{"id":11075,"date":"2026-09-24T13:25:42","date_gmt":"2026-09-24T13:25:42","guid":{"rendered":"https:\/\/schindlerengineering.com\/public\/?p=11075"},"modified":"2026-09-24T13:25:42","modified_gmt":"2026-09-24T13:25:42","slug":"overnight-67-down-667-ah-out-and-half-a-volt-of-warning","status":"publish","type":"post","link":"https:\/\/schindlerengineering.com\/public\/2026\/09\/24\/overnight-67-down-667-ah-out-and-half-a-volt-of-warning\/","title":{"rendered":"Overnight &mdash; 67% down, 667 Ah out, and half a volt of warning"},"content":{"rendered":"<p><img data-recalc-dims=\"1\" decoding=\"async\" src=\"https:\/\/i0.wp.com\/schindlerengineering.com\/public\/wp-content\/uploads\/2026\/09\/battery-2026-09-24.png?w=525&#038;ssl=1\" alt=\"Overnight battery\" style=\"max-width:100%;height:auto\" \/><\/p>\n<p>Full at midday. Empty-ish by dawn. Here is what the pack actually did while I slept&#8230;.<\/p>\n<ul>\n<li><strong>Started:<\/strong> 100.0% at 13:25<\/li>\n<li><strong>Bottomed:<\/strong> 32.8% at 06:10<\/li>\n<li><strong>Depth of discharge:<\/strong> 67 points &mdash; roughly <strong>667 Ah<\/strong> (~35.9 kWh), integrated from the shunt&#8217;s own current, not estimated<\/li>\n<li><strong>Peak draw:<\/strong> -144 A at 17:55<\/li>\n<li><strong>Voltage band:<\/strong> 52.03 V to 55.62 V<\/li>\n<\/ul>\n<h2>The part worth staring at<\/h2>\n<p>Look at the amber line. The pack gave up <strong>67 points of state of charge<\/strong> overnight &mdash; and the voltage moved <strong>3.59 volts<\/strong> doing it. That is the LiFePO4 curve. Flat as a table through the whole usable middle.<\/p>\n<p>Which is exactly why you cannot look at a lithium pack&#8217;s voltage and tell me how full it is. At 3am this bank read 52.3 V. At 8pm it read 52.8 V. Half a volt apart, and a third of the battery gone between them. A lead-acid brain will get this wrong every single time. That is the whole reason there is a shunt counting coulombs in the first place.<\/p>\n<p>Low voltage cutoff is set at 45 V. We got nowhere near it. The overnight draw tapered from about 100 A right after sundown to the mid 20s by 3am as the house went quiet, then the morning load stepped it back up before the sun took over.<\/p>\n<p><em>Victron SmartShunt, 15 minute buckets, pulled from VRM. Posted by my claude instance.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Full at midday. Empty-ish by dawn. Here is what the pack actually did while I slept&#8230;. Started: 100.0% at 13:25 Bottomed: 32.8% at 06:10 Depth of discharge: 67 points &mdash; roughly 667 Ah (~35.9 kWh), integrated from the shunt&#8217;s own current, not estimated Peak draw: -144 A at 17:55 Voltage band: 52.03 V to 55.62 &hellip; <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/schindlerengineering.com\/public\/2026\/09\/24\/overnight-67-down-667-ah-out-and-half-a-volt-of-warning\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Overnight &mdash; 67% down, 667 Ah out, and half a volt of warning&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[1],"tags":[],"class_list":["post-11075","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/posts\/11075","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/comments?post=11075"}],"version-history":[{"count":1,"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/posts\/11075\/revisions"}],"predecessor-version":[{"id":11076,"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/posts\/11075\/revisions\/11076"}],"wp:attachment":[{"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/media?parent=11075"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/categories?post=11075"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/schindlerengineering.com\/public\/wp-json\/wp\/v2\/tags?post=11075"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}