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electrical:12v:diysmartpass [2023/06/23 15:17]
frater_secessus [20A DC-DC + 20A solar controller + isolator: $191-$252] |
electrical:12v:diysmartpass [2025/01/26 19:03] (current)
frater_secessus [the problem the Ctek solution addresses] |
| ====== DIY Ctek D250 + Smartpass setup ====== | ====== DIY Ctek D250 + Smartpass setup ====== |
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| This article is about the Ctek combo and possible approaches to duplicating the major functionality for less money and/or better specs. | This article is about the 1st-gen Ctek combo and possible approaches to duplicating the major functionality for less money and/or better specs. |
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| This article assumes you want and the bank will accept >20A of alternator charging, and that your alternator can handle it. If you only have a 80Ah AGM then the combo setup is massive overkill. The bare D250 would handle that with ease. | This article assumes you want and the bank will accept >20A of alternator charging, and that your alternator can handle it. If you only have a 80Ah AGM then the combo setup is massive overkill. The bare D250 would handle that with ease. |
| [[electrical:12v:b2b|DC-DC chargers]] can boost alternator voltage to the required Absorption voltage but doing so with Big Current can be impossible or at least very expensive. So DC-DC chargers are usually relatively small. | [[electrical:12v:b2b|DC-DC chargers]] can boost alternator voltage to the required Absorption voltage but doing so with Big Current can be impossible or at least very expensive. So DC-DC chargers are usually relatively small. |
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| Digression: this means that for **short drives** the isolator will likely return more Ah to the battery ban k than DC-DC. On **longer drives** the DC-DC will both return more current and charge at a more appropriate voltage for the battery chemistry. | Digression: this means that for **short drives** the isolator will likely return more Ah to the battery bank than DC-DC. On **longer drives** the DC-DC will both return more current and charge at a more appropriate voltage for the battery chemistry. |
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| What if we paralleled an isolator with a small DC-DC to get the both of best worlds? That is what the Ctek combo does. | What if we paralleled an isolator with a small DC-DC to get the both of best worlds? That is what the Ctek combo does. |
| - stop the isolator from passing voltages >Vfloat from alternator to house bank during Float stage. This should be a minimal problem with lead batteries((which can usually [[electrical:12v:eternal_absorption|tolerate high floats]])) and with driving times limited to a few hours. It //could// be a problem with Li batteries and many hours of driving. Note: it is not clear that the Ctek combo addresses this issue. The only approaches known to prevent excessive voltage during float are the combo DC-DC and the solenoid + HVD in conservative mode (see below). | - stop the isolator from passing voltages >Vfloat from alternator to house bank during Float stage. This should be a minimal problem with lead batteries((which can usually [[electrical:12v:eternal_absorption|tolerate high floats]])) and with driving times limited to a few hours. It //could// be a problem with Li batteries and many hours of driving. Note: it is not clear that the Ctek combo addresses this issue. The only approaches known to prevent excessive voltage during float are the combo DC-DC and the solenoid + HVD in conservative mode (see below). |
| - **isolators have no control over current**. In reality the combo might make **20A+120A** (dead house bank, big alternator, cool temps, Bulk stage) or it might make **20A+1A** (when battery bank is approaching alternator voltage). There is no guarantee that the DC-DC will be making 20A, either. If your bank is only accepting 15A then having 140A theoretical on tap will not matter. | - **isolators have no control over current**. In reality the combo might make **20A+120A** (dead house bank, big alternator, cool temps, Bulk stage) or it might make **20A+1A** (when battery bank is approaching alternator voltage). There is no guarantee that the DC-DC will be making 20A, either. If your bank is only accepting 15A then having 140A theoretical on tap will not matter. |
| | - provide for [[electrical:12v:self-jumpstarting|self-jumpstarting]]. The method Ctek uses for this appears to be FET-based like main isolation: "Is a smart combination of relays (actually MOSFETS) that connects starter and service batteries. This enables current from your alternator to charge both batteries".((https://www.ctek.com/storage/5CDB4E293A03CBF6442A620EC8E49CFB548CB48E9BF93425638077279A13BBA1/ac5639c5feaa46d38411ebd69f915b5b/pdf/media/65589cee7d4342e0891e2130149be66f/SmartPass%20120S.pdf)) [Dual MOSFET packs in series? - secesssus] |
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| * MPPT | * MPPT |
| * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. | * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. |
| * [[https://amzn.to/3Aj7NjP|EpEver 20A 100v MPPT]], $80. | * [[https://amzn.to/3Aj7NjP|EpEver 20A 100v MPPT]], $80. |
| * [[https://amzn.to/3QGwihC|Cole-Hersee continuous duty solenoid]], $55. | * [[https://amzn.to/3QGwihC|Cole-Hersee continuous duty solenoid]], $55. |
| * [[https://amzn.to/3AhdNti|High voltage disconnect]], $13. | * [[https://amzn.to/3AhdNti|High voltage disconnect]], $13. |
| * PWM | * PWM |
| * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. | * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. |
| * [[https://amzn.to/3PMlFIS|HQST 20A PWM]], $19. | * [[https://amzn.to/3PMlFIS|HQST 20A PWM]], $19. |
| * [[https://amzn.to/3QGwihC|Cole-Hersee continuous duty solenoid]], $55. | * [[https://amzn.to/3QGwihC|Cole-Hersee continuous duty solenoid]], $55. |
| * [[https://amzn.to/3AhdNti|High voltage disconnect]], $13. | * [[https://amzn.to/3AhdNti|High voltage disconnect]], $13. |
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| ==== 20A DC-DC + 20A DC-DC + 20A solar controller + diode isolator: $192-$253 ==== | ==== 20A DC-DC + 20A solar controller + diode isolator: $192-$253 ==== |
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| * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. [[https://amzn.to/3Aj7NjP|EpEver 20A 100v MPPT]], $80. [[https://amzn.to/3T9JKft|Cole-Hersee 90A diode isolator]], $69. | * MPPT |
| * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. [[https://amzn.to/3PMlFIS|HQST 20A PWM]], $19. [[https://amzn.to/3T9JKft|Cole-Hersee 90A diode isolator]], $69. | * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. |
| | * [[https://amzn.to/3Aj7NjP|EpEver 20A 100v MPPT]], $80. |
| | * [[https://amzn.to/3T9JKft|Cole-Hersee 90A diode isolator]], $69. |
| | * PWM |
| | * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. |
| | * [[https://amzn.to/3PMlFIS|HQST 20A PWM]], $19. |
| | * [[https://amzn.to/3T9JKft|Cole-Hersee 90A diode isolator]], $69. |
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| ==== 20A DC-DC 20A DC-DC + 20A solar controller + MOSFET isolator: $243-$304 ==== | ==== 20A DC-DC + 20A solar controller + MOSFET isolator: $243-$304 ==== |
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| * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. [[https://amzn.to/3Aj7NjP|EpEver 20A 100v MPPT]], $80. [[https://amzn.to/3wnJpfE|Victron ArgoFET 200A isolator]] (100A for each "leg", so both starter and house batt get ≤100A). $120. | * MPPT |
| | * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. |
| * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. [[https://amzn.to/3PMlFIS|HQST 20A PWM]], $19. [[https://amzn.to/3wnJpfE|Victron ArgoFET 200A isolator]] (100A for each "leg", so both starter and house batt get ≤100A). $120. | * [[https://amzn.to/3Aj7NjP|EpEver 20A 100v MPPT]], $80. |
| | * [[https://amzn.to/3wnJpfE|Victron ArgoFET 200A isolator]] (100A for each "leg", so both starter and house batt get ≤100A). $120. |
| | * PWM |
| | * [[https://amzn.to/3pCW5eY|Renogy 20A DC-DC]], $104. |
| | * [[https://amzn.to/3PMlFIS|HQST 20A PWM]], $19. |
| | * [[https://amzn.to/3wnJpfE|Victron ArgoFET 200A isolator]] (100A for each "leg", so both starter and house batt get ≤100A). $120. |
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| ==== 50A DC-DC combo chargers: $265-$328 ==== | ==== 50A DC-DC combo chargers: $265-$328 ==== |
