1/BOTH/2/OFF Switches Thoughts & Musings

Mar 14, 2012
131
Beneteau Oceanis 40CC Brisbane, CA
I think I'm chasing a false economy. To connect up two banks I'll end up spending $70 to $150 on an additional ACR/dc charger plus an extra $50 for a dual bank monitor compared to a single. Which means I'm spending $120 to $200 to keep from spending $190 on 2 new batteries. It seems replacing the aging T-105s is more economic than trying to squeeze out whatever life is left in them.
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
I think I'm chasing a false economy. To connect up two banks I'll end up spending $70 to $150 on an additional ACR/dc charger plus an extra $50 for a dual bank monitor compared to a single. Which means I'm spending $120 to $200 to keep from spending $190 on 2 new batteries. It seems replacing the aging T-105s is more economic than trying to squeeze out whatever life is left in them.
Not to mention the wear & tear on a smaller bank that you don't have nearly as bad on a larger one. Sell the T105's on Craig's List, they will sell..... Ask $50.00 each and take $90.00 for the pair and now you only need to buy one battery....
 
Mar 14, 2012
131
Beneteau Oceanis 40CC Brisbane, CA
So, I re-wired the switches to look like this.



I wanted to run it past the collective knowledge here before I connect up the batteries. Plus I still have to make a couple battery jumpers to replace over-long and under-gauge jumpers. (thanks for the cable making tutorial Maine.)

Also, I presume the shunt on the battery monitor is best between the battery cables and the ground disconnect switch rather than the other side of the switch.
 

arf145

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Nov 4, 2010
484
Beneteau 331 Deale, MD
I know it's been almost a year, but I see no answer to Dantodd's last post. I'm curious because I now have a boat with the standard Beneteau setup of separate on/off switches for a house bank and backup bank and am looking for the best way to use them (or not?) while eliminating the human error factor. I went with the on/off/emergency use of the battery switch with Echo Charge for the backup with my last boat and loved it. I plan to do the same or equivalent. So, do I just rewire the alternator to the house and relabel the switches to House and Backup and make sure no one switches both on? Use the two on/offs as masters and add an A/B selector upstream?
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
I know it's been almost a year, but I see no answer to Dantodd's last post. I'm curious because I now have a boat with the standard Beneteau setup of separate on/off switches for a house bank and backup bank and am looking for the best way to use them (or not?) while eliminating the human error factor. I went with the on/off/emergency use of the battery switch with Echo Charge for the backup with my last boat and loved it. I plan to do the same or equivalent. So, do I just rewire the alternator to the house and relabel the switches to House and Backup and make sure no one switches both on? Use the two on/offs as masters and add an A/B selector upstream?
Three ON/OFF switches is another great alternative provided it is wired correctly, many are not.

An ON for HOUSE

An ON for ENGINE

AN BOTH for EMERGENCY COMBINE or ISOLATION

HOUSE bank goes bad - Turn OFF the HOUSE switch, turn ON the COMBINE switch and turn ON the ENGINE switch...

START bank goes bad - Turn OFF the START switch, turn ON the COMBINE switch and turn ON the HOUSE switch...

The three switch method is a great way to do it if you have the room and don't already have a 1/2/BOTH. Most boats shipped with the 1/1/BOTH hence the article...

I prefer a "key" switch for "COMBINE" so it is less confusing. It also helps to label it EMERGENCY COMBINE, HOUSE and ENGINE...


If you add an ECHO the alt and all other charge sources go to the house bank. Then using the COMBINE/BOTH switch charges both banks or better yet just let the ECHO do all the work and just turn the HOUSE & ENGINE switches to ON when you get there and OFF when you leave.
 

arf145

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Nov 4, 2010
484
Beneteau 331 Deale, MD
Just so I'm clear, are you suggesting that the other bank be dedicated to starting the engine? With my other boat, I've been thinking of that battery as "Backup" and have normally just started the engine from House. In your scenario, with Combine OFF, and both banks ON, where is the juice coming from?
 
Jun 25, 2012
942
hunter 356 Kemah,the Republic of Texas
Never combine larger house bank with smaller start/reserve for charging...... Always start engine on house bank, engine alternator only sees house bank. Leave Echo charger to take care of the charging of start/reserve battery needs. Reserve is just that only for emergency starting of main engine.
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
Never combine larger house bank with smaller start/reserve for charging...... Always start engine on house bank, engine alternator only sees house bank. Leave Echo charger to take care of the charging of start/reserve battery needs. Reserve is just that only for emergency starting of main engine.
Robert sorry but this is just incorrect advice. Banks are combined for charging on thousands and thousands of boats without issue. Prior to Echo type chargers this was the ONLY way to charger two banks efficiently... All Echo's Duo's, ACR's or other B2B chargers do is make it easier and remove human error... You can combine banks for charging provided the charge voltages are similar and the battery "type" is similar eg: FLA/FLA or AGM/AGM or GEL/GEL.....
 
Jun 25, 2012
942
hunter 356 Kemah,the Republic of Texas
Robert sorry but this is just incorrect advice. Banks are combined for charging on thousands and thousands of boats without issue. Prior to Echo type chargers this was the ONLY way to charger two banks efficiently... All Echo's Duo's, ACR's or other B2B chargers do is make it easier and remove human error... You can combine banks for charging provided the charge voltages are similar and the battery "type" is similar eg: FLA/FLA or AGM/AGM or GEL/GEL.....
Mainsail...I was trying to keep my comment to the simplest of terms....I agree on combining matching battery banks for possible safe charging....but maybe I was not clear enough on. Let me see if I can explain better what I was trying to convey... Example... larger house bank be it wet cell,optima spiral bound agm or typical gel/fake agm , etc. Then combining a smaller wet cell or gel. to the larger bank for charging. Will not the smaller battery having a different charging rate then the larger Bank. And lets not forget any age differences between the two. Or damaging a good battery by combining it with a gone bad battery. Basically I was just trying lean my comment toward the safer side of the argument. What do you think? Am I getting it right yet?
BTW... Please define FLA ... down here in the Republic of Texas we try not to used fancy complicated big words.:naughty:
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
Mainsail...I was trying to keep my comment to the simplest of terms....I agree on combining matching battery banks for possible safe charging....but maybe I was not clear enough on. Let me see if I can explain better what I was trying to convey... Example... larger house bank be it wet cell,optima spiral bound agm or typical gel/fake agm , etc. Then combining a smaller wet cell or gel. to the larger bank for charging. Will not the smaller battery having a different charging rate then the larger Bank. And lets not forget any age differences between the two. Or damaging a good battery by combining it with a gone bad battery. Basically I was just trying lean my comment toward the safer side of the argument. What do you think? Am I getting it right yet?
BTW... Please define FLA ... down here in the Republic of Texas we try not to used fancy complicated big words.:naughty:
Each battery will take the current it can or needs at what ever the system voltage is. If you mix a low internal impedance battery with a high impedance battery eg: FLA (flooded lead acid) / TPPL AGM then the TPPL/AGM will get what it needs first and when full or there is left over current the other battery will take what it needs. If the charge source can satisfy both banks than each bank will simply take what it needs or can accept at a given voltage.

The most common mixing of "types" I see is FLA deep cycle with AGM start/reserve. Seeing as the AGM is nearly almost always full, when used as a reserve or start battery, you can easily combine them for charging as the AGM is full and won't take current so it flows to the bank that needs it..

Just today I was working on a boat and had my portable inverter wired to the start bank for my heat gun. When I fired up the engine after using the start bank 2.2A was flowing to the pretty much "full" 400Ah house bank and 50A was initially flowing to the start/reserve bank which then tapered down to about 22A once it came up to 14.6V... The alternator is capable of 120A when hot...

The house bank is Trojan L16's true deep cycle batteries, very thick plates, and the start bank is two group 31's... Current goes where it is needed....

This start bank has an ECHO but I by-passed it with the BOTH feature to bulk it up before letting the solar and Echo take over...
 
Jun 25, 2012
942
hunter 356 Kemah,the Republic of Texas
Each battery will take the current it can or needs at what ever the system voltage is. If you mix a low internal impedance battery with a high impedance battery eg: FLA (flooded lead acid) / TPPL AGM then the TPPL/AGM will get what it needs first and when full or there is left over current the other battery will take what it needs. If the charge source can satisfy both banks than each bank will simply take what it needs or can accept at a given voltage.

The most common mixing of "types" I see is FLA deep cycle with AGM start/reserve. Seeing as the AGM is nearly almost always full, when used as a reserve or start battery, you can easily combine them for charging as the AGM is full and won't take current so it flows to the bank that needs it..

Just today I was working on a boat and had my portable inverter wired to the start bank for my heat gun. When I fired up the engine after using the start bank 2.2A was flowing to the pretty much "full" 400Ah house bank and 50A was initially flowing to the start/reserve bank which then tapered down to about 22A once it came up to 14.6V... The alternator is capable of 120A when hot...

The house bank is Trojan L16's true deep cycle batteries, very thick plates, and the start bank is two group 31's... Current goes where it is needed....

This start bank has an ECHO but I by-passed it with the BOTH feature to bulk it up before letting the solar and Echo take over...
Thanks mon!...... Very good explanation. You made it sound so easy even a caveman could figure it out. Me on the other hand?? I had a feeling you were talking about a wet cell .... But never had used the term FLA before.
 

Pat

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Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
I have one 'good' battery in the lazarete on my 272 LE...One bad battery (dead) is located under the starboard settee. I've ordered two new group 27 "dual purpose" DEKA
marine batteries....w/approx. 2 weeks needed for delivery to the store....Our boat has been in the yard, but since I had one charged battery and one dead battery (approx. 7 yrs old, I unplugged the shorepower cord and just let the boat sit for the winter. I did not want to burn up the statpower charger trying to charge a dead battery... After 2 years, we finally have enough water to launch...Question is, can I probably launch & get the little diesel running w/just the one good battery....without waiting for the arrival of the two new batteries to arrive? O'Day recommended 95 ah batteries so that is what I have bought.(2 of them)..I've read about the battery switch issue(s) above, but in this simple arrangement and small boat, where we come back and plug in the shore power/charger almost every night, when sleeping at the slip, why can't we just stay on both? Thanks for the advice....? Patrick
 
Feb 26, 2004
22,760
Catalina 34 224 Maple Bay, BC, Canada
Patrick, why not just disconnect the dead battery AT the battery? Your choice to remove it from the boat now or not. Your engine will start fine on the one remaining good battery.
 

Les

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May 8, 2004
375
Hunter 27 Bellingham, WA
Perhaps you've already said it in your post (which is excellent by the way 'cause I think I understand much of it) but what happens if I have a shore powered battery charger? Does it by pass the 1-both-2 switch and charge both batteries? I have a two battery (Group 29 AGM) system for my day sailor/weekender and leave the switch on 2 (1 being my reserve). My marine electrician said when I come in after a day sail, I hook up my shore power and it charges both batteries. Does it?
 
Feb 26, 2004
22,760
Catalina 34 224 Maple Bay, BC, Canada
Les, it all depends on how it's wired. The best recommendations anyone can give you is to spend the time to trace the wires and draw a simple diagram. Then we can help you.
 
Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Stu has an answer.

I would see no reason why you want your battery charger to be controlled by the battery switch.
 

Les

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May 8, 2004
375
Hunter 27 Bellingham, WA
Stu is right--I should just check the wiring. And had I thought this through I'll bet my marine electrician by-passed the switch all together. Makes sense. Thanks guys. My head wasn't thinking today.
 
Jan 22, 2008
880
Fed up w/ personal attacks I'm done with SBO
I would see no reason why you want your battery charger to be controlled by the battery switch.
Mine is;)

I have three banks controlled by two switches and a two bank shore charger. One bank is the isolated engine starter and gets a direct line from one charger feed. The other two banks are house banks controlled by their own battery switch. The second charger feed goes to the common post on the switch and then with the switch I can direct the charge to either bank or both. Same thing with the alternator output.

Note that there are no combiners, ACR's or isolators on my boat, battery switches only.
 

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Bazzer

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Feb 4, 2009
30
2 Newport 30 Benica
Why have a 1-2 switch at all? In fact Ample Power says that all battery 1-2-both switches are prone to failure because of the high loads put on them by water makers and the like. The only switch that they recommend is a emergency bypass switch should the dedicated starter battery fail.