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electrical:12v:alternator [2021/04/15 10:03]
frater_secessus [constant-duty solenoid] |
electrical:12v:alternator [2021/06/25 13:09]
frater_secessus [gotchas] victron ct |
| In a dual-battery system((starter battery and house battery)) some of the alternator output is used to charge the house batteries when the engine is running. When the engine is not running **the house battery is electrically isolated** from the starter battery to keep from draining it and leaving you stranded. So the devices that handle the isolating/combining duties are called //battery isolators//. There are several different types. | In a dual-battery system((starter battery and house battery)) some of the alternator output is used to charge the house batteries when the engine is running. When the engine is not running **the house battery is electrically isolated** from the starter battery to keep from draining it and leaving you stranded. So the devices that handle the isolating/combining duties are called //battery isolators//. There are several different types. |
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| | Normally only the POS((+, positive)) wire is used to route power with an isolator; the NEG side is the chassis ground. If no chassis ground is available a NEG wire will need to be run also. |
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| ==== voltage-sensing relays ==== | ==== voltage-sensing relays ==== |
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| [[https://amzn.to/2Ri2jQV|{{ https://images-na.ssl-images-amazon.com/images/I/418qcncjT0L._AC_US218_.jpg|}}]]voltage sensing relays are solenoids with a bit of extra logic to know when to connect/disconnect. The VSR does not get trigger voltage from the fuse panel but rather reads the voltages of one((vsr)) or both))dvsr)) batteries to know when to switch on. \\ This kind of isolator may have a "combine" override function to enable self-jumpstarting. | [[https://amzn.to/2Ri2jQV|{{ https://images-na.ssl-images-amazon.com/images/I/418qcncjT0L._AC_US218_.jpg|}}]]voltage sensing relays (VSR, also called Automatic Charging Relays or ACR) are solenoids with a bit of extra logic to know when to connect/disconnect. The VSR does not get trigger voltage from the fuse panel but rather reads the voltages of one((vsr)) or both))dvsr)) batteries to know when to switch on. \\ This kind of isolator may have a "combine" override function to enable self-jumpstarting. |
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| | > in its simplest form, all an ACR really does is parallel batteries when charging is present and un-parallel batteries when there is no charging present. It does this automatically with no human forgetfulness.((https://marinehowto.com/automatic-charging-relays/)) |
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| - [[http://amzn.to/2h2tDxp|single voltage sensing]] - this type reads the voltage of only one battery. In the case of an RV it would read the voltage of the starting battery. When it is high enough above resting voltage (ie, being charged by alternator) it connects the starting and house batteries. \\ [secessus says: "IMO the practical benefit (if any) to charging the starter battery "first" is keeping the load on the alternator reasonable. In practice, the isolator generally connects the two within a few seconds."] \\ Examples: [[http://amzn.to/2h2tDxp|Sure Power 1314]], [[https://amzn.to/2tEGp1e|BlueSea BatteryLink]], [[https://amzn.to/2Ri2jQV|Battery Doctor]]. | - [[http://amzn.to/2h2tDxp|single voltage sensing]] - this type reads the voltage of only one battery. In the case of an RV it would read the voltage of the starting battery. When it is high enough above resting voltage (ie, being charged by alternator) it connects the starting and house batteries. \\ [secessus says: "IMO the practical benefit (if any) to charging the starter battery "first" is keeping the load on the alternator reasonable. In practice, the isolator generally connects the two within a few seconds."] \\ Examples: [[http://amzn.to/2h2tDxp|Sure Power 1314]], [[https://amzn.to/2tEGp1e|BlueSea BatteryLink]], [[https://amzn.to/2Ri2jQV|Battery Doctor]]. |
| * **Idling the engine** to charge house batteries **can overheat the alternator**,particularly older-style ones that do not reduce output to control high temps. Workaround: Don't plan to idle to charge from alternator. If you do, a fan may help cool the alternator. | * **Idling the engine** to charge house batteries **can overheat the alternator**,particularly older-style ones that do not reduce output to control high temps. Workaround: Don't plan to idle to charge from alternator. If you do, a fan may help cool the alternator. |
| * In early morning when house battery voltage is lowest, **a plain solenoid may unintentionally allow depleted batteries to pull down the starter battery**. Workarounds: use a VSR, or start the vehicle immediately after inserting the key((ie, do not leave in the Accessory position which would drain the starter battery)). | * In early morning when house battery voltage is lowest, **a plain solenoid may unintentionally allow depleted batteries to pull down the starter battery**. Workarounds: use a VSR, or start the vehicle immediately after inserting the key((ie, do not leave in the Accessory position which would drain the starter battery)). |
| * Solar charging while the engine is running may [[opinion:frater_secessus:alternatorSolarStall|get "stuck" at alternator voltage]]. Workaround: higher solar wattage, DC-DC charger, or a switch to disconnect isolator after alternator voltage is reached. | * Solar charging while the engine is running may [[opinion:frater_secessus:alternatorSolarStall|get "stuck" at alternator voltage]]. Workaround: higher solar wattage, DC-DC charger, or a switch to disconnect isolator after alternator voltage is reached. The [[https://amzn.to/3h5iMUd|Victron Cyrix-ct isolator]] could be useful here, as it appears to disconnect >13.8v.((https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-ct-120A-230A-EN.pdf)) |
| * Alternator charging may bring some battery chemistries (like bare lithium cells with no BMS) to **unsuitably high voltages**. Workarounds: A [[electrical:12v:hvd|high voltage disconnect]] can [[electrical:12v:alternator charging hvd|restrict alternator charging to lower voltages]]. [[electrical:12v:b2b|DC-DC chargers]] can also regulate voltage provided to the house battery. | * Alternator charging may bring some battery chemistries (like bare lithium cells with no BMS) to **unsuitably high voltages**. Workarounds: A [[electrical:12v:hvd|high voltage disconnect]] can [[electrical:12v:alternator charging hvd|restrict alternator charging to lower voltages]]. [[electrical:12v:b2b|DC-DC chargers]] can also regulate voltage provided to the house battery. |
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