Multiple batteries

[pgenesta]

Hello to all..
I have a 2 battery system on my express cruiser with twin Crusaders 454ci.
One battery assigned for “house” and one for “starting the engines”. I have a fridge, microwave, hot water system and ac along with the usual cabin and deck lighting.
I would like to add 2 more batteries to the house side in order to supplement the house side when on the hook.
I will share that the boat did have a generator (intermittently worked) and I pulled it out.

Any diagrams available? Pros cons? Should I have an inverter? I do plan on picking up a portable generator with an inverter before the start of next year’s boating season.

 

[sandkicker]

IF you have two engines and two batteries, the correct setup is to have a dedicated start battery for each engine. It may be possible that you could use one of the batteries as double duty as a start and house battery, however that battery should be one that is designed for start/deep cycle operation.
If you want to add two more house batteries, the simplest way is to use a charge splitting device to charge the house batteries from one of the engines. You would most likely want to upsize the alternator on that engine.

I am not a fan of portable generators on powerboats.... nor is the USCG or your insurance company, unless you intend to beach the boat and use the generator only onshore.

 

[RicardoMarine]

Hopefully without stepping on Bob's toes here, I'll offer you a slightly different take on this, if I may.

HLBB = house load batt bank
SLBB = start load batt bank
MBSS = main battery selector switch (1/all/2/off)
BS = batt swich (on/off only)
ACR = auto charge relay

Since you have gasoline engines, you have no requirement for pre-heat, such as with diesels. So you don't really require any heavy start-up loads, other than cranking.

If you have limited battery space, you can eliminate a Stbd side cranking battery, and increase the HLBB with true Deep Cycle batteries, and can crank your Stbd engine from these.
The key to this, is having a Deep Cycle bank that is large enough!
It also helps greatly if the engine is quick firing!
I've been doing this for years, and with no issues.
This has allowed me additional HLBB space that would have otherwise been occupied by a cranking battery.

Now.... if space is not an issue, then this may not be for you.

For redundancy, I use a combining system that powers the Stbd side from the Port side dedicated cranking battery.
This can an automatic system (Blue Sea offers some great products for this), or it can be via a momentary helm switch that would trigger the combining solenoid switch.
This can also be done via the MBSS configuration that would allow for manual combining. (see image below)

I use a simple helm located momentary switch that triggers a solenoid switch that combines the two MBSS "common" connections.

Edit: by the way, the Stbd engine "start circuit" could also connect to the momentary solenoid, and would ensure that each and every time the Stbd engine was cranked, the two banks would be combined.
This would remove a portion of the start loads from the HLBB if you had any concerns.
In fact, this is something that I've considered doing..... just haven't gotten around to it.


BTW, I don't believe that there is a good combination battery. I think that cranking batteries should be just that...... a cranking battery!
I also believe that House Load battery banks should be Deep Cycle batteries.
(my HLBB is made up from multiple 6 volt deep cycle batteries (in series/groups of two)).
These offer more usable Amp Hours than what 12 v of similar size will offer.

The battery purists suggest that our HLBB should be of "Like" batteries, meaning same age, type, group number, etc.
Grouping one battery that has seen X number of cycles (and may be brand A), with another battery that has seen Y number of cycles (and may be brand E), may cause an issue.
IOW, all batteries within a HLBB should be purchased and installed at the same time.


Blue Sea also offers a great ACR unit that will allow a Port alternator to aid in charging the Stbd side HLBB.

This schematic allows for manual combining, as well as solenoid combining.
It shows two MBSS's, but two BS's could also be used.
The MBSS allows for manual combining.
An ACR could also be added.

Lots of ways to skin the cat..... this is just one.