battery monitor, one bank, no starting battery

[Troy Scott]

Folks,

I've read many articles about boat electrical systems, and I've successfully reworked a few systems. In the articles, one recurring theme has me thinking. The idea is that there may be no need to complicate our electrical systems by having a separate starting battery and a big battery switch. If there is one deep cycle bank, and if that bank is sensibly managed so that the charge is never allowed to fall below that required to start a cold engine, why not eliminate the complexity? I understand the peace of mind that comes from having a starting-only battery, but really none of us should be running our house banks flat anyway. It seems to me that the starting battery is an attempt to fool-proof our electrical systems. If there is a monitor with an alerting device of some kind that would tell us when it's time to charge, we should be OK with the simplified system. I understand that many of the answers to this question will be philosophical in nature, and I expect that. The folks from whom I would really like to hear are those who've tried this idea. How has it worked out? What monitor did you use? Do you regret the change? Any advice?

[Maine Sail]

I understand the peace of mind that comes from having a starting-only battery, but really none of us should be running our house banks flat anyway.

No, they should not, but they do. We should not be getting in car accidents either, but we do.

I like to refer to the back up bank as an "emergency bank" not a start bank because that's all you really need it for.

It seems to me that the starting battery is an attempt to fool-proof our electrical systems.

Yes that's exactly what it is, just like fuses and breakers.

If there is a monitor with an alerting device of some kind that would tell us when it's time to charge, we should be OK with the simplified system.

Cars have seat belt warning lights, fuel gauges, low oil lights, service now lights etc. etc. yet people continually run out of fuel and oil. Most battery monitors do not automatically program for cycle life and lifetime CCA/MCA capabilities which dwindle with time. If you are not good at programming & re-programming a battery monitor, which most boaters don't even know needs to be done, then you are at a higher risk of false readings.

I understand that many of the answers to this question will be philosophical in nature, and I expect that. The folks from whom I would really like to hear are those who've tried this idea. How has it worked out? What monitor did you use? Do you regret the change? Any advice?

I would think anyone who's tried this knows very well the implications and as such is more careful, thus, I think you'd hear what you want to hear.



Here are my thoughts on simplicity:

Two banks & a 1/2/BOTH/OFF switch.

1) House Bank: This will consist of two, three or four batteries purchased at the same time and wired in parallel if 12v or series/parallel if using 6v batteries and can be wired to position #1 on the batt switch.

2) Emergency/Start/Reserve Bank: This will consist of one battery with ample marine cranking amps to start your motor in an emergency. This will get wired to position #2, or second position for the second or back up bank.

Human Error Factor:

You do not really need nor want to be switching back and forth between house and emergency banks with the battery switch. Doing so can leave room for human error.

Any sufficiently sized deep cycle house bank will, and should, re-start your motor at 50% house bank depletion with zero issues. I have even once re-started, at roughly 15% capacity, a 330 HP Cummins using deep cycle 6V batteries..

I have been starting on the house banks on my boats for well over 20+ years. I've never really understood why anyone would need or want to switch back and forth on a small aux engine yet people do this all the time. A guy who's boat I race on even does this and the last time during an overnight race he forgot to switch back to teh house bank at night running lights and equipment. The group 24 "emergency bank" was dead in no time.

Sure, if you have a huge Caterpillar diesel then a dedicated start bank might be necessary but they generally are not on small sailboat aux engines.


Simplicity:

When we get to our boat we simply flip to bank 1 (house) and when we leave we switch it off. It's that simple.

How is this done?


First you'll want an automatic battery combining relay (ACR) or an Echo charger to keep the emergency bank topped off. I personally prefer the Echo Charger. These devices are reasonably priced and simple to install. They also remove the potential for human error while at the same time charging BOTH banks without the need to flip the 1/2BOTH/OFF switch.

Re-wire the alternator output:

One more change you'll want to make while in there is to run your alternators output wire directly to the house bank.

Most boats run the alternator the starter then over to the common post of the 1/2/BOTH/OFF switch. This allows for the switch to pass through the off position which can fry the diodes in your alternator if the motor is charging or running.

By doing this you will no longer run the risk of frying the alternators diodes by passing through the off position on the battery switch or having a guest flip the battery switch off, at the end of a sail, with the motor still running, thinking they are doing you a favor. You'll also put companies like "Zap-Stop" out of business. A product like "Zap-Stop" is only being sold because of DEMAND due to HUMAN ERROR. This upgrade may take all of 20 minutes to do and can save you hundreds of dollars in alternator repairs.

In summary using a 1/2/BOTH/OFF switch

1) House & emergency banks
2) Add an ACR or Echo charger to charge the "emergency bank"
3) Direct wire the alt to the house bank.


This is about as fool proof a system as you can get on a small budget. For well under $200.00 you can simplify and prevent fried alternators and eliminate needless switchig of the battery selector. You will get to your vessel and simply flip to 1/HOUSE that's it. When you leave flip it to OFF...

One more thing . You never want to, nor need to, "combine" banks 1&2, using the BOTH position, in a situation where one bank is dead! Use the fresh bank.

I know lots of people over think the system and replace the 1/2/BOTH/OFF switch, and do more than they need, but it is mostly unnecessary. You can have a very simple and reliable system for not a lot of money and seeing as most boats over 25 feet shipped with 1/2/BOTH/OFF switches why not keep it, and most of the wiring, intact.

I have done this upgrade on a number of vessels and every owner can't believe just how simple & useful it is..

[barfwinkle]

Maine Sail I like this a lot!!!!!

the biggest challenge for me would be how to re-direct the alternator to the "emergency" bank. Is that done at the back of the Battery Switch?

Fair Winds

[Maine Sail]

Maine Sail I like this a lot!!!!!

the biggest challenge for me would be how to re-direct the alternator to the "emergency" bank. Is that done at the back of the Battery Switch?

Fair Winds

The alt would get direct wired directly to the house bank not the emergency bank. The alt would charge the emergency bank via the ACR or Echo charger feeding off the house bank.

If either of those units should fail you can still use the BOTH position, like the old days, with the engine running, to charge both banks. This system is simple yet retains features of the old system like the ability to combine the banks if absolutely necessary like when running the engine in the event of a failure of an ACR or Echo. In short the system is redundant.

The voltage sensitive combiners like the Blue Seas ACR or the Yandina are extremely reliable. My Yandina combiner is over ten years old and has never failed to perform her duties combining banks. I have an Echo charger too but have not yet installed it as this boat already had the Yandina installed when I bought it from my friend. I plan to install the Echo this winter but to also leave the Yandina ACR in place but with an on off switch. Should the Echo fail me I'll simply flip a switch and be back to the Yandina, should the Yandina fail me, highly unlikely, I would just use the BOTH function while charging....

More on ACR's and Echo's


Automatic Charging Relays:
An automatic charging relay is essentially a voltage sensitive solenoid/relay that sits between two banks of batteries. When the unit sense a voltage rise of above about 13.2 volts the solenoid/relay engages and "combines" both banks so they get charged. The charging source is irrelevant and it will work with solar, wind, shore charge or alternator. They disconnect on a voltage drop the same way as they connect so when there is no charging source present the banks are again separated as the voltage falls below about 13.2 volts.

Echo Type Chargers:

The Echo charger is made by Xantrex. I like to call it a bleed charger. It operates as a DC to DC charger meaning it does not need 120 VAC to charge a battery and works off the regulated DC output of an alternator regulator.

An Echo type charger DOES NOT combine banks. The Echo charger takes incoming charge source DC current and diverts up to 15 amps to the emergency/start bank. Because your start bank will rarely if ever be used it will not take or bleed much of the primary charge source nor need to. On my last boat I rarely if ever saw more than one amp being bled to teh emergency bank because it was always nearly full.

It is very simple to hook up and it to sites between both banks but is fed off the house bank. The charge sources are wired directly to the house bank and the Echo takes care of feeding the start bank. It is important to note that the Echo is a voltage follower and does not regulate or change the output voltage any differently to the emergency bank than what is going to the house.

Combiners also send the same voltage to the both banks but they also "combine" meaning both banks are electrically combined and over time will equalize. An Echo does not allow large amounts of current to flow between batteries as a combiner does, which is good in a number of ways, especially if you run AGM's ..

[Steve Laume]

I have the exact system Maine Sail is describing with one minor difference. I added a second battery selector switch between the two house bank batteries before the main selector switch.

I did this because the house bank had been used exclusively before my ownership. There is probably a difference in the capacity of the two house batteries. I now leave them tied together almost all of the time as I have a small solar charger that keeps them topped up Rather than discharging into one another.

I usually start on the house bank. If it is a bit sluggish I switch to both.

Adding the start or emergency battery has added more to my peace of mind than you could imagine. Before this arrangement there was always a shadow of doubt as to weather the engine would crank. Now it is a given, Steve.

[John Danicic]

The simplest solution that Main Sail relates is the simplest.

I simplified it further by making it a bit more complicated. Two separate batteries systems controlled by two separate battery switches. The house bank is 4 six volt deep cycle golf cart batteries and the start bank is a standard diesel starting battery.

On Mariah, I ran the alternator wire directly to the battery switch house post (on mine that is Number 2) and it runs direct to the house batteries. Nice big battery cable that already exists and can easily carry the 80 amps nicely. This is on the original Cape Dory Master battery switch. Switching this switch has no effect on the output from the alternator what-so-ever.

I added a second battery switch and wired the starting battery to the #1 post. The start battery is recharged via an echo charger which charges the target battery when ever the house battery is being charged whether it be solar, alternator or AC charger. I always use the start battery to start the engine and the house battery for everything else. I am a firm believer that if you don't use a battery you lose it. There is also no voltage drop and subsequent resetting to the instruments and auto helm by starting the engine by this isolation.

I start a visit to the boat by switching the house switch to 2 (labeled house) and the starting switch to 1 (labeled start) then forget it. The two switches are wired together in such a way that if both are on "all", I can combine the two banks in an emergency. I can also isolate the starting battery if need be by switching the house switch to 1 and the start switch to 2.

See, I said it was simple but complicated.

The wiring diagram for the above came to me in a similar fashion as the Flux Capacitor diagram did to the Professor in the movie, "Back to the Future". If any one is interested, I can post it.

Sail on

John Danicic
CD36 - Mariah - #124
Lake Superior - The Apostle Islands
CDSOA # 655

[Doug Gibson]

I have my boat wired just as Maine Sail describes as well, with battery combiner. Has worked great for 4 years. I did replace the normal 1-2-both battery switch with one made by Blue Sea. It's a single throw, double pole switch, so by switching it to "on", it connects both house and starter banks (but keeps the two circuits separate). It does have a "combine batteries" position on the switch for emergency, but this requires a very deliberate act.

It makes it as simple as possible and you avoid the 1-2-both options and decisions entirely.

[Doug Gibson]

I meant to include the Blue Sea Model number: 5511e.

http://bluesea.com/category/1/productspecs/5511e

[Maine Sail]

I usually start on the house bank. If it is a bit sluggish I switch to both.

Steve switching to both with a depleted house bank can be dangerous. Why combine a perfectly charged emergency battery of perhaps 80 total ah with a dead or nearly dead bank of over 200, 300 or 400+ ah's. All you're doing is depleting the capacity of your emergency bank by combining as it tries to "fill" and equalize or get to equilibrium with the dead/low bank leaving all the batteries at an over all lower state of total charge.

If you have AGM's this situation gets even scarier as they can "accept" whatever you can throw at them for a charge. Let's say you have a 450 ah bank for the house and an 80 ah battery for start. You've killed the house bank to 5%. 5% of 450 is 22.3 amp hours of capacity left. If you combined that bank with an 80 ah battery you would be at about a 15%-18% overall state of charge across all banks once everything equalized and the charged battery tried to fill the empty bank. Is 15% of capacity enough cranking amps to start your engine? Perhaps, but why risk it? If you don't combine you have 100% of the MCA's in your 80ah battery to start the engine with.

Wet cells have low acceptance so in most cases unless the house bank is mammoth & dead you won't kill the start battery too quickly. What if you try to start the engine and it won't start, or you discover the intake is plugged and not spitting water and you leave them connected while fixing this you will soon have one large bank of equally depleted batteries that now may not start the engine.

When one bank is dead or low and will not start the engine pleas do not use the BOTH feature. All this does is take good energy from the smaller but charged battery and begin siphoning it off to the larger depleted bank thus sucking away precious cranking amps.

One should always start the engine on the good battery then once running combine to BOTH for charging all batts unless you have the system described above then you just flip back to bank 1 and leave it there....

[Steve Laume]

Thank you so much. I had never considered the discharge to the house back. I just figured total amps was what I would be gaining.

Fortunately the house bank is usually quite adequate for starting. When I first installed the start battery I was switching to it under normal starting circumstances. I soon discovered how easy it is to forget to switch back to the house bank for charging. I have an echo charger that always seems to keep things right.

Thanks again for pointing out what should have been obvious. I do have AGMs so your post is most appreciated, Steve.

[Matt Cawthorne]

Maine Sail

If you are not good at programming & re-programming a battery monitor, which most boaters don't even know needs to be done, then you are at a higher risk of false readings

The question that I struggle with, is not re-programming the monitor, but just what is the capacity of the the battery? We have a good idea when new, but unless the battery is periodically tested for capacity (read that as taken to a point where it can not start the engine) then we really don't know it. Take me for instance. I have a system with just two group 31, 12 volt batteries. I use battery #2 most of the time for starting and house duties. When we have hit that battery for more than about 30 ah then we switch to battery #1. Sometimes I take it to 40, but not often. Both are kept with the correct amount of water and the charge is topped off before leaving the boat each weekend.

Before the trip to Maine this year I decided to replace battery #2 since it was 6 years old. Battery #1 was only 4 years old. Both batteries seemed to work well when the trip was started and I was using about 40 AH from each on the trip before recharging (offshore legs). The first weekend out after returning from the trip the older battery started taking a significant charge, even though it had not been used. The batteries were charged to a normal 3 stage charging profile. That evening, battery 1 was dropping below 10 volts just running the house lights for 5 minutes. The boat now has a second new battery.

I used to work for the research facility that supported Exide, Ray-o-vac,etc and understand that the capacity curves of batteries can degrade very quickly. Unless one is to replace the batteries frequently how would anyone know how much was left in a single bank? Even if you do replace the house bank, what if you get a dud that only lasts a couple of months.

If you had a lifestyle where you did not need to keep to a schedule, and you did not need your engine, SSB, running lights or refrigeration then perhaps a dead electrical system is tolerable. Personally, I like to keep a back up battery, a charged hand held VHF, an oil powered light, a dinghy with a motor and a pair of oars.

[barfwinkle]

What I need to do is re-route the alternator output to the House bank directly, install an Echo type charge controller and wire it between the House and Emergency Bank.

Having done that then when I get on the Boat, I just turn the battery switch to 1 and leave it there (and turn it off when I leave dah).

Since I have a solar panel for the house battery, the Echo will also take the "excess" charge from there and re-direct the "excess" to the emergency bank as well. Correct?

TIA and Fair Winds and I hope to see you in Havre de Grace

[Joe CD MS 300]

Where did you guys that are using this type of "echo charger" set up learn about it? Is there a book or magazine article I could read about it?

Joe

[Steve Laume]

I probably heard about it on this site or one of my marine electrical books.

I ordered the echo charger from Jack Rabbit Marine.

http://www.jackrabbitmarine.com/%28stup ... c=0&type=0

I stuffed it inside, high up in the back of the cupboard below the electrical panel. As I recall it was pretty simple to set up.

That was the same year I did high output alturnator, smart charger, echo charger, battery fuse, start battery, new battery cables, changed the switching, cleaned up the panel wiring and added a battery monitor.

After all of that I got a pretty good understanding of the system and the echo charger should seem simple, Steve.

[Troy Scott]

This is an Excellent Thread. I'm taking 100% credit for having started it