Why three batteries?

[Mundaysj]

Hi all,

I was just wondering if anyone has any idea why my boat would have three batteries?  There is one under the cockpit seat and one each on either side under the v-berth.  There doesn't seem to be anything using them except the VHF, the original cockpit lights, navigational lights and bilge pump.  Would that need more that 1 battery?

One other question.. how long do I need to plug in to shore power to juice up the battery?  I know there is a mathematical equation, I'm just looking for a general idea.  The yacht club has a 20 minute limit for the dock with shore power and I was wondering if that will be enough time?

In case you can't tell, I'm a total newbie to a boat with a cabin!
Thanks!

[kchunk]

Hey there sj. IMO, three batteries is a bit excessive. I can think of a couple possibilities why: The previous owner once ran the batteries dead and is now paranoid; The previous owner had a battery getting weak and not holding a full charge so replaced it but figured he/she could still use the old one for backup power. At any rate, at least they're forward where the extra ballast is needed. When I bought my boat I immediately replaced both batteries. Got one marine starting and one marine deep cycle. My 9.9 has a charging circuit connected to the starting battery and a battery combiner between the starting and deep cycle batteries, so the alternator charge switched over the the deep cycle battery once the starting battery is charged.

As far as charging your setup, it depends on the type of battery and charger, but I don't think 20 minutes will do a whole lot.

[Bob23]

Sherie:
   3 batteries is way overkill. I have one coupled with a small solar panel and never ran even a bit low onpower last year. When I got Koinonia back home in the fall, I still had 95% in the battery. I didn't use the charging circuit on my outboard at all. I have about the same electrical equiptment that you do. Mayabe more...depth sounder, GPS, knot meter that doesn't work a darn.
   Hey...you don't have a diesel inboard, do you? The only reason to even have multiple batteries at all is to designate one soley for starting and the rest for house batteries. In any event, the starting only would not be the same type of battery.
   Iv'e read much discussion on batteries and charging time, etc, etc. If you start out with a new battery, deep cycle marine of course, you should be ok with an occasional charge at the yacht club. I know some folks who don't even do this and have more than adequate power for the entire season. We really don't have much high drain equiptment on our twins!
   No, I can't tell you are a total newbie to a boat with a cabin. Seems like you know a lot, have done research, and aren't afraid to ask questions- a great combination. And to boot, you picked the right boat. Here is an aside story:
  When looking for a boat, my friend and longtime sailor Bud, suggested numerous boats that he saw for sale. Some were quite nice, some great deals, some real dogs, but most were at least ok. I turned every one down and he was perplexed. When he asked my why one day, my reply was "I'll know the right one when she stirs my soul." When I saw my 1985 23 for sale, my soul was stirred and continues to be. Does that make sense? 
   Best to you,  Bob23, off to make coffee

[Mundaysj]

OK... I was following you, Kchunck, until you mentioned combined batteries and charging circuits.  I'm not really sure how mine are connected.  And how do I know what kind of batteries they are?  Do they say "Marine Deep Cycle"?


Bob...I know what you mean.  I took one look at the interior.. that beautiful woodwork.. as long as it didn't have any holes or blisters, I knew it would be mine!

[Bob23]

Sherie:
   I spent a lot of time on my interior woodwork. Don't use teak oil on it! Attacts mold like bribes attract politicians.
   I have a great little book that may help you out on your new career as a marine electrician: "Sailboat Electrics Simplified". Wonderful book that is true to it's name. It really came in handy when I rewired Koinonia and installed a new panel. I just happen to have 2 copies and I'll give you one if you email me your address. Or leave it on my office machine (609) 978-0012.
   The batteries should say marine deep cycle...there is a good section in the book on batteries. I installed a new single deep cycle...works fine. I do not need a battery to start the engine-good old pull rope and starts first time! Gotta love that.
   Having the electrical system correct was high on my list of repairs/improvements when I first aquired my ship. I have not regretted all the time spent. Someone in the past didn't have the same approach so I had to correct many previous "improvements". It always pays to do anything right the first time but cheaping out on electrical will come back to haunt you eventually.
  Bob23, out

[Mundaysj]

Hi Bob,
Thanks for the offer for the book, but I have a good book on boat electric systems.  Another one I haven't finished yet.  I'll have to move it to the top of the pile.
Regards,
Sherie

[mike gartland]

I'm kind of slow to responding to this topic but thought I would throw in my 2 cents...

My 23 is powered by an electric start Tohatsu 9.9 2-cycle with alternator.  It usually starts with a single very brief (1 second?) push of the starter button.  The only other 12v drain on the WindRush is her nav lights which only get used 3 or 4 times a year and then usually with the engine running.  I have never needed (or tried) to do any additional charging, other than that supplied by the Tohatsu and have been able to keep a sufficiently charged battery at all times.  Mine is a wet-cell dual-purpose battery from West Marine and appears to be in like-new shape after nearly two years of nearly weekly use.  Since I'm not trying to turn over a diesel (and can always revert to the pull cord for starting if need be) I plan to keep it simple and rely on the single dual-purpose battery.  But the thought of adding an additional couple of old batteries in the bow to help with fore-and-aft trim has me thinking......

Mike

[Bob23]

Mike:
   My two cents...
   It's a long way from the bow to run wiring. My guess is that you'd have to deal with quite a voltage (or amperage) loss from bow to back where the panel is. I also have a single marine battery charged bya a small solar panel. Sounds like my electrical needs are about the same as yours with the exception of a radio, GPS, and interior lighting. At the end of the season last year, the battery still was up at 95%.
   Bob23, keepin' it simple!

[curtisv]

Hi all,

I was just wondering if anyone has any idea why my boat would have three batteries?  There is one under the cockpit seat and one each on either side under the v-berth.  There doesn't seem to be anything using them except the VHF, the original cockpit lights, navigational lights and bilge pump.  Would that need more that 1 battery?

One other question.. how long do I need to plug in to shore power to juice up the battery?  I know there is a mathematical equation, I'm just looking for a general idea.  The yacht club has a 20 minute limit for the dock with shore power and I was wondering if that will be enough time?

In case you can't tell, I'm a total newbie to a boat with a cabin!
Thanks!

Sherie,

The three batteries might just be to get more capacity.  You didn't say whay size but most marine deep cycle batteries are in the 100AH range.  Checking to see how they are wired would help a lot.  If they are in parallel it would be to increase capacity.  It is possible that one is isolated and serves just the radio, but I doubt that.

I don't think a charger exists that will charge your battery in 20 minutes unless it is nearly full charged.  If you don't use the lights much it is likely to be close to full charged.  If you don't sail at night or stay up all night with the cabin lights on you won't use much and you'll never draw the battery down much.  In that case a solar panel will usually do the job.  Typical NAV lights are 10W or 1A per bulb times 2 bulbs.  The VHF is typically 1/3 AMP in standby.

A small solar panel is great because you can keep a float charge on the battery all the time including over the winter as long as you can keep the solar panel in the sun part of the day.  I have a 6W panel and FlexCharge controller.

Curtis