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Electric Start/Dual Battery Follow-up

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Monomachos
Deckhand

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Initially Posted - 06/20/2019 : 17:40:41

Salvete omnes,

I'm still working my way through adding a second battery with 1/2/OFF/BOTH switch. Wondering what gauge wire should be used to parallel the batteries. What I'm thinking of are the wires noted with astrices in the image below. ALSO, my outboard is a Nissan Marine 9.8 with electric start. The PO has battery cables for it (about an 8 ft) run beginning at a Blue Seas fuse block inside transom and running forward. Cables are 8 AWG. Wondering if this is sufficient for cranking load. Any help would be most appreciated. Please forgive my ignorance; I'm a philosopher and classicist by trade and am new the fascinating and maddening world of marine electricity.

Ago gratias vobis,

JLC

[img][https://photos.shutterfly.com/full/54611235255[img]

James Loxley Compton
C-25 SR/WK #5999 Erebus
Orange Beach, AL

Leon Sisson
Master Marine Consultant

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USA
1889 Posts

Response Posted - 06/20/2019 : 19:49:57

James,

Your image on shutterfly.com doesn't seem to be accessible without a membership.

To try to properly answer your question, I would need to know the starter motor maximum current draw, and the length of wire (within about 20%) between the cranking battery and the starter.

The wire length you can estimate by temporarily routing a rope or extension cord where the cable will go, then measuring it, or just fumble around with a measuring tape and call it close enough.

Determining the maximum current draw seems to be a bit trickier. First, it varies considerably depending upon engine temperature (starting up cold in the winter vs. restarting a warm engine in the summer). Second, starter current draw doesn't seem to be a commonly published specification like horsepower, weight, color, and list price.

After spending way too much time searching the Web, it appears to me that starter current for a 10 hp 4-stroke twin is likely between 50 amps and 100 amps.

When trying to apply those estimates (2-way length and max current) to the commonly available wire sizing lookup tables, one is next confronted with the question of acceptable voltage drop. The tables are usually for 3% and 10% drop as I recall. Using max starting current (an unlikely worst case) I'd use the 10% drop table. (I think I ended up using #4 awg.)

While we're on the subject of wiring up batteries, I strongly encourage you to include a main circuit breaker at each battery rated at that maximum anticipated cranking current used to select wire gauge.

How to interconnect more than one boat battery depends upon how you anticipate using them. Is one to be strictly for cranking, and the other as a house bank? Or both usually together serving both purposes?

The traditional OFF/1/BOTH/2 big red rotary switch has fallen out of vogue among some of us, replaced by two or three separate SPST big red rotary switches and/or automatic battery combiner relays.

Adding a second house battery complicates things slightly, but not too bad for anyone who survived figuring out a two battery system.

P.S.
Re: "...new the fascinating and maddening world of marine electricity."

If you haven't done so already, I encourage you to invest in "Don Casey's Complete Illustrated Sailboat Maintenance Manual" 892 pages, by Don Casey of course, and "Boatowner's Mechanical and Electrical Manual" 942 pages, by Nigel Calder, to go along with your well read copy of Chapmans Piloting and Boat Handling" 68th edition.

� Leon

� Leon Sisson

Edited by - Leon Sisson on 06/20/2019 20:02:22

Monomachos
Deckhand

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Response Posted - 06/20/2019 : 20:13:01

Leon, thank you so much. I really appreciate your time. Sorry the shutterfly image is not accessible (I'll try to find another way to post image). Re the starter current draw: indeed it is not an easily accessible number (even some average or parameters). I pored over my outboard manual and found nothing. So between 50 and 100 amps. Good to know! The run would be (round trip) about 16 ft. AWG 8 does seem a bit light . . . Not sure what PO had in mind. I may just need to go to for AWG 4 (and use same gauge for putting batteries in parallel). To your question about their use: the idea I have would be to have the option of 1 or 2, but often both depending on situation and management of the batteries. I have heard a lot about the old OFF/1/BOTH/2's falling out of favour. It's just what I'm used to one a powerboat and larger sailboat but do realise there are probably better options out there with the ACRs/combiners, etc. What a bloody complicated mess. But I'm pressing forward! Thanks, again, my friend. By the way, what preferred breakers do you use proximate to your batteries (once I figure calculations)?

JLC

James Loxley Compton
C-25 SR/WK #5999 Erebus
Orange Beach, AL

Monomachos
Deckhand

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21 Posts

Response Posted - 06/20/2019 : 20:22:17

Failed to see your PS. Yes! I've gotten Casey's 'Sailboat Electric Simplified' and mean to get his full volume classic. I've borrowed a copy of Calder from the colleague that got me into sailing and do have an increasingly worn copy of Chapman's! They all seem to be part of the 'canon' of marine literature.

James Loxley Compton
C-25 SR/WK #5999 Erebus
Orange Beach, AL

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 06/20/2019 : 20:43:30

I'm wondering about your objective... What is your purpose for a second battery? Your usages? We didn't have a second battery on our C-25, but we had fairly limited need for juice, and a Honda that put out 12 amps (about double most others). BTW, for boats like this, if you need a second battery, I think the 1-All-2-Off switch is good--the high-tech systems are mostly not for this category. You can charge both simultaneously off the motor, and when at anchor, use just one to run your "stuff" while saving the other to start the motor--although if it's not a Yamaha, you'll probably be able to pull-start if necessary. (I don't have that option now with my 3.5 liter V-6, so the switch is more useful to me!) I'm just saying you probably don't need to go beyond that on a 25' sailboat. You can have double your money back for this opinion.

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 06/20/2019 21:13:11

Leon Sisson
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Response Posted - 06/20/2019 : 21:54:48

James,

I agree with Dave about considering your intended use and budget. What I'm describing is what I decided on.

Re: "I'll try to find another way to post image"

I've had success going to TrailerSailor.com,
[https://forum.trailersailor.com/forum.php?id=1]
then using their server to host an image. Start as though posting a message or reply. Choose upload image option. When the URL of the uploaded image appears, copy that for use here. (I think you can then abandon the message on trailersailor.com and the uploaded image will remain.)

Re: "...Not sure what PO had in mind."

Sometimes it's best to consider the previous owner's mind one of life's unfathomable mysteries, and move on.

Re: "...the idea I have would be to have the option of 1 or 2, but often both depending on situation and management of the batteries."

One of the pitfalls of manual battery switching is remembering to do so. Charging both when power is available, then isolating the reserve cranking battery before burning through the house bank as though it were limitless. Automatic battery combiner relays can take care of almost all of this, only requiring manual intervention when abnormal circumstances arise.

The battery combiners in my Catalina 25 are "Combiner 100" model from Yandina:

[https://www.yandina.com/c100InfoR3.htm]

Re: "what preferred breakers do you use proximate to your batteries "

Let's not dwell upon how I did that in the past. I'm currently installing/upgrading electrical systems in three sailboats. This is the main circuit breaker I most recently purchased for an electric motor.

"Waterproof 100A Circuit Breaker with Manual Reset, Panel Mount"

[amazon.com/dp/B075KBM3Y7]
...or surface mount equivalent:

[amazon.com/dp/B07H9X78MC]
...with splash shield:

[amazon.com/dp/B06Y1YFW27]

There are lots of similar ones on the market. Pick your own balance of style, features, price, shipping delay, and happy buyer feedback.

Re: "I may just need to go to for AWG 4"

If you haven't priced fine stranded, fully tinned, true marine grade AWG 4 cable yet, be sitting down when you do. I predict you will want to buy exactly the amount you need or a few percent more, rather than the next larger pre-cut length just to have some extra around. The best known brand is "Ancor". However, I have also used "Lawrence Marine Products" brand, and consider it just as good. One good source is Defender Industries, [defender.com]. They show AWG 4 in single conductor. I used double insulated duplex, which they don't show on their website in that size. However, I expect they can still special order it, if you call them.

Also, be sure to use tinned copper ring terminals, properly crimped. I use a crimper intended for Nicopress rigging. I think most West Marine stores have one you can use there for free. If you prefer soldering and adhesive heatshrink, apply it after first crimping.

� Leon

� Leon Sisson

Lee Panza
Captain

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465 Posts

Response Posted - 06/20/2019 : 23:41:46

James, let's simplify this a little.

Unless you anticipate drawing down your battery (single or multiple units) by running heavy-consumption devices like electric heat or refrigeration, you may not need a dedicated battery just for starting. My 9.8 HP Tohatsu (identical to Nissan, because Tohatsu makes them both) nearly always starts within a few revolutions, and the few times that I've had to crank it a bit I only did so for a few brief seconds at a time. I use a 40A breaker near the battery and 8 feet each of red and black AWG#6 cables from the battery to a terminal block near the transom where the duplex cable that came with the motor is terminated. The 40A breaker has always been sufficient for me, so even if I had to crank for a cumulative time of one minute (I've never even approached that) it would amount to a whopping 2/3 of one amp-hour.

My electrical consumption is probably more conservative than some might want. Other than starting the motor I occasionally run my LED nav lights for a few hours, and I'll run the LED anchor light plus a relatively dim LED cockpit illumination light when I'm out overnight. For cabin illumination I'm still using surface-mounted "slap-lights" running on rechargable AA batteries until I get around to rewiring the entire interior. Oh, and I recharge my phone and tablet overnight. With such a minimal energy budget I haven't even installed an AC battery charger yet; a single 40W solar panel has been more than adequate and I don't even plug into the dock power at my marina berth.

Granted, this wouldn't be enough for some people. I have friends who use far more power than this in their floating-condo powerboats, but my main reason for having this boat is to sail and to and get away from the bustle and complication of land-side living. I used to enjoy back-packing and tent-camping when I was younger, and my energy budget in those activities was similarly minimal - especially compared to most of the people I used to see in RVs.

To each his own, and I don't mean to suggest that anyone else SHOULD use so little electricity, but I'm trying to point out that it's possible to derive a great deal of pleasure without using much. A Catalina 25 is not a luxury yacht, and I'd think that many of us can enjoy our little sailboats without the need for so much electrical power that separate house and starter batteries are really necessary. In fact, with the pull-start option on the motor, the most important function of electrical power for me is to have the VHF available to call for help if I ever need it.

So, before going much further in this, James, I'd encourage you to think about whether you actually need the dual-battery system you've been considering. It boils down to a classic question of one's personal boat-use philosophy.

Sorry; I couldn't resist that ;-)

Oh, by the way; when posting an image the second tag needs a forward slash mark in front of the "img" within the brackets.

Oh, and also, here are a couple of cost-effective sources for wire and wiring components:

http://genuinedealz.com/
https://tinnedmarinewire.com/

And another BTW; I'm in agreement with Leon regarding the use of circuit breakers instead of fuses, although others have expressed concerns regarding the reliability of breakers. I'll just point out that if a fuse trips in an emergency situation it can add to the confusion and delay in sorting things out; a breaker mounted out in the open is easier to check and faster to reset than a fuse. And conveniently mounted breakers can serve as quick disconnects for isolating components or portions of the electrical system.

The trouble with a destination - any destination, really - is that it interrupts The Journey.

Lee Panza
SR/SK #2134
San Francisco Bay
(Brisbane, CA)

Lee Panza
Captain

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465 Posts

Response Posted - 06/20/2019 : 23:49:02

Oh, and yet ANOTHER by-the-way:

Using a multi-position switch between the battery and the motor may introduce a risk of seriously damaging the motor by disconnecting the motor from the battery while it's running. I've read that this can fry the rectifier, although I don't know this to be true.

The trouble with a destination - any destination, really - is that it interrupts The Journey.

Lee Panza
SR/SK #2134
San Francisco Bay
(Brisbane, CA)

islander
Master Marine Consultant

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3992 Posts

Response Posted - 06/21/2019 : 05:35:28

Adding to the By the way, Having a fuse block mounted on the transom is really not the place for it. A fuse or breaker only protects what is down stream of it. It Should be as close to the battery as possible so it protects the entire circuit. Having it on the transom only protects the engine and the short wires running from it to the motor. The wires that run from the battery to the fuse block are unprotected. A battery post fuse/breaker is best.

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

Voyager
Master Marine Consultant

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5231 Posts

Response Posted - 06/21/2019 : 06:35:22

Wow Lee! The site tinnedmarirewire has some incredible deals for �by-the-foot� cable. If I were working on a boat wiring project I�d do some comparisons for sure.
I largely agree with your philosophy of keeping power consumption low when not on the dock connected to shore power, but everyone should create their own power budgets for daysails, overnights and long weekends.
I like good house lighting in the cabin so have installed a few more fixtures in the quarterberth, forward in the vee berth and in the head.
To build a power budget list all your power-consuming items like nav lights and cabin lights, VHF, entertainment, chargers for cellphones and tablets, instrumentation. Figure the amount of current in amps and number of hours and total them up over your trip.
Determine engine hours and solar panel AHs for recharging your batteries while underway or at anchor. And derate the charging by 30%.
And figure you�ve got about 35-45AH to play with in each battery (group 24 or 27).
That�s the basic power budget calculation.
It�s always nice to have a fully charged backup spare battery.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

bjoye
Navigator

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Response Posted - 06/21/2019 : 09:06:01

I've completed a similar project recently.

Centered around BlueSeas Mini Add-A-Battery Plus Kit 7655, which includes a 1/2/OFF/Both switch and 3 phase 10Amp battery charger with builtin ACR. Starting at the batteries, 6AWG to a BlueSeas 6010 Dual battery no combine kill switch. Then on to the positive House and Starter buses consisting each of a BlueSea 2019 Dual busbar/BlueSea 2151 Dual MRBF terminal fuse block, with BlueSea 5181 Dual MRBF (80Amp and 40Amp) fuses, total of ~7 inches of wire length to comply with ABYC standards.

Along with a BlueSea 2307 Common negative return busbar and a BlueSea 5035 ATC fuse block for charger and bilge pumps, all are mounted behind the battery box located under the aft berth.

Tohatsu/Nissan 9.8/9.9 has a starter draw at 30-50 amp and a Magneto Regulator/Rectifier output: 6 amp (80W) at 13.9v

From the House bus, with 6AWG, the 80Amp cable goes to the inverter and up to the 1/2/BOTH/OFF switch mounted behind the galley sink via the dumpster. The 40Amp cable goes to the charger. From the Starter bus, the 80Amp cable goes also goes up to the 1/2/BOTH/OFF switch and the 40Amp cable to the charger.

From the 1/2/BOTH Switch, 10AWG to the DC panel via BlueSea 50Amp Maxi fuse and 6AWG to the outboard. I also have a Balmar Smart Gauge monitor for battery SOC and Voltage, while the DC panel meters the voltage/amp at the panel.

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

islander
Master Marine Consultant

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Response Posted - 06/21/2019 : 10:12:05

Bjoye All I can say is Holy crap. That's something the local electric company would be proud of. Nice job!

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

Monomachos
Deckhand

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Response Posted - 06/21/2019 : 13:33:26

Bjoye, that is amazing. Looks like excellent work. If you were close by, I'd be of a mind to pay you well to walk me through a similar set-up. I'll try to keep some that in mind and refer back as I move forward.

Lee, thanks for all. Very good stuff. And great point about 'philosophy of use': mission drives equipment. I don't anticipate any real heavy loads. No heating or refrigeration. I'd like to be able to stay out a couple nights at most and make some sail up and down the coast here (areas between Mobile and Destin). Nav, anchor, steaming lights, VHF, chartplotter, and occasional use of interior light (I still use a headlamp on red for most tasks at night on my buddy's Niagara 35). So not too much of a load, I don't think. But I would like the security of an extra battery, though there is always the pull start option

Dave and Leon, thank y'all again. And, yes, I've priced out upgrading that run of wire to outboard and it is a rather significant impact to a man's purse . . . but may need to be done. I appreciate all the links to the breaks. Do you have or can you recommend a good diagram showing their wiring to the battery?

Bruce, thank you too! You are all very helpful and kind. Much obliged, ladies and gentlemen. Finally, what do y'all make of the 'second-battery' wiring schematic that comes in the C-25 manual? I would post pic here but still fighting with that.

Valete!

JLC

James Loxley Compton
C-25 SR/WK #5999 Erebus
Orange Beach, AL

Monomachos
Deckhand

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USA
21 Posts

Response Posted - 06/21/2019 : 13:35:38

quote:
Originally posted by islander

Adding to the By the way, Having a fuse block mounted on the transom is really not the place for it. A fuse or breaker only protects what is down stream of it. It Should be as close to the battery as possible so it protects the entire circuit. Having it on the transom only protects the engine and the short wires running from it to the motor. The wires that run from the battery to the fuse block are unprotected. A battery post fuse/breaker is best.

Yeah, good point. I'm not sure what the PO's plan was there. It makes a good place to connect outboard cables (from factory) to cables run to battery, but not sure the fuse purpose. It's some BlueSea setup. Thanks, Scott!

James Loxley Compton
C-25 SR/WK #5999 Erebus
Orange Beach, AL

Monomachos
Deckhand

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Response Posted - 06/21/2019 : 15:22:57

Seeing if I can get a link here. Does outline/diagram 6 look to y'all at the following site? https://newwiremarine.com/how-to/wiring-a-boat/

James Loxley Compton
C-25 SR/WK #5999 Erebus
Orange Beach, AL

Leon Sisson
Master Marine Consultant

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1889 Posts

Response Posted - 06/21/2019 : 20:16:01

That is most impressive electrical craftsmanship on "Frayed Knot"! I particularly admire the neatly formed wires around terminal strips, and groups tied up in tidy organized bundles. In spite of my best efforts, my wiring ends up looking like a dense colorful jungle.

Re: "...philosophy of keeping power consumption low when not on the dock connected to shore power, but everyone should create their own power budgets for daysails, overnights and long weekends." �� Bruce

Words of wisdom there.

James,

Re: "...outline/diagram 6 ...at the following site?"

Here's a link to the pic. Not embedding it here as an image because it's wide.
[https://newwiremarine.com/wp-content/uploads/Boat-Wiring-Diagram-step-5-min.jpg]

That looks like a good generic summary or outline of a basic small boat electrical system.

A couple things worth pointing out: The use of a terminal strip between the main long run wiring harness and the switch panel (or other localized rats nest, such as instrument cluster, inboard engine, etc). Appropriate use of a grounding buss bar. There's also a +12.V buss bar implied behind the switch panel. I see a couple fuses, but didn't notice any mention of separate current protection for branch circuits. I'm not a fan of single-use fuses. I much prefer circuit breakers. Those little black dots below each rocker switch are likely LED indicator lights.

Back when I rewired my Catalina 25, I used the traditional toggle switch/circuit breakers, mostly because I stumbled upon a deal on a used electrical load center out of a motor yacht.

When I started rewiring my Catalina 22 recently, I used SPST rocker switches with built in assorted color LEDs (plus a few DPDT toggle switches where appropriate), and a smaller number of separate push-button-reset circuit breakers.

I omitted separate switches for most end items which include their own on/off switches. A couple exceptions are all cabin lights off at once, and all non-esential circuits enabled/disabled at once. Those allow me to turn on whatever cabin lights were last in use from one convenient spot just inside the companionway, and similarly to shut off everything except the solar panels or shore power charger, and automatic bilge pump when leaving the boat.

There's a 20.A toggle style main circuit breaker near the battery which disconnects the (+) terminal from everything.

� Leon

� Leon Sisson

Monomachos
Deckhand

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21 Posts

Response Posted - 06/21/2019 : 20:36:31

Thanks, Leon. And forgive all my typos in various posts above. I should be more careful. So good . . . I'm thinking that (at minimum) I need a breaker/fuse going to my switch panel (based, I think, on slightly over max load) and a breaker/fuse for cable headed to outboard (but close to battery source). Going to do the math on those amp requirements. Again, this seems to be a minimum of what I ought to do. Currenly I have an in-line fuse for bilge pump which will stay on all the time. Working on getting some quotes on larger gauge wire to run to outboard. The site, tinnedmarinewire.com, looked to have some great prices and they will pre-fab my cables for me. Sound good so far?

Also, did you check out the dual battery diagram in the C-25 manual? It seems a bit anaemic to me. It's p. 12 in the PDF for the post-1988 manual in 'Manuals and Brochures' above. Incidentally, the PO bought CD's 'Add A Battery Kit' and the wiring included with it seems small (I'm away from the boat and its miscellany now and can't recall the gauge). I called CD and they didn't know surprisingly.

Thanks, all.

James Loxley Compton
C-25 SR/WK #5999 Erebus
Orange Beach, AL

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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.