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electrical:12v:lifepo4_batteries_thread [2017/12/09 17:49] frater_secessus [Synopsis of C&S LiFePO4 batteries thread] |
electrical:12v:lifepo4_batteries_thread [2021/09/25 20:30] frater_secessus [Suitability for RV use] |
* 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 use more nominal capacity than lead-acid (80-90% v. 50% [[electrical:depth_of_discharge|depth of discharge]]) | * can use more nominal capacity than lead-acid (80-90% v. 50% [[electrical:depth_of_discharge|depth of discharge]]) |
* are not damaged by low SoC | * are not damaged by [[electrical:12v:psoc|partial stage of charge]] |
* 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)) |
* smaller and lighter than like-capacity LA | * smaller and lighter than like-capacity LA |
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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 ==== |
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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 | |
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| Since the defining feature of this approach is the lack of BMS, it will be referred to as "barefoot" on this page. |
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For lack of a better term, this barefoot (no BMS)/ middle 80% / fractional-C approach will be called **Terrycharging** below. | |
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==== LiFePO4 characteristics ==== | ==== LiFePO4 characteristics ==== |
| 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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