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opinion:frater_secessus:agm2lifepo4 [2024/01/27 11:11]
frater_secessus [Can I just drop in the LFP and go?] 		opinion:frater_secessus:agm2lifepo4 [2024/03/23 13:13] (current)
frater_secessus [shore power charging]
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     * charging only above freezing 32F/0C     * charging only above freezing 32F/0C
   - what your existing charging system provides (or can be configured to provide).    - what your existing charging system provides (or can be configured to provide). 
-    * chassis voltage((the voltage the alternator provides to the vehicle)) +    * alternator voltage and rating if a [[electrical:12v:alternator|combiner]] or [[electrical:12v:b2b|DC-DC]] is present 
-    * alternator output rating (100A, 130A, etc)((if your alternator is successfully charging AGM then it will likely work fine with Li of similar Ah))+    * [[electrical:solar:charge_controller|solar charging]] (profiles, configurability, output rating,  protections if any) 
 +    * [[electrical:converter|shore power charging]] (voltage, output rating, stages if any)
  
 If the existing system cannot be configured to meet LFP's needs within [[electrical:12v:alternator_details#current|the  alternator's comfort zone]] then you are looking at replacing some components. For more specific guidance please share details about your setup, use case, budget, and priorities.  If the existing system cannot be configured to meet LFP's needs within [[electrical:12v:alternator_details#current|the  alternator's comfort zone]] then you are looking at replacing some components. For more specific guidance please share details about your setup, use case, budget, and priorities. 
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 ==== Will I need a special LFP solar charge controller? ==== ==== Will I need a special LFP solar charge controller? ====
  
-Probably not, assuming your existing [[electrical:solar:charge_controller|controller]] has a profile that meet's the LFP's stated needs, or has [[electrical:solar:charge_controller_setpoints|configurable setpoints]].    +Probably not, assuming your existing [[electrical:solar:charge_controller|controller]] has a profile that meet's the LFP's stated needs, or has [[electrical:solar:charge_controller_setpoints|configurable setpoints]] that you can adjust to meet needs. 
  
  
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   * 1.0C - typical limit enforced by BMS   * 1.0C - typical limit enforced by BMS
  
-From the battery's point of view, alternator charging rates should probably be ≤0.5C, with 0.4C probably being the sweet spot.  So ≤80A for a 200Ah bank.  From the alternator's point of view, current should be limited to [[electrical:12v:alternator_details#current|what the alternator can comfortably provide]] under expected charging conditions.  +From the battery's point of view, alternator charging rates should be ≤0.5C, with 0.4C likely being the sweet spot.  So ≤80A for a 200Ah bank.  From the alternator's point of view, current should be no greater than [[electrical:12v:alternator_details#current|the alternator can comfortably provide]] under expected charging conditions.  
  
 As the Battle Born quote above suggests, for average LFP banks and average cargo van alternators these criteria will often be met with no reconfiguration.  If the criteria cannot be met then we will need [[electrical:12v:b2b|DC-DC charging]] or some other approach to manipulate voltage and/or current.((diode-based isolator, dedicated second alternator, etc)) As the Battle Born quote above suggests, for average LFP banks and average cargo van alternators these criteria will often be met with no reconfiguration.  If the criteria cannot be met then we will need [[electrical:12v:b2b|DC-DC charging]] or some other approach to manipulate voltage and/or current.((diode-based isolator, dedicated second alternator, etc))
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-IF **other forms of shore power charging are available** or **shore power charging will last at least overnight** the [[electrical:converter|shore power charger]] can be a simple, inexpensive, single-stage charger set to ≤13.4v.  This will allow near full charge and load support without overcharging. +IF **other forms of shore power charging are available** or **shore power charging will last at least overnight** the [[electrical:converter|shore power charger]] can be a simple, inexpensive, single-stage charger set to a relatively low voltage (13.4v - 13.6v?)  This will allow near full charge and load support without overcharging.
  
 If **shore power charging is the only source of charging** or if **time on the charger is limited** then a more aggressive, expensive, higher-capacity multistage charger may be warranted.   If **shore power charging is the only source of charging** or if **time on the charger is limited** then a more aggressive, expensive, higher-capacity multistage charger may be warranted.  
  
 +If the van will **be on shore power for an extended period** (days, weeks, months) then a small single-stage converter charger set to quite low voltage (13.2v?) would hold the battery at middling states of charge.  It only needs to be a bit bigger than the expected loads so gradual charging can occur.  
  
  
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-[Note from secessus:  there is [[https://diysolarforum.com/threads/why-you-cannot-charge-lifepo4-below-0-degrees-celsius.2912/post-199774|some evidence]] that LiFePO4 fares better when cell temps are held to warming temps than just above freezing.  For this reason I warm my bank to 50F.]+[Note from secessus:  there is [[https://diysolarforum.com/threads/why-you-cannot-charge-lifepo4-below-0-degrees-celsius.2912/post-199774|some evidence]] that LiFePO4 fares better when cell temps are held to warmer temps than just above freezing.  For this reason I warm my bank to 50F.]
opinion/frater_secessus/agm2lifepo4.1706371872.txt.gz · Last modified: 2024/01/27 11:11 by frater_secessus

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