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electrical:12v:b2b [2024/08/18 16:11]
frater_secessus [triggering / isolation] changed subsection name and added section. 		electrical:12v:b2b [2025/03/10 11:54] (current)
frater_secessus [examples - power stations] added link to solar input limit workaround
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 See [[electrical:12v:mandatory_dcdc|this companion article]] See [[electrical:12v:mandatory_dcdc|this companion article]]
  
-===== triggering  ===== 
- 
-The general idea is to feed power from the chassis (usually the starter battery) to the house battery **only when the alternator is making power**, and isolate the two from each other when it is not.  The DC-DC will handle this in one of two ways: 
- 
-  * **voltage sensing** - watching chassis voltage like [[electrical:12v:alternator#voltage-sensing_relays|a VSR]] 
-  * by receiving a **trigger signal** (AKA "D+", "IGN", "ignition", etc) from the chassis:  signal = ON, no signal = OFF.  This method requires the user to find a chassis circuit that has power only when the key is turned.   Caveat:  leaving the key in the ACC ("accessory") position can trick the DC-DC into starting before the engine is running;  so don't do that.  
- 
-Product documentation will tell you how the unit is triggered.((sometimes both methods are used together)) 
- 
-==== installation ==== 
- 
-A DC-DC charger is installed as close to the battery bank as practical, in order to minimize [[electrical:12v:voltage_sag|voltage sag]]. 
- 
-To simplify the installation and minimize expense you may be able to run the input NEG to the chassis rather than all the way back to the starter battery NEG.  If the chassis introduces too much resistance to allow hitting the desired charging output you can punt and run heavy NEG wire all the way back to the starter batt.  
- 
-The product manual will give specific guidance on wire gauge, fusing, mounting orientation, etc.  
 ===== sizing ===== ===== sizing =====
  
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   * **AGM lead-acid** accepts a max of about 0.33C, or 33A per 100A of battery capacity, and requires a minimum of 0.2C (20A).  In this case, **20-33A of charging capacity would be appropriate**.  Less than 20A would be insufficient for battery health  and more than 33A would be wasted expense.((Exception:  high-end AGM often have very high current minumums like C/2))   * **AGM lead-acid** accepts a max of about 0.33C, or 33A per 100A of battery capacity, and requires a minimum of 0.2C (20A).  In this case, **20-33A of charging capacity would be appropriate**.  Less than 20A would be insufficient for battery health  and more than 33A would be wasted expense.((Exception:  high-end AGM often have very high current minumums like C/2))
   * **Lithium** has very low internal resistance and //may// be able to slurp up all the alternator has to give.((in practice, due to wiring resistance and other factors [[electrical:12v:directcharginglfp|Li tends to charge at about the same C-rate as AGM]]))  0.2C-0.4C charging may be the sweet spot between charging time and longevity, which would be **20A - 40A charging**.  If you are charging by alternator alone and have limited time to do so, some BMS allow up to 1.0C charging (100A).  The bank will not be expected to last as many cycles or stay balanced under aggressive charging but the option is there for people who need it.    * **Lithium** has very low internal resistance and //may// be able to slurp up all the alternator has to give.((in practice, due to wiring resistance and other factors [[electrical:12v:directcharginglfp|Li tends to charge at about the same C-rate as AGM]]))  0.2C-0.4C charging may be the sweet spot between charging time and longevity, which would be **20A - 40A charging**.  If you are charging by alternator alone and have limited time to do so, some BMS allow up to 1.0C charging (100A).  The bank will not be expected to last as many cycles or stay balanced under aggressive charging but the option is there for people who need it. 
 +
 +
 +===== triggering  =====
 +
 +The general idea is to feed power from the chassis (usually the starter battery) to the house battery **only when the alternator is making power**, and isolate the two from each other when it is not.  The DC-DC will handle this in one of two ways:
 +
 +  * **voltage sensing** - watching chassis voltage like [[electrical:12v:alternator#voltage-sensing_relays|a VSR]]
 +  * by receiving a **trigger signal** (AKA "D+", "IGN", "ignition", etc) from the chassis:  signal = ON, no signal = OFF.  This method requires the user to find a chassis circuit that has power only when the key is turned (IGN, ACC) or when the alternator is actually making power (D+).  Caveat:  leaving the key in the ACC ("accessory") position can trick the DC-DC into starting before the engine is running;  so don't do that. 
 +  * **voltage sensing + trigger signal** - this is often used to tell voltage-sensing DC-DC that the alternator is smart (variable voltage).  IOW, "voltage is weirdly low but the D+ signal tells me this is a smart alt //and// the engine is running so I can charge regardless."
 +
 +
 +Product documentation will tell you how the unit is triggered.((sometimes both methods are used together))
 +
 +===== installation =====
 +
 +A DC-DC charger is installed as close to the battery bank as practical, in order to minimize [[electrical:12v:voltage_sag|voltage sag]].
 +
 +To simplify the installation and minimize expense you may be able to run the input NEG to the chassis rather than all the way back to the starter battery NEG.  If the chassis introduces too much resistance to allow hitting the desired charging output you can punt and run heavy NEG wire all the way back to the starter batt. 
 +
 +The product manual will give specific guidance on wire gauge, fusing, mounting orientation, etc. 
 +
    
  
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 Update:  [[https://store-fhnch.mybigcommerce.com/content/RBC2125DS-21W/Manual_RENOGY%2012V%2024V%2050A%20Battery%20Charger-2.pdf|the manual]] has been updated. Update:  [[https://store-fhnch.mybigcommerce.com/content/RBC2125DS-21W/Manual_RENOGY%2012V%2024V%2050A%20Battery%20Charger-2.pdf|the manual]] has been updated.
  
-== solar+alternator behavior ==+= solar+alternator behavior =
  
  
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 [[https://www.renogy.com/content/RBC3050D1S-G1/RBC3050D1S-Manual.pdf|manual]] [[https://www.renogy.com/content/RBC3050D1S-G1/RBC3050D1S-Manual.pdf|manual]]
 +
 +== RBC40D1S ==
 +
 +40A DC-DC w/MPPT that appears very similar to the Redodo/LiTime/etc 40A combo units. 
 +
 +  * 30v PV input
 +  * smart and traditional alternators
 +  * no float in LFP profile, rebulking at 13.6v
 +
 +[[https://store-fhnch.mybigcommerce.com/content/RBC40D1S-US/Renogy%2040a%20dcdc%20user%20manual%20v1.0%2020240320.pdf|manual]] (pdf)
 +
 +
 +
 += starter battery maintenance behavior =
 +
 +not described, and presumed not present
 +
 += solar+alternator behavior =
 +
 +When both are present it defaults to alternator priority (only).  It can be set to solar priority.  
  
  
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 >> For DMT1230, 1250 using CH 2 (Solar Array/Panel): Turn unit off. Use a proper jumper to temporary connected CH2 “+” to Ch 1 “+”. Remove the jumper when CH 1 is above the unit start up voltage (8Vdc) and restart the unit. >> For DMT1230, 1250 using CH 2 (Solar Array/Panel): Turn unit off. Use a proper jumper to temporary connected CH2 “+” to Ch 1 “+”. Remove the jumper when CH 1 is above the unit start up voltage (8Vdc) and restart the unit.
  
 +=== disabling the Kisae ===
 +
 +  * tricking the Battery Temperature Sensor port  - [[https://www.promasterforum.com/threads/kisae-dmt1250-dmt1230-low-temp-cut-off-and-couple-of-advanced-wiring-options.97444/|Kisae DMT1250/DMT1230 low temp cut off and couple of advanced wiring options]]
 +  * modifying the existing ON/OFF switch - [[https://diysolarforum.com/threads/kisae-dmt1250-partial-disassembly-and-remote-disconnect-addition.15454/|Kisae DMT1250 partial disassembly and remote disconnect addition]]
 +
 +The brute force method would be a battery cut-off switch or relay on the POS wire coming from the chassis. 
  
  
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 ==== Renogy ==== ==== Renogy ====
  
-[[https://amzn.to/33HJ8ns|{{ https://images-na.ssl-images-amazon.com/images/I/51Hu4-7NxOL._AC_UL160_SR160,160_.jpg?150}}]]+[[https://amzn.to/33HJ8ns|{{ https://images-na.ssl-images-amazon.com/images/I/51Hu4-7NxOL._AC_UL160_SR160,160_.jpg?250}}]]
  
 === DC1212 series === === DC1212 series ===
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 [[https://store-fhnch.mybigcommerce.com/content/RCB1260DO-100506PR/RBC1260DO-12B_UserManual_A0.pdf|manual]] (pdf) [[https://store-fhnch.mybigcommerce.com/content/RCB1260DO-100506PR/RBC1260DO-12B_UserManual_A0.pdf|manual]] (pdf)
 +
 +=== RBC series ===
 +
 +{{ https://cdn11.bigcommerce.com/s-fhnch/images/stencil/640w/products/2177/27702/_01__78889.1721714867.jpg?150}}
 +
 +  * seems to be in [[https://www.renogy.com/12v-40a-dc-to-dc-battery-charger/|40A]] and 20A versions
 +  * configurable output current via the app
 +  * Voltage-sensing (with D+ for smart alts)
 +  * can use [[https://amzn.to/47kjqqD|BT-2 module]]
 +
 +[[https://www.renogy.com/content/RBC40D1U-US/QG_RENOGY%2012V%2020A40A%20Battery%20Charger_A0.pdf|manual]]
 +
 +
 +
 ==== Redarc ==== ==== Redarc ====
  
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-==== examples - without current limiting ====+===== examples - without current limiting =====
  
 The [[https://sterling-power.com/products/alternator-to-battery-chargers-up-to-130a|Sterling A2B]] uses DC-DC conversion to boost voltage but has no ability to limit current.   The [[https://sterling-power.com/products/alternator-to-battery-chargers-up-to-130a|Sterling A2B]] uses DC-DC conversion to boost voltage but has no ability to limit current.  
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 Also see the Votronics section above for their DCC 25A 1224 charger.  Also see the Votronics section above for their DCC 25A 1224 charger. 
 +
 +===== examples - power stations =====
 +
 +Power stations often suffer from low DC input limits.  DC-DC chargers (//boost converters// in this case) can work around the limit by increasing the voltage to the power station input.((also see [[12v:sg_troubleshooting#maxxing_out_the_solar_input|this subarticle]] about solar input.  The source of the charging is different but the math and concepts are the same.)) If separate DC inputs are present these typically feed power to the solar input;  see your power station's product documentation for specifics. 
 +
 +**Warning:** exceeding the power station's **input voltage limit** will/may damage it.  Verify specs //before// purchasing, configuring, or installing.
 +
 +  * [[https://amzn.to/3DCGu9m|Bluetti 560w charger]] - Adjustable output voltage in the app.  Presets for Bluetti products, or you can manually set the output voltage. 
 +  * [[https://amzn.to/3PlwcNv|Ecoflow 800w charger]] - Adjustable output 40V-60V.  Starter battery maintenance charging/maintaining modes. Firmware updates may be available.
 +  * [[https://amzn.to/41XDQ8o|Etaker 1000w charger]] - ≤500w alternator + ≤500 solar (up to 48v and 20A input).  Output ≤42V, 25A
 +  * [[https://amzn.to/3Pidm9V|Pecron DC1242-500]].  500w, 42v.
 +
 +Functionally, the ones with a set output voltage are akin to [[https://amzn.to/4fNKrpe|this]] and the ones with configurable output voltage are akin to [[https://amzn.to/3BRoQxZ|this]], plus a method to [[electrical:12v:b2b#triggering|trigger]] the device when the engine is running. 
 +
 +==== a word about nomenclature ====
 +
 +These are listed in the DC-DC article because that is how they are used and how many people think of them.  They are really voltage boosters that output a steady voltage, whether configured by the user or set at the factory.  
  
 ===== installing inline with a relay ===== ===== installing inline with a relay =====
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   - repeat forever   - repeat forever
  
-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. +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. Or (if the model has [[electrical:12v:self-jumpstarting#maintaining_starter_batteries|starter battery maintenance]]) apply the maintainer to the house battery instead.
  
 ===== further reading ===== ===== further reading =====
  
 [[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.
electrical/12v/b2b.1724011866.txt.gz · Last modified: 2024/08/18 16:11 by frater_secessus

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