LiFePO4 reference diagram, Alternator version

[s/v Jedi]

Here is my version that makes the alternator a major charge source, meaning that it charges the LFP batteries directly rather than via a dc-dc converter.

The alternator shown can be the oem alternator or an additional alternator. I have left both dc-dc converters as well, so if this is the only alternator, you can simply keep the start batteries in float using the dc-dc converter.

You need an alternator that outputs the voltage of the LFP batteries. You also need an external regulator that has a charge profile for LFP chemistry as well as a temperature sensor on the alternator to prevent overheating the alternator. Balmar makes this, so I chose their images (and it's what I have).

There is an ON/OFF battery switch to disconnect the alternator. This is used when working on the engine, to prevent a short (Rod Collins recommendation).

I show a fuse on the LFP busbar but I am not sure if there needs to be a second fuse at the alternator. Let me know if this is required and I'll add it.

In real life, for the regulator B+ wire, I would use a fuse position in the fusebox that is connected to the busbar, but in the diagram it is all the way down, too far away from the relays for clarity.

Now comes the tricky part: you need to shut down alternator charging before a BMS disconnects the battery. If you don't, the rectifier diodes in the alternators will burn out. The documentation of the alternator regulator will show how to have it shut down the field current, which stops the charging. In the case of Balmar, they recommend the brown ignition wire, but also allow using the red B+ wire for rare cases where it is crucial that the alternator stops charging, so I use the red B+ wire in the diagram.

For each BMS you now need to add a relay with a NC (normally connected) contact (the blue thingies near the BMS's). The coil of the relay is energized by the warning signal from the BMS. The regulator B+ wire starts with a fuse at the busbar and from there has to go through the BMS controlled relays. Now you can choose between two options: I show the relays to be in series, which means that charging stops when any one BMS raises the warning. You can also put them in parallel, which means that charging continues, which will probably trigger a HVC of the battery that triggered the warning before. This doesn't damage the diodes yet because there is a second battery still online, which didn't warn yet. I find my shown method the preferred option because you need to try to prevent a HVC, which it does.

That's it, not difficult but of course you need to run the ICE (internal combustion engine) to charge the battery.

[newhaul]

Originally Posted by s/v Jedi

Here is my version that makes the alternator a major charge source, meaning that it charges the LFP batteries directly rather than via a dc-dc converter.

The alternator shown can be the oem alternator or an additional alternator. I have left both dc-dc converters as well, so if this is the only alternator, you can simply keep the start batteries in float using the dc-dc converter.

You need an alternator that outputs the voltage of the LFP batteries. You also need an external regulator that has a charge profile for LFP chemistry as well as a temperature sensor on the alternator to prevent overheating the alternator. Balmar makes this, so I chose their images (and it's what I have).

There is an ON/OFF battery switch to disconnect the alternator. This is used when working on the engine, to prevent a short (Rod Collins recommendation).

I show a fuse on the LFP busbar but I am not sure if there needs to be a second fuse at the alternator. Let me know if this is required and I'll add it.

In real life, for the regulator B+ wire, I would use a fuse position in the fusebox that is connected to the busbar, but in the diagram it is all the way down, too far away from the relays for clarity.

Now comes the tricky part: you need to shut down alternator charging before a BMS disconnects the battery. If you don't, the rectifier diodes in the alternators will burn out. The documentation of the alternator regulator will show how to have it shut down the field current, which stops the charging. In the case of Balmar, they recommend the brown ignition wire, but also allow using the red B+ wire for rare cases where it is crucial that the alternator stops charging, so I use the red B+ wire in the diagram.

For each BMS you now need to add a relay with a NC (normally connected) contact (the blue thingies near the BMS's). The coil of the relay is energized by the warning signal from the BMS. The regulator B+ wire starts with a fuse at the busbar and from there has to go through the BMS controlled relays. Now you can choose between two options: I show the relays to be in series, which means that charging stops when any one BMS raises the warning. You can also put them in parallel, which means that charging continues, which will probably trigger a HVC of the battery that triggered the warning before. This doesn't damage the diodes yet because there is a second battery still online, which didn't warn yet. I find my shown method the preferred option because you need to try to prevent a HVC, which it does.

That's it, not difficult but of course you need to run the ICE (internal combustion engine) to charge the battery.

Looks similar to my system just one question why is the positive fused on both sides of the dc to dc converters?

[s/v Jedi]

Originally Posted by newhaul

Looks similar to my system just one question why is the positive fused on both sides of the dc to dc converters?

Because it is required as it has a battery connected at both sides. It’s configured as a dc-dc charger.

[s/v Jedi]

Who knows how ABYC wants to see fuses for an alternator? Just at the battery/busbar or also one at the alternator?

[Sailmonkey]

Originally Posted by s/v Jedi

Who knows how ABYC wants to see fuses for an alternator? Just at the battery/busbar or also one at the alternator?

As the alternator is a current limited device, if the conductor is sized properly only the battery end need be fused.

[newhaul]

Originally Posted by s/v Jedi

Who knows how ABYC wants to see fuses for an alternator? Just at the battery/busbar or also one at the alternator?

The ABYC writeup just a recommendation not a requirement. But I don't sail in a nanny state area.

[s/v Jedi]

Originally Posted by Sailmonkey

As the alternator is a current limited device, if the conductor is sized properly only the battery end need be fused.

Great so the diagram is good to go, no changes needed

[s/v Jedi]

Originally Posted by newhaul

The ABYC writeup just a recommendation not a requirement. But I don't sail in a nanny state area.

It’s tricky around the main engine. When you keep the wiring as delivered by oem, you don’t need any fuse or switch, but when you separate starter from alternator I think you must and I agree with it. I have short circuited it while working on the engine, replacing the belt.

[Baronkrak]

Originally Posted by s/v Jedi

Great so the diagram is good to go, no changes needed

The Reference Diagram at post 1. How do you recharge a battery if the battery is load disconnected?

[s/v Jedi]

Originally Posted by Baronkrak

The Reference Diagram at post 1. How do you recharge a battery if the battery is load disconnected?

There is no load disconnect. Please don’t start the same arguments again, do it in the thread you already filled up with it.

[zurk]

you shouldnt do it this way. i posted a diagram of mine in the other thread. look at it.

[s/v Jedi]

Originally Posted by zurk

you shouldnt do it this way. i posted a diagram of mine in the other thread. look at it.

These are my reference diagrams. There are threads with two other options.

[zurk]

Originally Posted by s/v Jedi

These are my reference diagrams. There are threads with two other options.

what im trying to tell you is you should not do it the way you are doing it. look at the way i did it - i posted it to the last page of your big thread.
people are telling you this is not the way. but somehow you think this is the way. understand why the way youre doing it is not correct by looking at the difference between the two diagrams - yours and mine.

[s/v Jedi]

Originally Posted by zurk

what im trying to tell you is you should not do it the way you are doing it. look at the way i did it - i posted it to the last page of your big thread.
people are telling you this is not the way. but somehow you think this is the way. understand why the way youre doing it is not correct by looking at the difference between the two diagrams - yours and mine.

I hear what you are telling me, but you should post your diagram in your own thread, where we can discuss it and I can tell you everything that is wrong about it.

The diagrams that I post here are correct and in successful use by countless boats. This is why I call it a reference diagram.

[zurk]

Originally Posted by s/v Jedi

I hear what you are telling me, but you should post your diagram in your own thread, where we can discuss it and I can tell you everything that is wrong about it.

The diagrams that I post here are correct and in successful use by countless boats. This is why I call it a reference diagram.

reference diagrams are supposed to be correct. yours has obvious flaws. mine is designed by an electrical engineer.