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electrical:12v:b2b [2021/05/19 12:11] frater_secessus [examples - with MPPT] |
electrical:12v:b2b [2021/06/21 15:12] frater_secessus [Redarc] |
- enough //time// at that voltage for the battery to stop accepting much current.(([[electrical:12v:battery_capacity|C/100]] to C/200)) If you aren't //driving// for (say) [[opinion:frater_secessus:charging_faster|5 hours]] then the charger can't //charge// for 5 hours to meet the battery's needs. ((DC-DC chargers were first marketed for cruisers (powered boats) since they run the engines ("cruise") for hours each day.)) This is where [[electrical:12v:alt_and_solar|a bit of solar helps with the long-duration duties]]. | - enough //time// at that voltage for the battery to stop accepting much current.(([[electrical:12v:battery_capacity|C/100]] to C/200)) If you aren't //driving// for (say) [[opinion:frater_secessus:charging_faster|5 hours]] then the charger can't //charge// for 5 hours to meet the battery's needs. ((DC-DC chargers were first marketed for cruisers (powered boats) since they run the engines ("cruise") for hours each day.)) This is where [[electrical:12v:alt_and_solar|a bit of solar helps with the long-duration duties]]. |
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DC-DC chargers are often triggered by the IGN circuit, but [[electrical:12v:voltage_sensing_delay|voltage sensing can be added]]. | DC-DC chargers are often triggered by the IGN circuit, but [[electrical:12v:voltage_sensing_delay|voltage sensing can be added]] to that circuit. Others are triggered by chassis-side voltage alone. |
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Dual-input (alternator + solar) units make charging source decisions that are sometimes quirky. See below. | Dual-input (alternator + solar) units make charging source decisions that are sometimes quirky. See below. |
===== examples - with MPPT ===== | ===== examples - with MPPT ===== |
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Combining the [[electrical:solar:charge_controller|solar charge controller]] and DC-DC charger in one unit can have benefits in cleaner/simpler installation and perhaps cost over separate components. The downsides are less configurabilty((you aren't choosing your own highly-configurable components)), single points of failure, and limited options on solar input. | Combining the [[electrical:solar:charge_controller|solar charge controller]] and DC-DC charger in one unit can have benefits in cleaner/simpler installation, starter battery maintenance from solar, and perhaps cost over separate components. The downsides are less configurabilty((you aren't choosing your own highly-configurable components)), single points of failure, and limited options on solar input. |
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Combo units typically have much **lower maximum panel input voltages** (as low as 23v) than a standalone charge controller would (60v - 150v). This limits the solar configuration in a few ways: | Combo units typically have much **lower maximum panel input voltages** (as low as 23v) than a standalone charge controller would (60v - 150v). This limits the solar configuration in a few ways: |
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* DCC50S [[https://amzn.to/2QYuswm|50A model with MPPT charging]]. MPPT input limited to 25v.((per the manual)) - [[https://www.renogy.com/content/RBC50D1S-G1/RBC50D1S-G1-Manual.pdf|manual]] (pdf) Total output is limited to 50A from either independent source (see below). | * DCC50S [[https://amzn.to/2QYuswm|50A model with MPPT charging]]. MPPT input limited to 25v.((per the manual)) - [[https://www.renogy.com/content/RBC50D1S-G1/RBC50D1S-G1-Manual.pdf|manual]] (pdf) Total output is limited to 50A from either independent source (see below). |
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| Note: a [[https://amzn.to/3fSFDD2|30A combo model]] is also available |
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=== solar+alternator behavior === | === solar+alternator behavior === |
* driving in daytime: 25A alternator + 15A solar = 40A total charging | * driving in daytime: 25A alternator + 15A solar = 40A total charging |
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| [[https://www.renogy.com/content/RBC3050D1S-G1/RBC3050D1S-Manual.pdf|Behavior is the same for the 30A model]] (pdf) except 15A + 15A //vs// 25A + 25A above. |
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When the alternator input terminals detect at least 13.2v the charger will be switched to alternator charging.((trigger wire allows use of smart alternators)) | When the alternator input terminals detect at least 13.2v the charger will be switched to alternator charging.((trigger wire allows use of smart alternators)) |
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| ==== Redarc ==== |
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| Redarc "dual input" DC-DC chargers have integrated MPPT controllers. They appear to do both buck and boost conversion as solar input voltage is 9v-32v.((https://www.redarc.com.au/Content/Images/uploaded/Manuals/BCDC%20Dual%20Input%20Instruction%20Manual.pdf)) |
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| [[https://amzn.to/2TLGhtv|{{ https://m.media-amazon.com/images/I/71CqS887T8L._AC_UL320_.jpg?125}}]] |
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| * [[https://amzn.to/3iZY3Uw|BCDC1225D]] - 25A |
| * [[https://amzn.to/2TLGhtv|BCDC1240D]] - 40A |
| * [[https://amzn.to/3zFgmUZ|BCDC1240D]] - 50A |
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| === solar+alternator behavior === |
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| > The unit will always take as much power from the unregulated Solar input as it |
| can before supplementing that power, up to the maximum rated output, from Vehicle power input((https://www.redarc.com.au/Content/Images/uploaded/Manuals/BCDC%20Dual%20Input%20Instruction%20Manual.pdf)),((https://www.redarc.com.au/Content/Images/uploaded/BCDC1250D%20Instruction%20Manual.pdf)) |
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[[http://www.bogartengineering.com/products/solar-charger.html|Bogart's SC-2030]] can work as a DC-DC charger as well as a PWM charge controller. | [[http://www.bogartengineering.com/products/solar-charger.html|Bogart's SC-2030]] can work as a DC-DC charger as well as a PWM charge controller. |
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| ===== gotchas ===== |
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| Observe voltage input maximums on units with built-in solar charge controllers. |
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| Voltage-sensing units((triggered by elevated chassis voltage)) can misbehave when an undersized starter battery charger/maintainer is attached. For this example we assume a 10A maintainer and a 20A DC-DC charger. |
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| - starter battery voltage rises from 10A maintainer charging... |
| - triggering the DC-DC charger... |
| - which begins pulling up to 20A from the chassis |
| - pulling down the starter battery since the 10A maintainer cannot keep up |
| - starter battery voltage drops far enough the DC-DC turns off |
| - repeat forever |
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| The workaround is to either charge the house battery first or to buy a big enough starter battery maintainer to support both the starter battery and DC-DC charger loads. |
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===== further reading ===== | ===== further reading ===== |
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[[https://diysolarforum.com/threads/dc-dc-charger-b2b-options-and-general-discussion.17211/|DC-DC charger (B2B) options and general discussion]] on DIY Solar Power Forum. | [[https://diysolarforum.com/threads/dc-dc-charger-b2b-options-and-general-discussion.17211/|DC-DC charger (B2B) options and general discussion]] on DIY Solar Power Forum. |