Adding an Inverter and a 2nd 2-battery bank...HELP!

[Rusty S]

Have 2002 Larson 274 with a single 5.7GXi engine, and I assume a standard 60A alternator. I'm sure one of you knowledgeable people will know more about the alternator being a single wire or 3-wire stock from the factory. Currently has a 2 battery setup (27 series) with 1,2,Both,Off switch.
I will be adding an inverter and am planning an additional 2 batteries (27 or maybe 31 series pending needs).
My question is does anyone have a recommended wiring diagram for the 4 batteries? Should I maintain the existing switch I have in place, or start fresh?
I have been reading about the BEP vsr and Blue Sea (??) equivalent, but have also read different information indicating if the House (Inverter) bank is discharged too far the device will "chatter" resulting in a failure to charge house bank.
Also have been viewing some recent threads and have seen some pretty awesome pics of some wiring jobs by some of you guys! These boats seem to be a smaller type with outboards; I'm not for sure what adding an inverter does to the diagram.
I like the idea of having starter battery charged and reserved via the use of a vsr; should I maintain both existing batteries for this, or separate so just one is reserved, and run 3 batteries for my house bank?
Many questions on how to complete this set-up, and very much appreciate input from you pros. Thank you in advance.

 

[kmarine]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

I recomend using an isolator for your house batteries. The number of batteries depends on how long you wish to run your inverter. As is what size inverter you use. I prefer to keep an engine starting battery independent and add a swith to assisst starting battery if necessary.

 

[Silvertip]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

1) the size of the inverter you need depends on what you intend to run with it. 2) The size of the battery bank you need depends on the total load it must feed (12 volt stuff and whatever you run from the inverter and for how long). 3) Wiring for the INPUT side of the inverter must carry amperate at a value that is 10 times what the AC load is. 120/12 = 10. If you are sucking 10 amps from the inverter you need to put 100 amps at 12 volts into it. 4) The size of the alternator will limit the amout of current you replace in the batteries. If you suck 60 amps from the battery bank, you need to run the engine (assuming the alternator is a 60A unit) for one hour at half throttle or so to make up that useage. 5) Constant full output on an alternator is a good way to shorten its life. Your existing battery switch cannot provide any isolation between multiple batteries in the house bank. It can provide isolation between the starting battery and multiple batteries in parallel in the house bank. Figure out the actual electrical needs so you can accurately determine what the house battery bank needs to be (one, two, or three batteries as the case may be).

 

[cyclops2]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

List each electrical load you have. Seperate the 12 vdc from the 120 volt & possibly a 120 or 240 vac AC in the future unit.

That way we can FLOOR you with what you will need from the battery bank.
You might very well want a very quiet Marine generator that uses the same gasoline as the main engine. Batteries take up space quickly. There is a powerlevel that a generator in August becomes very desireable. It can keep starting batteries TOTALLY ISOLATED from all ac & dc house loads.
That is a failsafe always, fully charged starting batteries.

Very easy to combine starting & house batteries with switches accidently. Then everything can not run.

 

[Rusty S]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

Thank you for the responses.
I didn't want to get into the inverter sizing and battery capacity conversation because I have seen and understand the complexity of this. For the sake of going forward I have been looking at and am favoring the PowerBright PW2300-12 and am expecting a pair of group 31 batteries. My use will respect the capacity and abilities of this combination as we typically will need this setup for overnights with the use of a tv, small micro, small coffee maker, and other items. So let's leave all that goes along with this in the background for now; I didn't want this thread to go in that direction.

A Buddy at the marina has a setup with 2 separate 2-battery banks. 1 bank powers the engine starting and 12v needs of the boat; other bank powers strictly the inverter, and inverter is wired only to the 120v outlets. Each bank is controlled with a typical Atwood 1,2,both,off switch. I like this because it is simple, but at the same time want to expand upon it because of the seemingly possible drawdown.

I stopped and discussed this with a service tech at a marina. After a lot of chit-chat and circling the wagons he suggested the use of a vsr over the isolator because of what I understand is the isolator draws power (1v of something like that??). The vsr sits in the background being obedient and simply protecting you from a drawdown on starting battery.

The diagram he suggested places the vsr between the 2 battery banks, with a sensor wire monitoring voltage to the common out of existing bank switch I have (leaving the existing setup in place, and no modification). Then he suggested an on/off only switch placed to control the new battery bank. From there the inverter is wired to batteries, and ultimately tied in to the 120v panel with a new safety switch preventing Shorepower/inverter same time on situation. I don't expect nor want the inverter/2nd battery bank to power anything 12volt; only needs served from 120v panel.

My question to you pros is do you feel this is a good design? I was ready to go with this until I started looking at forums and specs about the vsr with possible chatter if overdraw of 2nd bank, as I mentioned in post above. Of course monitoring the battery bank capacity will prevent this, but we all live in the real world knowing the drawdown will probably occur. Other than an isolator which places a constant draw (as I understand it) on your system, is there any other suggestion?

Then there is the alternator. My buddy's system seemingly is adequate served from his alternator. I understand Silvertip's response on alternator capacity, overuse, etc. but at the end of the day I was hoping the existing alternator would suffice.

Also, beyond all of this, are in-line fuses necessary? I want to do this safely, and neatly. I have seen the negative busbars, and other items on the BEP website that can seeminly make a huge difference in the safety/professionalism of the installation.
Thanks again, and sorry for ramblin on-and-on.

 

[Silvertip]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

Remember that VSR/ACR always looks at the PRIMARY system (assuming that's the starting bank) first and all charge current goes to that bank until the cutover threshold for the the VSR/ACR is reached. At that point the house bank begins receiving a charge. So the long and short of that system is depending on how much your pull down the primary system, the house side may never get a charge on just a short run between stops since the full charge is going to the primary system. Rather than using words to attempt describing this, draw out the system you "think" you want and post it here so everyone is on the same page. In my view way too much emphasis and worry is placed on running down the start battery when that is generally not the case if the engine is tuned properly, the battery is servicable and there are no significant electrical loads on that system.

 

[bruceb58]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

Remember that VSR/ACR always looks at the PRIMARY system (assuming that's the starting bank) first and all charge current goes to that bank until the cutover threshold for the the VSR/ACR is reached.

Not true. The VSR/ACR looks at the voltage seen on both sides. If either side reaches a threshold, it connects the two banks of batteries together. Even if your primary battery is severley discharged(not likely if you actually use that to start your engine), this threshold is reached almost immediately upon the charging starting.

Personlly, I would never run a coffe maker off an inverter. Too much current for too long a time. If a coffee maker draws 12A on 110 its going to be drawing 105A off of your battery. If the coffee maker runs for 20 minutes, you have just used over 35AH off your battery bank.

As far as what battery to get. I would by 6V Trojan batteries and put a pair in series to form 12V. You also never want to discharge any deep cycle battery below half capacity if you want them to last very long.

There would be no chatter with a solid state VSR like a BluSea model. There is already hysteresis built in so that the VSR would not be opening and closing constantly. Also, it has safegaurds so that if the house bank is severley discharge(under 10.5V or similar) it won't even allow it to connect.

 

[Rusty S]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

Well, I have attempted a diagram. It's not as pretty as the ones you do, but hopefully is clear enough to convey my understanding and the design the marine service manager (msm) gave to me that I mentioned above.

Silvertip has made a comment referring to the primary battery bank (existing in my diagram) being sensed and the device open/close pending voltage of it. This is the same understanding I took away from the msm; he was speaking directly to the BEP device. If the sensor wire was run to the common out of the existing switch as shown, the 2nd bank would not receive any charge until bank #1 was served.

Bruce's comment is speaking to voltage being seen on both sides. I'm pretty sure I understand and agree with that. Silvertip's statement was specific to a sensor wire being included, I believe; if I'm incorrect please clarify.

The BEP device reads both, but the sensor wire will open/close device pending outcome of sensed bank; right? Does the BluSea Systems device perform this action in a different manner? You expressed the BluSea device wouldn't allow chatter; I'm liking that...and hoping the BEP device has these same solid state elements?

Other readings have stated the installation of device sensing a switch vs. individual battery may not be a good idea. With that said, could/should the device sensor wire be eliminated and sense voltage of starting battery alone? I may be a bit confused on the ACR/VSR. If there is a difference between the two devices please explain, and recommend better solution for my purpose.

I want the assurance/comment from you pros that the intentions expressed in diagram would be ok; or should I eliminate the existing switch and go another route? I'm open to any ideas and invite your comments. Thanks again for your help.

 

[Don S]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

What all are you planning on using the inverter for? Was it just to run a coffee maker?
As far as the chatter goes, most inverters will kick off due to low input voltage before they cause any. Besides, the only reason it would chatter is if you was running the engine at the same time, which kind of kills the need for an inverter, might as well get a small honda generator and set it on the swim step for 110 power.
A propane stove a percolator makes great coffee on the boat. Then you could use a small inverter for TV and other small 110V loads and use the house bank for the inverter as well as the rest of the house systems.

 

[Rusty S]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

Inverter will be used for different things, including: tv/dvd player for grandkids while underway; while overnighting we will be using cell phone/laptop charger, small coffee maker for brewing only (no extended time on inverter), possible intermittant microwave use, cpap machine, and other odds and ends. Don't want a noisy generator; just convenience of 110v without shorepower as we do quite a few overnighters on St. Lawrence river in Canadian waters where they have transient dockage at remote islands with no services.

I'm just looking for advice on an effective wiring solution without breaking the bank while protecting the starting batteries.

 

[bruceb58]

Re: Adding an Inverter and a 2nd 2-battery bank...HELP!

The BEP and BluSea work identically. The BlueSea has a threshold of 13.6V (30 seconds) 13.0 (90 seconds)and the BEP 13.7. When that threshold is reached, they combine. Doesn't mean your start battery has reached full charge at all. Basically the Blue Sea has a timer in it that combines once a threshold is reached with different delays depending on the threshold.

The BlueSea can sense voltage on both sides. The BEP can as well if you pick one with dual sensing. You probably only need single sensing.

I have the BlueSea on my boat.

Coffee making and microwave usage will really kill your batteries quickly.