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DIY powerwall

edited 30 November -1 at 1:00AM in Green & Ethical MoneySaving
8 replies 4K views
ard123enard123en Forumite
265 Posts
edited 30 November -1 at 1:00AM in Green & Ethical MoneySaving
See a few stories about people building there own powerwall using reclaimed 18650 batteries

Just wondering if anyone on here is doing it I've done some research pretty sure I have the required skills just need a cheap supply of old laptop batteries

Replies

  • ard123enard123en Forumite
    265 Posts
    Managed to get my first 100 cells to building a proof of concept
  • EctophileEctophile Forumite
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    Ninth Anniversary 1,000 Posts Name Dropper
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    Have you worked out how you're going to integrate it with the rest of the system yet? I assume you either need a compatible solar inverter, or a separate G.83-compliant inverter for the batteries.
    If it sticks, force it.
    If it breaks, well it wasn't working right anyway.
  • Not sure yet thinking I'm going to have an off grid inverter back into the house via transfer switch.

    Saves the issue of battery been pushed back to the grid
  • edited 5 November 2017 at 12:59PM
    HeedtheadviceHeedtheadvice Forumite
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    edited 5 November 2017 at 12:59PM
    Consider an on grid compliant inverter (run from the batteries) switched into circuit (or the battery supply to it) when main generation plus battery potentially derived current is less than the 16 amps max allowable under G83?

    Have considered this using the switched output from my Immersun for a while (but doubt if it could be configured)...for when batts become economic!
    Alternatively a current sensor on the export wire could be used and that just needs a comparator and relay!!

    I hereby publish my idea and claim copyright! Patent pending if I ever get round to it!

    Ummmm,
    Thinks......is it allowed to have two (or more) inverters capable (under a theoretical fault condition) of exporting over the allowed 16Amp limit......?
  • I'm now upto 2.5kwh of good tested batteries reclaimed from old laptop batteries.

    The project so far has coated in the region of £100 will be doing bus bars and fuses over Christmas
  • forgotmynameforgotmyname Forumite
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    2.5KWh? how many batteries do you have? What voltage are you running the system at?

    How are you going to balance that many cells?
    Censorship Reigns Supreme in Troll City...

  • 336 batteries arranged on 14 modules of 24 cells. Have a small smart BMS with Bluetooth from China for testing cost £45. Have a lithium charger anyway plus other stuff like raspberry pi for making interface etc.

    The higher voltage makes it easier as can use smaller cables as drawing less amps for same Watts

    Test inverter is only 300W so won't be running much but will keep my lights and TV on at night

    Once this proof of concept is working and have enough cells will use a larger BMS like rec-bms or batrium
  • Have to say I doing this is not for everyone I have an electronics and computer engineering background.

    There are lots of things to consider along the way
This discussion has been closed.
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