Deep Cycle vs. Starting Battery

[Finaddict]

I have a question for the smart guys on LOU.  I have 2 batteries on my boat, a deep cycle and a starting battery.  My starting battery does not hold a charge well, so needs to be replaced.  My question is whether I should replace it with another starting battery, or should I switch to a second deep cycle battery.  My starting battery powers everything on my boat (lights, 2 downriggers, dash, fish finder, and outboard starter), while my deep cycle only powers my electric trolling motor.   Looking for your thoughts.  Thanks.

[rbonnell]

I would replace it with a deep cycle hands down just my opinion

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[rolmops]

Ok good question!

First of all make sure that both are marine batteries. They can withstand being thrown around a lot better than car batteries and they have less trouble with humidity

A starting battery is for starting and will do just fine powering all that stuff as long as you have an engine running so it is constantly recharged. If you use it without constant charging,it will drain fast,but unlike a deep cycle it cannot really be drained too much because it will shorten its life considerably. You can drain a deep cycle way farther down and you can still recharge it to full capacity.

In my opinion,you should dedicate one battery for starting and starting only. Being stuck on the water because you cannot start sucks.

I have a starter battery and a deep cycle. Both are much more capacity than officially needed. Over the winter keep your batteries  in the basement on a piece of wood .

[finsntins]

rolmops is right.you should do some rewiring and have a battery just for starting your motor and then a deep cycle battery for riggers and trolling motor.if you use your trolling motor and riggers alot,depending on the size of your boat,you may even want to run 2 deep cycle batteries.

[Sk8man]

Basically these two batteries have two different functions: the deep cycle is for long amperage draw down and a starting battery is for quick short term heavy amperage draw. You should be able to run small things like a low draw solid state depth finder from the starting battery OK but for the other stuff (downriggers, electric trolling motors etc. you need the deep cycle marine battery which can be taken right down to near nothing left without harming it. It is designed to be used that way and then recharged. The starting battery will quickly give out on you (shortens its life) if you use high draw (over time especially) items connected to it. My Merc Optimax motor requires that the starting battery be at least 1/2 charged or over or it won't even start the engine because of the high amperage draw. You do have another alternative to just one or the other and that is the hybrid combination starting/deep cycle battery. If you go that route get the heaviest duty one (they are pricier than the others too). I use the hybrid for powering my riggers and other stuff and it is charged by my 9.9 electric start trolling motor alternator which has to be cranking along pretty good to charge it much and the heavy duty marine starting battery is used for the main engine and my depth finder and I have never had a problem other than normal replacement after several years of use. I keep them fully charged all the time and the reason for the hybrid is so that if the starting battery ever happens to give out I can still hook up to the hybrid and start the main engine yet most of the time it is used as deep cycle. Rolmops made a good qualification too regarding the fact that you should stick to a marine grade battery as they are designed to be more resistant to vibration and knocking around.

Edited November 30, 2014 by Sk8man

[Broadhorizons]

Just my opinion from what I've experienced on my own boat without an elwctric trolling motor...

Keep one a starting or dual-purpose for trolling on the motor and running everything else while the motor is running and keep the deep cycle for the electric trolling motor. You have to draw the deep cycle down, I ruined 2 in 2 seasons by just running it trolling on the motor. The deep cycles eventually wouldn't hold a charge overnight to even run the bilge pump. I never drew them down enough.

As far as running everything on the deep cycle, do you really want to run your downriggers on it until they can't come up or your fishfinder quits from low voltage? If you operate on your motor with the deep cycle, you won't draw it down enough for the motor to not maintain a good charge.

Run the deep cycle for your electric trolling motor and whatever you run without the motor and keep a starting or dual-purpose for everything you run with the motor on.

[Has Been]

What kind of motor your boat have?

[LongLine]

Replace it with a good marine starting battery.  While putting on the main engine, its alternator is running all the gadgets and keeping the starter battery topped off.  Your alternator may not have enough kick to keep a deep cycle topped off.

 

Tom B.

(LongLine)

[Finaddict]

Getting a variety of comments, which I appreciate.  Most seem to think that I should replace the starting battery with the same instead of replacing with a deep cycle.  I just thought that perhaps a deep cycle could be run down more than a starting battery between charges, but was concerned that a deep cycle would not have enough "wallop" to kick over my main motor (60 hp Yamaha).  I also have a 9.9 hp Merc for trolling, without electric start, not collected to any battery.  I plug in my on-board charger before just about each trip out to top off both batteries.

[rolmops]

Instead of plugging in your onboard charger before each trip,plug it in immediately after each trip.Always try to have the battery fully charged all the time.

[cheese]

I put my batteries away for the winter on a 2amp trickle charge n I heard a screeching noise from one of them does anyone no what could cause that,n is it safe to just keep it on that trickle charge for the winter

[Has Been]

I would get a big deep cycle for my cranking motor. That is what I have for my 35 hp merc. Also used one for my 55hp johnson. Have had  no probs ever .  An outboard does not need a whole lot of juice to turn over .

 

I have the walmart best & biggest marine batteries & never once had one fail. I put one in my big boat for my 305 

 chevy that runs everything on my boat. I have 2 0n my small boat that run my trolling motor & the rest w/ no alternator on my outboard. For 100 bucks , best deal out there after a lot of research.I buy a new one ever 3 years. 

 

 The secret IMO is to keep the batteries charged. I got a Schumaker marine charger at Walmart . Tells how much charge batt has, 2 /10 /15 amps,  reg/ deep cyc/gel setting.Also automatic cleaning cycle to clean plates. Won't overcharge or overheat .

 

 I would think that screaching sound is gas escaping from the cells . Have heard some of those trickle chargers can over heat/charge ,so check it out.

[jimski2]

Your fish finder has more interference on the screen when at high speed the alternator puts out more pulses. It is best to run your graph on the deep cycle battery.

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[Sk8man]

I put my batteries away for the winter on a 2amp trickle charge n I heard a screeching noise from one of them does anyone no what could cause that,n is it safe to just keep it on that trickle charge for the winter

 I would carefully check out the batteries and the charger itself. On the one hand it could be gas escaping (which can be toxic as well as flamable/explosive under certain conditions so don't have it near any open flames such as a pilot light on a furnace or hot water heater when charging). The screeching can also come from a warning alarm on some chargers when something is wrong. In any case it is something that shouldn't be happening.

 

As far as the deep cycle vs. starting battery goes. Many outboard motors have a very high instantaneous amperage draw when the key is turned on in the ignition and the starter turns over and that is what the starter battery is designed to deal with...the deep cycle is designed to deal with an extended draw down over time but NOT the instantaneous high draw and continued use of it that way frequently shortens the life of the battery.  A deep cycle battery is designed to be taken down nearly all the way and then recharged or at least past half way. They aren't meant to be recharged after each use (when only slightly used) again it can shorten the life of the battery.  I've had my boat (new) since 2002 and I'm on my second set of batteries right now after replacement 3 years ago. Get good quality marine batteries and use them in their intended way and they will last (if not defective).

 

Regarding the interference issue - it is often related to poor shielding somewhere along the power lines, running the wires of sensitive electronics too near (or along with) other power wires, sometimes when hooked up through a power block and not directly with a fused line to the battery itself, or an external source such as another depth finder or electronic operating at similar frequency too nearby corrupting the signal. Sometimes resistor spark plugs can help with the interference encountered with internal sources.

Edited December 3, 2014 by Sk8man

[holy mackerel]

Going on 10 years with an Optima starting marine battery. V6 Johnson outboard, 9.9 Yamaha high thrust kicker. One or the other is always charging. Running 4 riggers, auto pilot, radar, f.f. gps.

[cheese]

Thanks sk8man I made sure there was enough water n also made sure the caps were on tight,I went to auto zone to make sure it was still good they checked it n said yes,took it home n still heard that sound from the battery not the charger,at this point should I just get rid of it for safety

[Sk8man]

If it has been checked out and holds a charge I 'd just carefully look it over for cracks or anything that looks suspicious and if nothing noted make a decision about whether you feel comfortable with it. I wouldn't leave it (or any other one) on a charger for long periods (like over the winter) though. Just charge it fully and place it in a dry area for the winter and then in the Spring check it for charge and it should be still well above 3/4 or even full or so...if not I'd get a new one. The trickle charge is fine for charging a battery over say a few days because the battery will hold the charge longer than if charged at say 5 amps or 12 amps quickly and even though many folks use trickle chargers for long extended periods it can also be a danger if done in unventilated (or poorly ventilated) places or places where there might be any open flame (e.g. cellar or other internal room). 

[Has Been]

Lead acid batteries do not develop memory . You should recharge them after use from research I have done.IMO, keep them charged. I have 4 of the same batteries on a shelf in my basement, one that is 8 years old and still good.I charge them once a month or so this time of year.

 

 There was debate as to how to deal w/ NI/CAD batteries for cordless tools and the same "let them go dead till recharge" theory was out there.Now I just keep them charged & They see have a longer life. I use them every day on my job.  I think the smart chargers we have now for tools & for my boat batteries compensate for some of the bad things the old chargers that just put out  direct amps did.

[cheese]

K will do sir I'll check it in the spring thanks again

[muskybob]

This is an excellent article on "The 12 Volt Side of Life"

 

http://www.marxrv.com/12volt/12volt.htm

 

I switched my rv over to two 6 volt batteries & couldn't believe the difference compared to the 1 12v deep cycle battery I had been using.  Granted, the 6's are a lot heavier, but worth it for my application.

 

Good reading

[Has Been]

Good stuff Musky & confirms what I pretty much already knew. Now I know why my charger acts like it does. I credit the charger I have for the long lifespan of  my batteries.
Money well spent IMO.

Edited December 5, 2014 by Has Been

[marcstevens]

For the few extra bucks get the deep cycle

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