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Comment by fgsfds028374 | Hacker News Reader

Sailors are big into LFPs these days. I just upgraded my Beneteau to a 11kWh LFP bank and it's been game changing. I cook with a 1800W inductive cooktop, use the microwave, run the desalinator, for multiple consecutive days at anchor without running a generator or the motor. Unthinkable in the days of AGM deep cycles, they'd be dead in months.

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get an instapot! Save lots of energy while cooking faster. (depends on what you're cooking of course).

Already got one (3qt), love it.

Also: https://100r.co/site/solar_cooking.html

how long will the lfps last that way

In theory they should be good for several thousand cycles, so -- a long time. As long as you don't overcharge them, drain them too low, or try to charge them in below freezing temperatures.

Also, they say that usually LFPs will last a bit longer if they're installed such that they're under a bit of sideways compression. I don't know why that is.

That only goes for prismatic cells (boxes rather than cylinders). The reason is that they tend to swell up while charging if you don't compress them so manufacturers will specify a clamping force required for the cells to keep their shape. If they change shape in such a way that you can observe it then your cells are toast so better stick to that mfg indicated compression. There are a number of articles out there that show how to do this the right way and also some that get it hilariously wrong. The direction to compress the cells in is in such a way that the electrodes remain under compression perpendicular to their surface. So compressing from the top and compressing from the front will do absolutely nothing.

thank you very much for explaining

it makes sense that cylinders would be immune to swelling

You're welcome. I've been working for more than a year on a blog post about the various safety aspects of building battery packs but it's a never ending rabbithole of stuff to research and learn about so I haven't gotten around to publishing it.

Maybe multi-part series would fit it better ? Probably better SEO for one-subtopic-per-article if you care about that.

No, I don't care about SEO at all. I just would like this info to be out there for hobbyists and tinkerers as well as people that are contemplating designing something with Lithium Ion based batteries in it. But because it is safety related I really want to get it all right and with little room for error I get a lot more careful about what I publish. It will happen.

That's very understandable and I can't wait to read it once it's ready :-)

Not sure why, but when I saw your name in this thread - it was entirely expected ¯\_(ツ)_/¯

No idea either... it's jm bait ;)

Hah. Post it on HN, and let Cunningham's law help you :)

Snark aside, I feel that on HN, there are enough actual proper experts who will point out avenues of research and gotchas that a single person chasing down rabbitholes on their own is unlikely to discover.

you might be surprised what this particular single person is likely to discover on their own

one of jacquesm's previous personal rabbitholes was designing and building a wind turbine from scratch, down to cutting out the stator and rotor windings for the generator from sheet metal

Fair point. Either way, my ulterior motive was to be able to read what they have, and learn vicariously that way :)

If you drop me a line I can share the google doc with you so you can comment on it.

Email in profile.

And if you google my name + long range e-bike you get an article about a pack that I laid out (170 cells, 2.2 KWh).

It feels to me that the battery compression discussion is a bit of a game of telephone.

I think this video by off-grid-solar explains it quite well. https://www.youtube.com/watch?v=63-Nx75_xXM

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