Battery Setup - 1998 405 Aft Cabin

[Viper]

To simplify, if you have a battery/bank selector switch, you likely have 2 battery banks plus a separate battery for the generator (usually). This is the way most OEMs do things. Whichever position your selector switch is on is where you will draw current from for all systems including engines and house DC systems/accessories.

A battery bank can consist of one or more batteries but when there is more than one battery in a bank, all batteries in that bank should be of the same type and spec. There should be a bank that consists of deep cycle batteries for house loads, and a different bank of start batteries for starting your engines. These two designs should be used as they're designed for, so selector switch management is important here. The different banks and battery types should be isolated from one another, so leaving the switch on "BOTH" or "ALL" defeats that purpose and will let you down one day on the hook as you drain every battery on board and can't start your engines to get home. BTW, look at the switch, if there's a label on it telling you to turn the engine off before changing the position of the switch, you must abide by that or you'll toast your alternators. There are selector switches however that are "make before break" and can be switched while the engines are running.

An ideal setup would be a start battery for the port engine, a start battery for the starboard engine, a start battery for the generator, and a deep cycle bank for house loads. All battery banks must have a means to charge at the dock and at sea while still maintaining isolation from other banks. There are devices on the market that make it possible to charge several banks from just a single charger and one or two alternators, KM mentioned one such device.

In this type of setup, I would use only "ON/OFF" switches for each bank, no selector switch allowed, I don't think they're a good idea at all. The only good thing about them is that they allow you to parallel two banks in case of an emergency where your engine bank fails to start an engine. The problem is that you have to remember to set the switch back to isolate the banks which is often forgotten and gets folks in trouble. You're better off with an emergency parallel switch at the helm that disengages once you let it go. There are also ACRs that parallel banks automatically when an engine is started. There's several ways to do it that are way better than the selector switch that most OEMs install at factory. This system sounds complicated to retrofit but it really isn't with a little guidance.

[g36]

I know theres all kinds of ideas on what and how on batteries. I am not making any inferences that my setup is better than any others this is how i chose to setup my boat. I did not modify the oem setup. Original selector switch under the steps. I have a separate battery for the genset (which charges by it running), I have a single starting battery for 1 engine and my house bank is on the other. I have a 3 bank charger for use at the dock and a 80 amp charger for house bank only while at anchor . The house bank will also charge while running from engine altenator. First off I am on a lake much as you will be. I go out Friday anchor out for the weekend and come in Sunday occasionally longer. I monitor my house bank with a victron battery monitor and have my house bank sized that I won't be near 1/2 capacity before I run the genset and the ac at night to cool the boat or run genset in the am for cooking breakfast and charge house bank. I do not sleep with genset running. Fwiw. I don't have any charging relays , parallel setup etc. etc. I choose to keep this simple. Keeping the 1/2/both in 1 isolates my house and the other engine starting battery. I have never had to use both or switch over to strart engine to get home. Even if i did i have a perfectly good genset battery as another starting option. I don't care that the golf cart batteries are technically not starting batteries what energy i used to start up is mostly replaced by the time i anchor. My last set of Trojans T105 were 8 years old before I changed them to a new set. I only did that then because my golf cart needed replacements, those are still in my golf cart and going so I don't belive that my useage has shortened any life from them. I had this same setup on my Trojan f32 for many years before my carver purchase. I know what works in my boating situation.

[Mikwallace]

Thanks for all the input. After reading the comments I couldn’t wait until next week so I went to the Marina and started digging again. Here’s what I determined:

The generator has one dedicated battery isolated from the other batteries with its own ON/OFF selector switch. And by the way the Carver owners manual says, “The generator starter is powered by a dedicated and separate 12 volt deep cycle battery.” The only reason I can deduct why it’s a deep cycle is the power curve is higher longer and it’s a small engine??

The battery bank consist of two batteries with a selector switch comprised of 1/2/BOTH/OFF. The selector switch is under the bottom step going from aft deck area to the salon. The selector switch is attached to and part of the Safety Breaker Panel (SBP). The SBP has “Safety Equipment” breakers that provide 12vdc power to equipment regardless of the selector switch position. They are helm voltmeters 1 & 2, stereo memory, shower sump fwd and aft, 3 auto bilge pumps, and CO detectors (of which there’s also a 12vdc accessories plug - the old cigarette lighter type on that circuit). The SBP also has breakers for 3 battery chargers, of which mine are probably disconnected as the chargers are after market and wires go from the chargers direct to each battery. And a breaker for the windlass, and Main Bridge & Salon. If both main breakers are off it kills 12vdc to the salon 12v panels.

The battery selector provides 12vdc to engines and house. If. Selector is set to Batt 1, engines and the house have 12vdc, if set to Batt 2, engines and house have 12vdc, and if set to both - guess what? Engines and house have 12vdc! There’s no way to isolate the house from the battery bank (engine cranking batteries). I’m guessing a previous owner added the other 2 batteries to Bank 1 with the intent of selecting Batt 1 when at anchor; therefore, saving Batt 2 for engine cranking in the event Batt 1 is depleted while at anchor.

So I guess this mystery is solved. I’ll probably just keep it as is and use the selector for batt 1 when at anchor. One of the questions I’ve yet to answer is: will battery 1 charge by the engine alternator if Batt 2 is selected? The owners manual indicates it will not. Someone mentioned above about switching the selector from Batt 2 to BOTH or Batt 1 with Engines running? The owners manual says you can do that and there nothing on the selector switch that says not to either.

I’ll probably tackle the inverter issue also and find a Pure SW inverter with transfer switch to replace this Modified SW inverter (assuming this one workers). Suggestions appreciated!!

Again, thanks for all your input! AND - now I know how the 12vdc system gets power, and what each of the 5 batteries run.

[g36]

It wont charge both. I never switch my selector switch ,could if I need to but never have needed to. I check it occasionally and verify operation and power switched. If the house has power on both selections figure that out. I would get your banks setup so that you don't need to rembember to change the switch setting on a regular basis or everytime you use the boat, use it to isolate the other starting battery that's its intent. I wouldn't get to bent out of shape if your not always charging all batteries all the time. You should make sure at the dock everything is getting charged . A typical weekend for many would be start up the boat on friday/Saturday go out drop anchor. Start up Sunday come back in. So you have started the engines 2 times. Do you really need to charge all the batteries underway for this? , no. A battery is not going to discharge just being there without a load on it (over a long time ,yes) Youve probably started the genset while out thats also run with your battery chargers. Charge the house bank since its been used while underway , if its a deal then put the selector in both or the other bank and start up and charge . Your going to be back at the dock in a while and they all will get charged again. If your useage is way different then some things may need to change . Keep it simple.

[g36]

Looking at your diagram. If you disconnect your positives on battery charger 1 which goes to port engine and stbd engine (battery 1 and battery 2)do you still have the same power scenario that you have now with house and everything being powered all the time or does it change to be isolated by the switch in a single position 1 or 2? Like it should.
The helm will obtain power directly from the main dc panel at the dinette.
Also there's a panel behind and below the aft cabin tv cabinet(,lower cabinet back wall, look up) that allows access to the back of the selector switch mounted in the steps.

[Viper]

Source of the post....there's a panel behind and below the aft cabin tv cabinet(,lower cabinet back wall, look up) that allows access to the back of the selector switch mounted in the steps.

What a pain it is to do any work on the electrical under the stairs. If they had cut the wires just a little longer, it would have made a world of difference for access from above. I find access from behind just as difficult if not worse on some models. They could have also made it possible to remove that electrical panel easier. In some models, you had to dismantle that step to get the panel out. It's a convenient spot for what's in there but access for repairs could be improved upon.

[bud37]

Source of the post So I guess this mystery is solved. I’ll probably just keep it as is and use the selector for batt 1 when at anchor. One of the questions I’ve yet to answer is: will battery 1 charge by the engine alternator if Batt 2 is selected? The owners manual indicates it will not. Someone mentioned above about switching the selector from Batt 2 to BOTH or Batt 1 with Engines running? The owners manual says you can do that and there nothing on the selector switch that says not to either.

That is how I handled ours........made a start bank and a house bank........remember the switch just allows you to take power from the bank you select #1 or #2 or both......I chose the start bank based on which one the windlass was wired to, then the engines would be running or should be whilst operating the windlass , also the windlass requires start type batteries for proper operation. This will require some manual switching but its not that big a deal.

Doesn't matter how many batteries in each bank just have one positive and one negative cable from and to and one charger feed to each. You could have 2 start type batteries in parallel in the start bank and however many 6 volt in series parallel to make your 12volt house bank or just 12v deep cycle batteries in parallel.
Perhaps think about a Victron BMV with a shunt to monitor your house bank.

Just remember not to switch the selector switch to OFF while the engines are running. It really just takes some time to digest all this and really understand the panel/switch/breaker relationships....you are on your way as I figured. Like I said earlier watch your helm voltmeters when the switch is in different positions. Good luck....

[Mikwallace]

Source of the post Looking at your diagram. If you disconnect your positives on battery charger 1 which goes to port engine and stbd engine (battery 1 and battery 2)do you still have the same power scenario that you have now with house and everything being powered all the time or does it change to be isolated by the switch in a single position 1 or 2? Like it should.
The helm will obtain power directly from the main dc panel at the dinette.
Also there's a panel behind and below the aft cabin tv cabinet(,lower cabinet back wall, look up) that allows access to the back of the selector switch mounted in the steps.

I must revisit the drawing. When I drew the diagram, my little pea brain was thinking single engine past experience and was thinking one battery per engine. But I now believe that to be incorrect. It’s as bud37 stated above, “ ...remember the switch just allows you to take power from the bank you select #1 or #2 or both....”.

BTW on the diagram where I show a red & black wire from Battery 1 to the helm. It looks like an “aftermarket previous owner add-on. I’ve got to trace that wire to see what it feeds. It’s a gray plastic wire with a red/black inside. It goes from Batt 1 to the starboard side of engine compartment and upward through a wire tunnel behind the CO detector in the salon. I suspect it’s dedicated power to a rear view camera and video screen mounted at the helm. It’ll be easy to figure out if that’s it by disconnecting the wire from batt 1 and turn on the monitor.

If understand your question correctly; (If you disconnect your positives on battery charger 1 which goes to port engine and stbd engine (battery 1 and battery 2)do you still have the same power scenario that you have now with house and everything being powered all the time or does it change to be isolated by the switch in a single position 1 or 2? Like it should.), yes. During my test, I disconnected all positive cables in this order.

Batt 2 - disconnected the Pos (Red) cables. Selector switch to 2; result was no power to house or engine. Move selector to Batt 1 (with Batt Pos cables disconnected on Batt 2) and had power to house and engines. Re-connected Pos cables to Batt 2.

Batt 1 - disconnected all Pos (Red) cables. Selector switch to 1; result was no power to house or engine. Move selector to Batt 2 (with Pos cables disconnected on Batt 1) and had power to house and engines. Re-connected Pos cables to Batt 1.

Edit: I hit the “Submit” button instead of the “ Preview” button. Add comment:

So after soaking all this in, I’ll swap Batt 5 and Batt 2. This will give me a 1000cca cranking battery on bank 2. Then I’ll have 3 Deep cycle batteries in parallel on Bank 1. Using as G36 has been successful with by selecting bank 2 to crank engines and run to favorite spot, then after dropping anchor switch to bank 1. Let bank 1 with 3 batts in parallel run the house and saving bank 2 to crank engines for recovery to the marina.

Then as these batteries deplete I’ll probably move to house setup with 6v golf cart batteries in series on bank 1. And 1 battery on bank 2 for cranking. Then I’ll only have 4 batteries!


Next question:

With both engines running, do the two alternators go to same place? Back to the selector switch and only charge what the selector switch is connected to? And how does the Generator battery get charged?

Thanks for all the help!!

[bud37]

Source of the post And how does the Generator battery get charged?

Two ways....One, if you have the on board charger connected....two, the genny charges its own battery while it is running. This is why some of the ways these boats are set up is complete overkill with the generator battery size. In reality these are just small equipment engines that require only around 250 cca to start depending on your genny size (hp), also of course this will not apply if you have a diesel genny.

Horror of horrors, I just had two start batteries in parallel to start the mains, to this bank I connected the generator so it started off the same bank, thereby eliminating the generator battery ( more room ). Now this may rub some folk the wrong way but it worked just fine and while the generator was running it was charging the mains start battery bank.

Now your on board charger probably has the capability to charge three banks, it doesn't have to, check the wiring for that.

[g36]

Yes , oem the alternators only charge what the selector switch is set to. Unless somebody has done something different. Which sounds like maybe they have on your wiring, Cause the only common points to both battery banks on your drawing is the battery 1 charger and the selector switch. It may be not be working correctly.
Not sure if you understood what I explained, about my selector switch useage it is only moved if I have an emergency start condition I do not change its state on a routine basis when I go out to anchor or just cruise.