Pylontech and Axpert settings

[CBNel]

I have a 4kW Synapse (Axpert) inverter and a 2.4kWh Pylontech battery. Can anyone help me with the settings of the inverter. Voltage settings.

[Fazil]

do a search for pylontec settings with Axpert. There is a full document. 

[Dex_]

from what i understand:

Program 2 - 20A (max charge current - this should be 25 but it increments in 10's)
Program 5 - USE (battery type)
Program 12 - 48V (setting voltage point back to utility source)
Program 13 - 51V (setting voltage point back to battery mode)
Program 26 - 53.2V (bulk charge voltage)
Program 29 - 47.5V (low DC cut off voltage)

[Coulomb]

There is also setting 27 (float voltage). For some reason, there seems to be this idea that LFP batteries never float. Well, they should, and with an Axpert inverter, they will.

You can set it to the same as the absorb/bulk setting (setting 26) to defeat the float stage, or set it slightly lower, many use 53.0 V. I prefer a rather lower voltage, like 50.3 V, but anything in the range of 50.3 - 53.2 V will work. Higher values will keep the battery slightly better charged (so you get slightly more use out of it in a blackout), at the cost of slightly lower life (no lithium battery should stay at very high SOC and therefore voltage for too long for maximum life).

The other settings look fine.

[Dex_]

On 2019/07/25 at 10:36 AM, Coulomb said:

There is also setting 27 (float voltage). For some reason, there seems to be this idea that LFP batteries never float. Well, they should, and with an Axpert inverter, they will.

You can set it to the same as the absorb/bulk setting (setting 26) to defeat the float stage, or set it slightly lower, many use 53.0 V. I prefer a rather lower voltage, like 50.3 V, but anything in the range of 50.3 - 53.2 V will work. Higher values will keep the battery slightly better charged (so you get slightly more use out of it in a blackout), at the cost of slightly lower life (no lithium battery should stay at very high SOC and therefore voltage for too long for maximum life).

The other settings look fine.

I have made this adjustment now, and when i check the battery voltage according to the inverter it seems to be ~50.6 when the unit has been sitting a while, the unit seems to think that the battery is low though when the battery doesnt think so, i.e if i drop like to 50 (i know voltage isn't a good SOC indicator), from what i can tell my settings are right, any idea why the inverter thinks this even though imo at this range it should think the battery is still good?

[Coulomb]

The Axperts base their crude SOC on how far the battery voltage exceeds the low battery cutoff setting. So you could try adjusting that up or down.

[Dex_]

On 2019/07/28 at 9:43 AM, Coulomb said:

The Axperts base their crude SOC on how far the battery voltage exceeds the low battery cutoff setting. So you could try adjusting that up or down.

still struggling along with this, I found two interesting things:

this thread: https://powerforum.co.za/topic/2519-mpp-solar-inverters-support-pylontech-some-models/ my unit doesn't seem to support this even though i purchased it in may  i checked now and the barcode means it was manufactured in September 2018  

https://www.mppsolar.com/manual/Pylontech Lithium/Pylontech inverter setup SOP.pdf

these guys are suggesting to set the float voltage to the charge voltage, which as you say might affects the batteries longevity?

i did a small test earlier, battery shows SOC is full, unit shows it is at what float was set to, eg 50.5 for example, trip the mains and the unit starts dropping off on voltage quicker than i would expect and load was low at like ~250W

I am struggling to figure out the best way to deal with this, like i get my bank is small, but i want to safely manage and get the best out of it, no point in spending all this money and the system doesn't last or work properly.

[Coulomb]

5 hours ago, Dex_ said:

battery shows SOC is full, unit shows it is at what float was set to, eg 50.5 for example, trip the mains and the unit starts dropping off on voltage quicker than i would expect and load was low

If the battery shows the SOC as full (all SOC LEDs on), then it probably is full (or at least very nearly so). If the battery volts drop a bit, that's OK, it doesn't necessarily mean that the battery has lost a lot of charge. It's just that with a small battery, even a 250 W load will cause the battery terminal voltage to drop. Just watch the battery LEDs to judge how fast the battery is discharging. Remember that in battery mode with small loads, the self consumption of ~50 W can be significant, and that while the inverter is some 93% efficient, that means you lose some 7% between the battery and the load. So a 250 W AC load will be something like a 250 x 1.07 ~= 270 W load on the battery, plus about 50 W idle, so that's more like 320 W or some 6.4 A @ 50.2 V.

If you have solar power available, then solar can supply some or all of the load power, but it has to see a dip in battery voltage to trigger charging it back to the float voltage. This can add a delay of a minute or two.