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Advice needed on Axpert 5kva Inverter and Solar Sizing


Nick
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Good Evening All,

Firstly I'd just like to say how impressed I am by this forum, the topics covered, content available and responsiveness of the experts! Thank you!

I am based in Victoria Falls, Zimbabwe and given Zim's notoriously erratic power supply am about to put a 5kVA system into my house but having spent hours reading through the info on the forum have realised that there are quite a few potential pitfalls that I'd like to avoid so would appreciate some input please.

Firstly on the inverter, we have Afritech 5kVA inverters available locally (screenshot of the specs attached). From what I can see these appear to be re-branded Axpert MKS units however I cannot find anything about 'Afritech' online so am suspicious that they might be clones? Is there any way of telling from the specs provided? Or is there anything else I should be concerned with about this particular option besides the known Axpert issues highlighted elsewhere in the forum.

My second question is regarding the battery bank, we have Ritar AGM 260ah options available locally, ideally with our average power consumption I would like to end up with 8 x 260ah batteries BUT the supplier only has 4 in stock now and will only be able to deliver the additional 4 in approx 1 month. I understand that adding new AGM's to an existing battery bank is problematic but wanted to find out if this is really that serious over the course of a month? Should I go ahead with the 4 batteries they have now and then add the additional 4 in when they arrive in a month or should I wait until I have all the batteries here before installing?

Thirdly, and finally, as far as the panels are concerned. My supplier only has 365W Canadian Solar modules available locally so am looking at going with either 8 / 9 modules depending on the answer to this question. Having looked at the specs of the panels, the VOC is 47.2V and the VMP is 39.8V. The max allowable PV input for the Axpert is 145VDC and the voltage range is 60 - 115VDC. If I were to connect 3 panels in series I will end up with a total VOC of 141.6V which is within range of the inverter but the VMP will be 119.4VDC which is just over the 115VMP max of the inverter. Will this cause an issue? Would it be better to go with 8 panels (2S4P) or 9 panels (3S3P) for this configuration?

Thanks in advance 

Regards

Nick           

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10 hours ago, Nick said:

Good Evening All,

Welcome.

10 hours ago, Nick said:

Firstly on the inverter, we have Afritech 5kVA inverters available locally (screenshot of the specs attached). From what I can see these appear to be re-branded Axpert MKS units however I cannot find anything about 'Afritech' online so am suspicious that they might be clones? Is there any way of telling from the specs provided?

They look genuine at first glance, but I suspect that the cloners are getting good at their "craft". It would be best to get a photo of the label on the side, then check against this post: Do I Own a Clone?

10 hours ago, Nick said:

My second question is regarding the battery bank, we have Ritar AGM 260ah options available locally, ideally with our average power consumption I would like to end up with 8 x 260ah batteries BUT the supplier only has 4 in stock now and will only be able to deliver the additional 4 in approx 1 month. I understand that adding new AGM's to an existing battery bank is problematic but wanted to find out if this is really that serious over the course of a month?

One month should be OK. But do try to get the battery module rested voltages as close as you can before you connect the second set. Perhaps look into a lead acid battery balancer. I know nothing about these, except they sound like a really good idea.

10 hours ago, Nick said:

Thirdly, and finally, as far as the panels are concerned. My supplier only has 365W Canadian Solar modules available locally so am looking at going with either 8 / 9 modules depending on the answer to this question. Having looked at the specs of the panels, the VOC is 47.2V and the VMP is 39.8V. The max allowable PV input for the Axpert is 145VDC and the voltage range is 60 - 115VDC. If I were to connect 3 panels in series I will end up with a total VOC of 141.6V which is within range of the inverter but the VMP will be 119.4VDC which is just over the 115VMP max of the inverter. Will this cause an issue?

Yes. Save yourself some grief and go for 2S.

Quote

Would it be better to go with 8 panels (2S4P) or 9 panels (3S3P) for this configuration?

2S4P definitely better. Though 2S5P is still only 3650 W nominal, so if you can afford 10 panels, go for 2S5P, possibly even 2S6P. You can add extra panels afterwards, but it helps to plan for them (allocate roofspace, possibly leave rails long enough for the extra pair or pairs). Don't forget string fuses; these are needed for safety.

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