Charging 4 banks from 1 alternator?

[Davidhoy]

Originally Posted by ramblinrod

You can use either but be sure to use a fuse to limit the current from the ACR to the thruster. In practice, have the engine running before operating the thruster or windlass, and after using them, always leave the engine running until the thruster bank is recharged. (People commonly shut the engine down, the instant the anchor is set or the vessel is tied to the dock; bad move, if the thruster bank has had more drawn than the alternator can provide.)

Good advice! On the fuse and on running the engine a while after using the windlass or thruster. Not too worried about leaving the engine running for very long after docking, as I'd generally have shore power at the dock to recharge everything. After anchoring it's definitely a good idea. At some point I'll probably increase the bank to give it more reserve power. I have a Raritan ElectroScan MSD that is also connected to that bank, haven't figured out whether that is a good thing or not...


Sent from my iPad using Cruisers Sailing Forum

[mitiempo]

Quote



Rod

I am not sure exactly where you read that Blue Seas recommends the alternator be wired to the start battery. While it works if the banks are of equal size (eg a small boat with one start battery and one equal size house battery) it does not work in the case of a single start battery and a multi-battery house bank. Blue Seas specifically states that the alternator should be wired to the larger of the battery banks. This will prevent chattering. With the alternator wired to the start battery when the house bank is larger the start battery first comes up to the combine voltage. The ACR closes connecting the banks and the rush of current to the house bank lowers the voltage of the start battery causing the ACR to open. This repeats until the much larger house bank is at a high enough voltage to keep this from happening.

The wire sizes you posted are for the ML-ACR. The wire sizes for the SI-ACR are below and quite a bit smaller.

As far as fusing, it is not there to limit current but for safety reasons, as all fuses are. The current is limited to alternator output (or AC charger or solar etc) and they should always be close to the positive connection for each battery bank when installing an ACR.

[skipmac]

Originally Posted by mitiempo

Rod

I am not sure exactly where you read that Blue Seas recommends the alternator be wired to the start battery. While it works if the banks are of equal size (eg a small boat with one start battery and one equal size house battery) it does not work in the case of a single start battery and a multi-battery house bank. Blue Seas specifically states that the alternator should be wired to the larger of the battery banks. This will prevent chattering. With the alternator wired to the start battery when the house bank is larger the start battery first comes up to the combine voltage. The ACR closes connecting the banks and the rush of current to the house bank lowers the voltage of the start battery causing the ACR to open. This repeats until the much larger house bank is at a high enough voltage to keep this from happening.

The wire sizes you posted are for the ML-ACR. The wire sizes for the SI-ACR are below and quite a bit smaller.

As far as fusing, it is not there to limit current but for safety reasons, as all fuses are. The current is limited to alternator output (or AC charger or solar etc) and they should always be close to the positive connection for each battery bank when installing an ACR.

Excellent and accurate.

[mitiempo]

We are not talking about combining with the alternator running - that is not an issue. We are referring to combining a good battery with a dead battery to start the engine. This is something that should never be done. If the house bank is low enough what current it has will try to charge the start battery. In certain circumstances you can be left without any way to start the engine.

This happened to a neighbor after a weekend on the hook. You need quite long jumper cables to jump a 49' Grand banks.

As I stated in an earlier post I am not a fan of 1/2/both/off switches. I prefer separate on/off switches with a third allowing either starting the engine from the house bank or using the start battery for house loads if needed.

[Stu Jackson]

Years ago, Maine Sail & I got into spirited discussions with sailors in the U.K. about alternator output to the start vs. house bank. They didn't "get it," insisting that they "needed" to recharge the start bank first. They still don't get it. We eventually gave up.

mitiempo is right.

Any reasonably sized start bank should be able to start a small recreational boat engine 30 - 40 time before reaching 50% SOC.

This continuing urban myth has me mystified.

It makes no sense. The larger house bank on a sailboat ALWAYS has more "need" to be recharged than any start bank.

[skipmac]

Originally Posted by Stu Jackson

Years ago, Maine Sail & I got into spirited discussions with sailors in the U.K. about alternator output to the start vs. house bank. They didn't "get it," insisting that they "needed" to recharge the start bank first. They still don't get it. We eventually gave up.

mitiempo is right.

Any reasonably sized start bank should be able to start a small recreational boat engine 30 - 40 time before reaching 50% SOC.

This continuing urban myth has me mystified.

It makes no sense. The larger house bank on a sailboat ALWAYS has more "need" to be recharged than any start bank.

Not just people in the UK that don't get it.

[ramblinrod]

[QUOTE=mitiempo;2225014]Quote
Rod

I am not sure exactly where you read that Blue Seas recommends the alternator be wired to the start battery.

In their instructions. For the SI (start isolation) ACR...

http://assets.bluesea.com/files/reso.../990170140.pdf

...for the inboard engine example, they state that the alternator may be connected to 4 different things, one being the start battery (with caveats to follow...)

While it works if the banks are of equal size (eg a small boat with one start battery and one equal size house battery) it does not work in the case of a single start battery and a multi-battery house bank. Blue Seas specifically states that the alternator should be wired to the larger of the battery banks.

Actually, they state the alternator can be wired to the start battery, but that it is "more efficient" if wired to the larger bank.

This will prevent chattering. With the alternator wired to the start battery when the house bank is larger the start battery first comes up to the combine voltage. The ACR closes connecting the banks and the rush of current to the house bank lowers the voltage of the start battery causing the ACR to open. This repeats until the much larger house bank is at a high enough voltage to keep this from happening.

Actually, they state that if the bank demand is greater than the alternator can deliver, it may cause cycling. For the case of the 120 A alternator, this would mean a 480 A-hr standard lead-acid bank that was nearly dead.

In the case of the OP posted, the alternator could be wired to the start battery, though I would recommend it be connected to the house bank for the reasons stated.

The wire sizes you posted are for the ML-ACR.

Correct, that is the ACR I was initially referring to.

The wire sizes for the SI-ACR are below and quite a bit smaller.

Correct.

As far as fusing, it is not there to limit current but for safety reasons, as all fuses are.

All fuses are current limiting devices. That is how they invoke safety in a circuit, by not permitting current to exceed the current carrying capacity of the wires or devices they are connected to.

The current is limited to alternator output (or AC charger or solar etc) and they should always be close to the positive connection for each battery bank when installing an ACR.

Yes, because if the fuses weren't there, and a large load was connected to a bank when the ACR combined, high current could be drawn from the other bank through the ACR.

But most importantly they state...

"The 7610 ACR is not intended to carry starting currents."

The SI (start isolation) function, requires special wiring to the ignition key.

They state that if the feature is not implemented, that when the engine is initially cranked, the house and start bank is combined, and the current drawn may cause the house bank to dip.

The ML-ACR provides for manually combining the connected banks; the SI-ACR does not. (I erroneously stated the SI unit does in a prior post.)

http://assets.bluesea.com/files/reso.../990180180.pdf

This is the one that should be used when combining a start battery to a house bank with a high load (like a windlass or inverter), or a thruster bank to either a house bank or start battery.

This will prevent the condition of fuses blowing (that will occur with the SI unit) if the high load is on when the engine is running and the directly connected bank is significantly discharged, as the ACR will pass all of the current the other bank can deliver to meet the load (including discharged bank) demand.

[ramblinrod]

Originally Posted by mitiempo

We are referring to combining a good battery with a dead battery to start the engine. This is something that should never be done.

Again, combining a charged and discharged battery is done every day, many times a day, to start engines.

If the house bank is low enough what current it has will try to charge the start battery.

Correct, and if the house bank is high enough, it will start the engine, which puts the boater in a much better position than having a dead start battery and no way to combine the house bank to the starter.

In certain circumstances you can be left without any way to start the engine.

Only if one leaves the batteries combined for considerable time, after it is realized that the house bank won't start the engine. If the starter battery is just discharged (not shorted) and the house bank is reasonably charged (not nearly dead) it will easily start a smaller engine and possibly a larger engine, depending on the SOC of the batteries, engine compression, decompression features available, and a whole host of other variables.

If when the house bank is combined with the starter, it is immediately clear that there is not enough oomph to start the engine, they should immediately be uncombined, the start battery negative terminal disconnected and the house bank recombined for starting, and the start battery reconnected before uncombining. For those who aren't too savvy, they may be better off to call their friend, tow company, or Pan Pan instead. (

This happened to a neighbor after a weekend on the hook.

You need quite long jumper cables to jump a 49' Grand banks.

Too bad they hadn't read my post above. But yes, if one is foolish enough to kill all their batteries, it can make it hard to start the engine. ;-)

As I stated in an earlier post I am not a fan of 1/2/both/off switches. I prefer separate on/off switches with a third allowing either starting the engine from the house bank or using the start battery for house loads if needed.

I don't understand why you feel 3 discrete switches, that do exactly the same thing as a single 1/2/B/Off switch, is better? In my opinion, this just creates more components, more wiring connections, more possible failure nodes, at greater parts AND labour expense.

1/2/B/Off switches can handle a lot more current than the SI-ACR, and they are a lot less expensive than the ML-ACR. However, an ML-ACR is a more failsafe solution, helping prevent operator error from discharging the start battery with house loads.

A 1/2/B/Off switch can be used to combine the house bank to the start battery should the start battery not be able to start the engine (just like a paralleling relay in a 2 x start battery dual engine vessel, and just like a ML-ACR when the manual combine feature is used).

[ramblinrod]

Originally Posted by Stu Jackson

Years ago, Maine Sail & I got into spirited discussions with sailors in the U.K. about alternator output to the start vs. house bank. They didn't "get it," insisting that they "needed" to recharge the start bank first. They still don't get it. We eventually gave up.

mitiempo is right.

Any reasonably sized start bank should be able to start a small recreational boat engine 30 - 40 time before reaching 50% SOC.

This continuing urban myth has me mystified.

It makes no sense. The larger house bank on a sailboat ALWAYS has more "need" to be recharged than any start bank.

First of all, no argument here. I also agree that when using an ACR, the alternator is better connected to the house bank.

This is in direct contrast to the same scenario but when a 1/2/B/Off switch is used, where the alternator should be connected to the start battery directly, so that it gets charged no matter what position the switch is in, ie, the more "failsafe" condition and protection from operator error (if one considers being able to start the engine more important than keeping the beer cold ;-).

[mitiempo]

Originally Posted by ramblinrod

I don't understand why you feel 3 discrete switches, that do exactly the same thing as a single 1/2/B/Off switch, is better? In my opinion, this just creates more components, more wiring connections, more possible failure nodes, at greater parts AND labour expense.

1/2/B/Off switches can handle a lot more current than the SI-ACR, and they are a lot less expensive than the ML-ACR. However, an ML-ACR is a more failsafe solution, helping prevent operator error from discharging the start battery with house loads.

A 1/2/B/Off switch can be used to combine the house bank to the start battery should the start battery not be able to start the engine (just like a paralleling relay in a 2 x start battery dual engine vessel, and just like a ML-ACR when the manual combine feature is used).

There are several problems I see with 1/2/both/off switches. For one many do not know how to use them. Many boats I see they are left in the "Both" position. The other issue is that whatever position they are in both house loads and engine are hot. If you are anchored for a day or for weeks there is no reason to energize the starter.

2 single on/off switches, one for House and one for Start are simpler to understand. A third switch for using house bank for starting and using start battery for house loads - which does not have to be visible, it can be in a locker - keeps things very simple for any on the boat to understand and use.

[ramblinrod]

Originally Posted by mitiempo

There are several problems I see with 1/2/both/off switches. For one many do not know how to use them. Many boats I see they are left in the "Both" position.

What is the difference than if someone leaves the On/Off switch used for the combine function in the "on" position?

In ether case, bad things are equally likely to happen in the event of operator error.

The other issue is that whatever position they are in both house loads and engine are hot.

Not in the "off" position. The house loads are isolated from all batteries. The starter is not "hot" but the starter solenoid is "hot" on the battery side. So what? The solenoid is a switch just like the start battery isolation switch you are installing.

If you are anchored for a day or for weeks there is no reason to energize the starter.

So don't. So what?

2 single on/off switches, one for House and one for Start are simpler to understand. A third switch for using house bank for starting and using start battery for house loads - which does not have to be visible, it can be in a locker - keeps things very simple for any on the boat to understand and use.

If one can't understand a single switch with 3 positions and "Off" (4 possible states), how the heck can they understand 3 switches with one position and "Off" (6 possible states).

So now that I say this, I do see that there are more possible conditions, with 3 discrete switches than one 1/2/B/Off switch, but I don't see how it is better. I see absolutely no need for disconnecting the start battery from the starter solenoid, except in the unlikely event that the ignition start switch gets stuck on, but that is really no more likely than the discrete battery switch being inadvertently turned, or stuck, "off".

[Davidhoy]

Originally Posted by skipmac

Not just people in the UK that don't get it.

I didn't get it until you guys explained it in a way that made sense ;-)

[ramblinrod]

Originally Posted by skipmac

Not just people in the UK that don't get it.

Just one more point...

Where the alternator IS capable of delivering the max current (at 50% SOC) the house bank and usual house loads (when motoring) may draw, I do recommend connecting the alternator directly to the start bank.

This is a more "failsafe" approach, in that in the event the ACR fails, or ACR fuse blows, the start battery still gets charged.

In the case of the OP, with a 120A alternator and a 400+ Ahr house bank, it is cutting it close, so I recommend connecting the ACR directly to the house bank.

If an ACR is used for both the house bank and the thruster bank, I recommend using ML-ACRs rather than SI-ACRs due to the high potential current demands of the thruster.

However, due to the cost (of both the ACRs and the heavy cables) I recommend using an ACR (ML-ACR is high loads may be present) for the house bank, and considering charging the thruster bank with a discrete AC charger mounted forward, and running the AC generator to charge it up after any significant thruster or windlass use. Especially because a non-operator initiated load (Electrosan) is also on the thruster bank, a remote battery monitor, (even just voltage) on the thruster bank would be a good idea.

[ramblinrod]

Originally Posted by ramblinrod

Just one more point...

Where the alternator IS capable of delivering the max current (at 50% SOC) the house bank and usual house loads (when motoring) may draw, I do recommend connecting the alternator directly to the start bank.

This is a more "failsafe" approach, in that in the event the ACR fails, or ACR fuse blows, the start battery still gets charged.

In the case of the OP, with a 120A alternator and a 400+ Ahr house bank, it is cutting it close, so I recommend connecting the ACR directly to the house bank.

If an ACR is used for both the house bank and the thruster bank, I recommend using ML-ACRs rather than SI-ACRs due to the high potential current demands of the thruster.

However, due to the cost (of both the ACRs and the heavy cables) I recommend using an ACR (ML-ACR is high loads may be present) for the house bank, and considering charging the thruster bank with a discrete AC charger mounted forward, and running the AC generator to charge it up after any significant thruster or windlass use. Especially because a non-operator initiated load (Electrosan) is also on the thruster bank, a remote battery monitor, (even just voltage) on the thruster bank would be a good idea.

OK, yet another point, it is very hard to recommend the best solution without knowing the boaters sensibilities and intended boat use. This usually takes a one on one discussion.

1. If money is no object and the OP is loathe to using the generator any more than necessary, the ML-ACR on house and thruster batteries may be the way to go.

2. If money is tight and the OP is loathe to using the generator, an Echo Charger to the thruster battery may be the way to go, especially if one is likely to motor sail the next day for some time, to recharge the thruster/windlass/Electrosan bank.

3. If the OP is likely to use the generator at anchor anyway, such as for AC appliances or Air Conditioning use, then the discrete charger forward is likely the best way to go.

[skipmac]

Originally Posted by Davidhoy

I didn't get it until you guys explained it in a way that made sense ;-)

Don't feel alone. I didn't get it when I first started cruising about 40 years ago and a couple of times it caused me a bit of a hassle. Once I got on this forum and started following the discussions on the subject the light bulb came on.

When you follow the logic of the whys and wherefores the basic theory is pretty easy to grasp. Once you have an understanding of the theory then the implementation becomes easier to understand as well.

It does take a little thought and study but followed step by step most can get there. I do have one friend to whom electrical matters, no matter how simple, are about as clear as ancient Sumerian cuneiform. Smart guy otherwise but just baffled with electrical stuff.

Have you found the wiring diagram put together by Maine Sail (CF handle for Compass Marine?). He has worked out an excellent diagram that incorporates all the features discussed here.