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electrical:12v:lifepo4_batteries_thread [2017/11/22 09:31]
frater_secessus [Suitability for RV use]
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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 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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 |  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.  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.  Best for storage?((http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-384.html#post2383574))  | |  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 
  
  
electrical/12v/lifepo4_batteries_thread.1511361086.txt.gz · Last modified: 2020/10/11 19:48 (external edit)