How big a battery

F

fishinAK

New member
I appologize in advance. I am sure this has been covered before. But, I have just read so many past posts my head is swimming.

Simple question. how big a battery do I need? I have not taken my new/used boat on an overnight trip yet. And I just want to make sure I have enought battery. Right now I have the basic "1,2, both, off" switch, a starting batt and a deep cycle batt (need to chech the ah).

While on anchor overnite I will have on: the Wallas (with the fan), chartplotter, 2 fans, and an achor light. I dont know the exact amp draw of all of these but lets assume normal.

Will my one deep cycle (I think its a grp 27) be enough for all this. Likely only one nite on anchor then a least 1 hour of cruising, then anchor again then run home.

Oh ya I also want to get an on board charger. Is the guest the way to go?

Any and all info apprecated!
 
I can't say exactly what size battery you will need but the Wallas and your chartplotter are extremely voltage sensitive so overkill on battery capacity would be a good thing.
 
FishnAK,

A couple of thoughts... I would think a Group 27 in good condition would be enough for normal camp cruising. Have you added up the current draw of each of the devices to see how it stacks up against your battery?

Some alternatives...

You might consider an Eco Fan instead of running the Wallas with the lid down/fan running. They work nicely when at anchor. You may find that you will not need the additional fans. You will also appreciate the quiet. My Wallas is pretty noisy.

A LED anchor light would significantly bring the draw down from that of an incandescent bulb. There a several threads on that topic in the archives.

Are you running the chart plotter, just to have an alarm if you move at anchor? I wonder if a handheld unit could suffice.

I am considering bringing a second group 27 along when cruising, first to run an electric motor for the dinghy, and second as a backup for the house battery. What I have not done/figured out is how I want to connect it so that it charges, and where I want to store it.

Hope this helps...

Steve
 
The biggest draw would be the anchor light if that is incandescent. If you can switch that to an led you should be fine with either a group 24 or 27. Your starting battery is isolated so you should be fine. Not sure that one hour of cruising will charge the house battery all the way back up though. Depends on speed and how depleted the battery is. Trolling speed just holds it own on my boat depending on how many accessories are running but that is with one of the twins. A bigger engine/alternator will charge faster as would running both motors and running them faster.
 
LED anchor lite, :thup :thup

Chart plotter on at night -- draw will depend on size of display, and brightness level. I'd look into using a Handheld for an anchor alarm if thats why you are using it. If it is for the nightlight effect, It'll be like a lite up ice rink and you'll hardly not be able to see outside. Go for a very dim, led. (My power on indicator LED on the stereo is bright enough to find my way around on the boat at night.)

Our twin Yami 40's do a pretty good job of bringing the bats back up after a night of use. Generally close to full after an hour. (We usually drop from about 12.9 to about 12.5 running 2 CPAP machines, and a couple of LED lights.)

Our on board charger is a Guest 10/5/5. Not too fast a charger, but it works.

Harvey
SleepyC :moon
 
Not sure of my battery size, but like you I have a cranking battery along with a Deep cycle. Both my batteries are in the starboard laz and are as large as will fit. Shortly after leaving port I switch over to the deep cycle and leave it there for the duration of our trip, 2 or 3 days in most cases. In the spring and fall we run the Wallas along with interior lights at night, my chart plotter and fish finder remain on all the time. Do to the remoteness of most of your trips I never use the anchor light because our dink hangs over too much and I’m not able to attach the post, I have only seen a couple of boats use them up here; we just don’t have any boats around use on anchor. I don’t generally run any fans other than the one on the Wallas lid if it’s down, we usually just place and EcoFan on the cook top, but on cold night I’ve had the Wallas fan running all night.

I have never had a problem starting the motor using the deep cycle battery in the morning, but my fully charged cranking battery is ready just in case. None of my interior lights are LED and we often have them on for hours when on the hook.

I don’t think you’ll have and problems. If the cranking battery didn’t come with my boat I would have 2 deep cycles, my father in-law has had a deep cycle in his old Ford F250 for over 12 years and it still works fine.
 
I have twin motors and the boat was set up so each motor had it's own battery. The one that powers most equipment was a group 24 which I just swapped out to a 27 combo battery. I forgot to pull the fuse on the Wallas and in 2 weeks the battery read 1 volt. Fortunately it took a charge fine and now I pull the fuse for storage and also have a battery charger/maintainer hooked up. There is a chart in one of the forums that has the typical draw for the lights, frig ect. You can easily do your calculations off of that.
 
fishinAK

I'm not sure what size or even kind of boat you have. Assume it's a C-Dory, because of the Wallis.

What you really need to do is figure out the amp-hours you'd typically draw from the battery. For instance do you plan to use the Wallis all night or just for an hour or so? A Wallis uses 1/4 amp with the lid up and 3/4 amp with the lid down. So that can range from 2 to 6 amp-hrs for a night. How about the cabin lights? I assume that you don't have a refrigerator or you'd mention it. An anchor light uses about 1 amp/hr., so I allow 10 amp-hrs for that light per night. Add it all up, see how many total amp-hrs you estimate and see if your battery is big enough.

A deep cycle group 24 has a capacity of 90 amp hrs. Since you only want to use 50% of that, that gives 45 amp-hrs you can draw from that size. If you're using that battery to also start you motor(s) you may want to use less. A group 27 has 110 amp-hr capacity, group 31, 140 amp-hrs. You do the arithmetic.

Journey On has a refrigerator and a few other things so I stuffed 2 golf cart batteries in the port lazerette. Removes all worry about overnight battery drain.

I love the LED anchor light Journey On has. Uses so little power, that I can leave it on all the time and not worry about not having an anchor light or the power it uses.

Boris
 
I just changed mine over, I now have 2 GRP 27 deep cycles for the cabin, and a GRP 27 as a starting battery. Last summer we had no problem with a single 27, but SHE get tired of me harping "1 light for 1 person, 2 lights for 2 people - TURN IT OFF if you don't need it!"

Add a little info to your profile - what boat do you have, where are you located ? We'd REALLY like to get to know you.

Dave W
 
Thanks for all the help guys!

Actually....I dont have a C Dory :wink: . I really like C Dorys though and this site has been super helpful. I have a 24 foot Olympic with a 200 hp yamaha saltwater series ob.

You guys have been very helpful! It sounds like my one deep cycle will be enought for the few things I will be running. I will hopefully get an onboard charger installed this weekend. Freshly topped off batteries will give me a bit more confidence.

Thanks again!
 
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