Differences

This shows you the differences between two versions of the page.

--- electrical:depth_of_discharge [2020/06/10 13:01]
frater_secessus [effect of SoC on battery life]
+++ electrical:depth_of_discharge [2020/08/02 12:55]
frater_secessus [SoC by voltage]
@@ Line 36: / Line 36: @@
-===== SoC by amps =====
+===== estimatating SoC =====
+==== SoC by specific gravity ====
+> "The truest measure of a [lead chemistry] battery's state of charge is the specific gravity of the battery acid." -- Rolls battery.((http://support.rollsbattery.com/support/solutions/articles/428-state-of-charge-charging-flooded-lead-acid-batteries))
+Only flooded-type batteries are practical for SoC assessment by SG of the electrolyte.  Needed for this operation:
+  * temperature of the battery
+  * SG chart from the battery manufacuturer
+  * [[https://amzn.to/3dOHGEU|battery SG tester (hydrometer)]]
+==== SoC by amps ====
 A [[electrical:12v:battery_monitor|battery monitor]], usually a amp/coulumb counter with a shunt, will measure the current going to/from the battery.  It will often show real-time current flow and a state of charge percentage.  It may also show voltage (see below).
+Note that deep cycle battery [[electrical:12v:battery_capacity|capacities]] are given at the "20 hour rate", roughly depleting the battery over the course of a day/night cycle. Heavier loads will cause apparent capacity to decrease.  Lithium is much less susceptible and tends to deliver more predictable capacity.
-===== SoC by voltage =====
+==== SoC by voltage ====
 % SoC (~12.7v) is measured [[electrical:12v:charging|after the bank has been fully charged]] and then rested. It is measured "on the way down";  measuring "on the way up" while charging will lead to false confidence and leaving the battery [[electrical:12v:psoc|less than fully charged]].
@@ Line 56: / Line 72: @@
   * intermittent heavier loads that leave the system with measured >=12.2v when that load is removed
-===== SoC by specific gravity =====
+The more challenging task is judging when to kill the circuit based on voltage **under heavier loads**.  It may take experimentation with your system to see where the battery voltage rebounds after removing the heavy loads.  An approach might be:
-> "The truest measure of a battery's state of charge is the specific gravity of the battery acid." -- Rolls battery.((http://support.rollsbattery.com/support/solutions/articles/428-state-of-charge-charging-flooded-lead-acid-batteries))
-Only flooded-type batteries are practical SoC assessment by SG of the electrolyte.  Needed for this operation:
-  * temperature of the battery
-  * SG chart from the battery manufacuturer
-  * [[https://amzn.to/3dOHGEU|battery SG tester (hydrometer)]]
+  - apply expected load
+  - run battery down to 11.5v (then 11.25, 11, 10.75, 10.5 etc until battery no longer rebounds to 12.1-12.2v)
+  - remove load
+  - observe battery voltage
+If the battery rebounds to the desired voltage then repeat to deeper discharge.  Stop when the battery no longer can rebound to the setpoint.  The LVD voltage is the lowest voltage the system can  drop to and still rebound to the desired setpoint when the load is removed.

RV and vandwellers wiki

User Tools

Site Tools

Differences

Page Tools