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electrical:12v:lifepo4_batteries_thread [2017/04/14 09:29]
frater_secessus [So how do experts charge?]
electrical:12v:lifepo4_batteries_thread [2020/10/11 19:48] (current)
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 The Cruisers and Sailing forum has a 300+ page [[http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069.html|LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks]] thread.   The Cruisers and Sailing forum has a 300+ page [[http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069.html|LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks]] thread.  
  
-There is gold in the thread but it can be hard to find.  This page attempts to distill the thread down to currently known best practices with LiFePO4 batteries, providing links back to the thread for context-checking.+There is gold in the thread but it can be hard to find.  This page attempts to distill the thread down to best practices for RV/campervan use of LiFePO4 batteries.  Links are provided so readers can go back to the thread for context-checking and critical examination.
  
  
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 LiFePO4  LiFePO4 
   * can take full current during charging;  there are no //stages// in the lead-acid sense   * can take full current during charging;  there are no //stages// in the lead-acid sense
-  * can cycle down to very low SoC (20%) vs 50% for lead acid+  * can use more nominal capacity than lead-acid (80-90v. 50% [[electrical:depth_of_discharge|depth of discharge]])
   * are not damaged by low SoC   * are not damaged by low SoC
   * can be mounted vertically or on a thin edge (but not flat)((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-234.html#post1452743))   * can be mounted vertically or on a thin edge (but not flat)((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-234.html#post1452743))
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   * sensitivity to excessive ambient heat (>95F?)((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-175.html#post1207749))   * sensitivity to excessive ambient heat (>95F?)((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-175.html#post1207749))
   * cannot be charged below 32F   * cannot be charged below 32F
-  * capacities over 200A (roughly equivalant to 400A of lead-acid) are not recommended for mobile use((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-358.html#post2213264)) 
  
 +Maine Sail has discussed [[http://www.cruisersforum.com/forums/f129/lithium-batteries-or-agm-194029-2.html#post2522585|the most common errors made by RVers]] vis-a-vis lithium.
  
  
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 ==== three stage chargers ==== ==== three stage chargers ====
-LFP batteries do not require multi-stage charging like lead-acid batteries; they are **charged until full and charging is stopped**.  LFP does not have an absorption phase like LA((LFP will pull full current until very nearly full)) and does not need floating in the LA sense((due to low self-discharge rates)).  +LFP batteries do not require multi-stage charging like lead-acid batteries; they are [[electrical:12v:charging#charge-and-stop|charged until full and then charging is stopped]].  LFP does not have an absorption phase like LA((LFP will pull full current until very nearly full)) and does not need floating in the LA sense((due to low self-discharge rates)).  
  
 That said, smart chargers //can// be used to charge LFP.  Maine Sail describes the thought process of utilizing LA smart chargers with LiFePO4: That said, smart chargers //can// be used to charge LFP.  Maine Sail describes the thought process of utilizing LA smart chargers with LiFePO4:
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 There are important differences between how RVers/boaters and Electric Vehicles (EVs) charge and discharge LFP battery banks.  EV batteries are used aggressively:  charged at high current to full and drained at high current to empty.  This can cause individual cells to get out of sync, voltage-wise, with others and warrant a BMS. There are important differences between how RVers/boaters and Electric Vehicles (EVs) charge and discharge LFP battery banks.  EV batteries are used aggressively:  charged at high current to full and drained at high current to empty.  This can cause individual cells to get out of sync, voltage-wise, with others and warrant a BMS.
 +
 +In Fractional C scenarios BMS failures may cause more damage than they prevent.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-post2421606.html#post2421606))
  
  
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 This can make LFP banks less complex and less expensive in an RV application.  Assessing SOC by voltage is also more accurate with Fractional C charging/discharging than with high currents.   This can make LFP banks less complex and less expensive in an RV application.  Assessing SOC by voltage is also more accurate with Fractional C charging/discharging than with high currents.  
-==== LiFePO4 charging for RVs: Terrycharging ====+==== LiFePO4 charging for RVs: running barefoot ====
  
-Although his setup does not use it, T1 Terry describes a "middle 80%" approach that works well with Fractional C systems. It can eliminate the need for [[electrical:12v:BMS|BMS]] balancing+T1 Terry describes a gentle, relatively low-tech approach that can work well with vandweller use patterns It does not use a [[electrical:12v:BMS|BMS]], judging that in a vandwellers' use the BMS introduces more hazards than it alleviates.  This approach: 
-  * starts with a balanced battery when installing.+ 
 +  * starts with a balanced battery
   * uses moderate terminal voltage (13.8v) to gently rebalance cells((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-77.html#post1132126)),((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-44.html#post1096480)), and even become more balanced over time.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-109.html#post1142675))  If they do get out of balance for some reason, run more conservative SoC voltages until they can be manually rebalanced.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-294.html#post1779359))   * uses moderate terminal voltage (13.8v) to gently rebalance cells((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-77.html#post1132126)),((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-44.html#post1096480)), and even become more balanced over time.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-109.html#post1142675))  If they do get out of balance for some reason, run more conservative SoC voltages until they can be manually rebalanced.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-294.html#post1779359))
-  * charges at less than 1C, common in solar charging+  * charges and discharges at less than [[electrical:12v:battery_capacity|1C]], common in solar charging.  i.e. less than 100A with a 100Ah bank. 
   * keeps the voltage "between the [voltage] knees", 13.8v - 11.8v.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-103.html#post1140470))  This is also called the "middle 80%".   * keeps the voltage "between the [voltage] knees", 13.8v - 11.8v.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-103.html#post1140470))  This is also called the "middle 80%".
-  * does not //require// strapping((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-59.html#post1118000)) although it is a recommended best practice((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-253.html#post1574064)) +  * does not require strapping((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-59.html#post1118000)) although it is a recommended best practice((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-253.html#post1574064)) 
-  * no BMS required+ 
 + 
 +Since the defining feature of this approach is the lack of BMS, it will be referred to as "barefoot" on this page. 
  
-This barefoot (no BMS) and Frac-C approach will be called **Terrycharging** below.   
  
 ==== LiFePO4 characteristics ==== ==== LiFePO4 characteristics ====
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     * RV     * RV
       * On solar **blars** does a short 14.v "absorption" by a 13.4v "float" He notes the float is high-ish but that the sun goes down so it will not be at that voltage a long time.((http://www.cheaprvliving.com/forums/Thread-Lithium-Ion-has-anyone-considered-these-batteries?pid=160365#pid160365)) When charging from shore power through a converter he does a very short "absorption" at 14.2v followed a 13.25v "float".((http://www.cheaprvliving.com/forums/Thread-Lithium-Ion-has-anyone-considered-these-batteries?pid=160365#pid160365))           * On solar **blars** does a short 14.v "absorption" by a 13.4v "float" He notes the float is high-ish but that the sun goes down so it will not be at that voltage a long time.((http://www.cheaprvliving.com/forums/Thread-Lithium-Ion-has-anyone-considered-these-batteries?pid=160365#pid160365)) When charging from shore power through a converter he does a very short "absorption" at 14.2v followed a 13.25v "float".((http://www.cheaprvliving.com/forums/Thread-Lithium-Ion-has-anyone-considered-these-batteries?pid=160365#pid160365))    
-      * **29chico** charges at 13.9v-13.9v((http://www.cheaprvliving.com/forums/Thread-Renogy-100w-suitcase-and-Lithium?pid=195318#pid195318)) and recommends going no lower than 12.6v, approx. 10% SoC.((http://www.cheaprvliving.com/forums/Thread-Renogy-100w-suitcase-and-Lithium?pid=195318#pid195318)) +      * **29chico** charges at 13.8v-13.9v((http://www.cheaprvliving.com/forums/Thread-Renogy-100w-suitcase-and-Lithium?pid=195318#pid195318)) and recommends going no lower than 12.6v, approx. 10% SoC.((http://www.cheaprvliving.com/forums/Thread-Renogy-100w-suitcase-and-Lithium?pid=195318#pid195318)) 
-      John61ct recommends charging at 13.8v and floating at 13.2v, when float is required by the controller.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-368.html#post2318216))+      * **John61ct** recommends charging at 13.8v and floating at 13.2v, when float is required by the controller.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-368.html#post2318216))
  
 ===== notable voltage reference points ===== ===== notable voltage reference points =====
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 |  16.80|  4.20|cell damage((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-93.html#post1137808))  | |  16.80|  4.20|cell damage((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-93.html#post1137808))  |
 |  14.40|  3.60|High Voltage Cutoff((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-109.html#post1142567))  | |  14.40|  3.60|High Voltage Cutoff((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-109.html#post1142567))  |
-|  **13.80**|  3.45|**Terrycharging Vabs**, with gentle overcharge for balancing.  Max safe non-BMS voltage.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-44.html#post1096480))  |+|  **13.80**|  3.45|**barefoot Vabs**, with gentle overcharge for balancing.  Max safe non-BMS voltage.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-44.html#post1096480))  |
 |  13.60|  3.40|fully charged  | |  13.60|  3.40|fully charged  |
-|  **13.40**|  3.35|**Terrycharging Vfloat**  |+|  **13.40**|  3.35|**barefoot Vfloat**  |
 |  13.25|  3.31|20% Depth of Discharge  | |  13.25|  3.31|20% Depth of Discharge  |
-|  12.80|  3.20|50% Depth of Discharge FIXME.  Recommended for long-term storage.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-172.html#post1201146)) +|  12.80|  3.20|50% Depth of Discharge FIXME.  Long-term storage.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-172.html#post1201146)) 
-|  12.40|  3.10|80% Depth of Discharge +|  12.40|  3.10|80% Depth of Discharge.  Best for storage?((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-384.html#post2383574))  | 
-|  **11.80**|  2.95|**Terrycharging Low Voltage Disconnect**.  Min safe non-BMS voltage.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-103.html#post1140470))  |+|  **11.80**|  2.95|**barefoot Low Voltage Disconnect**.  Min safe non-BMS voltage. ((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-103.html#post1140470))  |
 |  11.20|  2.80|100% Depth of Discharge((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-104.html#post1140620)).  Low Voltage Cutoff.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-109.html#post1142567))  | |  11.20|  2.80|100% Depth of Discharge((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-104.html#post1140620)).  Low Voltage Cutoff.((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-109.html#post1142567))  |
  
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 ===== alternator charging ===== ===== alternator charging =====
-Unless the alternator's output voltage is dropped with an external regulator the charging voltage will probably be high enough to damage your LFP cells.+Unless the alternator's output voltage is reduced it can be high enough to damage your LFP cells (ie, > 13.8v).
  
-Diode-based battery isolators FIXME 
  
  
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