Please Help Me Understand

OK, I have been around boating for a number of years and this is the first boat I have owned with a battery switch. I don't quit understand the purpose of it.

Here is what I do know:

• There is a #1 and #2 side. Each side is connected to a different battery bank. I have 2 banks with golf cart batteries.
• I know not to turn the switch while the engines are running.
• I keep the switch on "both"

So fill me in on the rest I am missing.......

The switch let's you chose which battery you are running off of. If you select #1, in your case everything on board is using bank 1. If you chose #2, you are using bank #2. If you select all, then you are drawing off of banks 1 and 2. Usually you will only use one bank at a time. This procedure keeps one bank at full charge. If you use "all" you are draining all your batteries and could have a hard time starting your engine if they are dischrged to low. I choose which bank to use by the calendar date; batt 1 on odd days, batt 2 on even days.

Your battery selector switch does not determine charging--they all get charged no matter which position the switch is on.

Good luck, Howard

>I know not to turn the switch while the engines are running

This because the diodes on the alternator that convert the AC to DC current are very voltage sensitive; if you disconnect the battery load the voltage spikes and fries the diodes.

All modern battery selection switches allow you to select either battery bank without affecting the diodes, maybe worth updating the system....

Thanks Howard.


I have set up my battery system where the start batteries (both engines and genny) are not connected to the house side. When running the charger, only the house batteries are charged. When the engines are running, then everything get charged through a smart battery isolator. I start my engines enough to not have to place them on a battery charger. But I also carry a portable battery charger, just in case......

Rustybarge said:

>I know not to turn the switch while the engines are running

This because the diodes on the alternator convert the AC to DC current are very voltage sensitive; if you disconnect the battery load the voltage spikes and fries the diodes.

All modern battery selection switches allow you to select either battery bank without affecting the diodes, maybe worth updating the system....

Click to expand...

Good point. I would love to switch to all digital battery gages etc....I just placed something else on the "to-do-list!!!

A common arrangement with two battery banks is one for starting the engine and the other for the "house" to serve remaining electrical needs, with the house bank having considerably higher capacity. I normally have the parallel switch "off" as when it is on the two banks are effectively made one. It's wise not to deplete the engine start battery.

The fear of moving thebrotary switch is not between batteries. They internally are make before break, so no hassles.

The FEAR is turning the switch OFF and disconnecting the alt from the batts.

POOF maybe new diodes.

The cure for 4 decades is a better rotary switch that will disconnect the alt Field before cutting off the batts.

There will be 2 little terminals on the rear of theswitch to cut the field.

These are set as break (field) before break (circuit) .

Here iswhat you need to see from the switch mfg.

"5444 includes Alternator Field Disconnect (AFD) which protects the diodes in the alternator in the event of the switch being switched to the OFF position while the engine is running."



Blue Sea Systems HD Series 4 Position Battery Switches, 500A




These Blue Sea Systems four position battery switches offer 500 amps for large diesel engines. These switches switch isolated battery banks to all loads or combines battery banks to all loads and feature tin-plated copper studs for maximum conductivity and corrosion resistance. The studs accept 1/2" (M12) ring terminals and have a 7/8" stud length (22 mm) that can accept multiple cable terminals. Accepts up to 4/0 AWG battery cables. Blue Sea Systems one-piece terminal stud design never loosens over time. One-piece stainless flange nuts ensure safe and secure connections. Fits most Perko and Guest low amperage battery switch hole patterns. Case design allows surface or rear panel mounting options. Tactile indicator conveys knob position by feel. 5444 includes Alternator Field Disconnect (AFD) which protects the diodes in the alternator in the event of the switch being switched to the OFF position while the engine is running. If the AFD is not used to protect the alternator, an LED can be connected to the AFD terminals to indicate when the battery switch is in any position but OFF.

• OFF-1-BOTH-2
• Cranking Rating (10 Sec.) 2,750A; Cranking Rating (1 Min.) 1,150A
• Intermittent Rating (5 Min.) 700A
• Continuous Rating: 500A @ 32V DC Maximum
• CE marked, ISO 8846, UL listed - UL1107 electrical power switches. Meets ABYC requirements. Meets UL 1500 and SAE J1171 external ignition protection requirements.
• IP66

SINGLE CIRCUIT
3 POSITION
4 POSITION

markpierce said:

A common arrangement with two battery banks is one for starting the engine and the other for the "house" to serve remaining electrical needs, with the house bank having considerably higher capacity. I normally have the parallel switch "off" as when it is on the two banks are effectively made one. It's wise not to deplete the engine start battery.

Click to expand...

This is the way I do it also. I had two house banks and a 1/2/both switch, but after researching systems I switched to one large house bank and one designated start with a crossover switch, just in case. My parallel switch is keyed, and I have the key removed and hanging on the ignition key so if someone "helps" me with the batteries I am covered.

FF,
I just installed one of those selector switches. The old one looked as if it came out of a 37 Plymouth.

I always use the switch in the start (#1) position to start the engine .. then switch to #2 (house bank). Xantrex controls the charging from the alternator or shore power. And I leave the shore power on all the time at the marina so the batts float at 13.75vdc. They charge at 14.25 when needed. AGM batts.

In the simplest twin engine boat system each engine has a start battery directly connect to that engine usually via an on/off switch.


the two batteries are also connected to separate legs of the switch you ask about. That switch can then be used to select either of the two batteries or combine them in the both position. In such a system all house 12Ve electrical power is drawn from the engine start batteries as determined by the switch position.




I don't like using the both position because if a battery fails the other bank will discharge into the failed battery possibly overheating it and leaving you stranded if you don't have separate start batteries or a genny charger..

bayview said:

I don't like using the both position because if a battery fails the other bank will discharge into the failed battery possibly overheating it and leaving you stranded if you don't have separate start batteries or a genny charger..

Click to expand...

Good point.......

As mentioned above in an ideal world you should have two battery banks and two battery switches. The larger "house" battery bank should have a simple on/off switch> The start battery bank should have the 1-2-both switch to allow you to parallel the two banks for emergency starting if the start batteries are low.

Finally, your alternator should be wired directly to your start battery bank. The prevents damaging the alternator diodes by accidentally turning the battery switch off, or by changing the setting on an older battery switch. The start and house battery banks should be connected by a battery combiner so that both banks are charged as soon as your start battery goes above about 13 volts.

A good way to do it is with Blue Seas Auto Charge Relay (ACR) and Remote Battery Switch (RBS). Normal mode is just leave in Auto position, and when on charger or with engines running the batteries are all paralleled. As soon as house bank draws down voltage to a set point they auto isolate from the two start batteries. You can manually switch either at the helm or in the ER.
Sorry for not being able to read labels in photo. Ill see if I can get a better one. Top is helm panel.

Part of the decision process should be based on the capacity of the banks and your resting average consumption rate. If your drawing down the combined banks below 75% overnight, it would be tougher on the batteries if you seperated the banks and drew them down below 50%. Also a sustained higher draw rate (such as cooking dinner in the microwave through the inverter) would be much tougher on the batteries if only using one bank.

Ted

With a start batt on 1 and the house on 2 if the house is so dead it can not start the engine !#1 can be selected.

Usually the house bank is far larger than the start batt and will have no problem starting the engine as long as it is at 50%.

Traveling in both is safe and no electronic hook up is required as most starts are almost full so little of the 14V charge will get absorbed by the start and the house will get it all.Esp after the first 10 min.

Usually on shut down the low oil pressure alarm will sound , your key to set #2 House for the evening.

KISS

If you regularly loan your boat to someone that might not return to #2 house , there are other methods of making it even simpler for a novice , but the parts count is higher, and costs another $40.

hmason said:

The switch let's you chose which battery you are running off of. If you select #1, in your case everything on board is using bank 1. If you chose #2, you are using bank #2. If you select all, then you are drawing off of banks 1 and 2. Usually you will only use one bank at a time. This procedure keeps one bank at full charge. If you use "all" you are draining all your batteries and could have a hard time starting your engine if they are dischrged to low. I choose which bank to use by the calendar date; batt 1 on odd days, batt 2 on even days.

Your battery selector switch does not determine charging--they all get charged no matter which position the switch is on.

Good luck, Howard

Click to expand...

I used to manage my 2 banks as Howard outlined but have changed to running both instead of switching... my new reasoning is that running one bank will discharge to a lower SOC and is more detrimental to batty life...by running both SOC is higher and better for batty life. If start is a problem run gennie which has a separate betty or combine gen batty to start main eng.
Not sure if above makes sense but so far its working ok and havent gotten stuck or had trouble starting.
Don
'08 MS 34HT
"Bacchus"

Bacchus said:

...to running both instead of switching... my new reasoning is that running one bank will discharge to a lower SOC and is more detrimental to batty life...by running both SOC is higher and better for batty life. If start is a problem run gennie which has a separate betty or combine gen batty to start main eng.

Click to expand...

Ditto.

Just so, but some folks prefer to have an engine start batt , as a standby .

So I'll add another question to the "Please help me understand" thread:

Why do you need two start batteries for a twin engine vessel? It seems like over-redundancy, if you isolate the start from the house bank. One the first engine is started, isn't the alternator on number one more than enough to provide charge for the battery and current to start number two? Also, shouldn't a healthy battery be able to have more than enough whoomph to start both engines?

It's a moot point for me as PH has a single engine.


Jim
Sent from my iPad using Trawler Forum

Like others, I run my battery selector switch on All. My figuring is, should I kill the battery bank, the sun will shine and the wind will blow. I can recover with my wind generator and solar panels.

As I understand it, to use the bank down the least percentage is Best Policy. At least that's what Nigel Calder advocates.

My best idea though is to have a multitude of voltage meters on Seaweed. Wherever I look I can see one. Constant monitoring prevents those "ut oh" moments. There are no surprises.

You can buy hard-wired ones from eBay China for $2 or $3. Or for the same price, again Chinese products, a cigarette lighter that plugs in and gives voltage. It's not a perfect solution, but for me is Good Enough.

hmason said:

...
Your battery selector switch does not determine charging--they all get charged no matter which position the switch is on.

...

Click to expand...

Don't assume that this is true until you have checked. I owned a sailboat with the same setup (it's very common on sailboats) and only the bank that was connected being charged. To charge both (either from the charger or the alternator) require the battery switch to be set to "both".

In order to charge both all the time the charger would have to have two outputs or an echo charger would need to have been installed. Check this on your boat to be sure.

I personally do not like the two battery bank setup. It means you have to hold half of your battery capacity "hostage" just to start your engine. It's been pointed out that a relatively small battery is capable of doing the job for most engines. It also means that you tend to discharge each bank lower than you would if they were combined. On my sailboat I paralleled the two banks and added a smaller starter battery. I also installed an automatic battery combiner that ensure that all batteries were charged by either the charger or alternator without allow one to discharge into the other.

Richard

Britannia said:

Don't assume that this is true until you have checked. I owned a sailboat with the same setup (it's very common on sailboats) and only the bank that was connected being charged. To charge both (either from the charger or the alternator) require the battery switch to be set to "both".

In order to charge both all the time the charger would have to have two outputs or an echo charger would need to have been installed. Check this on your boat to be sure.

I personally do not like the two battery bank setup. It means you have to hold half of your battery capacity "hostage" just to start your engine. It's been pointed out that a relatively small battery is capable of doing the job for most engines. It also means that you tend to discharge each bank lower than you would if they were combined. On my sailboat I paralleled the two banks and added a smaller starter battery. I also installed an automatic battery combiner that ensure that all batteries were charged by either the charger or alternator without allow one to discharge into the other.

Richard

Click to expand...

Richard: Calder agrees you should have one large house bank rather than two banks at half size.


Jim
Sent from my iPad using Trawler Forum

Personally I like a single starting battery and a large house bank. I have a single grp 31 start battery and 4 grp 31 batteries in the house bank. They are connected by a combiner relay and also charged by a dual output solar controller that sends 10% to the start battery and 90% to the house batteries.

JDCAVE said:

So I'll add another question to the "Please help me understand" thread:

Why do you need two start batteries for a twin engine vessel? It seems like over-redundancy, if you isolate the start from the house bank. One the first engine is started, isn't the alternator on number one more than enough to provide charge for the battery and current to start number two? Also, shouldn't a healthy battery be able to have more than enough whoomph to start both engines?

It's a moot point for me as PH has a single engine.


Jim
Sent from my iPad using Trawler Forum

Click to expand...

The problem is when one of the engines wont start and you run down the battery trying to start it. Then there may not be enough juice to crank the other engine.

I'm of the crowd that thinks all engines get a cranking battery and the house gets it's own bank of deep cycle batts.

JDCAVE said:

So I'll add another question to the "Please help me understand" thread:

Why do you need two start batteries for a twin engine vessel? It seems like over-redundancy, if you isolate the start from the house bank. One the first engine is started, isn't the alternator on number one more than enough to provide charge for the battery and current to start number two? Also, shouldn't a healthy battery be able to have more than enough whoomph to start both engines?

It's a moot point for me as PH has a single engine.


Jim
Sent from my iPad using Trawler Forum

Click to expand...

Actually two batteries are not required. Everything, including house could be run off one or one bank. Twins offer redundancy that gets lost without two batteries.

Alaskan Sea-Duction said:

OK, I have been around boating for a number of years and this is the first boat I have owned with a battery switch. I don't quit understand the purpose of it.

Here is what I do know:

• There is a #1 and #2 side. Each side is connected to a different battery bank. I have 2 banks with golf cart batteries.
• I know not to turn the switch while the engines are running.
• I keep the switch on "both"

So fill me in on the rest I am missing.......

Click to expand...

Britannia makes a good point. Most sailboat setups as they come from the factory have a 1/2/Both/Off switch. I imagine that many of the smaller powerboats are the same. In most cases, they are wired so that the switch selects both the battery to be used, but also which battery is to be charged. Take a look at your wiring to be sure. On the 1/2/All switch there are three posts, a #1, #2, and common. If your alternator output is going to the common post, then that switch determines which bank is being charged by your alternator.

Down the road, you may want to consider a setup where you have a large house bank and a smaller start battery, much as Britannia described. If your alternator output is connected to your 1/2/Both switch, then I would keep it on both so that your alternator is charging both batteries while under way. As others have mentioned, your battery bank will tend to last longer if less deeply discharged. Having the selector on Both will do that for you. However, you have to be aware of the state of charge so you aren't stranded after being at anchor for a couple of days.

If I was you, I would get combine those 6v into 1 bank and put them on #1 and get a small starter battery and put it on #2. Run your alternator and charger directly to your house bank and install an Echo Charger to keep your starter battery charged up. Very simple wiring, much easier than a combiner, and relatively inexpensive.

You can go one better and add an Engine On/Off switch. Run your starter battery to the the On/Off switch and connect your starter to the On/Off switch. Connect your House bank to the #1 post on the 1/2/Both and your DC panel to the common post (as it is now). Then connect your On/Off switch to the #2 post of your 1/2/Both switch. Install an Echo Charger between the House bank and the Start battery and you are set.

Normal operation, you leave the 1/2/Both in the #1 position and the Engine On/Off in the On position. If your start battery fails, you switch the 1/2/Both to Both, the Engine Switch to OFF and your House bank will start your engine. If your House bank has failed and you need emergency power for nav lights or VHF, then switch the 1/2/Both to Both and the Engine Switch to On. Here is the diagram for my setup. Now, if you have a larger boat with a more complex electrical system, such as generators, inverters, etc... then this won't help at all.

dhays said:

... Take a look at your wiring to be sure. On the 1/2/All switch there are three posts, a #1, #2, and common. If your alternator output is going to the common post, then that switch determines which bank is being charged by your alternator....

Click to expand...

On my Catalina 36 the alternator used the starter motor +ve wire to charge the batteries. So whatever was connected to the starter motor (1, 2, both) would get charged by the alternator. Clever reuse of some thick gauge wire!

Richard

Thanks everyone. Looks like I have some updating to do....

Britannia said:

On my Catalina 36 the alternator used the starter motor +ve wire to charge the batteries. So whatever was connected to the starter motor (1, 2, both) would get charged by the alternator. Clever reuse of some thick gauge wire!

Richard

Click to expand...

Yup, but the power from the Alt went from Alt -> starter post -> 1/2/Both common post -> battery. Depending on the year of your C36, there may have been an Engine On/Off switch between the starter and 1/2/Both switch as well. I prefer a direct line from Alt to Battery.

BTW Alaskan Sea-Duction, if you are going to be making any changes to your setup, now would be a good time to ensure that you have a fuse in any Wire/cable that is connected to the house bank. Current ABYC standards call for a fuse to protect the wire within 7 inches of the battery and many older boats never had this.

dhays said:

Current ABYC standards call for a fuse to protect the wire within 7 inches of the battery and many older boats never had this.

Click to expand...

...and that maybe hard to achieve in some setups. At least it is on my boat. The fuse protection is after about 5' of 2/0 cable.


Jim
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