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Electrical/battery switch setup

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dalelargent
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USA
198 Posts

Initially Posted - 08/14/2023 : 06:50:48

I just dropped in two new batteries and while re-wiring I got to thinking about how the PO wired this boat. I�m not sure it�s the best design. I desire your input on how YOU would do it.

I have:

2 dual-purpose 80 ah wet cell batteries.

A battery selector switch: off/1/2/both

The outboard has an alternator and electric start.

Small solar panel with controller.

And, of course, an electrical panel with the usual breakers for usual circuits.

There is not a battery charger onboard. (No point as I don�t have shore power on the dock.)

I want the outboard to charge both batteries.

I want the solar panel to charge both batteries, and preferably be able to do so with the battery selector �off.�

How would you run wires for this setup?

1989 c25 WK/TR #5838
1998 Catalina 36 mkii
1983 Vagabond 14

Edited by - dalelargent on 08/14/2023 07:04:17

Leon Sisson
Master Marine Consultant

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Response Posted - 08/14/2023 : 12:51:25

Re: "I want the outboard to charge both batteries.

I want the solar panel to charge both batteries, and preferably be able to do so with the [OFF-1-BOTH-2] battery selector in the OFF position. How would you run wires for this setup?"

I'm assuming your solar panel is wired to your house battery, and the engine alternator to the cranking battery.

I suggest you look into a device called a "Battery Combiner" (with a electro-mechanical relay, not just solid state diodes) which can automatically connect batteries in parallel if either of them have excess charging capacity (at least about 13.5 VDC), or isolate them from each other if their voltage drops below some minimum (around 12.5 VDC). I'm pulling those example voltage values out of thin air, but I hope you get the idea. The battery combiner I use has the option of controlling it with a SPDT switch, in which case the switch modes are ON-AUTO-OFF.

It's my impression those traditional high current [OFF-1-BOTH-2] battery selector switches have become less popular, although I don't expect to convince anybody who has one to get rid of it. (My boat still has one.) Last I checked, the latest thinking is to install a high current SPST ON-OFF switch for each battery, and a 3rd one if you need more than a 150.A connection between batteries. (You probably don't.)

I also installed a high current circuit breaker in each battery's positive cable as close as practical to the battery. I think I used 100.A breakers after measuring 50.A electric starter current (10hp 4-stroke twin).

You might also look into one or more power monitors so you can see battery voltage, current, and cumulative power flow.

Let me know if you would like clarification or additional info.

� Leon Sisson

OLarryR
Master Marine Consultant

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3408 Posts

Response Posted - 08/14/2023 : 22:39:06

Leon has excellent recommendations and I probably should consider them as well. However, the setup you mentioned in your posting is common and similar to what I have on my '89. The main issue is that without using a battery combiner, the 2 batteries pretty much act as one and if you have or develop a bad cell in one battery, it's going to impact the benefits of having 2 batteries.

I also have a solar panel (20 watts) and that has worked well since 2006 when I installed it. My flooded batteries lasted a very long time, then 5 years or so ago, I replaced them with AGMs and they have so far been working fine. My solar controller provides a digital readout of the battery voltage and charging amps.

My battery switch is almost always in the "Both" position. My solar panel does not charge the batteries if the battery switch is in the "Off" position.

My website has a section on it devoted to my wiring mods - Adding a switch panel. I wanted to add addl loads (ie. fans, etc) and there was no room on the existing panel for addl loads. In fact, the existing panel had at least one positive terminal that actually had an adapter hooked up to it to accept 3 positive loads. I moved some of the loads (ie. Nav Lights) to my new panel and the VHF radio to a separate , now available, switch on the existing panel.

Below is a link to what the back of the existing panel looked like as I was reallocating the loads to switches. To see all the wiring mods - Go to my website opening page.

http://catalina25.homestead.com/Old_Switch_Panel_Back_wLabels.jpg

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

Edited by - OLarryR on 08/14/2023 22:59:07

dalelargent
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198 Posts

Response Posted - 08/15/2023 : 00:05:59

Here is some follow-up info and a few new questions:

I now realize the cable from the �number 2 battery� post on the battery selector switch isn�t connected to anything�it�s just hanging there. Should I go ahead and connect it to the positive post of battery number 2?

Also, should there be a jumper cable connecting the positive terminals on the two batteries? There is currently not one, but there is a cable connecting the two negative terminals. Or does the battery switch serve this purpose when on �both?�

1989 c25 WK/TR #5838
1998 Catalina 36 mkii
1983 Vagabond 14

Volksaholic
1st Mate

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Response Posted - 08/15/2023 : 04:17:53

quote:
Originally posted by dalelargent

Also, should there be a jumper cable connecting the positive terminals on the two batteries? There is currently not one, but there is a cable connecting the two negative terminals. Or does the battery switch serve this purpose when on �both?�

If you connect both positive and negative terminals together you're connecting the batteries in parallel and they'll act as one larger battery. You won't be able to select between them.

Also, a comment on Leon Sisson's post; I don't know why you'd prefer an electro-mechanical relay... but maybe it's just to differentiate between something that actively switches as opposed to a device that combines the batteries all the time without draining the one with a higher charge into the other. I haven't shopped battery combiners, but my experience with electro-mechanical relays vs solid state relays is that the solid state has a longer life span with no moving parts and no contacts to arc and erode. Maybe that's not an option in battery combiners, but that's what I'd be looking for if I were in the market.

Paul
1981 Catalina 25 TR/FK
Soon to be named either Fiddler's Dream or Fool's Errand depending on what it takes to get her into shape

dalelargent
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198 Posts

Response Posted - 08/15/2023 : 07:12:23

So, I think what I will do in the short term, is attach the cable from the battery switch terminal �battery 2� to the positive terminal of battery 2. And I will leave the selector on �both� all the time since I believe that�s how they will both charge from the motor and the solar.

To review, the two charging sources are currently positive leads on positive post of battery 1, and negative leads on negative post of battery 2. The negative battery posts are connected with a jumper.

Am I getting this right? Good plan?

1989 c25 WK/TR #5838
1998 Catalina 36 mkii
1983 Vagabond 14

Edited by - dalelargent on 08/15/2023 07:18:11

bjoye
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Response Posted - 08/15/2023 : 08:38:52

I'm on version 4.0 of my electrical refit. So I am well qualified on HOW NOT TO DO IT! Having spent way too much money and time tearing out the previous attempt, I have a few pointers that may help:

1. First, have an over all plan. You can not add to your system in an incremental fashion. And the best start is the following article by Rod Collins (MaineSail)

https://forums.sailboatowners.com/threads/building-a-dc-electrical-foundation.181929/

2. To directly address your question, you don't need a dual battery (House/Starter) system, been there, done that. We do not have a 50hp diesel to start. We do not spend days off shore. We rarely spend more than a night or two on the boat. If we suffer total electrical failure, we pull the starter rope. Not on option for larger boats.

3. Spend you money on:
a. proper fuses (I prefer MRBFs)
b. proper wire gage
c. proper connectors (heat shrink)

4. We have limited space for batteries and wiring. I set up my unswitch panel under the steps (motor, bilge pumps), and my switched panel behind the sink, and all wiring is in the dumpster:

5. My system is designed to support a number of items that most boats our size do not have: refrigerator, diesel heater/boiler, microwave, autotiller, N2K network, chart plotter. So I have an intergrated 1KW inverter/charger, AC subpanel, 2 Group 31 AGMs, 2 solar chargers.

"Frayed Knot" 1989 C-25 WK/SR #5878

Edited by - bjoye on 08/15/2023 12:32:02

Volksaholic
1st Mate

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Response Posted - 08/16/2023 : 07:20:27

quote:
Originally posted by bjoye

I'm on version 4.0 of my electrical refit. So I am well qualified on HOW NOT TO DO IT!

Wow!!! That's looks really clean and organized. I hate trying to chase down the rat's nest style installation. I'm going to save this post for when I get the first round of critical stuff done and get around to improvements. Thanks for sharing it!

One question I've got is why 2 solar charge controllers? You've got the batteries wired parallel so I don't understand how 2 charge controllers makes sense unless you have other batteries to charge (maybe usb/portal devices?) or one is idle as a backup. One thing I wasn't sure of is whether you can use one solar panel or array to feed multiple charge controllers or if you have them fed from a couple arrays.

Paul
1981 Catalina 25 TR/FK
Soon to be named either Fiddler's Dream or Fool's Errand depending on what it takes to get her into shape

islander
Master Marine Consultant

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4010 Posts

Response Posted - 08/16/2023 : 10:46:24

quote:
. To directly address your question, you don't need a dual battery (House/Starter) system, been there, done that. We do not have a 50hp diesel to start. We do not spend days off shore. We rarely spend more than a night or two on the boat. If we suffer total electrical failure, we pull the starter rope. Not on option for larger boats.

I totally agree. These aren't large crusers we have so I would follow the KISS principal. Get the largest amp/hr battery you can find and stay with the single thus eliminating switches and some wireing.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

dalelargent
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198 Posts

Response Posted - 08/16/2023 : 12:37:15

Ok, I want to keep this really simple and not prepared to be buying new equipment at this time.

So, perhaps my question is down to this:

IF I have two batteries, negatives connected and battery 1 positive is wired to �1� on battery selector switch and battery 2 positive is wired to �2� on the battery selector switch.

Outboard (with electric start and alternator) AND solar controller are both connected to battery 1 positive and battery 2 negative.

If the above is true, will the two charging sources charge both batteries? Would the switch need to be on �both� to charge both batteries? What gets charged if the battery selector is �off?� Perhaps just battery 1 since it has the positive lead from the charging source?

1989 c25 WK/TR #5838
1998 Catalina 36 mkii
1983 Vagabond 14

OLarryR
Master Marine Consultant

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3408 Posts

Response Posted - 08/16/2023 : 13:03:39

If the switch is in the �Both� position, your chargers will charge both batteries. But if the switch is in the �Off� or �2� position then your chargers will only charge battery �1� since there is a circuit always to battery �1� due to both chargers positive wire on the positive battery �1� terminal and the both chargers negative to the negative jumper to both batteries. My positive solar controller wire is not to either battery but to the switch panel positive bus terminal. When my battery switch is in �both� position, both batteries get charged and that is the way I leave it. However, if the battery switch was in the �1� position, then my solar controller would charge battery �1�, if in the �2� position then only battery �2� would be charged. If battery switch in �Off� position, then neither battery would be charged. I leave battery switch in �Both� position, both batteries get charged and my batteries have lasted a very long time doing it this way.
(My outboard, is connected to one battery positive terminal, probably the battery that goes to the battery switch �1� and so it would only charge the other battery if the battery switch was in the �2� or �Both� position - that�s why I always leave the battery switch in the �Both� position. Hope that clarifies the setup.)

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

Edited by - OLarryR on 08/16/2023 13:27:30

Voyager
Master Marine Consultant

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5312 Posts

Response Posted - 08/16/2023 : 19:15:12

Dale, I�m a little confused about where you connected the engine starter/alternator circuit and the solar panel controller. Are they connected across one or both sets of battery terminals, or on the output side (i.e.: house or panel side) of the 1-2-both switch?
I�m also confused by your statement: if I connect the positive battery terminals to one side of the switch and my negative battery terminals to the other side of the switch, will it be OK?
Answer: NO, because if you short circuit two batteries across your switch something will blow up or burn out.
Generally all black wires (negatives) all tie together without any switches or fuses (except any AC circuits - never mix the two). Wiring the positive sides is where the switches and fuses are installed.
May I suggest (as did Islander), tie both batteries together as 1 (with a 60A fuse between) and keep it real simple. Don�t switch your engine or solar controller, do switch your house panel and any cigarette lighter outlets and USB outlets.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - Voyager on 08/16/2023 19:32:26

Stinkpotter
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Djibouti
9044 Posts

Response Posted - 08/16/2023 : 20:18:51

This discussion is making me nervous. The 12V system is not benign--it is capable of hurting people and incinerating the boat. I would ask myself whether I'm working a little too close to (or beyond) the limits of my understanding of the system, and whether professional service is worthwhile. This is not the way to learn (possibly by error). Similarly, I would not install the AC electrical panel and wiring in my house. I think I pretty much understand it, but.........

Curmudgeon out.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 08/16/2023 20:20:51

dalelargent
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198 Posts

Response Posted - 08/16/2023 : 20:50:40

I must have confused Bruce, and therefore caused concern for Dave. Sorry! I in no way have negative and positive terminals crossing one another. I have a positive lead from each battery going to the battery selector switch. The negatives stay in their own little negative world. Ironically, I have done whole house wiring projects from scratch on projects I built (that passed inspection!).

Larry seems to understand what I meant to communicate. Thanks, Larry, for clarifying what I thought to be true. That matches my understanding of things�I just wanted some confirmation in case I didn�t actually understand the mechanics of the switch.

1989 c25 WK/TR #5838
1998 Catalina 36 mkii
1983 Vagabond 14

OLarryR
Master Marine Consultant

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3408 Posts

Response Posted - 08/16/2023 : 21:24:16

Okay - Thanks! Did not see your last posting as I was typing my posting. but here it is anyway:

I guess you figured you were asking simple questions and now you have answers, all well intended, ranging from responses about your current setup to enhanced setups.
You may also want to review the Manuals & Brochures link on the left of this screen - Go to the HTML Version of the Post 1988 Catalina Manual and then click on Electrical Section, then scroll down to Figure 4.2.5. That provides the 12 Volt DC wiring diagram.

Reviewing that diagram, it indicates the outboard positive terminal connected to the Battery Switch "Both"/"C" positive terminal and the negative from the outboard to the battery negative terminal (either one since there is a jumper cable between them). I thought my outboard positive cable is connected to Battery "1" positive terminal but I have to check, maybe it is connected to the Battery Switch. My solar controller is connected as I explained in my above posting.

Bear in mind that the Catalina Wiring Diagram represents the basic setup. But there are safety concerns to consider:

In the first posting, above, Leon mentioned installing high current circuit breakers in the each battery's positive cable. I know there are others that have posted doing this as well. While the control panel has a circuit breaker, it is supposed to function against short circuits in the wiring from the control panel going to the loads butl not from a short circuit before the current gets to the control panel from the batteries.

Also, when messing around with the 12 volts system it can be dangerous and considering all the above postings and clarifications to understand the current wiring on what mods may be considered, Dave's above posting about seeking professional assistance has merit.

While we are all trying to offer opinions, suggestions, we certainly should include a disclaimer, especially regarding electrical systems, that it is always at your own risk.

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

Edited by - OLarryR on 08/16/2023 21:36:13

bjoye
Navigator

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105 Posts

Response Posted - 08/17/2023 : 09:23:59

One question I've got is why 2 solar charge controllers? You've got the batteries wired parallel so I don't understand how 2 charge controllers makes sense unless you have other batteries to charge (maybe usb/portal devices?) or one is idle as a backup. One thing I wasn't sure of is whether you can use one solar panel or array to feed multiple charge controllers or if you have them fed from a couple arrays.

I have 2 solar panels: 110W on the Bimini and 50W on the companionway hatch. If you combine (by parallel or series) 2 dissimilar panels, your actual output is the lesser of the two. So by having 2 controllers, I have a total of 160W and not 100W. Both are Victron, so they are really good about working with other charging sources such as the dumb controller coming off the outboard (Tohatsu 9.8) or the AC charger/inverter.

"Frayed Knot" 1989 C-25 WK/SR #5878

Stinkpotter
Master Marine Consultant

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Djibouti
9044 Posts

Response Posted - 08/17/2023 : 20:16:49

quote:
Originally posted by dalelargent

I must have confused Bruce, and therefore caused concern for Dave...

Correct, and my apologies. Bruce, who I got to know after he purchased what was once my C-25 (from the person who bought her from me) is an electrical engineer, so when he's dubious about something like this, it gets my attention. Over a lot of years here, I've seen discussions that suggested questionable qualifications for planning and executing the wiring of a boat like this. Clearly that does not include you.

But I've raised the issue here before--this is not like wiring up a home entertainment system. I was 10 miles from anywhere off the California coast on another C-25 with smoke billowing out of the galley cabinet and the "dumpster"... Those things can shape your thinking!

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 08/17/2023 20:18:43

dalelargent
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198 Posts

Response Posted - 08/17/2023 : 20:59:02

You owe me no apology, Dave. I appreciate you looking after my welfare, for sure.

I went back and read my post that brought up these concerns. I see how my brevity and lack of specifics lead to the confusion. What I wrote was correct, but there was another equally plausible interpretation that would, indeed, be very bad if implemented.

I have never had a fire on board from any source, but it is my biggest fear�more than capsizing even. I pray I never experience one.

I truly value everyone�s time in sharing your experience!

1989 c25 WK/TR #5838
1998 Catalina 36 mkii
1983 Vagabond 14

Stinkpotter
Master Marine Consultant

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Djibouti
9044 Posts

Response Posted - 08/18/2023 : 05:51:54

It was just burning insulation--resolved quickly, first by shutting off the power. (Glad we had a handheld VHF on board.) Another boat accompanied us back to port--the dock was a welcome sight! My ditch bag now has a DSC handheld along with an electronic flare. (/hyjack)

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.