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Correct Cable size for 5Kva Axpert


Instinct

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8 hours ago, Instinct said:

Please varify if correct cable size of 10mm will be used to connect 5kv Axpert at a distance of 20met to main board.

Welcome instinct. Chris hasn't been active for quite some time, although 2.5mm will handle that with ease, I would recommend 4mm. 10mm  is a overkill.  

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4mm Surfix can handle 32A 

6mm Surfix can handle 41A

I would go with 6mm as the built in circuit breaker of the Axpert is 40A. (although it equals over 9kw, startup power always spikes) 

Not 100% sure but the input to the inverter can exceed 5Kva: Battery charging + 5kva load. Input cable must thus be a bit thicker. 

The important thing is the breaker sizes: breakers to be sized accordingly to the cable. 

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I use 4 mm² for the output (AC-out) cable, and 6 mm² for the AC-in. Theoretically, you could be supplying 5 kW to the loads in line (bypass) mode, and utility charging at 3 kW, so that's why you need a heavier cable for the AC-in.

20 metres is a moderate haul, so 6 mm² for both would not be unreasonable, slightly reducing the "lights dim with fridge start" effect. As others have noted, 10 mm² is way overkill, and is difficult to work with. You might not even get all the conductors into the terminal blocks.

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Hi there.

 

I also used 6mm for both in and out. My inverter is also about 20m from my db. As pointed out 6mm can handle 41 amp constantly, it will be able to carry higher amps for short periods.

If your plan is to later upgrade to a bigger system then it might be worth it to pull bigger cables. Run the biggest cables you can afford without going crazy. 

the Axpert will allow 10kw for 10s 

5000w/220 = 22.72A 

10000w/220=45.45A 

if you are going to use 2 axperts run bigger cables. 

Edited by Krokkedil
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  • 4 weeks later...
On 2020/01/23 at 5:57 PM, Jaco de Jongh said:

Welcome instinct. Chris hasn't been active for quite some time, although 2.5mm will handle that with ease, I would recommend 4mm. 10mm  is a overkill.  

Hi Jaco

Thank you for the advise. Used 6mm in the end. Rather safe than sorry. Hope you could assist me on the following.

I would like to get the program settings for my Axpert 5kv MKS as nobody seems to have any data on the battery.I'm using a Liiontech 6kwh lthium ion batt obtained from solar shop. The info on battery supplied is not enough.I'm not using PV panels yet, but will soon be. My daily utility usage is up with approx 5kw. Advise from guys here reckon batt is overcharging. Not sure if thats correct. Maybe you or somebody on the forum would be so kind to help.

Regards

Instinct

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11 hours ago, Instinct said:

I'm using a Liiontech 6kwh lthium ion batt obtained from solar shop.

I'd have a go at answering this, but I need a link to whatever information you have so far. I wasted about 10 minutes trying to find it; your post seems riddled with spelling errors.

You say your daily usage is "approx 5kw". Do you mean your power usage regularly peaks at 5 kW, or that your daily energy draw from utility is about 5 kWh?

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21 hours ago, Instinct said:

My daily(24hr period) usage is approx 20kw.

Since I connected Inverter and battery up the 24hr usage has climbed to 25kw?

Ah. You mean your daily energy usage has increased from 20 kWh to 25 kWh.

It's expected that if you are powering the same loads, when some of the load goes into and out of a battery via a charger and inverter, some energy will be lost. The charger and inverter have of the order of 7% loss, and the lithium battery will charge at a higher voltage than it discharges at. There there is the overhead of the inverter electronics, some losses from cables, etc. 25% extra seems a little on the high side, but it's believable.

You'll need to connect some solar panels to get your usage down. There are inefficiencies with them as well, but solar power is free.

Edit: don't you have at least some link to some incomplete information on your battery? Did it perhaps come with a paper manual, or are there numbers on a sticker on the battery?

Edited by Coulomb
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11 hours ago, DaveSA said:

@Coulomb  i think this is the battery...

Ok, thanks.

I'll proceed assuming it's not a stolen battery. Unfortunately, this battery is designed only for use with four types of inverter, and yours is none of those. They don't specify the charge parameters, because the charger is supposed to read the values over the CAN bus or whatever it is. So we have to guess.

The first really important question is: is this a 15S or 16S LFP battery? It makes a huge difference to how it's charged. Maybe you can peek inside and count the cells, but that may not be practicable. There is one clue from the web page: charge to 54.0 V. That suggests 15S. But maybe they are guessing that.

If possible, pick a time when the battery isn't being charged (not for at least half an hour), and the loads are very light. Then read the battery voltage; preferably with a known good multimeter, but failing that, just use the reading from the inverter. Preferably, there should be 3 LEDs on (one off), on the battery SOC LEDs (so 50-75% SOC).

For 15S, I'd expect 3.33 x 15 = 50.0 V.

For 16S, I'd expect 3.33 x 16 = 53.3 V.

That will determine the all-important settings 26 and 27 (bulk/absorb and float battery voltage settings respectively).

For 15S, I suggest the PylonTech values of 53.2 V and 53.0 V (for settings 26 and 27 respectively).

For 16S, I suggest 56.0 V and 54.4 V (that's 3.50 and 3.40 VPC respectively). That's lower than the PylonTech values, but higher than I run on my own 16S system. (I use 55.2 V and 53.7 V).

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6 hours ago, Coulomb said:

Ok, thanks.

I'll proceed assuming it's not a stolen battery. Unfortunately, this battery is designed only for use with four types of inverter, and yours is none of those. They don't specify the charge parameters, because the charger is supposed to read the values over the CAN bus or whatever it is. So we have to guess.

The first really important question is: is this a 15S or 16S LFP battery? It makes a huge difference to how it's charged. Maybe you can peek inside and count the cells, but that may not be practicable. There is one clue from the web page: charge to 54.0 V. That suggests 15S. But maybe they are guessing that.

If possible, pick a time when the battery isn't being charged (not for at least half an hour), and the loads are very light. Then read the battery voltage; preferably with a known good multimeter, but failing that, just use the reading from the inverter. Preferably, there should be 3 LEDs on (one off), on the battery SOC LEDs (so 50-75% SOC).

For 15S, I'd expect 3.33 x 15 = 50.0 V.

For 16S, I'd expect 3.33 x 16 = 53.3 V.

That will determine the all-important settings 26 and 27 (bulk/absorb and float battery voltage settings respectively).

For 15S, I suggest the PylonTech values of 53.2 V and 53.0 V (for settings 26 and 27 respectively).

For 16S, I suggest 56.0 V and 54.4 V (that's 3.50 and 3.40 VPC respectively). That's lower than the PylonTech values, but higher than I run on my own 16S system. (I use 55.2 V and 53.7 V).

Hi Coulomb

Thank you for all the effort and time spent to try and help.Appreciate.Yes that is definitely the correct battery.

Having gone into the menu screen on the battery it definitely only shows 15 cells.

The menu states following info:

Analog Info :   Pack V 51,95 V

                         Im  0,00A

                        Cell Volt    3460Mv (varies a bit on all 15)

                        Cell Capacity  SOC 99,41 %

                        FCC     105,9 AH

                        Rm  105,3 AH   

                        CC  9

System Setting     Braud 9600

Not sure if any of this info will help?

Regards,

Instinct

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