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--- electrical:12v:drop-in_lifepo4 [2025/08/15 17:18]
frater_secessus [myth: you can't charge Li with a lead battery charger] USER
+++ electrical:12v:drop-in_lifepo4 [2025/11/22 00:16] (current)
frater_secessus [BMS features and specs]
@@ Line 55: / Line 55: @@
 ===== choosing a drop-in LFP battery =====
-There are many factors here which only you will be able to assess.
+There are many factors here which only you will be able to assess. Basic due diligence will involve:
+  * reading and understanding the specs (see below)
+  * searching for youtube teardowns and testing on that particular model
+Shortcut:  Will Prowse has [[https://www.mobile-solarpower.com/lithium-batteries.html|a list of recommended, tested batteries]] which can be trusted.
+**Heads up**:  do not use lowest-possible-price as the main criterion for a battery unless there was a test/teardown available for it.
 ==== voltage ====
@@ Line 89: / Line 97: @@
 LFP cells can be damaged by overvoltage.  Charging is typically disabled when one or more cells rises to ~3.65v (~14.6vv for the pack)
+=== low temperature (~freezing) charge cutoff ===
+[not present in all BMS]
+LFP cells are damaged by charging when the cells are at ~freezing temperatures.((discharging too, but the limits are much colder))
+Lack of **low temperature cutoff** is not necessarily a deal-breaker.  Maybe you live in a hot location.  Maybe your chargers have low temperature cutoff.  Maybe you externally warm your battery.
+[[opinion:frater_secessus:self-heated_lifepo4|externally warmed vs. self-heated LiFePO4]]
 === high temperature charge/discharge cutoff ===
@@ Line 107: / Line 128: @@
-=== low temperature (~freezing) charge cutoff ===
-[not present in all BMS]
-LFP cells are damaged by charging when the cells are at ~freezing temperatures.((discharging too, but the limits are much colder))
-Lack of **low temperature cutoff** is not necessarily a deal-breaker.  Maybe you live in a hot location.  Maybe your chargers have low temperature cutoff.  Maybe you externally warm your battery.
-[[opinion:frater_secessus:self-heated_lifepo4|externally warmed vs. self-heated LiFePO4]]
@@ Line 143: / Line 155: @@
-Capacitive balancing wastes less power since most of the excess is transferred to the low cell[s].  There are efficiency losses involved (~50%((https://www.ti.com/download/trng/docs/seminar/Topic%202%20-%20Battery%20Cell%20Balancing%20-%20What%20to%20Balance%20and%20How.pdf))) but it's far less than the 100% loss of passive balancing.  The main drawbak of capacitive balancers is the current spec (like 5A) only occur at huge deltas;  the rest of the time the balancing current is much lower.
+**Capacitive balancing** wastes less power since most of the excess is transferred to the low cell[s].  There are efficiency losses involved (~50%((https://www.ti.com/download/trng/docs/seminar/Topic%202%20-%20Battery%20Cell%20Balancing%20-%20What%20to%20Balance%20and%20How.pdf))) but it's far less than the 100% loss of passive balancing.  The main drawbak of capacitive balancers is the current spec (like 5A) only occur at huge deltas;  the rest of the time the balancing current is much lower.
+Heads up:  because active balancers are just shuffling voltage between cells they can overdischarge the cells if left alone without adult supervision.  To avoid this:
+  * use [[electrical:12v:lvd|an LVD]] to cut the circuit to the balancer's single NEG lead when pack voltage is <13.0v or some other value of your choosing. Or,
+  * choose an active balancer that has a built-in LVD.((The cutoff tends to be something like 3.0Vpc, so 12.0v for a 4S 12v pack.))  Or,
+  * only run the active balancer manually when required
-In theory inductive active balancers would get around this delta/current relationship.  [as of this writing in 2024 I know of no drop-ins that use inductive active balancers - secessus]
+In theory **inductive active balancers** would get around this delta/current relationship.  [as of this writing in 2024 I know of no drop-ins that use inductive active balancers - secessus]

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