Do I really need Dual Batteries Installed?

[John Jones]

I had a paper published by Exide or someone that was "all you every needed to know about batteries" or something like that.  I'm looking for it.

The two things about deep cycles that did stick in my memory are:
1-never let a deep cycle sit if not fully charged.  Put it on the charger as soon as you get home.
2-Deep cycles need 10A charge or more for longest life.  All modern chargers are smart enough to not overheat a battery.

[Skoot]

Wow, 2 pages overnight, Thanks guys for all the suggestions

Sounds great what about a battery switch?

 I wasn't planning on installing one.  Should I get one?

http://bluesea.com/category/2/productline/overview/329

 That device is sweet, but again I dont think Im even going to install a switch. Im trying to keep this as cost effect as possible yet practical.

MM, My thoughts exactly on the single battery set up.

Fitz, N circle, Sounds like the deep cycle combo is the way to go and run large battery cables to the motor

gran398 - Thanks for stealing my thread.

So, all in all, It sounds like I'll be fine with a single battery for starting and electronics. I really like the idea of a dual purpose starting/deep cycle battery (someone  mentioned an AC Delco 27 series) Which sounds perfect.  Again, My current battery(age unknown) is going to become my back-up battery ICE. Nothing will be wired to this battery and I will manually switch the battery cables when and if needed. So the only question "for now" is a Battery Switch.  Should I get/install one, and why?  If so, should I hook both batts to the switch or just use it for the main battery to switch off when not in use, in case of  the "phantom" drain?  Im just thinking aloud here.

Thanks again for all the help. I really appreciate it.

[Capt. Bob]

So the only question "for now" is a Battery Switch.  Should I get/install one, and why?  If so, should I hook both batts to the switch or just use it for the main battery to switch off when not in use, in case of  the "phantom" drain?  Im just thinking aloud here.

Thanks again for all the help. I really appreciate it.

Two batteries, exactly the same, and the switch, wired to both so that you can switch between batteries without any need for tools.

If you have the coin, the proper deep cycle battery will also start your motor just fine. Buy both the same size/type. I personally run the G-27 gel type but a Group 27 is costly. 4/5 years is a good life cycle though I currently have one that is 7 years old. It resembles George Burns.

I have found that the gel type holds a charge in North Fla. weather quite well and can be discharged completely, recharged and perform well. You will however pay for that ability.

Good luck and install the switch. If you haven't already, check the Resource forum for basic wiring diagrams (via SeaBob4)
Good stuff.

[wingtime]

The switch is well worth the extra $$$.  You can use it to shut everything off when the boat is not in use, select with battery you want to draw from or charge.  And if you get in a situation where your your batteries are low and you need an extra kick you can select both and start using both batteries.  If you get what they call a "make before break" switch it is ok to switch batteries while running since it connects to the other battery before disconnecting from the one you are switching from.  DO NOT turn it to off while running though, that could fry your charging circuit.  

Here is how I use my switch.  I turn if to off while the boat is not in use.  I don't keep it in the water so my bilge being off is not a big deal.  I use my number one Batt as my starting battery since it has the shortest cable run.  So I start and run out on number 1.  Then when I get to a fishing spot I switch over to number two which is a combination battery so I can run my live well, radios, electronics and what have you without having to worry about not having enough juice to start the motor.  Once the motor is running I may switch back to whatever battery I have been running down to charge it.  You can switch to both and charge both but not if one battery is discharged more than the other.  What happens then is the stronger battery will charge the weaker battery.  They sort of even out to each other kind of like if you connected two tanks of water together one full and one empty.  You'll end up with two half full batteries.

[gran398]

Wow, 2 pages overnight, Thanks guys for all the suggestions

Sounds great what about a battery switch?

 I wasn't planning on installing one.  Should I get one?

http://bluesea.com/category/2/productline/overview/329

 That device is sweet, but again I dont think Im even going to install a switch. Im trying to keep this as cost effect as possible yet practical.

MM, My thoughts exactly on the single battery set up.

Fitz, N circle, Sounds like the deep cycle combo is the way to go and run large battery cables to the motor

gran398 - Thanks for stealing my thread.

So, all in all, It sounds like I'll be fine with a single battery for starting and electronics. I really like the idea of a dual purpose starting/deep cycle battery (someone  mentioned an AC Delco 27 series) Which sounds perfect.  Again, My current battery(age unknown) is going to become my back-up battery ICE. Nothing will be wired to this battery and I will manually switch the battery cables when and if needed. So the only question "for now" is a Battery Switch.  Should I get/install one, and why?  If so, should I hook both batts to the switch or just use it for the main battery to switch off when not in use, in case of  the "phantom" drain?  Im just thinking aloud here.

Thanks again for all the help. I really appreciate it.

Yep, looks like I did... I'm sorry.

Think you'll be happy with the 27, and it does have plenty of cranking power too.

[Skoot]

Two batteries, exactly the same, and the switch, wired to both so that you can switch between batteries without any need for tools.

Heres the thing everyone.  I dont want to buy 2 brand new M27 batteries.$$$ Thats why I plan on using my Old starting battery and buying a brand new Dual Purpose Battery to use as my house and starting battery.

Bob, you suggested Use a switch wired to 2 brand new/same type batteries, correct?
and... Do not use a switch wired to different type/age batteries But, still use a switch for single batt only?  Is that right??????  

Gran - no worries at all, Im just messin around :cyclops:

[Capt. Bob]

[
Bob, you suggested Use a switch wired to 2 brand new/same type batteries, correct?
and... Do not use a switch wired to different type/age batteries But, still use a switch for single batt only?  Is that right??????  

EDIT: 12 Feb 2011

Not exactly.

My setup on my WAC and CCP

Two batteries, same size and type controlled through a  Off-1-2-Both type switch.
Same size and type for conformity, redundancy and ease of maintenance with one charger.

Use Battery 1 first time out, Battery 2 the next time and "switch" back and forth each time. I can't give actual data but in my experience this allows both batteries to enjoy a fairly equal life span assuming they are about the same age and build quality.
For starting in an emergency i.e. weak or dead battery, you switch to the other or if it's weak too, switch to both.
No need to remember, did I charge one battery or both  In all the confusion I really don't remember .
Don't ask yourself if you feel lucky, just hope you are.  :o


Just having a battery sitting there not hooked up is wasted ballast IMHO.

If your "current" (see how I stay with the electrical theme) will crank the motor and handle your lighting and electronics load (not hard to calculate) then buy a new one like/similar to it or you can upgrade to the next larger (say G24 to G27) size but same type.

Wire the switch to both batteries and also run off it to you main buss. This will allow power to the buss when either battery is selected or even when in the "Both" mode. Less wiring, no fooling with connections (except when replacing) and you still retain the ability (as posted earlier) to wire another aux buss off either battery for switched loads (like stereo station memory).

I can't think of any reason, in the case you describe not to wire the batteries through a switch.

Good luck.

This link is what you want. I do not have the ACR module but the wiring is exactly the same. This is but one way to wire but I feel it's the simplest and works very well as it has for me lo these many years.
viewtopic.php?p=33929#p33929

[PSMJAX]

Learned something new...I have always operated under the assumption that leaving the switch on "both" would charge both batteries while running.....I guess thats not the case??
Confused.....

[wingtime]

Learned something new...I have always operated under the assumption that leaving the switch on "both" would charge both batteries while running.....I guess thats not the case??
Confused.....

 

I always thought that same thing.  And your sort of right, it will charge both if they both batteries start off with a similar state of charge.   If your engine is off and you have discharged battery #1 down to 11 volts and battery #2 is still 13 volts when you select both on your switch you'll have 12 volts available.  #2 battery will charge #1 until they bot have the same voltage. This also applies if you have a weak battery.  Since most outboards don't have a very high amperage alternator on them you won't have enough output to overcome the equalizing effect.  Now if your running long enough once they have equalized the motor will charge them both.  

If you leave your battery switch on both all the time you negate the advantage of having dual batteries...  lets say you go on an overnight fishing trip and your switch is on both..  you run your livewell, pumps, lights, radio, electronics etc all night.  You go to start up in the am and Both your batteries are dead.  Now if you had switched to your number #2 house battery when you stopped for the night you would still have your starting #1 battery ready to go.

[jcaesar625]

If I am not supposed to use my engine to charge my deep cycle battery, then what are the best options for charging it? Should I be charging it on my smart charger after each trip? I keep my boat in a dry stack at a Marina, so plugging in a charger to the battery on the boat isn't much of an option. I already carry one spare starting battery on and off the boat each time, that I keep on a trickle charger at the house. I really don't want to carry two batteries on and off each time.

[fitz73222]

Hi Jcaesar,

You will not hurt your deep cycle battery charging it with the outboard. I have been doing it for 20+ years. Outboards made over the last 20 years or so have voltage regulators that will not overcharge a battery. It will only charge as much as it needs to and "sense" the battery voltage an limit the charge rate. So a typical outboard with a 16 amp alternator will charge the battery up until it gets up around 13.8 volts and limit the amp output to keep from cooking the battery. My outboard(s) usually run around 14.2-14.5 volts while cruising. most decent depthfinders today will tell you what your volts are if you select the menu screen. I now run 1000 CCA dual purpose batteries in the AS and the flatsboat; just because they are designed to deliver high amp discharge for starting with the reserve capacity to operate trolling motors, electronics, etc for a long period of time without internal plate damage to the battery.

[pete]

http://www.westmarine.com/webapp/wcs/st ... sNum=10597

watch the video in the west ad...


Guys,The Blue seas combiner and switch is the way to go.It does all the work for you,keeps batt 2 charged while you use batt 1,I have had an older version for 3 years and I don't even think about it.I periodicly will check the voltage on batt 2.But it has worked flawlessly for me.Now the the promariner charger I'm set.

combiner,upper right


 

[RickK]

I agree - ACR is foolproof.

[MarshMarlowe196]

If I am not supposed to use my engine to charge my deep cycle battery, then what are the best options for charging it? Should I be charging it on my smart charger after each trip? I keep my boat in a dry stack at a Marina, so plugging in a charger to the battery on the boat isn't much of an option. I already carry one spare starting battery on and off the boat each time, that I keep on a trickle charger at the house. I really don't want to carry two batteries on and off each time.

I've read lots of different articles about charging deep cycle batteries, and it seems that half of the articles state to charge the batteries slowly because they discharge slowly, and the other half states to charge them with high amperage quickly to restore lost power as quickly as possible.  Of the majority of people I've talked to with experience in charging deep cycle batteries, both groups of people report success and longevity in either method.

The theme from all the conflicting information I've gathered is that there is less danger in how you charge a battery vs. how long you allow a battery to sit discharged.  When a battery drops below 12.4 volts is when the sulfation of the plates occurs, which is the main cause of shortened battery life/inability to hold a charge.

If you have a true deep cycle battery, I'm not sure how you would be able to safely charge the battery via the outboard's alternator as you'd have to switch over to the deep cycle before you start the engine (switching while the outboard is running is apparently very risky for the outboards charging system [could fry rectifier]).  Information on the net seems to agree that using a deep cycle battery to start an engine is detrimental to life of the deep cycle battery.  I've seen some wiring setups that safely switch over to the battery with the lower charge, but I don't know much about that.     Maybe SeaBob does??  

combo starting/deep cycle batteries generally have at least 700CCA's, whereas a true deep cycle has less.  Most outboards require at least 700CCA's to start.

AGM deep cycle batteries reportedly hold a charge longer than wet cells, gel cells.  There are "Smart" solar powered 3 stage chargers, with the 3rd stage being the "Float" stage that maintains a batteries charge at about 1 amp of steady charge.

I'm not sure how your dry dock is setup, but if you can attach a solar charger like this, then it would work.  If nothing else, go with an AGM deep cycle battery, if you don't have one already.

[Capt. Bob]

I'm not an expert but...

I've been using gel batteries (27 Group) for many years and have had extremely good luck with them. There currently resides a 7 year old gel along with a 2 year old in my WAC. It not only spins the 91 Yamaha 200 like a top, I also use it for lighting while working on the boat at night. It still will hold a charge all day long (knock on wood) doing double duty as the starting battery and running the GPS, depth sounder and live well. It will be interesting to see its performance on an all nighter but when it was younger, it never batted an eye.

Of course I'm not supporting a "power blender/fillet board" so its not really getting hammered like the Cappys that do. (pun intended CJ).

Real drawback of gels?  $GYWO$