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--- electrical:12v:deep_cycle_battery [2020/07/18 18:52]
frater_secessus [Gel cell]
+++ electrical:12v:deep_cycle_battery [2020/11/14 13:28]
frater_secessus [Non-LiFePO4 lithium-ion]
@@ Line 268: / Line 268: @@
   * voltage mismatch of 3S to nominal 12v systems
+===== health =====
+Batteries are typically replaced when they can no longer provide 80% of their rated capacity.   This requires fully charging, then discharging at the 20-hr rate (C/20) until the battery is depleted.  This is impractical with house batteries that are in actual use.
+Because of this, we use indirect methods to assess battery health.
+> Quickly rising to absorption voltage during bulk and never seeing tail current drop down to previous levels are good indicators that the battery is in a declined or seriously declining state.  mainesail((https://www.cruisersforum.com/forums/f14/my-aging-northstar-group-27-a-179072.html#post2312172))
+Tail current (aka endAmps, finishing amps) for healthy lead batteries is typically between C/200 and C/100 (0.5A to 1.0A at Vabs for per 100Ah of capacity).  If tail current cannot get down to 1A we can assume there is trouble.
+The rise to absorption voltage is rarely useful in the field since:
+  - solar charging alone is rarely able to hit charge current maximums
+  - alternator charging is rarely able to hit Vabs
+People charging off larger [[:b2b|DC-DC chargers]], [[electrical:converter|shore power]], or [[electrical:generator|generators]] may be able gauge the speed at which the bank comes up to Vabs.

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