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electrical:converter [2019/03/12 18:02]
frater_secessus [DIY converters] |
electrical:converter [2024/02/28 15:19] (current)
frater_secessus [DIY dumb converters] |
| - charge the [[electrical:12v:deep_cycle_battery|house battery]] | - charge the [[electrical:12v:deep_cycle_battery|house battery]] |
| - provide 12v to power [[electrical:12v:loads|house loads]] | - provide 12v to power [[electrical:12v:loads|house loads]] |
| - sometimes acts as a passthrough for 110v | |
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| For turning 12v into 110v see [[electrical:inverter|inverters]]. | For turning 12v into 110v see [[electrical:inverter|inverters]]. |
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| ===== charging the house battery ===== | ===== charging the house battery ===== |
| OEM converters are notoriously cheap and dumb (lacking [[electrical:12v:charging|smart charging]] functions). Since they are stuck at one voltage the manufacturer picks a compromise setpoint. If this is set too high or too low //for your usage patterns// it can damage lead-acid batteries ([[electrical:batterycide|batterycide]]). | OEM converters are notoriously cheap and dumb((single-stage)) (lacking [[electrical:12v:charging|smart charging]] functions). |
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| This compromise setpoint should coincide with standard float voltage (Vfloat) for your battery bank. Typically this would be 13.2v - 13.4v for converters that are always on the grid, and 13.8v for batteries that are cycled but get put back on grid charging regularly.((Solar charging at a single setpoint, as with a [[electrical:solar:charge_controller&#shunt|shunt controller]], is done at [[electrical:solar:shunt_tweaking|Vabs rather than Vfloat]].)) | Note: if you have sufficient solar to complete Absorption then a "dumb" converter can work fine and shore power will support the battery on subsequent days. In this model the converter + solar would contribute up to [[electrical:solar:charge_controller_setpoints|Vfloat]], then solar would raise the bank to Vabs and fall back to Vfloat when Absorption is done. Shore power holds Vfloat indefinitely thereafter. |
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| | Some single-stage converters allow the user to configure the float voltage, typically somewhere between 13.2v - 13.8v. If the converter does not allow this adjustment then pick one with an appropriate float voltage ([[electrical:solar:charge_controller_setpoints|Vfloat]]) for your battery bank. |
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| | ===== choosing a converter ===== |
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| | If money is no object you can buy a multistage ("smart") converter rated at the bank's maximum curent acceptance at the lowest normal state of charge: |
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| | * [[electrical:12v:battery_capacity|0.33C]] for AGM at 50% SoC |
| | * 0.2C for FLA at 50% SoC |
| | * 0.4C is not LiFePO4's //max// at 20% SoC, but is probably a max rate for good cycle life. 0.2C would be optimal if one has the time. |
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| | ==== cost ==== |
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| | The higher the rating and the more features the more expensive the shore power charger. There is also a practical limit on what we can pull from a 15A shore power connection for hours/days. |
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| | ==== limits of 15A shore power ==== |
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| | 13A off a 15A [[electrical:shore_power|shore power]] plug, or 1,560w is a safe limit for continuous power use. Assuming 10% conversion losses this would give us a **theoretical max of around 100A of converter charging** (14.4Vabs x 100A).((shore power amps are at 120vac, converter ratings are at their nominal DC voltage)) |
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| | ==== minimum charge rate ==== |
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| | Lead chemistries require a minimum charge rate to stay healthy. In the absence of documentation from your battery mfg we can assume |
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| | * 0.2C for AGM |
| | * 0.1C for Flooded Lead Acid |
| | * [LiFePO4 has no minimum current spec] |
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| | ==== charging time available ==== |
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| | If you have solar and will be on shore power for more than one day then a simple converter that charges at the batteries' recommended Float voltage is fine; solar will be able to do the relatively light duty of completing Absorption each day. |
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| | If you do not have solar or will be on shore power for only one overnight then we need a three-stage ("smart") converter that can handle Absorption duties. |
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| ===== aftermarket converters ===== | ===== aftermarket converters ===== |
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| Aftermarket converters tend to be higher quality than OEM, but some are still "dumb" single-stage chargers. Higher-end aftermarket converters often have multistage charging built in, or available as an upgrade.((See the PD w/Charge Wizard below)) | Aftermarket converters tend to be higher quality than OEM, but some are still "dumb" single-stage chargers. Higher-end aftermarket converters often have multistage charging built in, or available as an upgrade.((See the PD w/Charge Wizard below)) |
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| Three converter makers are generally respected on the CRVL forum. In alphabetical order: | Three converter makers are generally respected on the CRVL forum. In alphabetical order: |
| * [[http://amzn.to/2fduYjS|Iota]] | * [[http://amzn.to/2fduYjS|Iota]] |
| * [[http://amzn.to/2gsuxYa|Powermax]] | * [[http://amzn.to/2gsuxYa|Powermax]] |
| * [[http://amzn.to/2fumkhL|Progressive dynamics]] with Charge Wizard built in or added | * [[http://amzn.to/2fumkhL|Progressive dynamics]] with Charge Wizard built in or added. Note: the PD [[https://diysolarforum.com/threads/high-amp-dc-dc-charger.9308/post-101689|may be better suited for shore power sources]] rather than generator charging. |
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| SternWake says he leans toward Progressive Dynamics //"for the ability to choose stages, holding 14.4 for 4 hours at the press of a button"//((http://www.cheaprvliving.com/forums/Thread-charger-converter-vs-smart-portable-charger?pid=158374#pid158374)) | SternWake says he leans toward Progressive Dynamics //"for the ability to choose stages, holding 14.4 for 4 hours at the press of a button"//((http://www.cheaprvliving.com/forums/Thread-charger-converter-vs-smart-portable-charger?pid=158374#pid158374)) |
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| | ===== shore power chargers ===== |
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| | [[https://amzn.to/2SLzlwk|{{ https://m.media-amazon.com/images/I/81CYeL3EpWL._AC_UY218_.jpg?125}}]] |
| | When bulk charging is handled by other means a [[https://amzn.to/2SLzlwk|small (10-20A) smart charger/maintainer]] may be sufficient. They are generally not intended to be permanently mounted in the vehicle so mounting may have to be fabricated, or storage found for it when not in use. |
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| ===== DIY "converters" ===== | ===== DIY "converters" ===== |
| ==== DIY dumb converters ==== | ==== DIY dumb converters ==== |
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| Dumb converters output a single voltage (see above). | "Dumb" converters output a single voltage and work fine when solar charging is present (see above) or when the bank is lithium chemistry. In this scenario the 12v power supply can is set to ~13.x voltages to provide "low float" support while on shore power. |
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| FIXME | If loads are run off the converter in the daytime the converter will just be supporting the solar yield and can be rather small. If used at night the converter will be carrying the whole burden and should be sized accordingly([[https://amzn.to/2WNSIDL|20A]], [[https://amzn.to/3jwQGBO|40A]], whatever). |
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| * secondary use of charge controller as a spare if needed | * secondary use of charge controller as a spare if needed |
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| If you do not need smart charging an adjustable voltage power supply could do the trick. Since by definition the batteries aren't cycling when on shore power you could adjust it to something like 13.2v and let it "float" charge over time. | Further reading: |
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| | * [[https://diysolarforum.com/threads/variable-power-supply-and-mppt-for-charging-lifepo4-bank.23026/post-277337|an EE chimes in]] |
| | * Owner of Midnite Solar [[https://diysolarforum.com/threads/testing-mpp-charge-controller-function-with-bench-power-supply.11183/#post-124018|chimes in]] |
