bungeejumper wrote:Maybe it's me, but I'd assumed that M4 was pulling our various legs?
I'm BUSTED. You are perfectly correct, I do enjoy writing posts hovering on the borderline of credibility, naughty I know. My apologies.
I thought what I'd written was comfortably ludicrous enough not to be taken seriously, especially when I added my budget at the end. Those who have noticed my occasional comments that on TLF I have been using LiFePO4 batteries and solar panels for years on my boat will probably have realised immediately.
But the obvious fly in the ointment is that a roof-mounted solar panel will be 99% useless anywhere north of Southampton.
This is more than true. With the 24v installation on my boat the weather is the biggest factor. Apart from the fact that solar panels are generally rated with sun perpendicularly above, which never happens in the UK. I don't think I've ever seen my panels delivering more than about 60% of their rated output into the batteries in full midday sun in summer. But on a bright but cloudy day it will be nearer to 15%. I think the roof of my van is about the area of 800W of solar panels so at 15% average output for say a generous 12 hours a day, it would indeed take about a week to charge a 7kWh battery. But for a van carrying half a tonne of tools and stock to go 300 miles between charges I'd guess 15kWh of battery capacity would be nearer the mark.
** WRT what kills a Tesla battery,
https://insideevs.com/news/339193/3-way ... eplace-it/ might prove instructive. 100-150 miles a day with two 100% charges a day was enough to cook one feller's car within 130,000 miles.
Maybe he was just unwise to charge to the max every time?
This is consistent with received wisdom in the world of low tech canal boat LiFePO4 batteries. The rule of thumb is charge to 80%, discharge to 20%, so 60% of nominal LiFePO4 battery capacity is available to be used without knackering them.