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Help on new Axpert 5kva installation.


Sunny
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Hi Guys, I am very new to the world of Solar power, to beat the eskom failures I decided to invest in a system as opposed to a generator. I have a 5 kva Axpert inverter , with 4x 200AH goldshine batteries and 6x300w panels. I am very happy with how this works but I have a few questions that perhaps you guys can help on.

 

1. Would this charge batteries fully? As they only seem to get to 52v my setting is set to 55v. Does this mean that I require more panels to maximize this?

2. My switch over setting is on 47v , but when this is reached and the inverter switches to utility on resting I still have above 48v. Should I change this setting to 46v?

3. Is there some setting that can help me charge this adequately?

I am using this setup on the SBU setting all my other settings are the defaults. Battery more is AGM.

 

Any help or thoughts on this would be highly appreciated.

 

Thanks

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9 hours ago, Sunny said:

1. Would this charge batteries fully?

It depends. Factory firmware comes with the premature float bugs. If you use more energy in loads plus losses than you get with PV, then you'll not fully charge on average and need more panels.

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As they only seem to get to 52v my setting is set to 55v.

That's a float voltage. It sounds like classic premature float voltage. I would think you'd need over 56 V to fully charge any lead-acid battery.

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Does this mean that I require more panels to maximize this?

As above, it depends on your loads.

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2. My switch over setting is on 47v , but when this is reached and the inverter switches to utility on resting I still have above 48v. Should I change this setting to 46v?

No! For battery longevity, you should only allow 50% DOD, and 48 V rested is well below that. I'd set it to 48 V, which it possibly as high as it goes.

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3. Is there some setting that can help me charge this adequately?

Yes. You may be able to use patched firmware. Otherwise, you can work around the worst effects of the premature float bugs (which will murder your battery; lead-acid doesn't like chronic undercharging) by using either absorb time, the equalisation feature (if present), or both. See other posts, I'm in a hurry just now, sorry.

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  • 3 weeks later...
14 hours ago, Sunny said:

For my setup is fully charged at 54v or 52v.

Fully charged is getting to around 56 V for long enough for the charge current to drop to about 6 A. Then when the charge stops, the battery voltage should retreat to about 54 V, with nearly no charge current (roughly ≤ 2 A) required to hold it there.

14 hours ago, Sunny said:

I seem to get to 52v.

That's not fully charged. When the inverter thinks it's fully charged, the middle green LED should be on solid (this indicates it's at the float stage, and is aiming to keep the battery voltage at the voltage in setting 27).

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Hi , Thanks ,yes this seems to be my problem. The inverter thinks the batteries are charged but they are not. I have changed 27 to 58. Still did not help. Is there some other way to fix this? Would a separate solar charge controller help? Looking for an ideas on how to resolve this. The solar panels get enough energy but because the inverter thinks the battery is charged it doesn't pull slot as it just takes what it needs for the load.

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5 hours ago, Sunny said:

Would a separate solar charge controller help?

Yes.

5 hours ago, Sunny said:

Looking for an ideas on how to resolve this.

  • Patched firmware to fix the premature float bugs, if your machine is eligible.
  • Separate Solar Charge Controller, as you have suggested. Either in addition to, or instead of the internal SCC.
  • Depending on your exact model, you may be able to use either the "bulk charging time" (timed absorb? Setting 32) or the battery equalisation facility (settings 33-37, 39) to work around the bugs. The idea is to force the charger into absorb mode for a minimum period of time. The problem is that the battery may over-charge, or your guessed time might not be enough. You just have to watch the average charge performance over time, and adjust as needed. Stay below the gassing voltage (14.4 x 4 = 57.6 V at 25°C) if you are using a non-flooded lead acid battery.
Edited by Coulomb
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Hi,

Thank you, I think I have clone inverter so i think the firmware upgrade is a no go .... 

How accurate is watch power , as watch power seems to think 52v is 100% on the app on my PC. My batteries get to this but not 54v.

Can you perhaps recommend someone to install and provide a solar charge controller to resolve this issue.

I am in Gauteng.

Thanks

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15 hours ago, Sunny said:

How accurate is watch power , as watch power seems to think 52v is 100% on the app on my PC. My batteries get to this but not 54v.

Watchpower is just echoing what the inverter says, and that's just a wild guess based on battery voltage alone.

The battery charger doesn't stop charging when the SOC meter or battery % display gets to 100%; it's just meant to be a rough indication of what the battery state is.

I can't help with an installer; I'm based in Australia.

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  • 3 weeks later...

Thank you so much, you have really helped me gain perspective.

How would I add a solar charge controller to the system. Will I have to have seperate panels to charge the batteries and separate panels on the inverter to supply the home? Will I still have all the functionality of the inverter eg. Charge first then switch over to the solar power?

I think the solar charge controller is my only option.

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I've recently added an external MPPT to my Axpert - so let me try to answer your questions to the best of my knowledge

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Will I have to have seperate panels to charge the batteries and separate panels on the inverter to supply the home?

I believe it is possible to have both panels directly on the Axpert as well as on a separate MPPT - but I have moved all my panels off the Axpert and connected them only to the new MPPT. I believe it can be a bit difficult (though not impossible) to synchronize the charging of the battery between the Axpert and the external MPPT

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Will I still have all the functionality of the inverter eg. Charge first then switch over to the solar power?

Yes - even though I have to admit I do not fully understand what you mean by 'charge first then switch over to the solar power'

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How would I add a solar charge controller to the system

You connect Axpert, batteries, and the external MPPT all together via a common busbar (on the Axpert the battery connection is only used, not the PV connection). The Axpert is no longer aware of your PV panels but does receive the energy provided by the MPPT through the battery connection.

The external MPPT basically both charges your batteries and provides energy to the Axpert at the same time (depending on Axpert settings and energy available obviously).

If the Axpert is in Utility or SUB mode, the MPPT will only charge the batteries as the Axpert is set not to take energy from the batteries. 

If the Axpert is in SBU, then any available energy from the MPPT will first be used to supply the loads on the Axpert. If the MPPT energy is higher than what the Axpert requires for the loads, any excess MPPT energy will be used to charge the batteries. Once the batteries are fully charged, the MPPT will throttle the energy it provides to match the Axpert load requirement. If the MPPT energy is not sufficient to supply the Axpert load (e.g. in the evening) then the batteries will supply the difference.

The only time when this setup can be a bit problematic is when you want to charge your batteries both from utility and solar. Then you need to be careful with your max charge currents as well as synchronization between the two. As I have my settings that the Axpert does not charge the batteries with utility, this is not a problem for me

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  • 2 weeks later...

Excellent Guys, after lockdown this going to be my plan of action.

Can you recommend a charge controller to purchase?

I won't be using solar and utility but either solar or utility to charge the batteries. Where i am in South Africa load shedding Is something we have to live with so on days with bad sunshine , I would manually change it to charge from utility. SBU is my preferred mode.

On the unclear comment of mine ... I wasn't sure if the switching and functionality of the inverter would still be operational, if I ventured down this road.

Just to summate .... PV connected to external charge controller and connected to batteries. Inverter only connected to the batteries. I will go with your recommendation on the connection. Do I understand this correctly.

Thank you to all off you who helped me get much needed clarity. You guys Rock!

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3 hours ago, Sunny said:

Can you recommend a charge controller to purchase?

I went with a Victron MPPT. On their website, you will find links to both their Excel-based as well as online calculator tool to determine which model best suits your requirements

3 hours ago, Sunny said:

Just to summate .... PV connected to external charge controller and connected to batteries. Inverter only connected to the batteries.

Correct. If you want, PM me your cell number and I can send you some pictures of how my installer connected everything

4 hours ago, Sunny said:

Where i am in South Africa load shedding Is something we have to live with so on days with bad sunshine , I would manually change it to charge from utility. SBU is my preferred mode.

I am also based in SA and for scheduled load shedding I simply change my SOC setpoint for switching back to utility in ICC to a higher value to make sure that I still have sufficient battery when load shedding starts. So instead of using utility to charge the batteries, the system switches earlier over to utility and preserves the batteries for later. Of course this requires ICC and something to accurately determine your battery SOC (e.g. Victron BMV). Alternatively, instead of using SOC for switching you should also be able to raise the Back to Grid voltage to make the Axpert switch earlier (I do not have AGM batteries, so I am not an expert on that side)

Do you have ICC?

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