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Trober's new 12kW Off-grid system


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Hi all,

Thanks to so much good information on this forum, a lot of thinking, planning and building, I finally came online on Saturday.

So far everything works pretty well. Eskom mains  was turned off on Sunday and so far, no need even to run the generator.

I am still finding my feet with all the settings and discovery of the best options but 

My system:

24 X JAR 375 W Mono's (8.8kWp)

3 X Axpert Type 4kW inverters in parallel  (12kW)

7 X Narada NPFC100 Li-Fe-Po4 batteries (33.6kWh)

1 X Deutsz 15kVA generator

Pic attached.




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On 2020/01/23 at 8:54 AM, Trober said:

What would be the advantage to fuse both battery terminals?

In a floating system (ie where one side of the battery isn't earthed) you'd fuse both sides to protect against a situation where there are two earth faults.

Think about what is done in a car. The negative is earthed, so the entire chassis is at the negative potential (considered 0V). Any short to earth causes a large fault current and blows the fuse on the positive side, or the fusible link in the positive battery line. Hence, only one fuse required and you have protection against a single earth fault.

Now imagine a car that is not earthed to the chassis. If a positive cable rubs through, the chassis becomes positive (this is the first earth fault). If a second earth fault results it could bypass the fuse (the current can find an alternate route past the fuse via the two earth faults). Now you have no protection. You therefore have to put a fuse on the negative side too.

This is however ONLY if you expect a high likelihood of earth faults (eg in a vehicle where you have cables running in a metal hull). If an earth fault is unlikely, as is usually the case in battery backup systems where the single fuse is close to the battery and the cabling runs in trunking, you can get away with just one fuse.

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  • 3 months later...
  • 4 weeks later...

Hi GerhardK83,

a) I bought the batteries privately from a friend, Inverters from The Sun Pays, Panels from ANH Technologies. (JAR 375W 72 cell)

b) 2 houses and 2 workshops totals around 32 kwh daily - max load I've seen around 9kw.

c) no comms between inverters and batteries - I monitor inverters with WatchPower and batteries with my own interface and SW via the RS485 port.

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