Remove the alternator - crazy idea?

[Rohan]

If I understand correctly, seems like largest issue when switching to LiFeP0 from LA batteries is the alternator. You don't want it to burn out trying to charge lithium batteries, and you don't the BMS to kick in and cause a sudden overload.

So there are various solutions, like installing a temperature monitor, or a timer, or hook up to LA batteries and use a DC to DC charger.

Instead, has anyone considered a less complicated solution - getting rid of the alternator entirely? After all, your typical marine diesel engine doesn't use spark plugs, so you don't need a constant flow of electricity for that. You still need electricity for your gauges, lights, and things, but any halfway decent batteries can run those for weeks without a problem.

On top of that, people who made the switch to electric engines don't have alternators for obvious reasons. They rely on solar or a generator to charge the batteries if needed.

If I did this, I suppose I would still need a shell of an alternator to keep proper tension on the belts, but that wouldn't be a big deal.

Thoughts?

[Kettlewell]

I think I would keep the alternator and just hook it up to a regular flooded or AGM starting battery, and keep the LiFePO house battery system separate most of the time. A battery switch or two could allow you to start the engine with the house batteries if needed. The alternator could come in handy as a alternate charging source when/if you have some failure in your house battery charging system.

[s/v Jedi]

Originally Posted by Rohan

If I understand correctly, seems like largest issue when switching to LiFeP0 from LA batteries is the alternator. You don't want it to burn out trying to charge lithium batteries, and you don't the BMS to kick in and cause a sudden overload.

So there are various solutions, like installing a temperature monitor, or a timer, or hook up to LA batteries and use a DC to DC charger.

Instead, has anyone considered a less complicated solution - getting rid of the alternator entirely? After all, your typical marine diesel engine doesn't use spark plugs, so you don't need a constant flow of electricity for that. You still need electricity for your gauges, lights, and things, but any halfway decent batteries can run those for weeks without a problem.

On top of that, people who made the switch to electric engines don't have alternators for obvious reasons. They rely on solar or a generator to charge the engine if needed.

If I did this, I suppose I would still need a shell of an alternator to keep proper tension on the belts, but that wouldn't be a big deal.

Thoughts?

I’m afraid you missed the need for electric power to the starter motor but when your house battery is big enough it can do this too.

My 4LH Yanmar had three alternators: the oem 80A one charging the start battery and two huge Lestec 225A alternators, 450A total, to charge the house bank. Imagine the size and weight of the brackets. It didn’t end there, there was also an engine driven crash pump connected to it, weighing even more than one of those alternators.

So I removed the pump, removed all three alternators and every bracket related to this, as well as the extra pulleys. Then I installed the Balmar conversion pulleys to a serpentine belt and their 170A alternator with tensioner etc.
This simply charges a 12V Odyssey TPPL AGM battery that is used for starting and other 12V loads like powered winches.

As we don’t use the engine often, I also have dc-dc converters to keep the 12V powered and the battery is just to assist with peak loads.

[SailingHarmonie]

You don't need to change anything mechanical to try it and see if it works for you. Just disable the field current, and your existing alternator will free-wheel. Just do it. If you find live without an alternator doesn't work out, just reconnect it.

If you can make all the power you need from other sources, there is nothing magic about having an alternator.

Without knowing in gory detail your energy budget on both the consumption and generation side, as well as your current use of the boat, and long term plans, your question is impossible to answer for your specific case.

[Kettlewell]

Alternators will last for many years if they are mainly used to charge the starting battery. The one on my engine is a standard automotive type and has been running reliably for more than 10 years, and when I need a new one I can either get it rebuilt cheaply or pick up one at an auto parts store. I like having dedicated starting battery that I know is always topped up and ready to go no matter what the state of charge of the house batteries.

[FlyingScot]

You don't need an alternator, but:
You still need to start the engine.
You still need to power the engine room blower, if applicable.
Adding small incremental loads to a diesel is practically free from fuel & wear and tear prespective.
Do you really want to give up the ability to make power if/when your other sources fail to provide all you need?

I've set up our boat so that if the main house battery goes down, I can power the entire boat from either engine (catamaran). Msybe it's overkill, but it is hard to have too many ways to make power.

[Jammer]

Few monohulls have sufficient solar capacity to provide ongoing electrical needs particularly in unfavorable conditions -- where you are that's late in the season when the days are short and it is common to get several cloudy days back to back. Unless you're willing to accept a mandatory unplanned overnight stop at a marina to charge batteries, you need another power source.


It's great to have an alternator when motoring at night or in the fog, when the autopilot, radar, and chartplotter are likely in use.


The exception would be those boats that have a large stern arch with many full-sized panels. If that's you, great. If not, realize that there are tradeoffs, mainly windage.

[hjohnson]

It all comes down to your use case. If you’re just using the boat for day sailing/around the cans racing, or are the kind of person who goes from marina to marina, then getting rid of the alternator in its entirety can be done.

My boat is an Ericson 27, so not much room for solar, and we like going on multi day adventures off the grid in the winter in the Salish Sea. This pretty much necessitates alternator charging. Even in the height of summer, when we can lay out the portable solar panel, we only get about 300W of power. That’s good to extend our power by about 25%.

So yeah, for us, alternator charging is vital. Also, because we are sticking a large alternator (85A Hitachi) on a small motor (Yanmar 1GM10), we make full use out of the extra control coming from the wakespeed.

[sailingharry]

If this is driven by a discussion about lfp, and it sounds like it, then you may be missing an important fact. Lfp does not generate power. You can't drop in lfp and suddenly have all your power needs met. Lfp is a great storage medium, the 100% of the power that you take out has to be put back. If you survived with your lead batteries with solar and shore power, you will survive with l&p without an alternator. If you needed the alternator to make up your power deficit with lead batteries, you will continue to have that problem with lfp.

There is a small caveat to my statement above. Lfp doesn't have the taper off that lead does. So you do get slightly more effective use of your charging sources. This is especially notable with regards to an alternator (I have 278 of alternators), you can spend hours getting the last five to 10% into the battery.

[noelex 77]

The difficulty on a cruising sailboat is primarily related to generating rather than storing electrical energy. Removing one source of energy generation is a backwards step.

The problem with the BMS potentially suddenly disconnecting the batteries is not just related to the alternator. It can cause problems with other electronics and charge sources such as solar. There are also issues disconnecting important electronic devices at potentially inopportune times.

It requires a systemic approach rather than just removing the alternator.

[Bowdrie]

Originally Posted by hjohnson

It all comes down to your use case. If you’re just using the boat for day sailing/around the cans racing, or are the kind of person who goes from marina to marina, then getting rid of the alternator in its entirety can be done.

Sure thing, and for that usage the OP may as well remove all the anchors and related gear, it weighs a lot.
On shore he could eliminate the spare tire in his vehicle, after all, how often do you need it?
On boats it's not wise to put all your eggs in only one basket, (like solar).
The engine has an alternator, even if you up-grade it the additional gizmos/devices that ensure its survival is money well spent.

[The Yacht Rigger]

Or you could go the other direction, since you'll have a lithium system, and really maximize your charge rates, and also be able to just turn off the alternator when you wish to... like this setup. https://youtu.be/_XM4W0enlzg?si=zHEqWYonwesuy4Iz

[smac999]

Nobody would ever use a lithuim as a start battery.

So your simple solution is keep the alt going to the flooded / agm start battery. And don’t charge the house from the engine. Dock or solar only….

Buts that’s silly. From That point Just add a dc to dc from start to house batt. at least you get some power from engine. Still simple and safe.

[Karanga]

Originally Posted by smac999

Nobody would ever use a lithuim as a start battery.



So your simple solution is keep the alt going to the flooded / agm start battery. And don’t charge the house from the engine. Dock or solar only….



Buts that’s silly. From That point Just add a dc to dc from start to house batt. at least you get some power from engine. Still simple and safe.

The cat I bought 2 years ago had/has no start batteries. Professional setup. Only 4 x 125 ahr lithium house plus start batteries. Charging is solar and alternators. There is also one AGM aux battery that can be switched to, charging by dc2dc from the lithium.
Jus' sayin'...

[Fuss]

Originally Posted by smac999

Nobody would ever use a lithuim as a start battery.

So your simple solution is keep the alt going to the flooded / agm start battery. And don’t charge the house from the engine. Dock or solar only….

Buts that’s silly. From That point Just add a dc to dc from start to house batt. at least you get some power from engine. Still simple and safe.

why wouldn't they use lithium for starting?