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Axpert VM III 5Kw uses the battery for no reason.


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Posted

Hello everybody, (sorry my bad english)
I ask for help for my Axpert VM 3 5kw, it is connected to a 3Kw PV and to a single 2.4kw Pylontech (3 more will arrive soon).

It is set as SBU (solar battery utility) priority and charging to OSO  charging priority(Only solar can charge battery).
The BMS works fine, (the battery icon is blinking) and the inverter also works as expected except for a situation in "Battery mode".
When the battery is not full it takes all the energy from the PV, power the load and with the rest charge the battery, everything is perfect !, ..... but

 .... when the battery is fully charged, it takes the energy (1-2A ... 5A) directly from the battery and a little also from the PV (which has a lot of availability).

After a few minutes, when the battery is slightly discharged, it takes all the energy from the PV, powers the load and charges quickly  the battery again (100%).
This process is automatic and transparent, no errors and good functioning, but I have a strong doubt !!
May be these continuous small discharges and charges  reduce the life cycles of the expensive battery?
Why doesn't it respect the set priority? It is not Solar first, Battery after, and Utility after, but Solar and Battery together and Utility after !. Can I do something to correct?

If, in this situation, you set SUB, it works well, it takes all the necessary energy  from the PV and nothing from the Utility,  but obviously I can't keep this setting in other situations.
Any suggestions? thanks a lot!!

Posted
23 hours ago, pigo said:

After a few minutes, when the battery is slightly discharged, it takes all the energy from the PV, powers the load and charges quickly  the battery again (100%).

Typically, the float voltage is a little less than the bulk/absorb voltage. That's good for longevity of the battery. But it means that the battery will be discharged some 0.5% to allow the battery voltage to fall to the float voltage setting.

But then it should not charge the battery back all the way to 100%, IMHO. But I don't have a packaged LFP battery (I have a DIY LFP battery).

23 hours ago, pigo said:

If, in this situation, you set SUB, it works well, it takes all the necessary energy  from the PV and nothing from the Utility,  but obviously I can't keep this setting in other situations.

Why not? If the utility goes out, in SUB priority you will still run on battery.

Posted (edited)

Hi pigo,

The behavior described is that of maintaining floating charge. It's absolutely normal. As soon as you add additional battery capacity, it will improve as it will take longer to charge the batteries. You can bias it to some extend by varying the settings for floating voltage (27) and bulk charge voltage (26). My settings with LFP batteries are: 26: 53V, 27: 52.5V.

Edited by Beat
Posted

mine seems to be doing the same, at least it looks this way when i look at my graph, with my settings on SUB, it seems to pull the balance from the batteries and not utility??

or am i reading it wrong?

Untitled.thumb.png.d7e8482947eaa5f034e653b9565f6e16.png

Posted
4 hours ago, Coulomb said:

Typically, the float voltage is a little less than the bulk/absorb voltage. That's good for longevity of the battery. But it means that the battery will be discharged some 0.5% to allow the battery voltage to fall to the float voltage setting.

But then it should not charge the battery back all the way to 100%, IMHO. But I don't have a packaged LFP battery (I have a DIY LFP battery).

Why not? If the utility goes out, in SUB priority you will still run on battery.

this is not my goal, it is to use PV always when available, battery when PV is not available, and utility when nothing else is available exactly as SBU says.!

Posted
4 hours ago, Coulomb said:

But then it should not charge the battery back all the way to 100%, IMHO. But I don't have a packaged LFP battery (I have a DIY LFP battery).

Is also my opinion that a slight discharge does not hurt, but I assure you that after a while it recharges again, with at least 10 / 15A, for a short time.  it doesn't feel like a maintenance charge or even an equalization.  The equalization among other things, as well as other parameters is delegated to the BMS Pylon, I can only set parameter 12 (46V) and parameter 13 (49V).

I'll wait the new batteries and I'll see if something will change!! Thanks for support!!

Posted

..... I forget to send you photo and logs(every 30s)  of Axpert activity, as you can see charge and discharge alternate , note that PV can supply more powerand the battery has already been fully charged for several hours .  As soon as battery goes down 1% ...recharge begin..

1649093576510.jpg

DataLog_929321091013827.xls

Posted
6 hours ago, pigo said:

As soon as battery goes down 1% ...recharge begin..

My guess is that as soon as the SoC drops to 99%, the "do not charge" flag goes away, and the inverter, with its typical overshoots, fails to maintain the battery voltage at the float voltage setting, and "accidentally" charges it up. The battery BMS notices this, and sets the "do not charge" flag again.

This jitter from 100% to 99% SoC and back again seems harmless to me.

Posted

Hi Coulomb. your theory is interesting but I have another one that is a bit fanciful!

The problem starts before charging, with that sharing of energy between PV and battery. In my opinion, once the charge is complete, the inverter does not physically close the connection with the battery, so battery input / output and PV out are the same physical equipotential node from which Axpert takes the energy for AC load. It is therefore unable to guide or know whether the energy is coming from the battery or the PV. As soon as the battery drops to 99%, as you said, the BMS informs Axpert to recharge, the voltage on the node rises and the energy flows rightly towards the battery and towards the load, when the charge is complete the game starts again !. I therefore think that, by mistake, due to inability to do otherwise or for simplicity of operation, the designer decided this.

However, I hope it is not serious too, the BMS will know what it is doing! But I don't know how the battery life cycles are counted, complete discharges .... partial discharges ... even minimal discharges !!.

My system is totally "do it yourself", I have not chosen to put power into the grid (here in Italy it would be convenient to do so, but a lot of bureaucratic permits are needed) 

I would like to take as little as possible from the grid, so 70% of the cost is for batteries only!

Posted
9 hours ago, pigo said:

70% of the cost is for batteries only!

Just keep the battery voltage from getting too high. That and heat are what kills any battery (energetic electrons that are able to tunnel through energy gaps and cause destructive chemical reactions). That energy can be thermal or electrical potential energy.

Posted (edited)

Hi Pigo,

I have the same operation as you with the inverter and the battery.
Once charged to 100% (53.2 volts bulk and float) it starts discharging 1 or 2 A and then charges again.
In my house I have another inverter with a self-built 5kwh 24 volt lithium battery bank and I have never 
noticed this strange operation as my battery bank charges to 100% with 1 full day. 
It is practically always charging. 100% I lowered the bulk voltage by tricking the inverter and you wanna laugh? 
He started to drain the battery by a few amps.

My idea is that with low-capacity batteries and many solar panels the battery charges immediately and starts discharging.

The solution could be to increase the battery capacity to ensure that it almost never reaches 100% but maybe at 90 95 
extending the life of the batteries. Unfortunately I only installed 1 pylontech but before spending more money I would like 
to be sure of my idea. It is not nice to have 4 kw of panels and have the battery in the evening only at 60 - 70% since 
during the day it continues to discharge.

When you mount the other batteries keep us updated on how they will work for the other members of the group as well.

Sorry if the post is long but the topics were many and sorry for my English but it is not my first language.
Good sun to all

SP24 Primo VM IV (PF1) 5.6Kw 48 Volt

Pylontech US3000C Batteria LifePo4 3.55Kw 74Aa

Edited by solardavid
  • 5 weeks later...
Posted

Hello everyone,
now I have mounted all 4 batteries (9,6Kwh) and it seems to me that the system is right for me.
With 3Kw of PV In a month I have never taken a single Kw/h from the grid, on average the batteries are fully charged at 1 or 2pm and this also allows me to overcome even 1 or 2 days of bad weather.

Unfortunately, in the afternoon, when the charge is complete, Axpert VM III still uses the batteries! (the setting is SBU), especially if the load is very low, there is no real rule !, the only certainty is that when the batteries go down 99%  it recharge immediately.
The only solution is to set SUB at that moment, in this case it behaves well and uses only PV for the load, bypassing at grid only when PV is insufficient, but I don't know how to automate this setting !, my goal is do not use grid!
I don't like it but that's it!
As partial solution, to reduce the time of this nasty behavior I bought an inexpensive 80l electric boiler with a timer that operates it only from 10AM to 5PM.

I put the output of the boiler as the input of the gas boiler, so if the water is already hot the gas boiler does not start.

Therefore, I save some gas for domestic water and delays the full charge of the batteries.

Posted
3 hours ago, pigo said:

Unfortunately, in the afternoon, when the charge is complete, Axpert VM III still uses the batteries! (the setting is SBU), especially if the load is very low, there is no real rule !, the only certainty is that when the batteries go down 99%  it recharge immediately.

So what's the problem with that? Is it that the panels are not supporting the load at all during that 1% discharge?

If so, that sounds like a problem that King owners have been complaining about for some time. Interestingly, Kings and VM IIIs use the same removable display firmware. Sounds like the display firmware, when it gets a "do not charge" order from the BMS, is telling the inverter to shut off solar altogether, instead of limiting the solar output to the needs of the load. In other words, it's ordering negative battery charge current, when it should be ordering zero.

Posted

Yes, of course, the PV at that moment has great capacities but it uses it partially and alternately without apparent rule, and alternatively uses batteries.
Only when the batteries have discharged by 1% does it use all available PV power for charging and the rest for charging.
It would obviously be preferable to leave the batteries alone if it doesn't need them!
The thing that seems positive is that after a month of work the 3 new batteries, which have never completely discharged, only mark 10 cycles done, while the first battery that has worked for a month alone has 45 cycles. If the data is correct and reliable, it means that the partial discharges are really considered in proportion.

Thanks !

Posted

Hello everybody.

I have done two installations with kodak OG PLUS 5.48 and FL5.2 battery combinations and have the same issue with both installations. Only difference is that it discharge to 95%. No utility is available except when the generator is started. When battery reaches 100% the solar charger switches off and output uses battery power instead of solar until the battery drops to 95%, then it switches back to solar again and repeats the process. I used PYL for battery setting. I tested it on all three output source priority settings with utility disconnected and it behaves the same. Asked the suppliers for assistance but did not get any clarity on this. I am concerned that this cycling between 95% and 100%,  several times per hour, could have a influence on the battery life as this is both off grid installations. Panel configuration is as follow: 2S4P Canadian solar 335w. Sounds like there are no solution to this issue... 

 

Posted
7 hours ago, Machiel said:

I am concerned that this cycling between 95% and 100%,  several times per hour, could have a influence on the battery life as this is both off grid installations.

I agree with you, it is not serious but it is worrying, certainly some influence on cycles has it !.
In this Axpert VM 3 seems to be better than Kodak or Axpert MKS as this video (in Spanish) shows well.

https://www.youtube.com/watch?v=7-AJvnqgFsQ

I confirm that Axpert VM 3 in SUB mode doesn't use the grid without reason, and when it does it takes only the missing quota.

I had watched this video before buying it !!
Unfortunately that doesn't do the same in SBU mode.
When battery reaches 100% the solar charger DON'T switches off but always uses a different PV quota, as I said .... "without apparent rule" ... it uses the battery more often if the load is low.
It is my idea (or maybe it's just fantasy!) That the inverter, after charging, must reduce the voltage produced by the Charge Regulator which at this point is very similar, if not equal to the batteries themselves. The flow that is created cannot therefore have a precise direction and the software cannot control it, but sooner or later the technicians will succeed !!
Take comfort in thinking that the effect on battery cycles is probably not so heavy, in the meantime try to concentrate the loads in the morning or during the battery charge.
I try to persuade my wife to iron or use the washing machine in the late morning but  ......  it's more difficult than changing the inverter software !!

  • 7 months later...
Posted
On 2022/05/13 at 12:09 AM, pigo said:

Hello everyone,
now I have mounted all 4 batteries (9,6Kwh) and it seems to me that the system is right for me.
With 3Kw of PV In a month I have never taken a single Kw/h from the grid, on average the batteries are fully charged at 1 or 2pm and this also allows me to overcome even 1 or 2 days of bad weather.

Unfortunately, in the afternoon, when the charge is complete, Axpert VM III still uses the batteries! (the setting is SBU), especially if the load is very low, there is no real rule !, the only certainty is that when the batteries go down 99%  it recharge immediately.
The only solution is to set SUB at that moment, in this case it behaves well and uses only PV for the load, bypassing at grid only when PV is insufficient, but I don't know how to automate this setting !, my goal is do not use grid!
I don't like it but that's it!
As partial solution, to reduce the time of this nasty behavior I bought an inexpensive 80l electric boiler with a timer that operates it only from 10AM to 5PM.

I put the output of the boiler as the input of the gas boiler, so if the water is already hot the gas boiler does not start.

Therefore, I save some gas for domestic water and delays the full charge of the batteries.

I have a similar inverter, can u tell me how you have added the additional batteries and how is the BMS connected in your setup, please ? 
I have a US3000 and I want to add another 5Kw battery. 

  • 5 months later...
Posted
On 2022/05/15 at 4:25 PM, Machiel said:

Hello everybody.

I have done two installations with kodak OG PLUS 5.48 and FL5.2 battery combinations and have the same issue with both installations. Only difference is that it discharge to 95%. No utility is available except when the generator is started. When battery reaches 100% the solar charger switches off and output uses battery power instead of solar until the battery drops to 95%, then it switches back to solar again and repeats the process. I used PYL for battery setting. I tested it on all three output source priority settings with utility disconnected and it behaves the same. Asked the suppliers for assistance but did not get any clarity on this. I am concerned that this cycling between 95% and 100%,  several times per hour, could have a influence on the battery life as this is both off grid installations. Panel configuration is as follow: 2S4P Canadian solar 335w. Sounds like there are no solution to this issue... 

 

I have exactly this setup, 2 x OG Plus 5.48 (in parallel) & 4 x FL5.2 and I experience the exact symptoms, tonnes of PV available, but it prefers  BAT, regardless of the settings, also - no solution

 

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