Paul Posted September 30, 2021 Share Posted September 30, 2021 Hi, I'm Paul from the East of the UK. I decided to join this forum after watching some of the excellent GS videos about powerjack inverters and the wealth of useful information on this forum. I started off my experimentation with off-grid solar about 4 years ago when a friend sold me very cheaply a 'classic' powerjack inverter (v3 boards dated 2013) rated at 8000 chinese watts and four 180Ah truck batteries (which were past their best). I bought all the other stuff myself such as six 60-cell solar panels, an EPever Tracer 4210AN charge controller, and started playing seeing what I could run off grid. In the end I had 4 solar panels mounted on the garage roof and another 4 mounted on metal framework in the garden, all SE facing with minimal shading except in winter months, in a 2S4P configuration, obviously with all the necessary fuses, diodes etc between the strings and a suitable rated DC isolator. I now have six 200Ah Rosen Solar gel SLA batteries in a 2S3P configuration, each string fused with 100A HRC fuses, an EPever Triron 4210AN controller with a cat5 cable back to a wifi module in the house, and the 'load' output of the inverter drives a relay to switch the inverter on/off remotely. The output of the inverter is protected by a 16A RCBO. Inside the house, I have rewired one ring main and the lighting circuit to a 40A 2PCO changeover switch with centre-off to enable me to switch those circuits fsafely rom the main grid CU to the inverter at will. This has worked well, and can provide 3.6kW before the PJ starts complaining. Thankfully in the UK as everything is 240V I don't have any of the issues that the US/AU guys have with 'split phase' 110v, which has always seemed an illogical complication to me. having a simple, single 220-240v output seems far more sensible to my little brain! Knowing that the PJ inverter was old and potentially unreliable (as well as having a high idle current of 2.5A @24V) I decided to try buying a new 'Upower' badged 8k inverter in Dec 2020. This arrived from China in good condition and working order, however I noticed that it only had an ASL3 transformer, and that LED lights would dim noticeably more than they did with the ancient PJ inverter when heavy loads were applied (e.g. 2000W induction hob) and after some inspection with a newly bought scope saw the waveform severely cropped with any load above about 1.5kW. This made sense to me as the new upower unit was much lighter than the old PJ unit which contained two (AS2 if memory serves) transformers in series. Therefore I concluded that the electronics were well up the job, but the weak link was the transformer. I decided to calculate and wind a transformer myself that wouldgive a properly formed sine wave and cope with a continuous 3.6kW+ for 20 mins at least. I found an ebay seller selling some big toroidal transformers that were originally designed for an audio amplifier application very cheaply. So I bought one. The core was 52cm2 CSA, which according to the calculations is good for up to 4VA. SO I stripped it down, and rewound it with 214 turns of 2mm dia (~3mm CSA) enamelled wire as the secondary, and 12 turns of 2*16mm2 PVC coated cable as the primary, each layer separated with fibreglass tape. This transformer works extremely well, giving a clean sine wave up to 3kW or more. However the idle current is again a stubborn 2.5A like the older PJ. So now I am working on making a suitable choke to put in series with the transformer to lower the idle current. 1 Quote Link to comment Share on other sites More sharing options...
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