Battery relocation question

[Macboy]

I'm looking at the WM wire size / ampacity charts in contemplating a battery move OUT of the lazarette this season either to under the sink / stbd seat or all the way to the v-berth. I know I can figure out the length of the wire run from the engine to the batteries - but what load do I use? I assume it's the cranking load? And then do I go by the battery CCA rating or is there a cranking draw figure on the engine specs? It's a mercury Bigfoot 9.9.

The secondary bit to the question which I've seen loads of mixed answers for but nothing definitive is don't these batteries off gas during charge and discharge? And if so, do we really want them in the cabin? The reason for the move is to get the electrical out of the Laz which is where the fuel tanks are housed. We don't want any potential for spark but like having the fuel down there out of the way while underway motoring. Don't want to bring the fuel into the cockpit.

Any help/direction is appreciated. I know Maine Sail had some great articles about this as did Sumner. I'll dig those up too. If someone can help me understand the source of the load so I can decipher those wire charts and get the main battery cable run decided and ordered that'd be great.

 

[Sumner]

I used #4 for the run to the batteries in the cabin. There were two 12 volt in parallel, one under the sink and ....

... the other near where the head was under the stern end of the enlarged V-Berth. Those were replaced with two 6 volt batteries in series in the same location. This has worked fine and the Tohatsu 9.8 HP fires right up. They also now make the Merc engines and give them .1 HP more , so I would expect similar results. You could probably get by with a smaller wire size, but I like to oversize things. I've used 60 amp battery fusing for the #4 cables and never blown a fuse.

I get almost all my boat wiring from http://www.genuinedealz.com/ .

You should have fusing within 6 inches of the battery. I made the above up but now use....

..... fuses like shown above. Less expensive, a better deal, readily available and mount right on the battery post.

More on the wiring here...

http://purplesagetradingpost.com/sumner/macgregor2/inside-30.html

Sumner
==============================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas

 

[walt]

Yes, its cranking current for the electric start you should size for. I measured my Nissan 9.8 starting current with a battery monitor which could possibly be missing transient peaks but I think its ballpark and the starting current was in the range of 35 amps on a warm day to near 50 amps when it was fairly cold.. I would guess your outboard would be similar.

You will need large wires for that much current and large wires with lots of energy available are better at starting fiberglass on fire than small wires so very important to fuse. My two six volt golf cart batteries are under the Vberth as far forward as they can go (which I have been happy with - both good for sailing and tongue weight for towing) and I have a 4 gauge run that runs the entire length of the boat to the outboard.. I have a 90 amp breaker/switch close to the batteries and I have never had this false blow when starting the outboard, also never any problem starting the outboard. The fuse should be sized to protect the wire on one hand but not false trip on the other hand and sounds like you are already looking at the right places for sizing to protect the wire.

I have a "tap" on the four gauge run under the sink area (near the mid part of the boat) that is the distribution area to all the electrical powered stuff on the boat. In this area, the distribution goes from 4 gauge to 14 gauge and any time you change wire gauge, you must add a new fuse in the run - also very close to where the wire run starts.. So that distribution area is also where I have all the switches and smaller fuses (like 5 to 20 amp).

Battery under the sink - just make sure its well secured because if that tube where the centerboard uphaul cable comes through gets busted off by a loose battery, water is going to come shooting up into the boat. Its also a hard place to be able to add water to maintain the batteries but maybe one of those battery watering systems could help here.

FYI, I have seen discussion here in battery venting.. hard to pick out what is reality. I have a air vent from the V berth area to the cabin. Is this adequate or safe.. my only data point is that the boat has not blown up yet.

 

[Sumner]

.....Battery under the sink - just make sure its well secured because if that tube where the centerboard uphaul cable comes through gets busted off by a loose battery, water is going to come shooting up into the boat. Its also a hard place to be able to add water to maintain the batteries but maybe one of those battery watering systems could help here.....

I'll second that, about being well secured in that area, along with anything else that is under there. Our boat came with a battery under there and it is held in place with a bracket that is bolted to the bulkhead between the galley and where the head is/was. I've left it there since it is in a spot that is hard to put anything else in being mostly behind the sink drain.

It isn't the easiest place to service but I've found that I only need to add water about once a year and then very little. Maybe that is because the batteries are only charged via the Blue Sky MPPT controller and the panels and that combination does a good job of not overcharging??

I find that a mirror makes it pretty easy to check the level and to fill when it needs it.

Sumner
========================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas

 

[walt]

Reminds me about another thing I might do.. add one of those watering systems to the batteries under the Vberth that make filling the battery water simple. I assume you can get them for the the six volt three cell config.. but havent checked into this. I lose some water but its usually after the hot summer. I have to pull a bunch of stuff out of the Vberth area, remove some panels to get to the batteries so some hassle. My boat came with a battery under the sink (reasonably well secured) but it was a big hassle to water so the battery died early from watering neglect.

 

[Macboy]

Hey guys, last summer came and went and through it all this project didn't see the light of day. However our house battery failed on our last outing (neglect I'm sure) so this project has come to the forefront for the upcoming season. Just wanted to thank you for the above responses. Looking forward to the peace of mind knowing the electrical stuff is away from the fuel stuff.

Walt - when you "tapped" off, I assume you tapped off the pos and the neg?

I'm certain more questions will come once the foot of snow is off the pop top. When this all takes place I'll be rewiring including moving the A/B switch (will I even need this anymore? I like having a redundant system so probably will set up two batteries/banks). Rewiring all of the accessories/adding a few new and incorporating two solar panels and related charge controllers. I hope this summer to be the summer of many weekends on board with the family.

 

[walt]

I have a "tap" on the four gauge run under the sink area (near the mid part of the boat) that is the distribution area to all the electrical powered stuff on the boat. In this area, the distribution goes from 4 gauge to 14 gauge and any time you change wire gauge, you must add a new fuse in the run - also very close to where the wire run starts.. So that distribution area is also where I have all the switches and smaller fuses (like 5 to 20 amp).

Walt - when you "tapped" off, I assume you tapped off the pos and the neg?

Yes.. Im assuming that the tap question was from the top quote. My 4 gauge run is both pos and negative wires and is fused by a single 90 amp breaker on the positive wire very near the battery. When I tap off that 4 gauge run to a smaller gauge (for example a wire run to a VHF radio), it would be both positive and negative 14 gauge wires run to the radio with a new fuse in the 14 gauge positive wire (like 15 amp) very near where the 14 gauge wire taps off the 4 gauge wire.

I just have one battery (composed of two 6 volt golf cart bats) so dont have A/B switches but do have a very important breaker with an on/off switch located very near the battery. This breaker is 90 amp so wont trip when the outboard electric start is used but will trip if the 4 gauge wires are shorted. 4 gauge wires running the length of the boat (batteries forward under the Vberth, outboard all the way aft) plus that big battery when shorted.. likely good at started even fiberglass on fire so that 90 amp fuse is very important.

 

[Sumner]

... When this all takes place I'll be rewiring including moving the A/B switch (will I even need this anymore? ...

On the Endeavour with a house bank and a start battery I don't use an A/B switch but do have an On/Off switch between the house loads and the battery bank and between the solar charge controller and the house bank and have the batteries fused at the batteries like I showed in my other post above. I have a combiner that keeps the start battery charged. I also use an A/B type switch from the starter on the diesel to both banks just in case I had to start using the house bank.

On the Mac I do have an A/B/Both switch but only because I have a house bank (two 6 volt batteries in series) and a 24v bank for the trolling motor (two 12 volt batteries in series). At night if I want I can throw 2 switches and convert the 24 volt bank into a 12 volt bank with the two batteries in parallel and the A/B/Both switch allows me then to combine that bank with the house bank if I want to. That way the house bank isn't drawn down as much at night.

I'd suggest not having two battery banks as one larger one will last longer and charge more efficiently. Wired like what Walt mentioned is good. If you do go with two banks then you will need an A/B/BOTH/OFF switch. Have one large bank and wire in a voltmeter and keep track of the state of charge.

Sumner
==================================================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas

 

[Macboy]

After posting that I stumbled upon the Calder (I think that was it) discussions about the single large bank, discharge rates, percentages and lifespans etc. and think that's the route to go. I imagine I can still use the A/B Switch as a shutoff?Or am I better to get a purpose-dedicated on/off switch instead? I also saw some simplified wiring diagrams from Maine Sail and think I best do the same for our Mac - it'll help with questions and answers here I imagine too. Looking forward to cleaning up the mess of wire in the boat and getting to know it's nervous system better.

 

[Sumner]

... I imagine I can still use the A/B Switch as a shutoff?Or am I better to get a purpose-dedicated on/off switch instead?.

I did until I added the second bank for the trolling motor. Just be sure to fuse near the battery for the wire from the battery to the distribution panel where you will have appropriate sized fuses for the secondary wiring,

Sumner
=================================================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas

 

[timebandit]

I must disagree with running two six volt batteries. No matter how you plan for it if one battery goes bad you have no power.
No radio, lights,starter motor, frig, instruments, nothing. You might even ruin your charging system on your motor when it tries to charge a dead 9, 10,11 volt battery.

 

[Ron20324]

I must disagree with running two six volt batteries. No matter how you plan for it if one battery goes bad you have no power. No radio, lights,starter motor, frig, instruments, nothing. You might even ruin your charging system on your motor when it tries to charge a dead 9, 10,11 volt battery.

+1 to Timebandit's reply. That is pretty much the common thought. Even if a 6 died, you'd go buy a new one, which would not be the same age as the exiting one- another common thought.

 

[Sumner]

Macboy has an outboard that will pull start. I carry ...

... one of the above which would power my LED lights and radio a long time. Also we are talking about trailer boats that normally are day sailed or weekend sailed on inland or coastal waters. Two 6 volt batteries will give you 2 'true deep cycle' batteries, more amp hrs. than 2 12v batteries, charge more effeciently and last longer in most cases. I like them, but agree, everyone has to decide what works for them,

Sumner
===========================================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas

 

[walt]

You might even ruin your charging system on your motor when it tries to charge a dead 9, 10,11 volt battery.

I dont think this would be true. Did this happen to you?

FYI, no problem in the slightest to mix two different 6 volt batteries because they are in series and not parrellel.

Remember this is a small boat system with an outboard that can be pull started. The outboard charging system will be weak and charging may mostly be from a smaller solar panel. If you go with two separate 12 volt batteries, you may want to go with a fuller blown system even having an ACR (which has its own power load that may become significant in a smaller system). If you somehow try and keep two batteries charged manually, you are likely to "chronically under charge" one or the other or both and that also is hard on batteries.

I just have one battery composed of two golf cart batteries that I can keep an eye on with a battery monitor and a good charging system. Im on my second set of golf cart batteries in nine years (present set seem reasonably fresh) and have never had a single issue. And that is even with the batteries spending the summer in the boat at one of the hottest places on the planet. If I had two separate batteries that I had to somehow keep charged up with manual switch.. Im fairly sure I would have all sorts of problems because of undercharged batteries. My opinion and its just that.. you are more likely to create a battery problem if you have two of them and dont go the full blown route to have the second one automatically charged.

If I did have a battery failure, I can manual pull start my outboard, one GPS, cell phone, VHS radio, flash lights all have their own batteries.

Valid opinions either way.. but no way am I switching back to two separate 12 volt batteries for my trailer boat with an under 10 hp outboard.

 

[JCall]

You might even ruin your charging system on your motor when it tries to charge a dead 9, 10,11 volt battery.

I have seen this on old generator systems on 1950 era cars. Old generators would give all they have until till they melted.
Alternators today are self limiting in out-put, not too much of a concern. I have seen aircraft that melted the alternator output circuit breaker when the aircraft was flown with a dead flooded lead-acid battery, the dead battery looked like a dead short to the system. I installed a new battery and replaced the circuit breaker then all was well.
I do not think a 6 to 10 amp outboard alternator will be harmed by a 12 volt battery run down to say 8 volts.
On my Mac, I have been using retired (from flight) aircraft AGM batteries. I never ran out of power for just running lights or recharging my phone and iPad. I only sailed on weekends, a small solar panel recharged the battery through the work week. Like Walt, I now want cold wine for the admiral and beer for me without lugging ice. I am thinking about a refrigerator. I will copy what Walt has done with two golf cart batteries in series. Walt is correct that two 6 volt will act as one 12 volt battery. Golf cart batteries are robust and very forgiving. My outboard does not have an alternator.
Now that I have a slip with 110 volt power, I will purchase a battery charger from Mainsail and install two golf cart batteries in the aft center area under the vee berth to help offset weight in the laz and the outboard motor.
I recommend that you read through Sumner and Walt’s electrical systems modifications. Both are well executed. Sumner has enough power on his boat to run a small village if the need ever arises.