Do you manage/switch house vs. starter batteries?

[goldenstate]

With the end goal of developing a cruising power budget in which I have confidence, I am curious if careful sailboat owners switch between starting banks and house banks of batteries regularly?

My previous owner instructed me to leave the battery switch on "both" under all circumstances, and that has worked fine.

I have neither a functional ammeter or battery monitor at present and I am considering purchasing a monitor with a shunt that can display state-of-health and state-of-charge. The instructions I have read for several monitor models indicate that users are typically only monitoring the house bank, as the starter bank rarely reaches a fully discharged state.

So this brings me around to my subject line. Do you switch between your battery banks for starting your boat every time you go out? Other than isolating that bank for starting purposes with the main switch, do you have another setup that is preferable?

Do you just switch to the 'house' bank if you are at anchor or at sea, wanting to protect your starting bank?

Thanks in advance for sharing your practices.

 

[Christian Williams]

Hmmm. I remain on house all the time, for starting and for appliances. The other battery is reserved strictly for emergency starting. I basically never use it.

The whole idea of the switch is to reserve a battery for emergency starting. Using "both" would defeat that idea, and you wouldn't need a switch at all.

I believe this is pretty standard procedure.

 

[toddster]

I think the proper sequence in the classic case is to turn it to "1" to start, then to "both" so that both batteries charge. Then to "2" when the engine is shut off, so that the start battery doesn't get discharged.

But in recent years, I have just gone with the One Bank To Rule Them All theory. That is, one big house bank, used for everything.

If you read up in the Calder or or Casey books, they discuss why different types of batteries are more suited for engine or house use, but really, the small engines in our boats shouldn't put that much strain on the house bank. Unless you chronically have to crank it a lot.

Drawbacks with OBTRTA are that you have no emergency back-up in case Something Gets Left On and drains it. Or the BMS in your fancy LiFePO4 batteries shuts them off for violations of the programmed operating conditions. And on my boat, cranking the engine does apparently create enough voltage drop that all the electronics reset. Which seems harmless, but can be a pain if you thought you were monitoring a particular VHF channel, but now no longer are. Or you thought the autopilot was steering, but it no longer is.

So I have been thinking of going back to a small "start" battery and a charging relay or DC/DC charger (so that mucking around with the main switch is not necessary).

Also, if solar panels are added to the system, one would think that the accidental discharge scenario becomes less likely.

 

[goldenstate]

Hmmm. I remain on house all the time, for starting and for appliances. The other battery is reserved strictly for emergency starting. I basically never use it.

The whole idea of the switch is to reserve a battery for emergency starting. Using "both" would defeat that idea, and you wouldn't need a switch at all.

I believe this is pretty standard procedure.

So then, for the purposes of calculating how much current you can safely use while underway, you ignore the capacity of your starting battery? There is clearly logic to your approach.

At the same time Ericson gave me two cavities of roughly equal size to hold batteries. It seems like one would want to take advantage of the full amount if possible or necessary.

Something like this could probably help in the emergency circumstance:

Amazon.com

 

[Christian Williams]

On the 32-3 I had two Group 27 deep cycle batteries, which was effectively all that would fit.* I never used the second battery. All house loads and engine start were handled one battery, recharging daily offshore with 100 amp alternator. There was never a doubt about cranking. As belt and suspenders and a hangman's noose, I also carried a portable car jumper battery--just in case. (It wasn't as fancy as the one in your link, and in fact it wouldn't hold a charge for more than a month.)

On the E381 there's more battery space, so I have two Group 31 AGMs as house bank, plus a third as emergency-only starter battery.

The way my setup is wired, I switch to "both" when running the engine in order to charge both banks. But at the dock, I can leave it on "house bank" and both batteries get charged and maintained by the charger.

*They didn't really fit. The molded box was apparently designed for Group 24s. The 27s stuck up an inch or more, which I accommodated by raising the cover with hidden rails.

 

[goldenstate]

On the 32-3 I had two Group 27 deep cycle batteries, which was effectively all that would fit.* I never used the second battery. All house loads and engine start were handled one battery, recharging daily offshore with 100 amp alternator. There was never a doubt about cranking. As belt and suspenders and a hangman's noose, I also carried a portable car jumper battery--just in case. (It wasn't as fancy as the one in your link, and in fact it wouldn't hold a charge for more than a month.)

On the E381 there's more battery space, so I have two Group 31 AGMs as house bank, plus a third as emergency-only starter battery.

The way my setup is wired, I switch to "both" when running the engine in order to charge both banks. But at the dock, I can leave it on "house bank" and both batteries get charged and maintained by the charger.

*They didn't really fit. The molded box was apparently designed for Group 24s. The 27s stuck up an inch or more, which I accommodated by raising the cover with hidden rails.

Very helpful, thank you.

 

[Jerry VB]

We have a 32-3 with two identical group 24 batteries. My methodology is:

• Sailing*: On even days, I use "A". On odd days, I use "B".
• At the dock (plugged in), I use "Both".

My theory is that this will equalize the wear on the batteries when running off batteries - each will get roughly the same number of charge/discharge cycles. At the dock they will share the workload, again equalizing the wear.

When running off batteries, this keeps one battery in reserve. It also prevents a failed battery from discharging the good battery when running off of batteries.

Disclaimer: We've only owned the boat one year, the batteries were purchased by the previous owner, and I don't know how he treated the batteries (very well, I suspect - mostly at the dock charging). In 20 years I probably will be able to tell if the theory works as well in practice as it does in my head.

* We don't do anchorages - the admiral wants the toilet to have a handle that makes it go "whoosh."

 

[jtsai]

Here are some lessons and practices worked for me after traveled 640 nm this summer/fall exploring portion of the Chesapeake Bay from NC and back. These lessons may or may not apply to west coast with vastly different geography, climate, and sailing/cruising style.

Ardea has three group 31 AGM batteries (barely fit), one for start, two for house bank, stock alternator, and no solar. After a night at anchor, before start the engine, I turn off all DC breakers and use only the starting battery to start the engine. This is a precaution to protect electronics from surge at engine start (overkill?). This habit also forces visual check on DC breaker panel, is the anchor light off?

Once engine started, turn battery position to house bank if going to be a day of sailing, to both position if motoring. In addition to the usual electronics, the refrigerator consumes 4.5 amp/hr and that needs be separated from starting battery when under sail.

This leads to daily energy consumption lesson learned. With refrigeration running during the hot summer days, even with motor running few hours a day (some days longer), the house bank begs for "deep charge" from shore power on the 3rd or 4th day.

During the return trip in October, I experimented without refrigeration and only had to visit marina once on the 12 day trip, mainly due to weather. However I was motoring a lot through the ICW and canal so the house bank was content with charge supplied via alternator.

I came to the conclusion after this adventure is that what I have is really a Prius. Depending on weather, where to go, how far, how soon need to be there, and whether to anchor or visit marina at the end of the day, I can motor, sail or motor-sail. So variations on how we use the boat influences how little/much we worry about the battery switch positions.

 

[Christian Williams]

Perfect. The nice thing about a diesel while cruising is that whenever you choose to motor, to keep to a schedule, you automatically return the batteries to full charge in a few hours. It's a good excuse to stop slogging along at 2 knots in the sun and just turn on the beast.

What makes it work best is a new alternator, rated somewhere around 80-100 amps, with "smart" regulator, which recharges quickly.

It's also possible to have the best of both worlds--save fuel and noise and have cold beer, too. Usually the scheduled daily recharging of less than an hour will also cool down beverages placed in the evaporator coil box. That's the only time I run the refrigeration.

 

[ddoles]

I use an automatic charging relay which combines the batteries when charging, but automatically separates them when not charging. The house bank is dedicated to only house loads and the starter battery is only for starting. The switch is on/off/both. In the On position they are connected as described and this is used all the time in normal circumstances. If there is a need to combine them (for example with a dead starting battery) switch to Both to get the full power of the combined bank. I like this because I never need worry about managing charge/discharge cycles between 1 & 2, and I know I should always have a fully charged dedicated starting battery no matter what is happening with house loads.

 

[Mike Siegel]

Alright so ill add my setup to discussion as a monkey wrench . I have a 3 position switch . On 1 just house battery is powered, nothing to engine. On 2 both the house is powered and the engine is powered but the alternator only charges the engine battery . On 3 both batterys are linked and both are charged by the alternator . Previous owner did this because he planned on changing the house battery to lithium and won't charge lithium with the alternator

 

[goldenstate]

Alright so ill add my setup to discussion as a monkey wrench . I have a 3 position switch . On 1 just house battery is powered, nothing to engine. On 2 both the house is powered and the engine is powered but the alternator only charges the engine battery . On 3 both batterys are linked and both are charged by the alternator . Previous owner did this because he planned on changing the house battery to lithium and won't charge lithium with the alternator

Is "don't charge a lithium battery with an alternator" a widely-accepted principle?

 

[Mike Siegel]

Yes , not directly anyway . Battleborn website has a ton of info about converting to lithium if interested

 

[bigd14]

***Rabbit Hole Warning***

1/2/BOTH Switch Considerations

1/2/BOTH Battery Switch Considerations - Ever wonder how to make the 1/2/BOTH switch easier to use, let this article explain how to do that.

marinehowto.com

 

[Kenneth K]

Do you just switch to the 'house' bank if you are at anchor or at sea, wanting to protect your starting bank?

Likely depends on the makeup of one's battery banks. While a deep cycle battery will start the engine just fine, a "start" (non-deep cycle) battery should not be deep cycled.

If the "start" bank is non-deep cycle battery(s), I'd be less likely to parallel it with the house bank, except maybe for combined charging from the alternator.

 

[goldenstate]

***Rabbit Hole Warning***

1/2/BOTH Switch Considerations

1/2/BOTH Battery Switch Considerations - Ever wonder how to make the 1/2/BOTH switch easier to use, let this article explain how to do that.

marinehowto.com

I'm not sure how I'm supposed to feel about a 5000+ word article on a 3-position switch. I have very strong mixed feelings.

 

[peaman]

As a 32-3 owner (and no battery expert), one thing that has caught my attention in this thread is that three different 32-3 owners have described their respective battery installations, all different, and all different from mine:
Christian's 32-3 had (2) group 27 (1985, hull#604)
JerryVB has (2) group 24 (1998)
jtsai has (3) group 31 (1990, hull #760)
compared to my (2) group 24 + (2) group 27 (1987, hull #737)

Did my PO go crazy for battery capacity? When it comes time to replace batteries, should I consider slimming down? The two smaller batteries are in what must be the factory-provided compartment at the forward end of the quarter berth, while the larger ones are in the aft bench of the dinette, just forward of the nav station.

 

[Christian Williams]

The, er, acid test is need. You can run a fridge longer, utilize solar, and generally hang on the anchor longer without running the engine. Did the PO also install an upgraded alternator with regulator? Anyhow, more juice is usually good.

I guess the downside is cost replacement when needed. But then you have an option.

 

[Sean Engle]

I think the proper sequence in the classic case is to turn it to "1" to start, then to "both" so that both batteries charge. Then to "2" when the engine is shut off, so that the start battery doesn't get discharged.

That's what I used to do...

 

[Loren Beach]

Other than a great coastal delivery on a 32-3, I have no direct battery info. That said, we have been happy with our battery setup for decades on our similar-size Olson 34.
We upgraded from the stock scheme of two group 24 batteries with a 1-2-all switch.

The pair of medium size 12 volt batteries were replaced with two large golf cart format batteries, https://www.trojanbattery.com/product/t-145_plus/
These give us 260 AH capacity in one main bank.

About 15 years ago I installed a separate spiral cell AGM 12 emergency battery, which is only switched into the system for.... an emergency. I start the diesel several times a year to test it, and it worked wonderfully that last time the house bank suddenly lost capacity while out cruising. That former house bank lasted 9 years, so I replaced it with two more of the same. I remain a fan of Trojan batteries.

Our house bank runs everything and starts the 25 hp diesel without any problem. Everything being 12 volt fridge, all lights, and currently a forced air furnace.

There seem to be multiple correct ways to accomplish this battery stuff...

And note that we have never used a "starting bank" at all.
Stock alternator, too - 50 amp on our former M25XP, and about 70 amp on the newer Beta25. Both internally regulated.