LFP alternator charge, LA-dc2dc in which order

[SOLAR SUPPORT]

You can find the schematic below.

Should the existing battery isolator be used or replaced or cancelled? If it is to be replaced, what type of insulator should be used, argofed or mechanical?

[Pete7]

You seem to asking a lot of different questions, the last one was 48v.

Are you asking because you plan to fit this stuff on your yacht? or is there another reason? After all given your commercial interests, I suspect you know the answer to the questions before posting them.

Pete

[SOLAR SUPPORT]

Originally Posted by Pete7

You seem to asking a lot of different questions, the last one was 48v.

Are you asking because you plan to fit this stuff on your yacht? or is there another reason? After all given your commercial interests, I suspect you know the answer to the questions before posting them.

Pete

It is up to you to decide whether to keep what you know to yourself or share it with others. It shouldn't bother you that people talk about the issues they are curious about and open a topic to reach the most accurate and safe solutions. I have to point it out because you asked. I have no personal commercial interest in these matters.

This is not a solution that I personally prefer and apply to charge my LFP batteries with an alternator. But it occupies my mind. I have read many discussion threads on this subject but the answers were not very clear. It's an issue that might come up in front of me, maybe in the future. It's a very common solution, but is the implementation standard fully established or is everyone following a different path?

[CaptainRivet]

Originally Posted by SOLAR SUPPORT

You can find the schematic below.

Should the existing battery isolator be used or replaced or cancelled? If it is to be replaced, what type of insulator should be used, argofed or mechanical?

Simple answer:
If you need the DC2DC to limit current for your alternator and/or your alternator has no temp protection/regulation then it’s number C

If your alternator has temp protection like Mitzi 115A then use an argofet due to less voltage drop and solution A where you can leave away the DC2DC. Argofet with lead supply’s cut off protection and your LFP gets charged by what your alternator can do.

Never B, no mechanical on a boat.

[s/v Jedi]

I think what people are wondering is if the questions you ask is for your work on customer boats. This sounds weird because one would expect you as the pro to provide those answers.

[SOLAR SUPPORT]

Originally Posted by s/v Jedi

I think what people are wondering is if the questions you ask is for your work on customer boats. This sounds weird because one would expect you as the pro to provide those answers.

My profession and education is not on electricity, but Mec. Eng. I am constantly improving my knowledge about solar energy and Lifepo4 batteries, which are in my field of interest, to be useful to myself and those around me. I've installed SS rollbars and solar power systems on a dozen or so boats. But that's not my main job.

So I am not a professional electrician but I have an idea of ​​what exactly the safest solution is on this thread, but; I want to make sure of that.

[SOLAR SUPPORT]

Originally Posted by CaptainRivet

Simple answer:
If you need the DC2DC to limit current for your alternator and/or your alternator has no temp protection/regulation then it’s number C

If your alternator has temp protection like Mitzi 115A then use an argofet due to less voltage drop and solution A where you can leave away the DC2DC. Argofet with lead supply’s cut off protection and your LFP gets charged by what your alternator can do.

Never B, no mechanical on a boat.

CaptainRivet I was hoping you understood that my alternator is indeed the original Mitsubishi 115A. Of course, the thermal current reducer of my alternator is also working.

I just don't find it right that the alternator is exposed to high current charging and extreme heat with direct Lifepo4 battery charging. As an alternator designed for LA batteries, maybe when the large LA battery pack works with the decreasing charge current strength over time.

The overheating alternator also causes the sound-insulated engine room to overheat. Periodically check the seawater filter pans in the engine room. Although I cooled the engine room and alternator using fans, the plastic container of the seawater filter was affected by excessive heat, and its regular shape was slightly distorted.

Therefore, the cooling water circuit took air, reducing the flow rate of the pump and not cooling the engine sufficiently. I've experienced this myself, and luckily I realized it before it was too late.

As for the main discussion point, dc2dc is present in all the options in the diagram. I'm trying to understand the following scenario for option [A]:

When the BMS in the drop-in LFP battery triggers the HvCutoff event when the alternator is charging it, can the extremely high voltage spike in the alternator be absorbed by the LA battery that is currently full? How does the isolator diode behave during this time?

[s/v Jedi]

Originally Posted by SOLAR SUPPORT

My profession and education is not on electricity, but Mec. Eng. I am constantly improving my knowledge about solar energy and Lifepo4 batteries, which are in my field of interest, to be useful to myself and those around me. I've installed SS rollbars and solar power systems on a dozen or so boats. But that's not my main job.

So I am not a professional electrician but I have an idea of ​​what exactly the safest solution is on this thread, but; I want to make sure of that.

Ah okay! So “support” in Solar Support stands for the mounting frame for solar panels?!

The problem with your diagrams is that I don’t understand them. I can’t see the difference between A and B except for some letters that I don’t know the meaning of.

In general, if a LA battery is connected to the alternator directly, with dc-dc converter connected as well, then there is no problem even if the LA battery is fully charged.

Also, when there is an isolator installed, they say things will be okay even though the voltage transient can be higher than the rating of diodes or MOSFET’s. I can’t confirm from personal experience though.

[goboatingnow]

I’m not sure why these questions come up repeatedly

The first thing that needs to be decided

1. Is it your primary desire to charge your LFP bank from your alternators

If you’re answer is yes then yiu mist desl with two issues

1.1can you limit the current from the alternators so as to ensure they are onto oberlosded y the LFP bsnk
1.1 can your alternator cope with the unexpected hvhbcurrebt disconnect ( called load dumps) without spiking

If 1.1 -2 is in within ability , there yiu are basically setup to connec5 your alternator to your LFP battery

If it’s not there a series of steps some are kludged in my opinion which can mitigate the problems , but they are poor workarounds and no alternative to,a properly designed solution

[s/v Jedi]

Originally Posted by goboatingnow

I’m not sure why these questions come up repeatedly

The first thing that needs to be decided

1. Is it your primary desire to charge your LFP bank from your alternators

If you’re answer is yes then yiu mist desl with two issues

1.1can you limit the current from the alternators so as to ensure they are onto oberlosded y the LFP bsnk
1.1 can your alternator cope with the unexpected hvhbcurrebt disconnect ( called load dumps) without spiking

If 1.1 -2 is in within ability , there yiu are basically setup to connec5 your alternator to your LFP battery

If it’s not there a series of steps some are kludged in my opinion which can mitigate the problems , but they are poor workarounds and no alternative to,a properly designed solution

I have oberlosded my hvhbcurrebt but 1.1.2 and yiu mist desl !

1.1 !

[SOLAR SUPPORT]

Originally Posted by s/v Jedi

I have oberlosded my hvhbcurrebt but 1.1.2 and yiu mist desl !

1.1 !

Could he have written while drunk? 😂

[SOLAR SUPPORT]

Regarding the schema:

ALT : Alternator

LA : Lead acid battery

dc2dc : dc to dc charger

LFP : Lifepo4 battery

ArgBI : Argofet battery isolator

MecBI : Mechanical battery isolator

[s/v Jedi]

Originally Posted by SOLAR SUPPORT

Regarding the schema:

ALT : Alternator

LA : Lead acid battery

dc2dc : dc to dc charger

LFP : Lifepo4 battery

ArgBI : Argofet battery isolator

MecBI : Mechanical battery isolator

A, B and C work but the unknown is the alternator and the regulator.

[SOLAR SUPPORT]

Originally Posted by s/v Jedi

A, B and C work but the unknown is the alternator and the regulator.

Mitsubishi 115A original alternator. It can be any alternator which is not modified and works with its internal regulator. Drop-in LFP batteries with their individual bms inside the box. Solar energy, ac-dc charger, inverter are not exist.

[goboatingnow]

Alternator direct d dc to lfps is entirely doable provided the dc dc is speced properly and the alternator has a protected output for security many modern alternators already do.

The alternator can protected by using the dc dc settings appropriately. A low cost dc dc can then be used to charge the starter if needed.

This solution ca be quite reasonable also.