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Axpert and Pylontech findings


mangetalife
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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.

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I would like to mention something i have noticed though, on my single pylontech US3000c the max charge current is set by the bms to 37 amps as would be expected. But when the battery gets to 90% the bms sets the max charge to 14 amps. Obviously mine is a 48v and yours a 24v system. No where do they mention a lower charge rate when the battery nears full for my battery and theres not really the ability to reduce the charge rates if you not using the bms connection. Would your batteries not then benefit from using a lower charge rate as well?

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8 hours ago, De0n19 said:

theres not really the ability to reduce the charge rates if you not using the bms connection. Would your batteries not then benefit from using a lower charge rate as well?

With the USE (user) battery type setting, the charge rate does slow down as the battery voltage approaches the absorb/bulk setting voltage. This would be close to 90% SOC. So that part is much the same.

The thing you don't get without a BMS cable is slowing the charge rate when a single cell or two go high voltage, or high temperature. Or the whole pack approaches 0°C. Or disconnecting the load when one or two cells go low voltage on discharge.

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