well and have experimented with the Bulk and Floating charge settings to optimize the battery SOC.

The UP2500 Charge Voltage is 28.2-28.5VDC and discharge at 23.3-28.5VDC. When the BMS reaches the set Floating Voltage the charge is stopped by Inverter and the BMS puts the Batteries go into Idle mode. The problem is, when do the UP2500 reach 100% SOC? If one sets the Floating charge to 27.2VDC the batteries hover at about 94-96% and this is because the individual cells are not charged to their full capacity. Thus I gently set the Floating charge to a point where 100% SOC was achieved.

Here is a breakdown of the system and setting that I used to achieve the results.

6x 300w panels with the potential on 50A charge split in 3, 1 the Inverter load and the balance split between the 2 Batteries. The batteries also balance each other when connected as Master-Slave. The recommended Charge rate for the Batteries are 55A but at an average of 18A each the charge to 100% within about 4H

My Inverter settings.

02 = 60A - (15A Grid)

05 = USE

16 = OSO

26 = 28.4VDC

27 = 28VDC (Individual Cells at about 3.4VDC) Please also Note the the BMS will shut the Charge down if the Battery capacity exceeds 28.5VDC

With the logging capabilities of MultiSIBControl and SOC settings I am able to control the low SOC to Grid and reconnect SOC levels with timers based on the SOC.

The Batteries are able to carry my appliances through the night with the a SOC at about 40% the next morning. I have set the minimum SOC to Grid at 35% giving enough space for charging to commence before going to grid. Of course, these results depend on the load during the night and my average is at between 2-3kWh.

Thus, Contrary to Fears on using Axpert with Pylontech, if one stays in the ranges of the Battery Charge and Discharge ratings the system should for one never undercharge the Batteries and keep the batteries happy and healthy as LiPo batteries like to be charger to the correct voltage up to 3.6VDC/Cell.

Please note my finding have been an exhaustive project for the last 6 months and I am sharing my findings with your and am in no way recommending these settings and will not be held liable for any damage you may incur with your own experimentation. However the math's should speak for itself.

 

[Freddals]

Hi All

I'm using Axpert King 3K with a single Pylontech UP2500 at a remote farm site, off Grid. Using 3x 410W panels to charge at 50A

I'm only drawing between 560-900W, and at night after bedtime, only a 450W fridge (switches on about 5min/hr) is connected with maybe 1 or 2 phone chargers

The one issue I'm not sure of is controlling DOD of the UP2500.

I don't want the battery to drain below 80%

My inverter setting:

29 - Low DC cut off voltage = 22V

a) What should this be?

b) Is there a calculation for DOD % vs Lithium-Ion voltage?  (I'd like to work out a table in 10% increments of DOD)

[Coulomb]

1 hour ago, Freddals said:

I don't want the battery to drain below 80%

I assume you mean you don't want to drain to more than 80% DOD (Depth Of Discharge).

For lightly discharging LFP cells at room temperature, that's about 3.22 VPC (gathered from graphs in various scientific papers). So that would be 25.86 for an 8S battery. 

1 hour ago, Freddals said:

My inverter setting:

29 - Low DC cut off voltage = 22V

a) What should this be?

I would try 25.9 V or perhaps 25.8 V. If you are really keen, measure the voltage at the battery when the inverter cuts off due to low battery voltage.

1 hour ago, Freddals said:

b) Is there a calculation for DOD % vs Lithium-Ion voltage?  (I'd like to work out a table in 10% increments of DOD)

It's not a simple linear curve (SOC versus terminal voltage), and there is hysteresis (so the SOC depends on whether you have been discharging for the last several minutes, or charging, or a combination of both). It also depends on temperature. I'm guessing that you mostly care about the discharge curve at room temperature. Find a reputable SOC versus voltage graph, preferably one that distinguishes discharge from charge, and work from that. LFP has two long plateaus in this curve, making it hard to estimate SOC from terminal voltage, unless the battery is very full or very empty.

[Freddals]

38 minutes ago, Coulomb said:

I assume you mean you don't want to drain to more than 80% DOD (Depth Of Discharge).

Yes, and it is at room temperature

 

39 minutes ago, Coulomb said:

I would try 25.9 V or perhaps 25.8 V. If you are really keen, measure the voltage at the battery when the inverter cuts off due to low battery voltage.

At my current setting 22V, I've not had the inverter cut out yet. (but only being running this setup for 2 weeks now)

I'll try 25.9V and see what happens. Since its light discharging, battery might not go down to this by sunrise. If I get time to do some more testing, will actually switch off my PV panels off before sunrise and check what happens

Thanks for your advise

[mangetalife]

Thank you for all you comments, 

1. DOD, I set my batteries to go back to grid @ 35% or 65% DOD for the reason that if there is Load shedding there is still room to go to 80% DOD

2.

On 2021/09/08 at 4:41 PM, Coulomb said:

Is there a typo?

Thank you yes, Typo