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<\/a>Our on-board electricity capacity is 12V\/210Ah …and it’s a sailing boat, so we don’t generate electricity when we’re travelling. We do<\/em> have an engine – a 1956 Perkins P4 – but prefer manoeuvring under sail because it’s more fun. Consequently electricity is always scarce.\u00a0So, contemplating going off-grid in the (straw-bale) house we were building gave us a feeling of ‘…here we go again’.<\/p>\nWe needn’t have worried – excepting a period of about one month, back in the summer, when something was clearly ‘wrong’ (of which more later) we have been fairly amazed at how well our installation converts sunlight into glorious power. Lashings of it.<\/p>\n
To put things into perspective:<\/p>\n
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- We have a 5kVA generator for back-up …during the last 12 months is has been run for just 20 hours.<\/li>\n
- We aim to use no more than 20% of our battery capacity (SOC = >79%).<\/li>\n
- We always use domestic appliances according to circumstance: Washing machine on sunny days. Fridge\/Freezer off in winter.<\/li>\n
- Because our battery SOC is always relatively high, power produced by our solar panels is often attenuated by the MPPT.<\/li>\n
- Typical daily power consumption is 8KWh in the summer; and 3KWh in the winter. (In the winter we turn the fridge-freezer off; and domestic hot water is heated by a wood-burning appliance.)<\/li>\n<\/ul>\n
I mentioned a moment ago that something went wrong in the summer: Back in July (we’re in the northern hemisphere) we noticed that our 4kW PV array was producing a maximum 1200W. Consequently the battery charge rate was permanently in ‘bulk’, and we were never achieving a full-charge. (It’s worth mentioning here that they’re not Victron supplied panels …and in any case the problem wasn’t with the panels).<\/p>\n
One problem was easy to diagnose \u2013 there’s an Ash tree growing to the South-East of our rooftop array, just ten metres away. Ash trees tend to come into leaf quite late in the spring. Their leaves are ‘spare’ at first, but fill-out as the summer progresses. When the tree is bare the panels get full-sun by 13:00. …but in late summer, that doesn’t happen until 14:30 \u2013 after peak power generation opportunity has already passed. So this winter we’re going to take the tree down.<\/p>\n
Checking the voltage of each of the 15 individual panels from inside the house I noticed that although twelve of them were reading 29V \u2013 32V (the polycrystalline panels have 60 cells); three of them were reading 14V \u2013 19V …and the reading was constantly fluctuating. On the roof the suspect panels read a full 30V – regardless of which side of the MC4 connectors I shoved my voltmeter probes. That suggested there was a fault in the new and unbroken wiring – which seemed unlikely. \u00a0I was so baffled I did nothing for about a fortnight. Then an electrical engineer friend of mine said; Oh well, go up and change the connectors anyway, and then you’ve eliminated them from the enquiry<\/em>.<\/p>\n
Fitting new connectors brought the ‘suspect’ panels straight back to circa 30V…and solved the problem.<\/p>\n
I noticed that the connectors I removed were damp and corroded – then it occurred to me that when I had tested them, and the voltmeter readings seemed OK. it was because the force I used to invaded the cable sheath with the sharp probe of the Voltmeter, actually improved the MC4 terminal contact \u00a0– so they they read a full 30V.<\/p>\n
Some people recommend ‘Denzo’ tape to prevent corrosion – that stuff that looks like bandage soaked in toffee. But having had the connector problem, I’m tempted to go back on the roof and hardwire<\/em> all MC4 connectors. \u00a0After all, the panels are supposed to have a 25 year life.<\/p>\n
We’re off grid for everything: electricity, water, sewerage – and we burn wood for heating, cooking and hot water. The freedom of that goes way beyond just being ‘bill-free’. I could write a whole blog on the misery of billing errors; supplier-switching; comparison sites – but no one would read it …including me! So if you, who read these words, are thinking of going off-grid for electricity – but hesitating – here’s my advice: Go for it!<\/p>\n
Our Victron system comprises:<\/p>\n
MultiPlus 48|5000|70<\/a>\u00a0inverter\/charger<\/p>\n
Soar charger is a \u00a0MPPT150|100<\/a><\/p>\n