{"id":2265,"date":"2026-01-29T23:36:51","date_gmt":"2026-01-29T21:36:51","guid":{"rendered":"https:\/\/nature-o.net\/?page_id=2265"},"modified":"2026-02-02T17:35:01","modified_gmt":"2026-02-02T15:35:01","slug":"flashlight-battery-runtime-calculator","status":"publish","type":"page","link":"https:\/\/nature-o.net\/?page_id=2265","title":{"rendered":"Flashlight Battery Runtime Calculator"},"content":{"rendered":"\n<div class=\"eco-tool wp-block-group\" id=\"eco-tool-flash-1c3a7\">\n  <div class=\"eco-tool__header\">\n    <h2 class=\"eco-tool__title\">Flashlight Battery Runtime Calculator<\/h2>\n    <p class=\"eco-tool__lead\">Estimate flashlight runtime based on batteries and power draw (simple estimate).<\/p>\n  <\/div>\n\n  <form class=\"eco-tool__form\" novalidate>\n    <div class=\"eco-tool__grid2\">\n      <div class=\"eco-tool__field\">\n        <label class=\"eco-tool__label\" for=\"eco-fl-batt-1c3a7\">Battery type<\/label>\n        <select class=\"eco-tool__input\" id=\"eco-fl-batt-1c3a7\">\n          <option value=\"2.4\">AA alkaline (\u22482.4 Wh each)<\/option>\n          <option value=\"3.0\" selected>AA rechargeable (\u22483.0 Wh each)<\/option>\n          <option value=\"1.8\">AAA alkaline (\u22481.8 Wh each)<\/option>\n          <option value=\"12\">18650 Li-ion (\u224812 Wh)<\/option>\n        <\/select>\n        <div class=\"eco-tool__hint\">Energy values are rough averages.<\/div>\n      <\/div>\n\n      <div class=\"eco-tool__field\">\n        <label class=\"eco-tool__label\" for=\"eco-fl-count-1c3a7\">Number of batteries<\/label>\n        <input class=\"eco-tool__input\" id=\"eco-fl-count-1c3a7\" type=\"number\" min=\"1\" step=\"1\" value=\"3\" inputmode=\"numeric\">\n        <div class=\"eco-tool__hint\">Example: 2\u20134 batteries.<\/div>\n      <\/div>\n\n      <div class=\"eco-tool__field\">\n        <label class=\"eco-tool__label\" for=\"eco-fl-w-1c3a7\">Flashlight power (W)<\/label>\n        <input class=\"eco-tool__input\" id=\"eco-fl-w-1c3a7\" type=\"number\" min=\"0.1\" step=\"0.1\" value=\"2\" inputmode=\"decimal\">\n        <div class=\"eco-tool__hint\">Lower modes last much longer.<\/div>\n      <\/div>\n\n      <div class=\"eco-tool__field\">\n        <label class=\"eco-tool__label\" for=\"eco-fl-eff-1c3a7\">Efficiency (preset)<\/label>\n        <select class=\"eco-tool__input\" id=\"eco-fl-eff-1c3a7\">\n          <option value=\"0.75\" selected>Typical (75%)<\/option>\n          <option value=\"0.85\">Good (85%)<\/option>\n          <option value=\"0.65\">Low (65%)<\/option>\n        <\/select>\n        <div class=\"eco-tool__hint\">Accounts for driver and battery losses.<\/div>\n      <\/div>\n    <\/div>\n\n    <div class=\"eco-tool__actions\">\n      <button type=\"button\" class=\"wp-element-button eco-tool__btn\" id=\"eco-fl-calc-1c3a7\">Calculate<\/button>\n      <button type=\"button\" class=\"wp-element-button eco-tool__btn eco-tool__btn--ghost\" id=\"eco-fl-reset-1c3a7\">Reset<\/button>\n      <div class=\"eco-tool__error\" id=\"eco-fl-error-1c3a7\" aria-live=\"polite\"><\/div>\n    <\/div>\n  <\/form>\n\n  <div class=\"eco-tool__result\" id=\"eco-fl-result-1c3a7\" hidden>\n    <h3 class=\"eco-tool__subtitle\">Result<\/h3>\n    <div class=\"eco-tool__card eco-tool__card--wide\">\n      <div class=\"eco-tool__metric-label\">Estimated runtime<\/div>\n      <div class=\"eco-tool__metric-value\" id=\"eco-fl-out-1c3a7\">\u2014<\/div>\n      <div class=\"eco-tool__metric-sub\" id=\"eco-fl-sub-1c3a7\">\u2014<\/div>\n    <\/div>\n  <\/div>\n<\/div>\n\n<style>\n.eco-tool{border:1px solid rgba(0,0,0,.12);border-radius:12px;padding:16px}\n.eco-tool__title{margin:0 0 8px}\n.eco-tool__lead{margin:0;opacity:.9}\n.eco-tool__grid2{display:grid;grid-template-columns:1fr;gap:16px;margin-top:12px}\n@media(min-width:860px){.eco-tool__grid2{grid-template-columns:1fr 1fr}}\n.eco-tool__field{display:flex;flex-direction:column;gap:6px}\n.eco-tool__label{font-weight:600}\n.eco-tool__input{width:100%;height:44px;padding:0 12px;border:1px solid rgba(0,0,0,.2);border-radius:10px;background:#fff;box-sizing:border-box;font:inherit}\n.eco-tool select.eco-tool__input{appearance:none;-webkit-appearance:none;line-height:44px;padding-right:40px;background-image:linear-gradient(45deg,transparent 50%,rgba(0,0,0,.6) 50%),linear-gradient(135deg,rgba(0,0,0,.6) 50%,transparent 50%);background-position:calc(100% - 18px) 50%,calc(100% - 12px) 50%;background-size:6px 6px;background-repeat:no-repeat}\n.eco-tool__hint{font-size:.92em;opacity:.78;min-height:34px}\n.eco-tool__actions{display:flex;flex-wrap:wrap;gap:10px;align-items:center;margin-top:16px}\n.eco-tool__btn{padding:10px 22px}\n.eco-tool__btn--ghost{background:transparent!important;border:1px solid rgba(0,0,0,.2)!important}\n.eco-tool__btn--ghost:hover,.eco-tool__btn--ghost:focus{background:rgba(0,0,0,.06)!important;border-color:rgba(0,0,0,.35)!important}\n.eco-tool__error{min-height:1.2em;font-weight:600;flex:1 1 240px}\n.eco-tool__result{margin-top:16px}\n.eco-tool__subtitle{margin:0 0 10px}\n.eco-tool__card{border:1px solid rgba(0,0,0,.12);border-radius:12px;padding:12px}\n.eco-tool__metric-label{opacity:.85;font-weight:600}\n.eco-tool__metric-value{font-size:1.7em;font-weight:900;margin-top:6px;line-height:1.1}\n.eco-tool__metric-sub{opacity:.85;margin-top:6px}\n<\/style>\n\n<script>\n(function(){\n  const S=\"1c3a7\";\n  const el=(id)=>document.getElementById(id+\"-\"+S);\n\n  const battEl=el(\"eco-fl-batt\");\n  const countEl=el(\"eco-fl-count\");\n  const wEl=el(\"eco-fl-w\");\n  const effEl=el(\"eco-fl-eff\");\n\n  const calcBtn=el(\"eco-fl-calc\");\n  const resetBtn=el(\"eco-fl-reset\");\n  const errEl=el(\"eco-fl-error\");\n\n  const resEl=el(\"eco-fl-result\");\n  const outEl=el(\"eco-fl-out\");\n  const subEl=el(\"eco-fl-sub\");\n\n  function setErr(m){ errEl.textContent=m||\"\"; }\n  function n(v){ return Number(v); }\n  function fmt1(x){\n    const v=Math.round(x*10)\/10;\n    return v.toLocaleString(undefined,{minimumFractionDigits:1,maximumFractionDigits:1});\n  }\n\n  calcBtn.addEventListener(\"click\", function(){\n    setErr(\"\");\n    const whEach=n(battEl.value);\n    const count=n(countEl.value);\n    const w=n(wEl.value);\n    const eff=n(effEl.value);\n\n    if(!Number.isFinite(count)||count<1){ setErr(\"Please enter number of batteries (minimum 1).\"); resEl.hidden=true; return; }\n    if(!Number.isFinite(w)||w<=0){ setErr(\"Please enter flashlight power (greater than 0).\"); resEl.hidden=true; return; }\n\n    const usableWh = whEach*count*eff;\n    const hours = usableWh \/ w;\n    outEl.textContent = hours>=24 ? `${fmt1(hours\/24)} days` : `${fmt1(hours)} hours`;\n    subEl.textContent = `Usable energy ~${fmt1(usableWh)} Wh \u00f7 ${w} W (estimate).`;\n    resEl.hidden=false;\n  });\n\n  resetBtn.addEventListener(\"click\", function(){\n    setErr(\"\");\n    battEl.value=\"3.0\";\n    countEl.value=\"3\";\n    wEl.value=\"2\";\n    effEl.value=\"0.75\";\n    resEl.hidden=true;\n  });\n})();\n<\/script>\n\n","protected":false},"excerpt":{"rendered":"<p>Flashlight Battery Runtime Calculator Estimate flashlight runtime based on batteries and power draw (simple estimate). Battery type AA alkaline (\u22482.4 Wh each)AA rechargeable (\u22483.0 Wh each)AAA alkaline (\u22481.8 Wh each)18650&hellip;<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":2457,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_sitemap_exclude":false,"_sitemap_priority":"","_sitemap_frequency":"","footnotes":""},"_links":{"self":[{"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/pages\/2265"}],"collection":[{"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/nature-o.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2265"}],"version-history":[{"count":2,"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/pages\/2265\/revisions"}],"predecessor-version":[{"id":2268,"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/pages\/2265\/revisions\/2268"}],"up":[{"embeddable":true,"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/pages\/2457"}],"wp:attachment":[{"href":"https:\/\/nature-o.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2265"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}