| Both sides previous revision
Previous revision
Next revision
|
Previous revision
Next revision
Both sides next revision
|
electrical:12v:alternator [2021/05/20 12:50]
frater_secessus [voltage-sensing relays] |
electrical:12v:alternator [2021/06/25 13:11]
frater_secessus [voltage-sensing relays] |
| 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. |
| |
| | 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. |
| |
| |
| |
| |
| - [[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]], [[https://amzn.to/3h5iMUd|Victgron CT]]. |
| - [[http://amzn.to/2gVmLFU|dual voltage sensing]] - this type reads the voltage from both batteries and when either is high enough it connects the batteries. This may or [[electrical:12v:alternator_charging_hvd|may not be what an RVer wants]] \\ Examples: [[http://amzn.to/2gVmLFU|Sure Power 1315]], [[https://amzn.to/37gcdIv|BlueSea SI-ACR]], [[https://amzn.to/2RFaXI7|JayCorp Smart Dual Battery 140A Isolator]]((bonus points to the Jaycorp for printing the connect/disconnect setpoints right on the isolator!)) | - [[http://amzn.to/2gVmLFU|dual voltage sensing]] - this type reads the voltage from //both// sides and when either is high enough it connects the batteries. This may or [[electrical:12v:alternator_charging_hvd|may not be what an RVer wants]] \\ Examples: [[http://amzn.to/2gVmLFU|Sure Power 1315]], [[https://amzn.to/37gcdIv|BlueSea SI-ACR]], [[https://amzn.to/2RFaXI7|JayCorp Smart Dual Battery 140A Isolator]]((bonus points to the Jaycorp for printing the connect/disconnect setpoints right on the isolator!)) |
| - DC-DC isolators (aka //[[electrical:12v:b2b|b2b]] isolators//) that boost alternator voltage to [[electrical:12v:charging|more appropriate levels for lead chemistries]] and can do multistage charging. These have [[electrical:12v:b2b|their own page]]. | - DC-DC isolators (aka //[[electrical:12v:b2b|b2b]] isolators//) that boost alternator voltage to [[electrical:12v:charging|more appropriate levels for lead chemistries]] and can do multistage charging. These have [[electrical:12v:b2b|their own page]]. |
| |
| * **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. |
| |
