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Old 24-01-2025, 13:56   #1
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LIFEPO4 Conversion. Alternator temperature monitoring

Gentlemen,
As I understand an alternator capacity is major bottleneck when charging house bank via Victron DC to DC charger/converter.
My alternator as dumb as it gets and I don't have access to it's specs right now.
I keep it and I have spare one.
Choosing between 30A and 50A. Leaning toward for extra $100 for 50A
I know I can configure to lower amperage throughout in configuration to stay on the safe side. The same time I want fully utilize charging capabilities.
I can use IR temp gun to take temp measurements.
I want to keep it as simple as possible to have simple ON/OFF swatch to isolate starter battery in case of alternator overheating. No relays, no automation.
Questions
Where on alternator honest points? What acceptable max temp?
Does it make sense to have more permanent solution with temp sensor and gauge?
Where and how to mount sensor? Share your ideas please.
Is alternator overheating is subject of engine RPM's?
Appreciated for your input.
Thank you.
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Old 24-01-2025, 14:29   #2
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Re: LIFEPO4 Conversion. Alternator temperature monitoring

I think that if you monitor your temperature with an IR gun, you will find that continuous monitoring and derating is not needed. Alternator temperature at constant output is definitely a function of engine RPM. If temperature exceeds 100 degrees C, try going to a fast idle.
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Old 24-01-2025, 14:34   #3
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Re: LIFEPO4 Conversion. Alternator temperature monitoring

Quote:
Originally Posted by donradcliffe View Post
I think that if you monitor your temperature with an IR gun, you will find that continuous monitoring and derating is not needed. Alternator temperature at constant output is definitely a function of engine RPM. If temperature exceeds 100 degrees C, try going to a fast idle.
Thank you. Could tell if LIFEPO4 house amperage draw is subject of current charge state? Or drawing amperage stays the same (to some degree of course)?
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Old 24-01-2025, 14:56   #4
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Re: LIFEPO4 Conversion. Alternator temperature monitoring

Quote:
Originally Posted by Ruso View Post
Thank you. Could tell if LIFEPO4 house amperage draw is subject of current charge state? Or drawing amperage stays the same (to some degree of course)?
With LFP, the Amperage mostly stays the same, and that will be the max output your system can supply, the LFP will take all of it. I think you plan to use a 50A DCDC and adjust it down is a good plan. The LFP will charge at whatever you set the DCDC to. The rule of thumb is 50% of what the alternator is rated, but for small alternators, I think you can go more than 50%

Example, a 120A alternator should be limited to ~60A. A 200A alternator about 100A. But, a 70A alternator could run at 50A, maybe even 60A(I run my 70A alternator at 60A). The reason is that the 70A and 120A have the same case and cooling capacity.
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Old 24-01-2025, 15:02   #5
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Re: LIFEPO4 Conversion. Alternator temperature monitoring

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Originally Posted by wholybee View Post
With LFP, the Amperage mostly stays the same, and that will be the max output your system can supply, the LFP will take all of it. I think you plan to use a 50A DCDC and adjust it down is a good plan. The LFP will charge at whatever you set the DCDC to. The rule of thumb is 50% of what the alternator is rated, but for small alternators, I think you can go more than 50%

Example, a 120A alternator should be limited to ~60A. A 200A alternator about 100A. But, a 70A alternator could run at 50A, maybe even 60A(I run my 70A alternator at 60A). The reason is that the 70A and 120A have the same case and cooling capacity.
Thank you. Now I suspect since existing configuration parallel lead start and house, I need review wiring to make sure it sustain high amperage. No way lead to lead can have 50A.
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Old 25-01-2025, 00:25   #6
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Re: LIFEPO4 Conversion. Alternator temperature monitoring

If you have a 115A Mitsubishi or similar Valeo alternator that reduces the charge current with temperature control, these can protect themselves from overheating. There may be other alternators that I have heard of that have the same feature. Dcdc 50A may be the simplest solution. If there is no battery isolator in the boat's electrical system to which at least one LA battery is connected, definitely use APD.
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Old 25-01-2025, 02:14   #7
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Re: LIFEPO4 Conversion. Alternator temperature monitoring

Quote:
Originally Posted by Ruso View Post
Gentlemen,
As I understand an alternator capacity is major bottleneck when charging house bank via Victron DC to DC charger/converter.
My alternator as dumb as it gets and I don't have access to it's specs right now.
I keep it and I have spare one.
Choosing between 30A and 50A. Leaning toward for extra $100 for 50A
I know I can configure to lower amperage throughout in configuration to stay on the safe side. The same time I want fully utilize charging capabilities.
I can use IR temp gun to take temp measurements.
I want to keep it as simple as possible to have simple ON/OFF swatch to isolate starter battery in case of alternator overheating. No relays, no automation.
Questions
Where on alternator honest points? What acceptable max temp?
Does it make sense to have more permanent solution with temp sensor and gauge?
Where and how to mount sensor? Share your ideas please.
Is alternator overheating is subject of engine RPM's?
Appreciated for your input.
Thank you.
Again ,but if you have mass production,original to engine alternator is not dumb. this alternator for example Mitsubishi 115A spend more money in design ,testing this alternator vs total valid company produced outside alternator.
if you charge Mitsubishi alternator on 600 rpm he lower down to 70-80A charge when temperature fise hi lower more charging current to 0 if needed. if in engine compartment over 160°C hi have 0 charging.

Also you must know modern diesel engine want be around 90°C some need working temperature around 96°C
Generally, the operating temperature of an diesel engine should be between 190-220 F degrees

alternator have working temperature 60-150°C some over 200°C

if you have dubt on market you have lot water cooled alternator 100-200A your engine is around 85-90°C buy this 20-100 cm pipe and don't worry.
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Old 25-01-2025, 09:23   #8
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Re: LIFEPO4 Conversion. Alternator temperature monitoring

Quote:
Originally Posted by SOLAR SUPPORT View Post
If you have a 115A Mitsubishi or similar Valeo alternator that reduces the charge current with temperature control, these can protect themselves from overheating. There may be other alternators that I have heard of that have the same feature. Dcdc 50A may be the simplest solution. If there is no battery isolator in the boat's electrical system to which at least one LA battery is connected, definitely use APD.
Thank you. I don't know if it can be called "isolator" I have something that disconnects house bank circuits during starter engagement. I believe it is Blue Sea Starting Isolation Dual Sensing Automatic Charging Relay
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Old 25-01-2025, 09:33   #9
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Re: LIFEPO4 Conversion. Alternator temperature monitoring

Thank you for input.
I probably should mention the engine is Perkins 4.108. The alternator definitively is not original - looks pretty fresh. I guess I have to play with IR temp gun and slowly jack up amperage on DCtoDC charger.
I hope the alternator max operational temp can be found based on model and brand.


Quote:
Originally Posted by more View Post
Again ,but if you have mass production,original to engine alternator is not dumb. this alternator for example Mitsubishi 115A spend more money in design ,testing this alternator vs total valid company produced outside alternator.
if you charge Mitsubishi alternator on 600 rpm he lower down to 70-80A charge when temperature fise hi lower more charging current to 0 if needed. if in engine compartment over 160°C hi have 0 charging.

Also you must know modern diesel engine want be around 90°C some need working temperature around 96°C
Generally, the operating temperature of an diesel engine should be between 190-220 F degrees

alternator have working temperature 60-150°C some over 200°C

if you have dubt on market you have lot water cooled alternator 100-200A your engine is around 85-90°C buy this 20-100 cm pipe and don't worry.
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