The fans on most of the better alternators today are internal to the casing.
Note, the amps they were producing, 96 on the one test, is well within what my single group 27 northstar AGM was able to consume when newer and healthy.
They also did not factor into the equation that the large drive pulley of an engine spins the small alternator pulley 5 to 7 times faster than engine rpm. They were using an electric motor whose pulley was nearly the same as the alternator pulley, for nearly a 1 to 1 ratio .
But their points and conclusions are very valid, low rpm the alternator might be able to make a lot of amps still, but it cannot dissipate the heat it generates and can burn itself out if it has no current limiting function/ ability.
While my single group 27 northstar, when it was new and well depleted, could suck up perhaps 96 amps for 10 minutes before that number would start tapering, a larger bank of AGMs and of course Lithiums, could suck up that much amperage, and much more, for much longer, creating much more opportunity to overheat and fry the alternator.
So many people think a huge alternator rating means it can always output that much current at almost any rpm, but in reality that is the absolute maximum it can produce spinning fast, when still cold, with huge loads capable of sucking up everything it can make.
Idling to recharge is unwise. More engine rpm not only makes more amperage, but keeps the alternator much cooler, not only as the alternators fan is cooler but the vehicle movement means the alternator is not ingesting 200F + air, but much cooler air instead. is a high idle enough to keep the alternator cooler, or is the high idle simply to allow the alternator to make more amps, or some degree of both.....Without data any declaration is conjecture, and useless opinion.
I don't carry much battery capacity but that which I do is a TPPL AGM which is a very low resistance lead acid battery, and it can and does suck up everything my alternator can make when it is well discharged, and my alternator gets hot fast, if I am idling, and it can only make 50 amps at 550 hot engine rpm and about 75 amps at 800, it can't make its 120 amp rating until about 2250 engine rpm, and cruising at 65mph in overdrive is ~1975 rpm.
12.2 amps are required to run just my ignition and fuel pump. The field current sent to the alternator can be as high as 8 to 10 amps when fully fielded, so in order to make alternator amps, 20+ of those are already spoken for, the rest goto loads, and a depleted battery is a big load. A big bank of depleted batteries, not just lithium, is a big load and can overheat alternators easily, especially alternators capable of high amperage rates at idle speeds with owners who place too much faith in their alternator's rating and ability yet have no idea of its temperature.
If one insists on idling parked to recharge, then one better be feeding some cold air to the alternator and not allowing it to ingest underhood heat. The back of my alternator is about 1.25 inches from the exhaust manifold of cyulinder number 2. A heat shield placed here had a huge effect on keeping the back of the alternator cooler.
Some people also put way too much faith in the designers, unaware the designers never intended for the alternator to be feeding a bank of depleted batteries so a van dweller can play on their laptop 8 hours each night and powering a fridge too. If engineers were to design vehicles and their alternators to charge large banks of depleted batteries the larger body alternator would be fed its own cold air tube and be located in the coolest part of the engine where the belt allows it to be mounted and its voltage regulation would be optimized for fast charging with higher voltages held longer, but also be able to throttle it way back if the alternator gets too hot.
Many automotive alternators have self protections built in, basically lowering voltage to the point the depleted battery is drowning with desire for higher amps, yet given a cocktail straw to breathe through.
The alternator can be tremendously effective in charging depleted batteries upto ~80% state of charge, when it is kept cool and told( by the voltage regulator) to produce enough amperage to maintain a high system voltage. Very Few are. A depleted battery can suck up 2/3 more amperage when 14.7v reaches the battery terminals compared to 13.6v. A battery above 80% charged can also suck up 1/2 to 2/3 more amperage at 14.7 than it can at 13.6v but that amperage number is a small fraction of the number when the battery is at 50%.
Lithium batteries can suck more amperage for longer than the best lead acid batteries, but thinking one's alternator is safe from overheating because they are using lead, not lithium, is unwise
I have a K type thermocouple adhered to my alternator casing. The K type thermocouple is what many digital multimeters come with. I have a unit which reads 4 K type thermocouples, and I have one on my alternator, voltaeg regulator, thermostat housing, upper radiator tank, and want one on my transmission output line and lower radiator hose and perhaps differential too.
No need to guess or hope. This time last year I was driving through Texas in cool weather, and my dash coolant temp gauge started reading higher and higher. The K type thermocouple on my T stat housing said temps were normal, and instead of stressing or assuming i was overheating or impending failure was near, I kept going without stress.
https://www.ebay.com/itm/4-Channel-K-Type-LCD-Digital-Thermometer-Thermocouple-Temperature-Sensor-Testers/143450426856?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3Dd3bd8cc4b02e465cb5d3bdc1298756de%26pid%3D100005%26rk%3D6%26rkt%3D12%26mehot%3Dco%26sd%3D264541486704%26itm%3D143450426856%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851
https://www.ebay.com/itm/Arctic-Alumina-Ceramic-Thermal-Adhesive-Epoxy-w-Application-Wand-5g/264501973708?epid=2254438459&hash=item3d958bd2cc:g:4vYAAOSwG8ldqJ6q
https://www.ebay.com/itm/1-FlexFix-Metallic-UL181B-FX-Listed-Film-Tape-48mm-X-109-7M-1-89in-X-120-yd/311786643419?epid=1409872181&hash=item4897ee9fdb:g:FBIAAOSwto5cyyvr
I cover the sensor tip of the thermocouple. which is thermo epoxied to the alternator casing, with 2 layers of reflectix held down with Nashua flexfix. Use rubbing alcohol beforehand to insure adhesion. The sensor reads about 12f higher under the reflectix insulation at 65mph. The rectifier inside the alternator would be a better location for the sensor, but I was not removing the alternator to get it in there.
Note, the amps they were producing, 96 on the one test, is well within what my single group 27 northstar AGM was able to consume when newer and healthy.
They also did not factor into the equation that the large drive pulley of an engine spins the small alternator pulley 5 to 7 times faster than engine rpm. They were using an electric motor whose pulley was nearly the same as the alternator pulley, for nearly a 1 to 1 ratio .
But their points and conclusions are very valid, low rpm the alternator might be able to make a lot of amps still, but it cannot dissipate the heat it generates and can burn itself out if it has no current limiting function/ ability.
While my single group 27 northstar, when it was new and well depleted, could suck up perhaps 96 amps for 10 minutes before that number would start tapering, a larger bank of AGMs and of course Lithiums, could suck up that much amperage, and much more, for much longer, creating much more opportunity to overheat and fry the alternator.
So many people think a huge alternator rating means it can always output that much current at almost any rpm, but in reality that is the absolute maximum it can produce spinning fast, when still cold, with huge loads capable of sucking up everything it can make.
Idling to recharge is unwise. More engine rpm not only makes more amperage, but keeps the alternator much cooler, not only as the alternators fan is cooler but the vehicle movement means the alternator is not ingesting 200F + air, but much cooler air instead. is a high idle enough to keep the alternator cooler, or is the high idle simply to allow the alternator to make more amps, or some degree of both.....Without data any declaration is conjecture, and useless opinion.
I don't carry much battery capacity but that which I do is a TPPL AGM which is a very low resistance lead acid battery, and it can and does suck up everything my alternator can make when it is well discharged, and my alternator gets hot fast, if I am idling, and it can only make 50 amps at 550 hot engine rpm and about 75 amps at 800, it can't make its 120 amp rating until about 2250 engine rpm, and cruising at 65mph in overdrive is ~1975 rpm.
12.2 amps are required to run just my ignition and fuel pump. The field current sent to the alternator can be as high as 8 to 10 amps when fully fielded, so in order to make alternator amps, 20+ of those are already spoken for, the rest goto loads, and a depleted battery is a big load. A big bank of depleted batteries, not just lithium, is a big load and can overheat alternators easily, especially alternators capable of high amperage rates at idle speeds with owners who place too much faith in their alternator's rating and ability yet have no idea of its temperature.
If one insists on idling parked to recharge, then one better be feeding some cold air to the alternator and not allowing it to ingest underhood heat. The back of my alternator is about 1.25 inches from the exhaust manifold of cyulinder number 2. A heat shield placed here had a huge effect on keeping the back of the alternator cooler.
Some people also put way too much faith in the designers, unaware the designers never intended for the alternator to be feeding a bank of depleted batteries so a van dweller can play on their laptop 8 hours each night and powering a fridge too. If engineers were to design vehicles and their alternators to charge large banks of depleted batteries the larger body alternator would be fed its own cold air tube and be located in the coolest part of the engine where the belt allows it to be mounted and its voltage regulation would be optimized for fast charging with higher voltages held longer, but also be able to throttle it way back if the alternator gets too hot.
Many automotive alternators have self protections built in, basically lowering voltage to the point the depleted battery is drowning with desire for higher amps, yet given a cocktail straw to breathe through.
The alternator can be tremendously effective in charging depleted batteries upto ~80% state of charge, when it is kept cool and told( by the voltage regulator) to produce enough amperage to maintain a high system voltage. Very Few are. A depleted battery can suck up 2/3 more amperage when 14.7v reaches the battery terminals compared to 13.6v. A battery above 80% charged can also suck up 1/2 to 2/3 more amperage at 14.7 than it can at 13.6v but that amperage number is a small fraction of the number when the battery is at 50%.
Lithium batteries can suck more amperage for longer than the best lead acid batteries, but thinking one's alternator is safe from overheating because they are using lead, not lithium, is unwise
I have a K type thermocouple adhered to my alternator casing. The K type thermocouple is what many digital multimeters come with. I have a unit which reads 4 K type thermocouples, and I have one on my alternator, voltaeg regulator, thermostat housing, upper radiator tank, and want one on my transmission output line and lower radiator hose and perhaps differential too.
No need to guess or hope. This time last year I was driving through Texas in cool weather, and my dash coolant temp gauge started reading higher and higher. The K type thermocouple on my T stat housing said temps were normal, and instead of stressing or assuming i was overheating or impending failure was near, I kept going without stress.
https://www.ebay.com/itm/4-Channel-K-Type-LCD-Digital-Thermometer-Thermocouple-Temperature-Sensor-Testers/143450426856?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3Dd3bd8cc4b02e465cb5d3bdc1298756de%26pid%3D100005%26rk%3D6%26rkt%3D12%26mehot%3Dco%26sd%3D264541486704%26itm%3D143450426856%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851
https://www.ebay.com/itm/Arctic-Alumina-Ceramic-Thermal-Adhesive-Epoxy-w-Application-Wand-5g/264501973708?epid=2254438459&hash=item3d958bd2cc:g:4vYAAOSwG8ldqJ6q
https://www.ebay.com/itm/1-FlexFix-Metallic-UL181B-FX-Listed-Film-Tape-48mm-X-109-7M-1-89in-X-120-yd/311786643419?epid=1409872181&hash=item4897ee9fdb:g:FBIAAOSwto5cyyvr
I cover the sensor tip of the thermocouple. which is thermo epoxied to the alternator casing, with 2 layers of reflectix held down with Nashua flexfix. Use rubbing alcohol beforehand to insure adhesion. The sensor reads about 12f higher under the reflectix insulation at 65mph. The rectifier inside the alternator would be a better location for the sensor, but I was not removing the alternator to get it in there.
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