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--- electrical:12v:voltage_sag [2022/03/16 13:11]
frater_secessus created
+++ electrical:12v:voltage_sag [2022/03/16 13:39]
frater_secessus [shorten the circuit]
@@ Line 6: / Line 6: @@
-Extreme example:  During heavy charging the controller might see 14v instead of the battery's 13v.  This 14v -> 13v difference is called voltage sag.  A similar thing happens in reverse when consuming power.  The battery might be 12.5v but an inverter running a big load might "see" 11.5v at its own terminals and shut off.
+Extreme example:  During heavy charging the controller might see 14v instead of the battery's 13v.  This 14v -> 13v difference is called voltage sag.  A similar thing happens in reverse when consuming power.  The battery might be 12.5v but an inverter running a big load might "see" 11.5v at its own terminals and shut off prematurely.((from the user's point of view)).  It also makes it difficult to assess [[electrical:depth_of_discharge|state of charge]] of lead batteries by voltage.
+Sag presents special challenges when charging [[electrical:12v:drop-in_lifepo4|lithium]] battery banks.    Since the majority of lithium's usable power is found in an **extremely narrow voltage range**((about 0.5v wide)) sag can result in wildly unpredictable/inconsistent charging.
 ===== approaches =====
@@ Line 13: / Line 14: @@
 ==== do nothing ====
-This is the majority position since most are unaware of the issue, or don't judge it to be important.
+This is the majority position since most are unaware of the issue, or don't judge it to be important.  And it may //not// be a problem since since
+  - solar-only charging is often low-current charging, minimizing charge-induced sag
+  - lead-chemistry batteries often have a range of Absorption and Float [[electrical:solar:charge_controller_setpoints|setpoints]] (see below)
+==== shorten the circuit ====
+All other things being equal, a **shorter wiring run will have less sag** than a longer run.  For this reason charging sources are mounted **as close to the battery bank as possible**.
 ==== beef up the circuit ====
+Once the length of the circuit is established voltage drop along the circuit can be minimized:
+  * run bigger wires to minimize sag - see [[https://www.bluesea.com/resources/1437|this BlueSea article]] with the well-respected wiring size chart
+  * minimize the number of connections/junctions
+==== adjust charging setpoints ====
-    run bigger wires to minimize sag

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