Wierd Overnight Battery Discharge Axpert VM II Hybrid

[ochaala]

I have a Axpert VM II 3kw Hybrid solar inverter with 2200 KW of solar panels and 2x 115AH deep cycle flooded lead acid batteries. The inverter is in SOL mode and charging priority is set to OSO (only solar) so what have I observed is that the batteries will reach floating voltage 27.0 volts during day and then when the sun goes down the voltage also goes down to 25.7 -26.0 volts and charging light blinks, when there is no solar i.e no sun the voltage goes to 25.2 (100% SOC) and then continue to decrease, 24.7 volts after a couple hours and when I wake up at morning it shows 24.2 volts (50 %)
the load is powered the whole night by utility, and the load is literally a router and a 10 watt led bulb.

I know that voltage is not good way to tell SOC
when I woke up this morning, I disconnected grid and solar , put load on the batteries and voltage drop to 23.9 volts which is normal under load.
and you may say that solar is not enough. so the sky remains clear, there is very less load during the day about 100 watts( no one is at home) and batteries reach floating voltage and not just instantly or in couple minutes or hours. it takes full time to get to float that I think is about 8 hours. I calculated charging time and it is 8 hours from 50% soc to 100%
And the charging current is 10 amps

could that be because of the cables I used to connect battery to inverter. I took 8 AWG and 12 AWG and twisted them at both ends and connected the batteries with them
and the 8 AWG says 220/440 volts on it(its a cheap one).

every thing is new especially the batteries only 2 days since installed.

 

[sunshine_eggo]

Assuming you're getting 24V from 2X 12V batteries. Did you charge both batteries to full as 12V before putting them in series?

 

[ochaala]

Assuming you're getting 24V from 2X 12V batteries. Did you charge both batteries to full as 12V before putting them in series?

nope.

 

[Mattb4]

24vDC at 115ah = 2.76kWh of which 50% is the discharge you notice thus 1380wh.
Likely your AIO pulls 50w or more to operate from the battery. The 8 hours to charge at 10a, or 80ah, is pretty close to what you can figure for 50% charge.

It is possible that your batteries are not getting fully charged via PV.

 

[ochaala]

24vDC at 115ah = 2.76kWh of which 50% is the discharge you notice thus 1380wh.
Likely your AIO pulls 50w or more to operate from the battery. The 8 hours to charge at 10a, or 80ah, is pretty close to what you can figure for 50% charge.

It is possible that your batteries are not getting fully charged via PV.

it pulls less than 30 watts (says the spec sheet) but during night loads are powered by utility not batteries,...

Regards

 

[ochaala]

bump

 

[ochaala]

bump

 

[AshleyL]

it pulls less than 30 watts (says the spec sheet) but during night loads are powered by utility not batteries,...

Regards

I guess you didn't get the memo. The inverter powers itself using the battery instead of grid/utility in the night regardless of the SOL settings.

Regards.

 

[ochaala]

p

I guess you didn't get the memo. The inverter powers itself using the battery instead of grid/utility in the night regardless of the SOL settings.

Regards.

OK, but 24*115=2760Wh/2=1380wh/35w=40 hrs
Regards

 

[AshleyL]

p

OK, but 24*115=2760Wh/2=1380wh/35w=40 hrs
Regards

Your calculation is totally missing all the important parts.

Peukert's law + power conversion loss + lead acid battery self discharged rate = don't dream on getting full 115ah even with deep cycle lead acid.

Let take the best case scenario which is 50% depth of discharge if you want a reasonable lifespan out of deep cycle lead acid battery . 24x115=2760wh x 50% = 1380wh. Now, let assume the best case for power conversion too at 90%. Remember, your inverter still power the house load under SOL mode as long as there is still tiny sunlight for around 1 or 2 hour during dusk . Factor that as well. You probably only left with around 60% or 70% of that remaining 1380wh depending on your load level during dusk. Now, deep cycle LA has self discharge rate at 2%........Dont forget about Peukert's law.

 

[ochaala]

Your calculation is totally missing all the important parts.

Peukert's law + power conversion loss + lead acid battery self discharged rate = don't dream on getting full 115ah even with deep cycle lead acid.

Let take the best case scenario which is 50% depth of discharge if you want a reasonable lifespan out of deep cycle lead acid battery . 24x115=2760wh x 50% = 1380wh. Now, let assume the best case for power conversion too at 90%. Remember, your inverter still power the house load under SOL mode as long as there is still tiny sunlight for around 1 or 2 hour during dusk . Factor that as well. You probably only left with around 60% or 70% of that remaining 1380wh depending on your load level during dusk. Now, deep cycle LA has self discharge rate at 2%........Dont forget about Peukert's law.

Oh sorry I didnot mention that my sol mode is like sub mode i.e utility remains connected to loads all time no matter what, if there is less solar in evening, utility provides power to loads, battery remains on float voltage.

 

[AshleyL]

Oh sorry I didnot mention that my sol mode is like sub mode i.e utility remains connected to loads all time no matter what, if there is less solar in evening, utility provides power to loads, battery remains on float voltage.

I don't think you understand what is SOL mode and what it is doing.

Voltronic Axpert inverter SOL mode means it works in SBU mode when there is sunlight hitting the panel and it switches to the SUB mode once there is no longer any sunlight detected at the panel. (or sufficient panel voltage/power).

In SOL mode, the inverter WILL NOT DRAW power from the utility as long as there is still sunlight. It will draw power from the battery to complement the dwindling solar power. As long as there is still power from solar panel detected, the inverter WILL STAY in SBU mode. I repeat, the inverter will switch ONLY to SUB mode after there is no longer any solar power available.

 

[ochaala]

I

I don't think you understand what is SOL mode and what it is doing.

Voltronic Axpert inverter SOL mode means it works in SBU mode when there is sunlight hitting the panel and it switches to the SUB mode once there is no longer any sunlight detected at the panel. (or sufficient panel voltage/power).

In SOL mode, the inverter WILL NOT DRAW power from the utility as long as there is still sunlight. It will draw power from the battery to complement the dwindling solar power. As long as there is still power from solar panel detected, the inverter WILL STAY in SBU mode. I repeat, the inverter will switch ONLY to SUB mode after there is no longer any solar power available.

I know what sol mode is and I understand what happens during sol mode but mine sol mode is what I have described. I have observed this myself and even the manual states that "solar will provide power to loads first.if solar is not sufficient, utility will provide power to loads at the same time.if utility is not present then solar,if sufficient and battery will provide power to loads"

Regards

 

[AshleyL]

I

I know what sol mode is and I understand what happens during sol mode but mine sol mode is what I have described. I have observed this myself and even the manual states that "solar will provide power to loads first.if solar is not sufficient, utility will provide power to loads at the same time.if utility is not present then solar,if sufficient and battery will provide power to loads"

Regards

You sure you read and quote the correct stuff?

*Seem like this particular inverter doesn't even have SUB mode*

 

[ochaala]

You are right the vm II sol mode is THE SOL MODE but mine is a rebranded one

 

[ochaala]

and thanks for pointing out the Peukert's law and efficiency loss, had completely forgot about that

 

[AshleyL]

View attachment 199101


You are right the vm II sol mode is THE SOL MODE but mine is a rebranded one

This is strange, you sure that is official Axpert VM II manual? Some unscrupulous dealer replaced the manual in order to trick people.
Inverter capable of blending solar/battery with AC is quite expensive, known as SUB mode (not exactly grid-tie sync type though). That SOL description clearly belonging to SUB description.

To be safe, can you take a picture of your inverter model sticker?

 

[ochaala]

This is strange, you sure that is official Axpert VM II manual? Some unscrupulous dealer replaced the manual in order to trick people.
Inverter capable of blending solar/battery with AC is quite expensive, known as SUB mode (not exactly grid-tie sync type though). That SOL description clearly belonging to SUB description.

To be safe, can you take a picture of your inverter model sticker?

PIP-4048MS and PIP-5048MS inverters - Page 92 - AEVA Forums

I have checked it.. not a clone, will post the picture

 

[AshleyL]

PIP-4048MS and PIP-5048MS inverters - Page 92 - AEVA Forums

I have checked it.. will post the picture

Uh oh......you means you bought clone? I can't be certain if the clone SOL mode is a proper SUB or actual SOL (SBU morning, SUB night) now.

 

[ochaala]

This is strange, you sure that is official Axpert VM II manual? Some unscrupulous dealer replaced the manual in order to trick people.
Inverter capable of blending solar/battery with AC is quite expensive, known as SUB mode (not exactly grid-tie sync type though). That SOL description clearly belonging to SUB description.

To be safe, can you take a picture of your inverter model sticker?