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electrical:12v:drop-in_lifepo4 [2025/08/28 15:09]
frater_secessus [BMS features and specs] changed order 		electrical:12v:drop-in_lifepo4 [2026/10/03 20:09] (current)
frater_secessus [BMS features and specs]
Line 55: Line 55:
 ===== choosing a drop-in LFP battery ===== ===== 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 ==== ==== voltage ====
Line 95: Line 103:
 [not present in all BMS] [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))+LFP cells are damaged by charging when the cells are at ~freezing temperatures.((discharging too, but the limits are much colder like -15° C; check your manual for specs.))
  
 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.   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.  
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 === high temperature charge/discharge cutoff === === high temperature charge/discharge cutoff ===
  
-LFP cells can be damaged by use at high temperatures, so the BMS will disable use at extreme temperatures.+LFP cells can be damaged by use at high temperatures, so the BMS will disable use at extreme temperatures caused by ambient temps or high current rates.
  
  
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-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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 The most popular drop-ins at various price points appear to be: The most popular drop-ins at various price points appear to be:
  
-  * premium - [[https://amzn.to/3LV85DI|Battle Born]], Lithionics+  * premium - [[https://amzn.to/3LV85DI|Battle Born]]((but see Will Prowse's [[https://www.youtube.com/watch?v=DUtbnbLpvFk|recent series on failures]])), Lithionics
   * midrange - [[https://amzn.to/3YxGPTh|SOK]], Epoch.  And there are companies like SunFunKits that will [[https://www.sunfunkits.com/category/3/pre-built-batteries|build LFP batteries with the customer's choices of options]].    * midrange - [[https://amzn.to/3YxGPTh|SOK]], Epoch.  And there are companies like SunFunKits that will [[https://www.sunfunkits.com/category/3/pre-built-batteries|build LFP batteries with the customer's choices of options]]. 
   * inexpensive - [[https://amzn.to/4cfU5Pm|Li Time]] (was Ampere Time),  [[https://amzn.to/4dwItZr|Weize]], [[https://amzn.to/4fwJhiQ|Power Queen]], [[https://amzn.to/4cgSKIj|Roypow / Power Urus]], etc   * inexpensive - [[https://amzn.to/4cfU5Pm|Li Time]] (was Ampere Time),  [[https://amzn.to/4dwItZr|Weize]], [[https://amzn.to/4fwJhiQ|Power Queen]], [[https://amzn.to/4cgSKIj|Roypow / Power Urus]], etc
electrical/12v/drop-in_lifepo4.1756393769.txt.gz · Last modified: 2025/12/24 22:41 (external edit)

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