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Battery Charging System - Am I Correct?

Jan 11, 2014
4,420
Sabre 362 113 Fair Haven, NY
So, as I asked Maine Sail, do you see this as a good foundation, or any other reason not to wire the system as shown in my last diagram?
A few thoughts.

You have the house batteries wired in parallel. I think this is a good approach. This makes the 2 batteries function as one and that should provide more useable energy and longer life for the batteries.

I would suggest a few modest changes.

Eliminate the positive feed from the charger to the start battery.

Eliminate the positive feed from the start battery to the house panel volt meter.

Add a SPST battery switch between the Start Battery and the Battery Select Switch

Fuse the Start battery with a battery terminal fuse at 250 amps.

Change the 1-2-both battery switch to a Blue Sea Dual Circuit Plus switch.

Add an ACR between the DC Positive busbar and the positive terminal on the start battery with appropriate fusing.

Add a battery terminal fuse on the house battery

Add a battery switch between the house battery and the positive bus bar.

I think that's it.
 
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
Dave,
(Uhm . . . you will need to expand your quote to read my answers.)

A few thoughts.

You have the house batteries wired in parallel. I think this is a good approach. This makes the 2 batteries function as one and that should provide more useable energy and longer life for the batteries.

You're right. It's the only way to wire a multi-battery bank. Unless your goal is to take two 24V in series to achieve a 48V bank. But even then, that now single 48V bank should be wired parallel into the electrical system.
I would like say this regarding batteries and my thinking. I'm not using "start" battery for my second bank. To me it's a reserve battery, working with a off-1 scenario - reserve is just that, reserve.

I would suggest a few modest changes.

1 - Eliminate the positive feed from the charger to the start battery.

The ProNautic charger charges the two banks independently. What would be the advantage of an ACR over using the charger's multi-bank functionality?

2 - Eliminate the positive feed from the start battery to the house panel volt meter.

Yes, no - I could go either way with this one. The charger's front panel, or a remote battery monitor would give me the same information.

3 - Add a SPST battery switch between the Start Battery and the Battery Select Switch

You have a suggestion? Other than those knife switches, I really haven't found a suitable surface mount switch.

4 - Fuse the Start battery with a battery terminal fuse at 250 amps.

Right, so noted and added to the design. However, if I'm using bank one as primary operational bank, running the house and starting the engine, would a 250 amp fuse be used there?

5 - Change the 1-2-both battery switch to a Blue Sea Dual Circuit Plus switch.

I've down loaded the instructions for the M-series Dual Circuit Plus, and they're about as help as - well not much. My feeling is this involves your suggestions of 1 and 6. With the functionality of the charger and that my current 1-both-2 switch acts as a selector and combiner; what are the advantages and disavantages?

6 - Add an ACR between the DC Positive busbar and the positive terminal on the start battery with appropriate fusing.

See responses 1 and 5.

7 - Add a battery terminal fuse on the house battery

Just as with the reserve battery, yes. As I asked though in response 4, 250 amps required here?

8 - Add a battery switch between the house battery and the positive bus bar.

See response 3.

I think that's it.
I think it's important to keep this conversation going. I'm beginning to feel we're pulling together thoughts and information for some one down the line.

Alec
 
Nov 16, 2012
856
Catalina 310, 2000, #31 Santa Cruz
Alec, I’m pretty sure the ProNautic doesn’t really charge two banks independently. It just splits the output current between the two (or three) lines. The voltage is the same for all of the outputs. The ACR has the advantage that it also works for the alternator, or any other charging source you might add later. I know that’s not an issue for your usage, but it adds future flexibility.

The Blue Seas m-Series 6006 is a great on/off switch. 300 A continuous. You might want to also use one for an alternator disconnect-cutting power to the alternator when you’re working on it.
 
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Maine Sail

Moderator
Feb 6, 1998
11,052
Canadian Sailcraft 36T Casco Bay, ME
The ProNautic charger charges the two banks independently. What would be the advantage of an ACR over using the charger's multi-bank functionality?
It does not charge the two batteries as independently as one might assume. There is one voltage regulation circuit, one power supply and two-three FET isolated outputs. This is not really "independent charging".. The benefit of an ACR is that it can charge both banks from all charge sources not just the battery charger.

A 250A fuse would be a bare minimum size for any bank that may be used to start a motor. A 300A fuse will minimize the risk of nuisance tripping...

This article goes into more detail about how the multiple outputs on marine chargers such as the ProNautic P actually work.
Making Sense of Automatic Charging Relays

For truly independent dual-bank charging a BCM or Battery Chemistry Module would be required however ProMariner does not make one only Sterling Power...

The only way we install Dual Circuit Plus switches on cruising boats is when each bank also has it's own isolation switch.
 
Oct 29, 2016
1,441
Hunter 41 DS Port Huron
If it were me, I would run the Alternator output directly to the batteries, running to the selector switch would actually allow you to disconnect the alternator output from a load, which would kill an alternator.
 

Maine Sail

Moderator
Feb 6, 1998
11,052
Canadian Sailcraft 36T Casco Bay, ME
If it were me, I would run the Alternator output directly to the batteries, running to the selector switch would actually allow you to disconnect the alternator output from a load, which would kill an alternator.
I believe he was referring to an "Alternator Service Disconnect Switch" that is typically located in the engine bay, clearly labeled and also cuts power to an external regulator so even if left off nothing bad can happen.

A product every boat should really have is a Sterling Power 12V - Voltage Spike Protection Device. They are also know as an Alternator Protection Device (APD). We are installing them routinely, especially with the growing use of drop-in LiFePO4 batteries that can throw and unexpected load dump without warning.
 
Nov 16, 2012
856
Catalina 310, 2000, #31 Santa Cruz
I believe he was referring to an "Alternator Service Disconnect Switch" that is typically located in the engine bay, clearly labeled and also cuts power to an external regulator so even if left off nothing bad can happen.
Sorry, I should have been more clear. That’s what I meant.
 
Nov 4, 2018
77
Hunter 28.5 Red Dog Catawba Island, OH
I've thought about all the suggestions made here. I agree they would make a superior system to the one I have proposed. It all comes down to money though. The budget for this project has mushroom more than I expected.

Is the system I proposed a viable, reliable and safe solution?
 

Attachments

Apr 22, 2011
561
Hunter 27 Pecan Grove, Oriental, NC
Your system is exactly what most of us ran on our boats a few years ago. I consider it perfectly safe, even more so with the addition of battery post fuses. If or when your Pronautic charger goes tango uniform, you can easily add an acr to your system which will insure that your start battery stays up when away from the dock.