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electrical:12v:charging [2019/05/17 21:09]
frater_secessus [charging AGM batteries] added C |
electrical:12v:charging [2020/10/18 12:32]
frater_secessus [watering batteries] |
| [[lifestyle:words_of_wisdom|Words of wisdom]]: “Three stage chargers are easier on your batteries, charge them faster, fuller and help you use less water”((https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/)) – HandyBob | [[lifestyle:words_of_wisdom|Words of wisdom]] |
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| | > “Three stage chargers are easier on your batteries, charge them faster, fuller and help you use less water”((https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/)) – HandyBob |
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| | > A [ [[electrical:shore_power|shore power]] ] charger is a stiff source with unlimited energy and time. Your solar is a very soft source of unknown power and only a few hours to get the job done. - sunking((https://www.solarpaneltalk.com/forum/off-grid-solar/batteries-energy-storage/299490-bulk-absorb-float-equalize-what-does-it-mean#post299490)) |
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| | > Charging lead acid batteries is not something that you decide to do, or start or stop. The old statement, "I need to idle the engine for a few minutes to "top off" the batteries." is a prescription for turning expensive batteries into paper weights. You want a system that puts the batteries on charge automatically, every time there is even a single ray of sun or that your engine is running -- DiploStrat((https://expeditionportal.com/forum/threads/dual-battery-system-with-ctek-d250-not-charging-battery-over-12-volts.174927/post-2342346)) |
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| ====== charging deep cycle batteries ====== | ====== charging deep cycle batteries ====== |
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| In general, manufacturers of lead chemistries specifiy a charging at [[electrical:12v:battery_capacity|C/10]]; this assumes more charging time than solar power allows.((http://www.cheaprvliving.com/forums/showthread.php?tid=23606&pid=288284#pid288284)) Regularly cycled banks may benefit from firmer charging at C/3. There may not be a practical maximum charging rate for cycled FLA batteries //when charged from solar//. As Sternwake put it when describing a C/1.5 (!) charging scenario, "solar is not instant max output."((http://www.cheaprvliving.com/forums/showthread.php?tid=23606&pid=288284#pid288284)) | In general, manufacturers of flooded lead chemistries specify charging at [[electrical:12v:battery_capacity|C/10]] to C/5; this assumes more charging time than solar power allows.((http://www.cheaprvliving.com/forums/showthread.php?tid=23606&pid=288284#pid288284)) AGM are typically charged at C/5 to C/3. There may not be a practical maximum charging rate for cycled FLA batteries //when charged from solar//. As Sternwake put it when describing a C/1.5 (!) charging scenario, "solar is not instant max output."((http://www.cheaprvliving.com/forums/showthread.php?tid=23606&pid=288284#pid288284)) |
| ===== three stage charging ===== | ===== three stage charging ===== |
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| Three stage or "smart" chargers (whether [[electrical:solar:charge_controller|solar charge controllers]] or [[electrical:converter|converters]]) will follow a common pattern. Battery manufacturers publish different specs for charging and a good charger will let the user configure the charging stages in accordance with that information. | Three stage((some mfg claim 4 or more charging stages, including equalization or proprietary stages. These three are the essentials.)) or "smart" chargers (whether [[electrical:solar:charge_controller|solar charge controllers]] or [[electrical:converter|converters]]) will follow a common pattern. Battery manufacturers publish [[electrical:solar:charge_controller_setpoints|specs for charging]] and a good charger will let the user configure the charging stages in accordance with that information. Less-expensive chargers may have presets for charging different battery types; if you get lucky one of the presets will match your manufacturer's charging recommendations. |
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| SternWake sums up smart charging: | SternWake sums up smart charging: |
| > "Bulk rate is maximum amps the charging source can supply until the absorption voltage is reached, at that point the amps required to hold the ABSV will taper. The longer the battery is held at ABSV, the more the amps required to hold ABSV will taper. At some point, either time, or the amps required to hold ABSV fall below a threshold and triggers float mode."((http://www.cheaprvliving.com/forums/Thread-Can-a-solar-panel-and-charge-controller-over-charge-a-battery?pid=96956#pid96956)) | > "Bulk rate is maximum amps the charging source can supply until the absorption voltage is reached, at that point the amps required to hold the ABSV((Vabs, absorption voltage)) will taper. The longer the battery is held at ABSV, the more the amps required to hold ABSV will taper. At some point, either time, or the amps required to hold ABSV fall below a threshold and triggers float mode."((http://www.cheaprvliving.com/forums/Thread-Can-a-solar-panel-and-charge-controller-over-charge-a-battery?pid=96956#pid96956)) |
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| | This graphic((from an unknown Amazon seller)) shows how current and voltage change during the full charge: |
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| The example below will use charging data for Trojan T-105 FLA batteries in serial for a nominal 12v bank at 77F.((http://www.trojanbattery.com/BatteryMaintenance/Charging.aspx)) | {{https://images-na.ssl-images-amazon.com/images/G/01/stores/auto/detail-page/B003FTA6F2.03.lg.jpg}} |
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| | Charging won't be as neat as the graphic due to [[electrical:solar:output|varying solar harvest]], varying [[electrical:12v:loads|loads]], etc. In practice "constant current" means "as much as your solar can produce". [[electrical:generator|Generators]] and [[electrical:converter|shore power charging]] will usually be able to hold a steady level of current. |
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| | The example below will use charging data for a 12v bank of Trojan T-105 FLA batteries at 77F.((http://www.trojanbattery.com/BatteryMaintenance/Charging.aspx)) |
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| ==== bulk stage ==== | ==== bulk stage ==== |
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| The bulk stage is a fast and furious rush to get **maximum power returned to the battery bank**. Since the stage by definition requires all the power the system can generate, this is when controllers typically get the most benefit from MPPT features. | The bulk stage is a fast and furious rush to get **maximum power((or max //recommended// power)) returned to the battery bank**. Since the stage by definition requires all the power the system can generate, this is when [[electrical:solar:charge_controller|controllers]] typically get the most benefit from [[electrical:solar:charge_controller#mppt|MPPT]] features. |
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| This stage **begins when charging starts** (as when the sun comes up) and **ends when the battery climbs to the acceptance voltage setpoint**, 14.8v in our T-105 example. | This stage **begins when charging starts** (as when the sun comes up) and **ends when the battery climbs to the acceptance voltage setpoint**, 14.8v in our T-105 example. |
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| ==== absorption stage ==== | ==== absorption stage ==== |
| The absorption stage, sometimes called //acceptance// or //boost//, is a constant voltage stage during which the battery is brought to full charge. This stage requires a **great deal of time** but decreasing amounts of current. | The absorption stage, sometimes called //acceptance//((which makes sense)) or //boost//((doesn't make sense!)), is a constant voltage stage during which the battery is brought to full charge. This stage requires a **great deal of time** but decreasing amounts of current. |
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| | Absorption **begins when the battery reaches the absorption voltage** ([[electrical:12v:electrical notation|Vabs]], 14.8v in our example) and **ends when the battery tapers off current acceptance** to something like [[electrical:12v:battery_capacity|C/100]] ("End Absorb", "endAmps"), and/or when a period of time has elapsed. |
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| | Example: if you have a 100Ah battery bank and the manufacturer states that endAmps is C/100, then the battery is fully charged when it is only accepting 1A of current((100Ah/100 = 1A)) **at Vabs**. An endAmps recommendation of C/200 would be the battery accepting 0.5A of current.((100Ah/200 = 0.5A)) at Vabs. |
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| | In practice absorption takes longer when the battery has been discharged deeply and shorter when it has not.((http://www.cheaprvliving.com/forums/Thread-Can-a-solar-panel-and-charge-controller-over-charge-a-battery?pid=96965#pid96965)) |
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| | **Mythbuster:** although it is commonly said that Vabs is attained at ~80% capacity... |
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| | > charge current affects the SOC transition point from bulk to absorption charging - MaineSail((https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/)) |
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| | MaineSail found that |
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| | * charging AGM at C/2.5 (max rate) resulted in the battery being 63.3% "full" at Vabs and being fully charged in **5hrs, 30 minutes** |
| | * charging AGM at C/5 (min rate) resulted in the battery being 77.4% "full" at Vabs and being fully charged in **5hrs, 42 minutes** |
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| Absorption **begins when the battery reaches the absorption voltage** ([[electrical:12v:electrical notation|Vabs]], 14.8v in our example) and **ends when the battery tapers off current acceptance** to something like C/100 ("End Absorb", "endAmps"), and/or when a period of time has elapsed. In practice absorption takes longer when the battery has been discharged deeply and shorter when it has not.((http://www.cheaprvliving.com/forums/Thread-Can-a-solar-panel-and-charge-controller-over-charge-a-battery?pid=96965#pid96965)) | |
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| Some controllers will allow the user to configure the time or ratio of capacity/current (C///n//). Sternwake says: | Some controllers will allow the user to configure the time or ratio of capacity/current (C///n//). Sternwake says: |
| > If your charge controller only holds [absorption] voltage for an hour or two, that is likely not enough time. As long as [there is a load] and you cycle the battery daily, you could set float voltage to 14.8v [to match absorption] without worry. Only when you stop cycling the battery do you need to return float voltage to more regular 13.2v levels. Premature application of float voltage by automatic charging sources is a battery killer.((http://www.cheaprvliving.com/forums/Thread-Solar-or-Battery-Problem?pid=229883#pid229883)) | > If your charge controller only holds [absorption] voltage for an hour or two, that is likely not enough time. As long as [there is a load] and you cycle the battery daily, you could set float voltage to 14.8v((for example - secessus)) [to match absorption] without worry. Only when you stop cycling the battery do you need to return float voltage to more regular 13.2v((for example - secessus)) levels. Premature application of float voltage by automatic charging sources is a battery killer.((http://www.cheaprvliving.com/forums/Thread-Solar-or-Battery-Problem?pid=229883#pid229883)) |
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| | If Absorption cannot be completed in the max amount of time configurable in the controller (due to damaged/old batteries), **charging at the minimum rate and/or at higher voltage may help [[electrical:severe_battery_use|compensate]]**. |
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| ==== float stage ==== | ==== float stage ==== |
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| Common Vfloat values range between 13.2v for stored batteries to 13.8v for banks that are deep cycled each day. | Common Vfloat values range between 13.2v for stored batteries to 13.8v for banks that are deep cycled each day. |
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| | also see [[electrical:12v:eternal absorption|Setting Vfloat to Vabs]] |
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| - vigorous Bulk charging((minimum current of [[electrical:12v:battery_capacity|C/5]] up to C/3)) sometimes greater than solar-only charging can provide.((http://www.cheaprvliving.com/forums/Thread-anyone-familiar-with-Worker-AGM-batteries?pid=97068#pid97068)) Consider augmenting with alternator or shore power charging. | - vigorous Bulk charging((minimum current of [[electrical:12v:battery_capacity|C/5]] up to C/3)) sometimes greater than solar-only charging can provide.((http://www.cheaprvliving.com/forums/Thread-anyone-familiar-with-Worker-AGM-batteries?pid=97068#pid97068)) Consider augmenting with alternator or shore power charging. |
| - long Absorption stages | - long Absorption stages |
| - but lower Absorption voltage (to prevent outgassing) | - typically lower Absorption voltage (to prevent outgassing)((there are exceptions)) |
| - absolutely no Equalizing (which would create heavy outgassing) | - no Equalizing (which could create heavy outgassing) |
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| Many charge controllers have AGM or GEL modes that handle these setpoints and durations. | Many charge controllers have AGM or GEL modes that handle these setpoints and durations. |
| ===== charging other chemistries ===== | ===== charging other chemistries ===== |
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| See [[electrical:12v:lifepo4_batteries_thread#charging|LiFePO4 (lithium) charging]] | Lithium packs don't need Absorption or Float stages in the lead-battery sense but those voltage setpoints can be put to good use. Follow your Li battery mfg's advice on charging. |
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| | - Absorption voltage - 4S LFP packs are actually 100% [[electrical:depth_of_discharge|state of charge]] at 13.8v, but Li manufacturers typically specify "absorption" charging a bit higher like 14.2v. This allows for quicker charging and also gives some overvoltage the BMS can use to "top balance" cells.((lower-voltage cells are given a chance to rise to their proper individual voltage of 3.45v)) |
| | - Float voltage - Li does not like to sit at 100% SoC,((the cells degrade faster at 100%+ SoC)) so a float voltage in the 13s allows them to come down off the peak and rest at a healthier voltage for them while still holding useful capacity. |
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| | Also see [[electrical:12v:lifepo4_batteries_thread#charging|LiFePO4 (lithium) bare cell charging]]. |
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| ===== equalization ===== | ===== equalization ===== |
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| Sometimes called the fourth stage, "equalizing is an overcharge performed after fully charging deep-cycle flooded/wet batteries. An equalizing charge prevents battery stratification and reduces sulfation which are leading causes of battery failure. Trojan recommends equalizing every 30 days or when batteries have a low specific gravity reading after fully charging... Deep-cycle AGM or gel batteries should NEVER be equalized."((http://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf)) | Sometimes called the fourth stage, "equalizing is an overcharge to stir up electrolyte in **stationary** deep-cycle flooded/wet batteries.((the electrolyte may stratify in stationary batteries, resulting in zones of stronger and weaker acid)) Since most vandwellers are mobile and electrolyte gets agitated by the van's movement //EQ may not be required for vandwellers//. Information provided below for completeness. |
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| | ----- |
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| | An equalizing charge prevents battery stratification and reduces sulfation which are leading causes of battery failure. Trojan recommends equalizing every 30 days or when batteries have a low specific gravity reading after fully charging... Deep-cycle AGM or gel batteries should NEVER be equalized."((http://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf)) |
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| House banks in rigs that are driven regularly are likely already mixed by jostling, so equalization may be less important. | House banks in rigs that are driven regularly are likely already mixed by jostling, so equalization may be less important. |
| - ambient temperature as measured by the charger. This can be different from the actual battery temp due to position, relative height to the battery, or if the charger gets confused by its own heat. | - ambient temperature as measured by the charger. This can be different from the actual battery temp due to position, relative height to the battery, or if the charger gets confused by its own heat. |
| - in the absence of actual measurements the charger will likely use the 77F laboratory standard. | - in the absence of actual measurements the charger will likely use the 77F laboratory standard. |
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| | This automatic voltage tweaking for temperature may result in your actual battery voltages being observably higher in cold temps and lower in hot temps. |
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| ===== watering batteries ====== | ===== watering batteries ====== |
| {{ http://www.trojanbattery.com/wp-content/uploads/2013/07/WaterDia_B.jpg?150}} | {{ http://www.trojanbattery.com/wp-content/uploads/2013/07/WaterDia_B.jpg?150}} |
| Flooded lead-acid batteries outgas during Absorption, causing a slow loss of water. They outgas intentionally in Equalization. To counteract this, the 'dweller must remove the caps and inspect the water level. If low, distilled water is added. | Flooded lead-acid batteries outgas during Absorption, causing a slow loss of water.((AGM and other VRLA outgas to, but use recombination to remake water from the gases)) They outgas intentionally in Equalization. To counteract this, the 'dweller must remove the caps and inspect the water level. If low, distilled water is added. |
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| - check to see if plates are covered with water. If not, add enough to cover the plates | - check to see if plates are covered with water. If not, add enough to cover the plates |
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| A [[http://amzn.to/2gEtVwL|battery waterer]] can make the job easier, and does not require one to judge water level visually. | A [[http://amzn.to/2gEtVwL|battery waterer]] can make the job easier, and does not require one to judge water level visually. The water "bloops" as it fills and stops blooping when the water is at the correct level. |
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| Batteries that are older, in poorer health, or are charged at higher voltages will be "thirstier". Check water levels 1x/month until you know how they behave. | Batteries that are older, in poorer health, or are charged at higher voltages will be "thirstier". Check water levels 1x/month until you know how they behave. |
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| **Manual chargers** will not be affected by load as they are controlled by the user. | **Manual chargers** will not be affected by load as they are controlled by the user. |
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| | ===== battery voltage while charging ===== |
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| | Battery Voltage = Battery Voc((resting voltage)) + (Charge Current x Ri((internal resistance))) |
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