Can I Put a Lower Amp Alternator on My Car

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25-10-2021, 08:08	#46
Registered User Join Date: Sep 2008 Location: Camden, ME Boat: A Thistle and a Hallberg-Rassy 36 Posts: 802	Re: Water cooled, high amp 12v alternator I think your calculations are correct. Rectifier losses are not large compared to an alternator that is only 50% efficient. There are alternators with efficiencies close to 75%, but I know nothing about them.

25-10-2021, 12:28	#47
Registered User Join Date: Mar 2021 Location: Flagler County, FL, USA, Earth Boat: Lagoon 380 Posts: 243	Water cooled, high amp 12v alternator Dont forget that there are 6 power diodes wired to a three phase winding set. The current thru the diodes is highly time variant thru the revolution cycle of the rotor. Other losses: windage, bearing friction, the entire field current, plus I sq R of the 3 phase windings. And, we havent left the inside of the case yet.

25-10-2021, 13:47	#48
Nearly an old salt Join Date: Jun 2009 Location: Lefkas Marina ,Greece Boat: Bavaria 36 Posts: 16,671 Images: 3	Re: Water cooled, high amp 12v alternator There are 4 major heat sources 1. IsquarecR winding losses 2. Dissipation in the diode trio 3. Regulator dissipation 4. Mechanical friction Moving 2. & 3 to external locations helps a lot __________________ Interested in smart boat technology, networking and all things tech

25-10-2021, 14:00	#49
Registered User Join Date: Jul 2016 Location: East Coast USA Boat: Boatless at the moment Posts: 842	Re: Water cooled, high amp 12v alternator Wouldn't #2 be the bridge rectifier rather than the diode trio?

25-10-2021, 14:04	#50
Registered User Join Date: Apr 2012 Posts: 73	Re: Water cooled, high amp 12v alternator Has anyone tried electrodyne alternators?

25-10-2021, 14:21	#51
Registered User Join Date: Mar 2021 Location: Flagler County, FL, USA, Earth Boat: Lagoon 380 Posts: 243	Water cooled, high amp 12v alternator The diode trio doesnt deal with much current. OTOH, those other 6 do the heavy lifting. Although, ALL the power going thru the diode trio ends up heating the field winding.

25-10-2021, 14:27	#52
Nearly an old salt Join Date: Jun 2009 Location: Lefkas Marina ,Greece Boat: Bavaria 36 Posts: 16,671 Images: 3	Re: Water cooled, high amp 12v alternator Quote: Originally Posted by kenbo Wouldn't #2 be the bridge rectifier rather than the diode trio? Sorry yes a meant to put the trio with the regulator __________________ Interested in smart boat technology, networking and all things tech

25-10-2021, 16:50	#53
Registered User Join Date: Feb 2017 Location: Germany Boat: Moody 34 Posts: 24	Re: Water cooled, high amp 12v alternator Alternators have changed in last 10 years. All the fancy regulators like the Balmar are already incorporated into most modern generators. https://www.bosch-motorsport.com/con...tor_B3_LIN.pdf This one is an example for a racing car and already a few years old. As you see it�s controlled by the LIN Bus. Most cars today are controlled by LIN Bus, With Lifepo4 its difficult to limit the charge current...my problem at moment. That's why I �m looking for another alternator. The big loss on the rectifier diodes is no more true either. It has all changed. Temperatur is 85 degrees... Belt manager is done by the controller. Look at the Lin commands. The big companies are focused on read the application careful. Somebody needs to build a small box with a micro to do the controlling. The special companies are all focused on the RV market, boating is only a small market. My french car has a small alternator ...since it�s a diesel and heating is electric, the generator has to produce a lot of Amps. At the moment I use a DC-Dc to charge the Lithium....next project is a different alternator for the boat.

26-10-2021, 03:28	#54
Registered User Join Date: Apr 2021 Posts: 61	Re: Water cooled, high amp 12v alternator Quote: Originally Posted by Dan Kimblad It's true that moving the rectifier externally is much easier and will certainly lower the temperature. I have not thought about that, but how much lower will the temp be? If we have bad diodes that have 0.7 volts in drip, it will be 70 watts at 100 Amp (please correct me if I am wrong about this). [...] I often read about alternators running much cooler after the rectifier has been removed and mounted externally, yet as you show the math doesn't really work out unless the alternator would be a very efficient one, in which case it would run cool anyway I guess. I wonder whether removing the internal rectifier greatly improves the airflow through the back of the alternator, thereby lowering the temperature for the same output current simply by improving the ventilation?

26-10-2021, 03:32	#55
Registered User Join Date: Apr 2021 Posts: 61	Re: Water cooled, high amp 12v alternator Quote: Originally Posted by baltic sailor Alternators have changed in last 10 years. All the fancy regulators like the Balmar are already incorporated into most modern generators. https://www.bosch-motorsport.com/con...tor_B3_LIN.pdf This one is an example for a racing car and already a few years old. As you see it�s controlled by the LIN Bus. Most cars today are controlled by LIN Bus, [...] Hmm, the datasheet mentions "Typical lifetime before service: max. 6,000 km / 30 h". I hope that 30 h lifetime is a typo, or does it mean something else?

26-10-2021, 05:01	#56
Registered User Join Date: Mar 2021 Location: Flagler County, FL, USA, Earth Boat: Lagoon 380 Posts: 243	Re: Water cooled, high amp 12v alternator The problem statement, as I see it, is that automotive/racing alt. designs optimize size, weight, and cost over efficiency. Yes, the regulators are now "smart", or at least controllable. However, these rather horrendous efficiencies are due to small stator wire. Yes, they can push tremendous currents, for a while, with the ubiquitous 3 phase windings with high air flows. But, if you compare a 3 phase induction motor rated at 200 Amp INPUT, with a lightweight alternator rated at 200 Amp OUTPUT, there are huge differences in copper wire size. A motor runs at near 90% efficiency, a number that alternators are not even close to. One thing that will very much help is going away from 12V and towards 48V. Now, you have 4x the energy conversion with similar copper losses. Its this low voltage demand that makes this a difficult problem to engineer around.

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Can I Put a Lower Amp Alternator on My Car

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