Customer’s DIY Solar Off Grid Project with 5kW inverter and US5000 Batteries

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Customer’s DIY Solar Off Grid Project with 5kW inverter and US5000 Batteries

I was originally going to put the equipment in an outbuilding, however, after reading that the lithium batteries are best kept between 10 deg and 40 deg I have put it all in the study, built into a “silent box” it has an extractor fan in the loft Operated by a simple heating thermostat. On the shelf, there is a wireless thermometer which sends alerts and data to my phone!

Before I fitted the fan when it was charging at night on the Octopus Go at 50 amps the temperature spiked up to 35 deg, now with the extractor it never goes above 26 deg, and the thermostat has flattened the curve.

The batteries are below the desk.


The data cable is routed away from the high-current cables and away from the mains. Earth go to a 1m earth spike via 16mm2 cable. Mains input via the changeover switch, Grid, Off or Generator.


I renewed all the electrics and built this consumer unit with the change over the 125 amp change over switch, you see more in the next photo. It’s designed so no matter how you switch the breakers you cannot have an accident!  It’s all normally switched for “Off Grid” but can easily be switched to the grid if the inverter was faulty or to maintain!


The 6mm armoured going into the bottom of the consumer unit is the feed from the inverter. The feed to the inverter comes from the big JFK 100a switch, then to the 32a breaker below, there is another 6 6mm armoured cable coming out below. These armoured cables go outside and then up the outside wall into the loft (together with an armoured cable for a feed from my generator). To make these look neat I put them up the outside wall in a 68mm guttering downpipe, next to the existing downpipe! + 16mm2 earth!


6mm2 armoured terminate here and change to 6mm2 twin earth to inverter box. All IP with glands in case the roof blows off, lol. The cables run with the air around for cooling!


Note PV cable runs 600mm above the mains cables to try to minimize induction problems! 40 years servicing electronic alarm equipment I had a lot of problems due to induction, with cables running incorrectly!


The simple thermostat I had spare only had a make/break contact, so a mains relay that had been in the tools for years was used to switch the fan! I am going to take this further, the fan is 2 speed, so am going to fit another thermostat in the silent box so if it’s a hot day and the temperature goes to say 28 deg it will switch off the slow speed and switch on the high speed

Designer and developer of solar photovoltaic systems from 1kW to Megawatt range. Steve worked for Alstom and General Electric for 11 years. He develops solar inverter and complete systems with energy storage that are affordable, easy to install, and have a quick return on investment.

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