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--- opinion:frater_secessus:self-heated_lifepo4 [2024/09/12 09:46]
frater_secessus [DIYing a solution]
+++ opinion:frater_secessus:self-heated_lifepo4 [2024/11/24 16:28] (current)
frater_secessus [robust charging] added blog post
@@ Line 5: / Line 5: @@
 ===== TLDR =====
-  * LiFePO4 cannot be charged when the cells are below ~freezing.
+  * LiFePO4 cannot be charged when the cells are below ~freezing, or discharged well below freezing
   * some kind of warming is required before charging
      * self-heated:   easier
@@ Line 65: / Line 65: @@
 If one was charging by alternator only and only driving to/from work while stealthing in freezing weather it's conceivable the self-heated batt would get //never get charged at all// because it wouldn't have time to get out of the heating phase.
+[Note:  those who want to charge vigorously might want to [[https://mouse.mousetrap.net/blog/2024-11-23-backchannel--charging-rates-and-self-heating-batteries-.html#temperature-and-charge-rate|keep the battery bank quite warm]]]
 ==== specific configurations ====
@@ Line 84: / Line 85: @@
 ===== DIYing a solution =====
-DIY solutions include warming and/or charging cutoff
+DIY solutions include warming and/or charging cutoff.  Multiple approaches can be combined into a "belt and suspenders" solution.
@@ Line 90: / Line 91: @@
-If your preferred battery has everything but heating you might want to [[https://diysolarforum.com/threads/lifepo4-heating-pad-for-cold-temperatures.5/page-26|DIY a heater]].  It is typically much cheaper than built-in heat and offers more control.  It typically involves:
+If your preferred battery has everything but heating you might want to [[https://diysolarforum.com/threads/lifepo4-heating-pad-for-cold-temperatures.5/page-26|DIY a heater]].  It is typically cheaper than built-in heat and offers more control.  It typically involves:
-  - a [[https://amzn.to/4d5MFii|low-wattage warming pad]], as one finds for reptile pets, animal comfort pads, etc.  [[https://amzn.to/4e1KGww|RV tank heating pads]] will work but the wattage is much higher (60w?) and might result in less even heating or overheating.
+  - a [[https://amzn.to/4d5MFii|low-wattage warming pad]], as one finds for reptile pets, animal comfort pads, etc.  [[https://amzn.to/4e1KGww|RV tank heating pads]] will work but the wattage is much higher (60w?) and might result in less even heating or overheating. Higher wattages will be required in colder areas.
   - a [[electrical:temperature_control|temperature controller]] to turn the warming off and on at a given temp ([[https://amzn.to/3zjubNp|examples]])
-Both pads and controllers are available in 12vdc and 120vac.
+Both pads and controllers are available in 12vdc and 120vac. In moderate climates the bank can likely just sit on a mat.  Colder conditions might require pads adhered to all sides, and/or insulating the batter.
@@ Line 105: / Line 106: @@
-==== belt and suspenders ====
+==== charging cutoff ====
-Multiple solutions can be combined into a more failsafe setup.

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