Charging 4 banks from 1 alternator?

[Davidhoy]

Oh yeah, I'm not going to install a second alternator. Why add the complexity of a second alternator, and the need to maintain it? I have a spare alternator still in the box that could be installed in the event of a failure - that, to me, is a far better backup plan that an installed second alternator.

-David


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[Dockhead]

Originally Posted by Davidhoy

Oh yeah, I'm not going to install a second alternator. Why add the complexity of a second alternator, and the need to maintain it? I have a spare alternator still in the box that could be installed in the event of a failure - that, to me, is a far better backup plan that an installed second alternator.

-David

That's your choice, of course!

But two alternator setups are LESS complex and more reliable than charging multiple banks with one alternator. Especially if that one alternator -- as is almost always the case -- is not up to the job.

The only maintenance required is keeping the belts adjusted, and you will fiddle with the belts a lot less, with dual alternators. That's because second alternator installations will have either a serpentine or dual belt setup which is designed for the job of driving a big alternator producing a lot of power. So it won't heat up and stretch as much.

Whereas the original car alternator on the main engine, driven by a single v belt, will need more frequent adjustment if you drive it hard. That system is not made to be run at high loads all the time. What is worse, is that this v belt usually drives your fresh water pump as well. If you load up that alternator and blow that skinny single belt, you not only lose charging, you lose engine cooling.


One other piece of advice related to these points: If you don't install a second alternator (no space, don't want to, etc.), at least replace the original engine alternator with a heavier duty one, and upgrade the belt drive system. If you don't have external regulation, add that as well. There's a lot of good information about why this makes sense; on MaineSail's site PBase.com, among many other places.

Good luck.

[mitiempo]

Originally Posted by Dockhead

That's your choice, of course!

But two alternator setups are LESS complex and more reliable than charging multiple banks with one alternator. Especially if that one alternator -- as is almost always the case -- is not up to the job.

The only maintenance required is keeping the belts adjusted, and you will fiddle with the belts a lot less, with dual alternators. That's because second alternator installations will have either a serpentine or dual belt setup which is designed for the job of driving a big alternator producing a lot of power. So it won't heat up and stretch as much.

Whereas the original car alternator on the main engine, driven by a single v belt, will need more frequent adjustment if you drive it hard. That system is not made to be run at high loads all the time. What is worse, is that this v belt usually drives your fresh water pump as well. If you load up that alternator and blow that skinny single belt, you not only lose charging, you lose engine cooling.


One other piece of advice related to these points: If you don't install a second alternator (no space, don't want to, etc.), at least replace the original engine alternator with a heavier duty one, and upgrade the belt drive system. If you don't have external regulation, add that as well. There's a lot of good information about why this makes sense; on MaineSail's site PBase.com, among many other places.

Good luck.

He has posted (post 60) that he has a Balmar 120 amp alternator with a Balmar ARS-4 external regulator.

David

I agree with your planned changes. I would use Blue Seas ACR's but the Echo Charge will work as well.

For switching I prefer simple on/off switches, one labeled Start and one labeled House. Install a third switch wired so you can start the engine with the house bank by itself without paralleling the start battery.

[ramblinrod]

Originally Posted by mitiempo

He has posted (post 60) that he has a Balmar 120 amp alternator with a Balmar ARS-4 external regulator.

David

I agree with your planned changes. I would use Blue Seas ACR's but the Echo Charge will work as well.

For switching I prefer simple on/off switches, one labeled Start and one labeled House. Install a third switch wired so you can start the engine with the house bank by itself without paralleling the start battery.

Yup
Proposed changes are OK except emergency combine switch is not required between house and start; the Blue Sea ML-ACR has a built in combine switch for emergency use.

I would personally use one 1,2,B,Off switch to split the house bank for servicing purposes. (Leave this switch in Both position at all times. Should you ever need to isolate half or all the bank for testing, servicing, or emergency purposes, just flick the switch rather than have to disconnect terminals and transfer wires.

Hard to mess up if one knows the switch should always be in the both position.

[ramblinrod]

Originally Posted by ramblinrod

Yup
Proposed changes are OK except emergency combine switch is not required between house and start; the Blue Sea ML-ACR has a built in combine switch for emergency use.

I would personally use one 1,2,B,Off switch to split the house bank for servicing purposes. (Leave this switch in Both position at all times. Should you ever need to isolate half or all the bank for testing, servicing, or emergency purposes, just flick the switch rather than have to disconnect terminals and transfer wires.

Hard to mess up if one knows the switch should always be in the both position.

Oh, and before finalizing on using an ACR for the thruster bank from a 120 A alternator, consider the cost of the 4/0 cables. Any of the other solutions mentioned (except additional alternator) will be a lower cost (but not necessarily better) solution.

[Davidhoy]

Originally Posted by mitiempo

He has posted (post 60) that he has a Balmar 120 amp alternator with a Balmar ARS-4 external regulator.

David

I agree with your planned changes. I would use Blue Seas ACR's but the Echo Charge will work as well.

For switching I prefer simple on/off switches, one labeled Start and one labeled House. Install a third switch wired so you can start the engine with the house bank by itself without paralleling the start battery.

Thanks! I'm learning a lot from all of you guys, much appreciated.

My one concern about the ACRs, please correct me if I'm off base, is that if there is a significant voltage difference between the two banks, when the ACR connects them there can be a massive surge in current from the full bank to the depleted one. Is this something I should be concerned about? With the Echo Charge, the current is limited to 15 amps, which will prevent any big surges but also means that the remote bank could charge rather slowly.

As to switching, I was thinking of an Off/1/2 (no Both) selector switch for the starting circuit, something like this - https://www.bluesea.com/products/110...witch_with_AFD. This would allow me to use either the start or house banks to fire up the engine, but never allow the banks to combine.

-David

[mitiempo]

Originally Posted by Davidhoy

Thanks! I'm learning a lot from all of you guys, much appreciated.

My one concern about the ACRs, please correct me if I'm off base, is that if there is a significant voltage difference between the two banks, when the ACR connects them there can be a massive surge in current from the full bank to the depleted one. Is this something I should be concerned about? With the Echo Charge, the current is limited to 15 amps, which will prevent any big surges but also means that the remote bank could charge rather slowly.

As to switching, I was thinking of an Off/1/2 (no Both) selector switch for the starting circuit, something like this - https://www.bluesea.com/products/110...witch_with_AFD. This would allow me to use either the start or house banks to fire up the engine, but never allow the banks to combine.

-David

With charge sources wired to the house (larger) bank an ACR will not combine until the house bank is at more than 13 volts. There will not be a surge. The charge source can and will supply more current than the start bank can accept.

That switch will work but you do not need or desire AFD - it is for alternators that wire through the switch and yours will not.

[ramblinrod]

Originally Posted by Davidhoy

Thanks! I'm learning a lot from all of you guys, much appreciated.

My one concern about the ACRs, please correct me if I'm off base, is that if there is a significant voltage difference between the two banks, when the ACR connects them there can be a massive surge in current from the full bank to the depleted one. Is this something I should be concerned about? With the Echo Charge, the current is limited to 15 amps, which will prevent any big surges but also means that the remote bank could charge rather slowly.

Can't speak to all relays, but no problem with the BLUE SEA ACRs. They are designed to handle significant surge current. If you have a standard lead acid 2 x Grp27 thruster bank, it will only accept about 50A max, so no issue. However, if the thruster bank is severely discharged, and the other bank is fully charged, when the 2 are combined, AND the thruster is operated, there can be significant current drawn from the other bank (this is why such heavy cables are required.) One can go with lighter cables and monitor the thruster bank to assure the thruster is never operated when the bank is low, but low and behold, this is a less "failsafe" (there's that word again) solution.

As to switching, I was thinking of an Off/1/2 (no Both) selector switch for the starting circuit, something like this - https://www.bluesea.com/products/110...witch_with_AFD. This would allow me to use either the start or house banks to fire up the engine, but never allow the banks to combine.

-David

If you wish to be able to start the engine from the house bank should the start battery be discharged, why not just use the emergency combine function of the ML-ACR?

There is no problem with emergency combining batteries to start the engine, and it is much simpler as the functionality and wiring is already there (with the ML-ACR installation so the start battery and house bank can be combined for charging).

[mitiempo]

Originally Posted by ramblinrod

Yup
Proposed changes are OK except emergency combine switch is not required between house and start; the Blue Sea ML-ACR has a built in combine switch for emergency use.

I would personally use one 1,2,B,Off switch to split the house bank for servicing purposes. (Leave this switch in Both position at all times. Should you ever need to isolate half or all the bank for testing, servicing, or emergency purposes, just flick the switch rather than have to disconnect terminals and transfer wires.

Hard to mess up if one knows the switch should always be in the both position.

The Blue Sea ML-ACR is more than twice the price of the more common SI-ACR. You also never want to parallel a dead battery with a good battery or bank.

I see no reason to split the house bank.

[skipmac]

Originally Posted by mitiempo

The Blue Sea ML-ACR is more than twice the price of the more common SI-ACR. You also never want to parallel a dead battery with a good battery or bank.

Exactly. This was already covered in a previous post. Parallel a good bank into a dead (or possibly shorted) battery then you have just lost your starting power.

[ramblinrod]

Originally Posted by mitiempo

With charge sources wired to the house (larger) bank an ACR will not combine until the house bank is at more than 13 volts.

There will not be a surge. The charge source can and will supply more current than the start bank can accept.

Oh yes it will. Per Blue Sea, if the alternator is connected to the start battery per their instructions (and I know you and others say not to do this) the start isolation function must be used to prevent drawing high current off the house bank when engine starting.

Similarly, if an ACR is connected between house and start (as you propose), and another ACR is connected between thruster and start (in similar fashion), when starting the engine, all batteries are initially combined.

This would not normally be a problem, because as you say, the acceptance rate of the batteries will limit the current to less than the alternator can deliver (most likely.)

However, should a large load be on either the house bank (like an inverter) or the thruster bank (like a bow thruster or windlass) be applied, while the intended bank is severely discharged AND the engine is being started (operator error, but we are trying to provide a "failsafe" system here), the instantaneous high load will draw all the current the connected bank is capable of delivering.

I believe this is why Blue Sea recommend inordinately high wire gauge for the battery connections (2/0 for 65 A and 4/0 for 120A)

If lighter cables are used, a fuse should be installed to limit current in the unlikely event of this happening, but should it happen, and the fuse blow, the bank will not be charged, unbeknownst to the operator until the blown fuse is detected.


That switch will work but you do not need or desire AFD - it is for alternators that wire through the switch and yours will not.

I stand to be corrected on this, but I am pretty sure.

[ramblinrod]

Originally Posted by mitiempo

The Blue Sea ML-ACR is more than twice the price of the more common SI-ACR.


Correct, both have start isolation functions, but the ML is capable of handling much higher intermittent and continuous current, as may be drawn by a discharged battery and windlass or thruster.

You also never want to parallel a dead battery with a good battery or bank.

What is the issue? While obviously nobody "Wants" a dead battery, combining good (with alternator running) with dead, happens all over the world, likely every second, when someone boosts a car to start it.
I see no reason to split the house bank.

As mentioned previously, splitting the house bank with a 1/2/B/Off switch provides a great solution to isolate batteries from each other, and the distribution panel, for testing and servicing purposes. In this case, the switch is always in "Both" position, except when performing service or testing.

Especially if one already has the switch installed to isolate house from start, and wants to install an ACR between house and start instead. It is already purchased, mounted, proven, requires only minor electrical wiring change to serve the new purpose, and removal will leave holes.

In the case of my own boat, it came with 2 x Rolls Royce deep cycles, separated by a 1/2/B/Off switch.

First, I added a start battery, altering the switch wiring to isolate the 2 x Deep Cycles from the start.

Then, I added another Deep Cycle, still using the switch to isolate the 3 x Deep Cycles from the start.

Then, I determined I would be better off replacing the start battery with yet another deep cycle. Now the 1/2/B/Off switch isolates the 2 x 2 deep cycle banks.

(This is a perfect solution for 2 x 2 by 6 Vdc battery banks, which is much more common in my experience that 3 x 2 x 6Vdc, yet it will work with the latter, albeit splitting the bank unequally, which really is no issue at all for almost all intents and purposes.)

In normal operation, it is always on "Both" (no isolation). But if I want to isolate part of my deep cycle bank, I can switch either half "1" or half "2" to the distribution panel (isolating the alternate bank), or to service the DC electrical system, I can switch it to off, and all loads except those bypassing the switch (bilge pump and VHF), are isolated from the house bank. (Remember how we have talked about taking voltage measurements with batteries at rest? This is a great way to do that, while loads are still operating on the other half of the house bank.)

While this system may be fairly unique to my boat, some provision for isolating batteries within a bank, and isolating the bank from the distribution panel, is an advantage on every boat.

On current production boats, it is common practice to have an isolation switch per battery.

But when modifying a system that has a perfectly functioning 1/2/B/Off switch, it's a wise move to re-purpose it for this function, if no longer needed for house/start bank isolation/combining.

[Davidhoy]

Originally Posted by mitiempo

The Blue Sea ML-ACR is more than twice the price of the more common SI-ACR. You also never want to parallel a dead battery with a good battery or bank.

Good point, the ML-ACR is probably overkill, and the SI-ACR will do the job quite nicely while saving a lot of $$.

-David

[ramblinrod]

Originally Posted by Davidhoy

Good point, the ML-ACR is probably overkill, and the SI-ACR will do the job quite nicely while saving a lot of $$.

-David

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.)

[twinboat]

I have my alternator charging my house bank.

From there I use a Cyrix combiner to my thruster/windlass battery.

My second combiner is between the thruster/windlass battery and the start battery.

I did it this way to limit the load on the alternator as the banks combine. Each bank is combined after the previous bank has reached 13.3 volts.