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Deep cycle battery


Kirtley Howe
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Can someone explain to me the difference between a Deep Cycle Marine Starting Battery, and a Deep Cycle Marine Trolling Motor Battery? I always kind of thought that a deep cycle battery was a deep cycle battery...the only difference being amp/hrs......

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Look up Optima Blue tops.

Been running them in my rig for a while.

Starts the motor and powers my electronic package.

Dual purpose 31M. 

A-Jay

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A-Jay is correct...some batteries say 'Starting', some say 'Deep Cycle' - those you should only use for that specific purpose...but there are those that are 'Dual Purpose' and you can use them for both starting and TM/Electronics.

 

Only downside is if you drain them too much, you better hope you got a pull-cord on that motor.

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Starting or dual purpose batteries have reserve amps, deep cycle trolling motor batteries don’t.

Tom

 

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17 hours ago, Kirt Howe said:

Can someone explain to me the difference between a Deep Cycle Marine Starting Battery, and a Deep Cycle Marine Trolling Motor Battery? I always kind of thought that a deep cycle battery was a deep cycle battery...the only difference being amp/hrs......

It all has to do with the thickness of the plates.  A normal deep cycle battery has very thick plates.  They're meant to be drained pretty heavily, as doing so can wear out the plates on a battery.  The process is a bit complex, but basically lead ions jump from one plate to the other during use.  So thicker plates allow for this process to go on for a longer time before the lead plate is destroyed beyond repair.  Then, when you charge the battery, you basically reverse this chemical reaction, and the lead ions go back the other direction. 

 

The downside to deep cycle batteries is because the plates are so thick, they don't have much surface area.  So starting batteries have much thinner plates, and they're usually wrapped around each other inside the cell.  This makes the plates much longer and creates more surface area, which allows more electrons to form on the plates, which gives you the possibility to draw more amps at once.  The downside to this is, if you drain the batteries too far, you'll damage the thin plates beyond repair.  

 

So a deep cycle marine starting battery is kind of in between the two, with medium thickness plates.  It can be drained further than a regular starting battery without permanent damage, but not as far as a regular deep cycle battery.  And it can provide more total amps at once than a deep cycle battery, but not as much as a true starting battery.  So they're often used as a starting battery that also powers your fish finder, bilge pump, and other accessories, assuming you can find one with enough cold cranking amps to easily start your motor.  But you'll probably want a true deep cycle battery for the trolling motor, as it's likely to put a pretty serious drain on your battery's overall capacity.  And if your motor is too big and requires too much current to start, you'll need a true starting battery to turn it over.  

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On 8/25/2022 at 6:05 PM, MN Fisher said:

Only downside is if you drain them too much, you better hope you got a pull-cord on that motor.

I'll bet most of the engines forum readers are using cannot be started by the cord, even if there is one.  I doubt if I can start my 60HP. 

 

There is another option which is not that expensive.  There are battery packs, very compact, about the size of good sized book , which can start an outboard engine with ease.  They hold their charge all season, can be stowed on the boat for the season, then put into your car.  They will start car engines, too.  Here is one of many:  https://www.amazon.com/Battery-NEXPOW-22000mAh-Portable-Q9B/dp/B082ZZ2W14/ref=sr_1_11?crid=3J4V2V6AIVQAU&keywords=emergency+battery+jump+starter&qid=1661604832&sprefix=emergency+batter%2Caps%2C264&sr=8-11

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On 8/25/2022 at 4:07 PM, Kirt Howe said:

Can someone explain to me the difference between a Deep Cycle Marine Starting Battery, and a Deep Cycle Marine Trolling Motor Battery? I always kind of thought that a deep cycle battery was a deep cycle battery...the only difference being amp/hrs......

Was this just an fyi post or do you have specific concerns?

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Another point for a dual purpose is that they are designed to give that high output blast (on some mercs 1000 MCA) whereas the straight deep cycle are designed for a slow discharge.  As for pull starting, with todays modern boat mounted battery switching devices, if you drain your starting battery you can get the juice to start your big motor from your trollers with the flick of a switch.  Let’s not even talk about lithium, those are game changers. 

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4 hours ago, Jig Man said:

Was this just an fyi post or do you have specific concerns?

No concerns....just wanted basic info. My overall knowledge of deep cycle batteries was fairly limited.

 

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Don’t intend to get onto a deep dive in batteries.

What you need to know you look up!

There are 4 basic types of marine deep cycle 12 VDC batteries.

1. Wet cell lead acid, need to maintain the water level over the plates.

2. Gel sealed lead acid maintenance free, nearly extinct today.

3. AGM Absorbent Glass Mat, sealed maintenance free, no plates. Most popular today, available in both Deep Cycle and Dual purpose.

4. Lithium Ion, available in Marine 12DC, 24VD and 36VDC, 1/2 the weight of the above batteries and 4X the price.

Tom

 

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Regarding pull cords.  My 50 Mercury has a pull cord taped under the cowl.  It also came with a wrench to remove a shroud to attach the pull cord.  I've never tried to start it with the pull cord though.  Being a computer controlled EFI engine, with an electric fuel pump it would need "some" voltage to start.  I suspect the stator wouldn't generate enough current to start using a pull cord, with a completely dead battery.   A 60 Mercury has the same powerhead as mine.  I wouldn't be surprised if it's the biggest engine with provisions for a pull cord.  I've had a dead battery once.  I keep a NOCO GB40 (jump box) in my boat to jump it if needed.  

 

 

The best decision I ever made was going to lithium for my trolling motor.   The trolling motor battery (as well as the cranking battery) were undersized from the factory in my boat.  I have them teamed up as one big cranking/electronics, pumps, lights battery now.  I'll probably go with a lithium cranking battery when they die.   

 

 

Regarding lead acid battery types.  Regular flooded lead acid batteries are getting less and less common.  Compared to other type batteries they're messy, fragile and require regular maintenance.   All AGM batteries....by design are somewhat "dual purpose".  Any AGM battery, even a deep cycle one will likely be damaged if it is discharged beyond a certain point.   FWIW lithium batteries are damaged by too deep of discharge also.  However, there's more usable energy stored in a lithium battery than a lead acid battery.   (of the same amp hour rating)

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50 minutes ago, Woody B said:

Regarding pull cords.  My 50 Mercury has a pull cord taped under the cowl.  It also came with a wrench to remove a shroud to attach the pull cord. 

I had a 2000, 225efi Mercury that had a pull cord in the cowling.  I chuckled every time took the cowling off to work on it.  

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The pull cord may start a 6 cylinder OB 2 cycle engine if the battery isn’t totally dead but doesn’t have enough power to crank it over.

You would need 2 people, one to pull the cord and another to try to start the engine with the low battery.

We used to pull start 6 inline 75hp Merc, no battery or computerized electronics.

Agree it’s Silly to have a pull cord in todays electronic ignition OB’s.

Tom

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