Battery Switch Use 1/2/Both?

[Tim Mills]

I have read some on this topic in the forum and still have a question regarding advice on how to use my duel battery switch. First some details. I recently purchased a 2004 Hunter 36. I think the previous owner had made some changes to the battery set up based on what I see in the owners manual. The current set up as best I can tell is as follows:
1. I have two battery banks.
2. Battery 1 is a single 12V starter battery.
3. Battery 2 is a bank of four 6V batteries configured to provide 12V with a capacity of 220 Ah. This battery has an electronic battery monitoring system attached to it to keep track of current, voltage, amp hours used, remaining hours, charge state.
4. The boat is normally in a slip and connected to shore power under most circumstances and I mostly day sail so I never think about having adequate charge.
5. The battery charger is a 30 amp charger which charges each battery separately through the battery selector switch. When the battery charger is turned on it will always charge both batteries regardless of how the battery switch is set.
6. The engine alternator will only charge the battery bank that is switched on at the battery switch at the time the engine is running.
7. When I bought the boat I was told to keep the battery switch set to "both".
8. Never ever change switch positions while the engine is running.

Based on what I have read here it would appear that the "set to both" advice is really bad advice. Each battery bank is quite different and therefore should not be connected to each other for an extended time and it would be possible to run down all the batteries leaving no emergency reserve. I did this once already by forgetting to turn on the battery charger and the refrigerator (on always) ran down both banks.

I believe switching from bank 1 to bank 2 on odd and even days wouldn't work in this scenario.

So what I am doing is this. I keep the battery switch on 2 all the time which is my house bank and leave battery 1 as my emergency to start the engine if necessary should I run down bank 2 after a day of sailing by not paying close enough attention to the charge state. Every once in a while I will start the engine using battery 1 just to make sure that it is charging.

My question relates to what do I do when cruising? I am going away for a week (first time I have been away from shore power that long). I am a little paranoid that I will run down my house bank 2 and find that battery 1 has lost charge either due to not being charged daily or because of, for example, the bilge pump ran it down which is not likely but possible I suppose.

When I am running my engine only and while cruising does it make sense to keep the switch set to "both" so that both batteries are charging when the engine is running and then switch to battery 2 when the engine shuts down?

 

[Ron20324]

When I am running my engine only and while cruising does it make sense to keep the switch set to "both" so that both batteries are charging when the engine is running and then switch to battery 2 when the engine shuts down?

Correct. I have 3 batteries and I rotate which one gets shut off whenever the engine is off.

 

[LeslieTroyer]

Your batteries willlast longer if you charge ONLY the house from charger or alternator and use a ACR to charge the start battery. Read MaineSail's 1/2/both thread

Les

 

[Benny17441]

Ok, you are doing good in most regards but over concerned about minor things. Yes you have two distinct battery banks so leaving the switch on both is not recommended and besides you need to maintain redundancy. It is logical to keep the house bank on and retain the starter bank for backup or emergency starting. To alternate battery banks would not be prudent as the starter bank cannot perform house duties with its limited capacity for deep discharge. A proper installation would have the bilge pump hard wired to the house bank and isolated from the starter bank. Mismanagement of the refrigerator use is one of the leading causes for depleting batteries when away from shorepower. As far as changing the battery switch selector with the engine running it depends on your switch. Most switches sold today are of the "make before break" type which insures there is a connection with the next circuit before disconnecting the previous one. These switches should not have the Off setting in between two of the other settings. These switches are safe to move the selector. Yes you can run the engine with the switch on Both to charge the two banks but you are defeating the safeguard of redundancy. What I would do is start the engine with the starting bank (#1) and run it a while until the engine recharged and then switch to #2. The secret is to work a routine all the time to minimize and avoid mistakes. Many will opt to leave the switch turned to the house bank all the time to simplify the procedure and avoid mistakes. If you are worried about having a discharged starter battery buy yourself some peace of mind by bringing aboard one of those portable battery packs used for automobiles. Charged it at home and take it with you on trips. I am one that never worried much about dead batteries as we basically have one of the most efficient hybrid vehicles that exists. Let the wind and sails power the boat. As far as being a week away from shorepower you need to budget your usage according to the batteries capacity. Your house bank is 220Ah. In order to preserve battery life the bank should not be discharged more than 50% or 110 Ah. Your budget should show how many Amps you will use in a 24 hour period and that will tell you how many days you can go and what your recharging requirements would be. A refrigerator can consume upwards of 50A a day which will use half of your capacity in a single day, so you would basically have to run the engine alternator for 6-7 hours to keep up with the demand. When we go on a trip we will schedule overnight stays at transient slips on marinas not only to recharge batteries but to get a hot shower, stretch the legs and go to a restaurant. We also carry a gas powered Honda 2000 portable generator which can be used to provide 13.3A shorepower service to the boat. It can run the battery charger and power our 12.5K btu air conditioner. I would rather kill a couple of portable generators over the years than the main boat engine. I don't mind running the engine when we need propulsion but to run it with the sole purpose of charging batteries is against my nature. There are many ways to skin a cat so do your homework and figure out what would work best for you.

 

[Tim Mills]

You folks are fantastic.

Thank you.

 

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[Crazy Dave Condon]

One thing on small boats with the outboard running, never switch the battery selector. Does this apply also to the larger boats when the inboard is running?

 

[Stu Jackson]

You got a lot of the ideas right. Here's the how & why of it:

OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

This is a newer primer for boat system wiring design with a thorough digram: Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/in...dc-electrical-foundation.181929/#post-1332240

The Short Version of the 1-2-B Switch Stuff: http://c34.org/bbs/index.php/topic,5977.msg38552.html#msg38552 This is a link to the Electrical Systems 101 Topic, reply #2

What are ACRs, Combiners & Echo Chargers? (by Maine Sail) [scroll to the top]
http://forums.catalina.sailboatowners.com/showthread.php?p=742417 and http://c34.org/bbs/index.php/topic,9404.msg70131.html#msg70131

 

[Stu Jackson]

four 6V batteries configured to provide 12V with a capacity of 220 Ah.

Nope. It's more.

 

[jeepbluetj]

Yup, 4 GC2s would be over 400 Ah.

What they all said - leave it on 2. Use the big bank for everything. Keep #1 in case you deplete bank #2. ACR is ideal, but you can just charge bank #1 sometime before you go. You will drain bank #2 in a week if you have refrigeration and no charging sources. Easy solution is to buy ice. Other solutions are lots of engine running, generator, or solar.

Most 1/2/both switches are make-before-break, i.e. they'll connect #2 before disconnecting #1 if switching 1 to 2. Therefore, you can change the switch during operation safely, except to turn it OFF. Never turn it OFF while the engine is running. If you have a much more rare break-before-make switch, don't turn it at all during engine operation. You can tell if it's break-before-make by turning it slowly with cabin lights on, if the lights go out between settings you know you cannot change it while the engine is on.

 

[Roland5048]

One thing on small boats with the outboard running, never switch the battery selector. Does this apply also to the larger boats when the inboard is running?

You can switch between B1 and B2 and All when motoring. Do Not go to OFF. You run the chance of blowing a diode in your alternator.

 

[Roland5048]

four 6V batteries configured to provide 12V with a capacity of 220 Ah.
Nope. It's more.

I have the same set-up. I believe the capacity is closer to 440Ah. That gives you 220Ah until 50% exhausted.

 

[Stu Jackson]

Most 1/2/both switches are make-before-break, i.e. they'll connect #2 before disconnecting #1 if switching 1 to 2. Therefore, you can change the switch during operation safely, except to turn it OFF. Never turn it OFF while the engine is running. If you have a much more rare break-before-make switch, don't turn it at all during engine operation. You can tell if it's break-before-make by turning it slowly with cabin lights on, if the lights go out between settings you know you cannot change it while the engine is on.

A far simpler "solution" is to never switch the switch when charging sources from the alternator are present. Just don't.

An even better solution is to read the links I provided and make the switch a USE ONLY switch by moving ALL charging sources to the house bank. Then you can turn the switch OFF even when the engine is running. Really.

Once you understand the concept, making the "switch" is pretty easy. Pun intended.

 

[Benny17441]

One thing on small boats with the outboard running, never switch the battery selector. Does this apply also to the larger boats when the inboard is running?

It depends on the switch. Most switches in use today have the "make before break" feature where the next battery bank is engaged before the other is disconnected. It is safe to switch the battery selector in these as long as you do not have to go through OFF. This switches also position the Off selection to one end of the dial. Yes, the same thing applies to inboard diesels as well as outboards; the object is not to damage the diodes in the alternator.

 

[jeepbluetj]

A far simpler "solution" is to never switch the switch when charging sources from the alternator are present. Just don't.

An even better solution is to read the links I provided and make the switch a USE ONLY switch by moving ALL charging sources to the house bank. Then you can turn the switch OFF even when the engine is running. Really.

Once you understand the concept, making the "switch" is pretty easy. Pun intended.

Oh, I agree completely, and we've agreed before

But the OP's boat is wired the way it's wired and it sounds like he was heading out pretty soon on a cruise. So I thought I'd provide a bit of info that may be helpful if he needed to start on #1 and then turn to #2 to charge.

 

[Tim Mills]

four 6V batteries configured to provide 12V with a capacity of 220 Ah.
Nope. It's more.

I have the same set-up. I believe the capacity is closer to 440Ah. That gives you 220Ah until 50% exhausted.

Yes that's right. I meant to say that I had 220 Ah of capacity at 50% charge. So I would work to keep them at least 50% charged.

Thanks all.

 

[Stu Jackson]

So I thought I'd provide a bit of info that may be helpful if he needed to start on #1 and then turn to #2 to charge.

Thank, I understand. What we should share with the OP, though, are his options. Unless he has started up all of his electronics before he starts his engine and REQUIRES that he use the start bank to avoid dropping out said electronics, then he is NOT wired the "simple, OEM" way, where the power to his distribution panel comes off the C post of the 1-2-B switch. He would, to do this, have to have more than just a 1-2-B switch.

So, if he just has the OEM 1-2-B, then if he is planning to charge, the simpler option is to start on B. Which is what altogether too many skippers used to do, erroneously thinking they needed both banks to start the engine, when indeed it was the switch that determined which banks got charged with the alternator running. Run the engine, charge both banks, and go to the house bank when the engine is off. No issues of make before break or that stuff, either.

 

[Crazy Dave Condon]

Years ago make for break, the industry referred to it as Quick Disconnect to avoid blowing diodes and the key was not go thru the off position. I am glad I brought this up so some can learn not to go thru the off position of a battery selector.

 

[The Book of Sail]

If I'm not mistaken, if you have 4 golf cart 6 volt batteries then don't you have 440 amp hours ? I've got 4 Trojan 105's and that's what I figure, or a little less since they are no longer new.

The Book