Alternator connected to starter WTH

[Wotname]

Just to clarify, while an alternator is a source, it does not need to fused at the alternator end providing the wire used is capable of carrying the maximum output current of the alternator.

Should one replace the short length #8 (between the alternator and starter motor) with a new lead from the alternator to the battery, it should be protected (fused etc) at the battery end (assuming the new wire is sized sufficiently large enough to carry the maximum alternator current as it should be).

An alternator is self limiting current device.

[sanibel sailor]

I had swapped my stock alternator for a 100A Balmar and regulator almost 10 years ago. Solar has advanced quite a bit since then and I am not sure that I would consider it- today- as money well spent. I have modest needs but solar alone is sufficient.



I suspect high output alternators are becoming less essential.

[mitiempo]

Originally Posted by OloteleMtn

I can't think of any reason for your alternator to be connected to your starter; the alternator would usually be connected to the battery via a wire harness, not taking power from the starter.

Engines from the factory have the alternator output connected to the starter. When installed the batteries, through the switch, are connected to the starter. This means that whichever battery you have selected on the switch will get its charge through the wiring from the alternator - starter - switch - battery. If you select the "all" position both banks get charged. If you forget
and leave the switch in the "all" position after the engine is stopped you will draw from all batteries and eventually drain both banks. If you turn the switch to the "off" position when the engine is running you will probably blow the diodes in the alternator.

The better way is to wire the alternator output (B+) to the house bank positive or its bus. Install either a combiner like the Blue Seas ACR or an EchoCharge between the house bank and the start battery to keep it charged. This changes the main switch from a selector/charge control to just a source selector that has no effect on charging, which becomes automatic.
All other charge sources - solar, shore power charger, etc should go to the house bank, always the bank most in need of charging.

[Charlie]

Originally Posted by smac999

I think your laz switch is drawn wrong. Likly the stater comes from the common. And the Batteries go to 1 and 2. Otherwise it is very strange.

The alternator is normal. And fine if you have a stock 50-60a alt.

I was thinking about this comment. It makes more sense for the common to be connected to the starter. I will need to trace the wires again to verify.

[CharlieJ]

#16 & #18: Spot on.

[capt jgw]

That's the way the engines come from the factory. That and the plug in wire harness with different lengths available make the engines much easier and quicker for the boat builder to install. One of the first mods that should be done on any brand new boat is to "fix" the engine wiring. Run a new heavy cable direct from the alt output to the house bank and an acr to charge the engine bank, and cut out the harness quick connects and trim the harness wires to the correct lengths.
I've repowered two different boats, both with used engines, and had to build my own harnesses. I've had none of these problems.

[seabreez]

Originally Posted by OloteleMtn

I can't think of any reason for your alternator to be connected to your starter; the alternator would usually be connected to the battery via a wire harness, not taking power from the starter.

Don't panic guys... the alternator is only connected there as a shortest path to the battery... not there to supply the starter.

[geoleo]

Originally Posted by Charlie

So the pandemic has given me time. I am trying to figure out and draw my electrical system. I just spent two hours in awkward positions before I realized that my 55 amp alternator is connected to my starter motor by a #8 wire. There is also a 1/0 cable that runs from the starter motor to a battery position switch (off, 1, 2, Com). The switch is connected to my house bank.

This has worked okay in the past but I am thinking the alternator connection should have a bigger wire, at the least.

Does connecting the alternator charging system through the starter make any difference?Attachment 216239

Probably 99% of all cars-boats -tractors - trucks are connected this way- its done so the charging current can flow to the battery thru the large cables used to connect the starter to the batteries...………..

[seabreez]

Originally Posted by OloteleMtn

I can't think of any reason for your alternator to be connected to your starter; the alternator would usually be connected to the battery via a wire harness, not taking power from the starter.

the connection to the starter is only a connection point and is usually the shortest path from the alternator to the batteries via the battery cables. Not to worry if this wire from the alternator is not fused. Now from the stater to your panel distribution you do have a fusible link in the wiring harness and wiring. 100% of cars are setup this way.... 95% of trucks are also setup this way and 95% of boats are setup this way. It is a very safe way to have this. Question me if you require more details... Roger

[Charlie]

Ran some more tracings and I stan by my drawing. Not saying it is the best. It is the way it is wired.

I am religious about turning the lazaret switch to off. I didn't once and it made it so I couldn't start my engine. I saw the light after that.

A problem with the way my boat is wired is that I have to start the engine with the batteries banks combined. If I turn the switch to 2 the start battery has no path to the starter. If I turn it to 1 the house bank starts the engine.

It would be easy(and free) to change the Com terminal to go to the starter. That would make it so I could start the engine with either the house or starter battery. But not both banks. I would need to leave it on Com in order to charge the system.

I am currently studying "How to Marine's" VSR wiring diagram to see how I can adapt it to my situation.

[rslifkin]

I wired my setup so that for my 2 engines, each one has a 1/2/both/off switch. That switch selects which of the 2 start batteries (or both) are used for that engine. Normally 1 battery per engine.

For house bank charging, there's an ACR on the engine side of each of those battery switches with an interlock to the ignitions. So when each engine is running and voltage is high enough, it parallels to the house bank to charge that. When you turn each engine off, it isolates immediately to protect the start batteries and also so that shore charging is independent for the start batteries and house bank.

There's also a 1/2/both/off switch for the generator that determines which of the 2 start batteries it uses. No manual switching required anywhere in normal use, only if a start battery fails. The house bank switch is just an on/off.

[Charlie]

I have drawn out my latest ideas for rewiring. This isn't the best in the world but I think it will be better. I intend to install a new bus bar and attach the following: 1)alternator output, 2)a connection to the "Both" terminal for the main battery banks, 3) Output to a Voltage sensing Relay, and Output to an On/Off switch that connects to the existing Lazaret switch.

If I am correct this will allow me to combine both bank when I turn the (N)switch on and leave the Lazaret switch on Both.

The existing House Banks have fuses. Let's assume they are the correct size but I will check.

I need to add fuses to protect the 1/0 wire from the reserve bank, both sides of the VSR, and probably one from the battery charger to the Both terminal of the switch, one to the new wire to the alternator. Is that all?

Please critique my diagram and let me know if the idea holds water.

[Uncle Bob]

Originally Posted by Charlie

I have drawn out my latest ideas for rewiring. This isn't the best in the world but I think it will be better. I intend to install a new bus bar and attach the following: 1)alternator output, 2)a connection to the "Both" terminal for the main battery banks, 3) Output to a Voltage sensing Relay, and Output to an On/Off switch that connects to the existing Lazaret switch.

If I am correct this will allow me to combine both bank when I turn the (N)switch on and leave the Lazaret switch on Both.

The existing House Banks have fuses. Let's assume they are the correct size but I will check.

I need to add fuses to protect the 1/0 wire from the reserve bank, both sides of the VSR, and probably one from the battery charger to the Both terminal of the switch, one to the new wire to the alternator. Is that all?

Please critique my diagram and let me know if the idea holds water.

Charlie, hi, I am a little confused, do you have a regular four position rotary switch, that is 1 2 both and off? if so then there are three connections on the back of the switch, one to each battery to select power source and one that connects the load. There is no both connection, that is within the switch and connects both batteries to the load.
On my boat I actually have two such switches, one supplies power to the engine and the other to the distribution panel. Each switch is connected to both battery banks enabling me to switch each to the selected bank without using the both function, which is there for emergency use if I suffer partial failure in both banks.
I also have a vsr that is wired to supply power to both banks while the engine is running.
The limited solar that I have fitted is run through a pwm controller (yes, old school ) that enables charging to both banks without combining them.
If I was doing the solar again I would go with an MPPT and an appropriate VSR.
Cheers

[mitiempo]

Originally Posted by Charlie

I have drawn out my latest ideas for rewiring. This isn't the best in the world but I think it will be better. I intend to install a new bus bar and attach the following: 1)alternator output, 2)a connection to the "Both" terminal for the main battery banks, 3) Output to a Voltage sensing Relay, and Output to an On/Off switch that connects to the existing Lazaret switch.

If I am correct this will allow me to combine both bank when I turn the (N)switch on and leave the Lazaret switch on Both.

The existing House Banks have fuses. Let's assume they are the correct size but I will check.

I need to add fuses to protect the 1/0 wire from the reserve bank, both sides of the VSR, and probably one from the battery charger to the Both terminal of the switch, one to the new wire to the alternator. Is that all?

Please critique my diagram and let me know if the idea holds water.

Wire the Iota charger to the charge bus - the VSR will ensure both banks are charged.

The 60 amp alternator should go to the start battery positive. Where is the other alternator? It should go to the charge bus as should the solar.

I would replace the 1/2/both switch with a simple on/off and parallel the 2 pair of 6 volts.

As Bob posted above there is not a "both" connection on the switch.

Yes the charger should have a fuse - 60 or 70 amp which is within the ampacity of #6 wire. The fuse should be just before the charge bus.

I do not understand the switch at the top of the schematic. As drawn it does nothing connected to a single bus. The starter is always live as well because there is not a switch between the start (reserve) battery and the starter.

[Charlie]

Uncle Bob & Mitiempo,

House power would come to the 1,2,Both,off switch at connection point 2. The house power would only be joined when the on/off switch was in the on position (default is off).

With the starter wired to the both position it would take power from both the 1 and the 2 terminals. 2 would not have power from house unless the on/off switch was on. With the 1,2,both switch in the off position then the reserve bank is isolated.

Does that make sense.

I may be using the term bus bar incorrectly. The existing(E) bar has 3 studs that are not interconnected. The (N) bar will be of a type that all studs are interconnected.