Mark II starter battery location?

[Rocco]

I'm think of installing a dedicated start battery this Spring and was wondering where the dedicated start battery is located on other MKIIs that have one?  There are a few possibe locations (I'll almost certainly go with an Optima) but, like everything, each location has it's trade-offs and I've been placing a mock-up in various locations to test fit and access.  Any opinions are very welcome.

Possible locations include:
- Under rear bunk next to the raw water intake (Very tight and a bit more challenging to wire).
- In the back of the port side locker next to nav station (Excellent wiring access, but loss of storage).
- Underneath the starboard settee in the compartment forward of the existing hotwater heater and batteries (Easiest to install, but lengthens starter cable length by 4-5 ft).

Thanks,
Rocco

[Stu Jackson]

Rocco

The third on your list would be the easiest.  Jon Arck, our Commodore in 2005 and 2006, did that.  When you realize the difference in the length of the cabling from that location compared to the aft (and most inaccessible) location, you'll find that the distance is really NOT that much of a difference and go with#2 wiring anyway, so the $ difference is simply the extra distance of the wiring.  So many people have said the problem is the distance, but that's not necessarily true, if the wire sizing is correct.

Please note that the older boats were wired with #4 wiring to the switch, for the grounds and to the starters.  Many have reported success with this wiring, even though many would suggest it's significantly undersized.  The quality of the connections is important.

If your negative from your house bank is adequate to the engine ground, and it is already run to the engine, so you just connect the new start bank negative to the house negative.  You could also simply butt connect the positive output of the new start bank to the existing positive going to what will be the start bank to the switch and minimize additional cabling if the existing size is adequate.

Also, we don't know how you're planning to wire it: separate switches for the two banks or using the existing switch.

References include Jim Moe's article and wiring diagram in Projects, as well as Mark Elkin's and Jon Gardner's.

Here's another thought: http://c34.org/bbs/index.php?topic=1425.0

Here's one of the longer discussions: http://c34.org/bbs/index.php?topic=2347.0

Another one about mark IIs: http://c34.org/bbs/index.php?topic=2143.0

I did a search on the words "battery location" and stumbled over a lot of posts, many about Mark IIs.  As many have said, there is not that much difference between the boats other than the battery compartment, so the only choices are pretty much the ones you've noted.

While you're at it, you may want to consider evaluating the wiring from your charging sources and the wiring to the 1-2-B switch, discussed in my Tech Notes article in the November 2006 Mainsheet, including the wiring diagram and a discussion of the wiring to and from the switch and charging sources.

Thanks for your earlier story/post on the prop shaft removal, well done.

[Jon Schneider]

You can see how one owner installed a starter battery under the aft berth in the Projects section (direct link to Mark Elkin's excellent write-up: http://home.san.rr.com/heysailor/sailing/projects/index.html).  Note the height issue he ran into.  That's where I'll probably be installing mine when I get around to it.  You mention under the starboard settee forward of the water heater.  Unless I'm misunderstanding you, that's where my three group 27 batteries are right now.  Where are yours?  I can't remember if there's room aft of the starboard water tank, but all of these other places are sub par because of the length of wire you need to run (pretty expensive to run #1 or #0 that length).  Every time I'm away from the boat and thinking about this, I keep wondering whether there's a way to burrow access in the head.  BTW, my raw water intake is in the cabinet below the sink in the head.  It's interesting that yours is in the aft berth.  That sounds like a PITA.

[Craig Illman]

More food for thought while you're considering a dedicated start battery. Check out Blue Sea's Dual Circuit Battery switch.

http://bluesea.com/category/1/products/5511e

Craig

[Stu Jackson]

Craig,

That switch is an interesting concept.  It requires running the alternator output to the switch, which would require increasing the size of the wiring from the alternator to the switch which then goes back to the batteries if a newer higher output alternator was being considered. 

With the existing #4 wiring from the switch to the bank, it's currently used for three purposes:  1) sending current from the bank to the switch and then to the starter  AND 2) sending current from the alternator output through the switch to the battery banks AND 3) taking current out of the bank(s) to the distribution panel.  Most boats come with the alternator output going to the C post of the switch, with a small jumper wire from the alternator to the starter.  That way one wire (from the switch to the alternator and starter) serves two purposes and is less expensive to build.  With the meager output of the stock alternators, the #4 wiring sufficed.

My reason for noting this is that anyone contemplating doing work on their battery banks and wiring should also consider how they are going to use their switch or switches (existing or new, single or double) and, perhaps more importantly, once they do this, they should plan ahead for a new alternator and its higher output when designing the wiring system and sizing the wiring.  I think that's because sooner or later the old OEM alternator will need to be replaced.  If you're going to pull new wiring anywhere, consider designing it for future use and equipment so you don't have to pull wiring twice. 

Of course, one could just replace the old alternator with another stock one, which would minimize wiring changes.  This would work for a skipper who didn't hang on the hook and used marinas and didn't depend on a higher alternator output -- a very reasonble and "normal" use of the boat.

Depending on how you use your boat, you'll be able to come up with a system that supports your use.

[Rocco]

Thanks everyone for the replies.  The starboard settee is quickly becoming the front runner for the start battery location.

The start battery is part of a larger effort to improve the electrical system. I'm planning on Installing a Balmar 100 amp 6 series alternator with a MaxCharge regulator.  Given my 3/8" belt size, 100amps is oversized, but I'm planning on "detuning" the alternator with the MaxCharge to run at an acceptable level for my belt size; running a larger alternator at 70-80% of capacity should increase reliability and longevity (Balmar confirmed that this is a great way to go).  The six series also gives the option of internal regulation in the event of a MaxCharge fault (a simple toggle switch installed on the ignition lead allows you to switch to internal regulation).

My two 4D batteries are located under the starboard settee forward of the galley island.  It's a tight squeeze (you have to unscrew and slide the HW heater out of the way to remove them).  I've looked at Trojan 6v batteries and several others, but right now the plan is for two Gel or AGM 4Ds in parallel to form a 400 plus Ah house bank (my wife can't wait!).  Frankly, I hate pulling the settee apart to check electrolyte levels.

A DuoCharge will keep the Optima start battery charged and a Xantrex battery monitor will help me keep an eye on things.  The BlueSea Dual Circuit Plus battery switch is already on my list.  It's hard to resist given it's cool design and the fact that the mounting screw holes match the existing battery switch (the hole cut-out just needs to be enlarged by 1/4").

Lastly, the new AC charger will likely be a Charles 30A with optional temp probe.  I like the Xantrex and know others have squeezed it in under the waste basket shelf, but the Charles is very close in size to the existing charger and should be an easier installation (anything I can do to save a few hours!).   I plan on replacing any undersized cables as needed and am considering upgrading the windlass cables as they seem woefully undersized given the current draw and length of the cable run.

The many posts and projects on this site have been an excellent source of information as I've researched this and other projects, I welcome any thoughts on what I've described above.

Jon,  Per your response on the raw water intake, there is an access hatch at the front of the rear berth that grants easy access to the raw water seacock, so it's not a problem at all.

Thanks,
-Rocco

[Craig Illman]

Stu - You wouldn't have to run the alternator back to the switch, but you would need to run the start battery up through the switch. There are probably as many design options as hull numbers. I run my alternator direct to the house bank, echo charging to the start battery. It's protected at the engine end with a fuse, at the bank end with a breaker. The panel switch just runs the house loads. My starter battery has a 150A breaker at the battery that I "trip" when I leave the boat. I have an emergency common switch under the head sink. In hindsight, I'm not sure I'd even use one of those switches myself. My start battery, installed by the PO, or PPO, is forward of the mast. I didn't want to lengthen the round-trip distance any farther than it already was.

You know, to answer Rocco's original question, I'd be tempted to leave the start battery in the original box and common up another house battery in a remote location, if you didn't go the 4-6V route. Charging amps are a lot lower than starting amps. You could common up a couple house batteries quite a distance with #4.

Craig

[David Sanner]

There are a few ways to break the battery system into starting and house
banks so I though I'd toss out yet another.  I chose this way because I
already had very heavy cabling between the batteries, main switch, and the
engine but the wire from the previously upgraded alternator to the common terminal
on the main battery switch was undersized.  I also chose this way because it
was completely flexible, cheap, and didn't require any additional long cable runs.

I started with my house on bank 1 and the starter on bank two.
I simply added a 1' cable from the alternator to the cable on
the starter motor and attached that cable to position/terminal
2 on the main switch instead of the common terminal.  I also put an
on/off battery switch between the starting battery and leg 2 on
the main battery switch.  (see attachment)

This allows me to start off of either battery, or both, and charge either
battery individually or together.    My normal mode  (switch on 1) keeps
the systems totally separated and the starting battery topped up
while the engine is running.  If I'm out for more than a day and need to
charge the house bank I just put the main switch on ALL and if necessary
I can turn the starting battery switch to off so that I don't overcharge it.
(Of course I have to make sure I don't disconnect both while running)

I don't think I would design a setup like this from scratch or do this if
the boat was in charter (could be confusing) but it provides as much control
as I need and only required 2 one foot pieces of battery cable and an
inexpensive on/off switch.  If my typical use pattern was days at a time I
might add an automatic combiner so both batteries would charge anytime the
motor ran but still allow me to pull the starting battery out of the circuit.

One note, though most 1-2-ALL switches are rated for high amperage
I read an article (I think in Practical Sailor) that showed some were
more up to the job than others.  So be aware if you have a monster
alternator and a large bank of AGM batteries that you don't overpower
you battery switch.

[ken003]

I placed my starting battery on the shelf above the engine in the aft cabin.  Very short wire runs.  I made the shelf and the supports that it sits on removable.  We use the aft cabin, minus the mattress, for storage.  I can remove the battery, the cabinet, and the flooring in less than 5 minutes.  This gives me good access to the rear of the engine, transmission, packing gland, fuel filters.  Access to the starter for the wiring upgrade was still difficult.  I essentially followed the schematic of Jim Moe 4/1/04.  I removed the original engine switch (beneath the nav table) and built it in next to the new start battery (between the start battery and the starter) but separate from the cabinet holding the battery.  This may be a higher placement than you would want, but I have not noticed any problems.  The battery and cabinet are fastened down very securely.

Ken

[Rick Johnson]

Rocco,

I just have to join in!  I also have essentially followed Jim Moe's schematic.  I did switch the starting battery location to the starboard settee (forward of the water tank on a Mk I 1/2).  My reasons were that I wanted a location that would be somewhat easy to get to ( I killed the last batteries because I ran them dry ) and as Ron Hill pointed out the weight would cancel some of the port side list. 

I'm happy with the new location and everything works great!

Good Luck!