• Naz@sh.itjust.works
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    8 months ago

    Hello, expert solarpunk here.

    TLDR: Car battery is 350Wh. Fridge uses 143W idle, so it’ll run a fridge for 2-3 hours.

    Explanation below:

    Car batteries are lead-acid (sulphuric acid and lead plates).

    They discharge according to Peukert’s Law as the negatively charged plate gets covered in lead via the acid (electrolyte).

    As the battery depletes, the negative plate can begin to take permanent damage, and so you can’t discharge a lead-acid deeper than 10-20%, or about 10.8V, with the safe limit being ~50% discharge.

    Most 12V, 60Ah batteries therefore only safely store and nominally discharge 350 Wh @ 350W.

    You can discharge that as fast as you want but the faster you discharge, the lower the capacity is (with 1000-1500W bringing you way down to like 65 Wh). Fridges have a surge when they start up to fire up the compressor. Starter batteries can take that, but once the refrigerant is cold, the fridge just maintains the temperature which uses a lot less energy - about 143W on average.

    • Aux@lemmy.world
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      8 months ago

      You have a very inefficient fridge! My fridge is rated for 272 kWh per annum, which is 745 Wh per day or 24 Wh per hour. You need to buy a new fridge.

    • Krudler@lemmy.world
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      8 months ago

      AI told me 75C/170F is ideal for hot tub water temperature.

      Sure no problem. Once I get used to that I’ll work my way up to boiling peanut oil.

      • Aux@lemmy.world
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        8 months ago

        75°C is definitely ok for a hot tube for a short session.

        • viking@infosec.pub
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          8 months ago

          Temperatures beyond 50°C are an acute risk. 75°C can cause lasting damages.

          • Aux@lemmy.world
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            8 months ago

            Ever been to sauna? Especially the Russian one? There’s no risk if you don’t have heart issues.

            • viking@infosec.pub
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              8 months ago

              I’m regularly going to a Finnish sauna with >80°C, but air with 100% humidity is not the same as immersing yourself in scalding hot water.

              • Aux@lemmy.world
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                8 months ago

                The Finnish sauna is dry. Russian and Turkish are wet with high humidity.

        • Zink@programming.dev
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          8 months ago

          Sure but you can only do it once!

          Seriously, even 75C water coming out of the tap would be dangerous and negligent.

        • Pazuzu@midwest.social
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          8 months ago

          Forget 75°, just 65°C (150°F) will give you third degree burns in 2 seconds:

          Most adults will suffer third-degree burns if exposed to 150 degree water for two seconds. Burns will also occur with a six-second exposure to 140 degree water or with a thirty second exposure to 130 degree water. Even if the temperature is 120 degrees, a five minute exposure could result in third-degree burns.

          (°F)