High crank amps, or deep cycle

[dnej]

A cold crank amp ( CCA) starting battery,discharges a high rate of amps for a short period of time,( 30 seconds ). Great for starting, having the capacity to rotate the crankshaft, while the engine fires.
The high CCA battery, also recovers quickly.

My question is, would we really notice, if we used a deep cycle battery, which has a slow discharge rate, and a slow recharge rate, to start our outboard motors?.

Now it may be different for the larger outboards, but I would doubt that it would cause the smaller operator, any grief, using 2 deep cycle batteries.

Your thoughts.
David

[finga64]

That would depend on the current drawn by the starter and would vary dramatically between outboard size and manufacturer.
What size outboard, or better, what's the full load current drawn by the starter are you talking about David??

[seatime]

Hi,
I recently purchased an AGM 40amp deep cycle for the electronics.
I discussed the option of using a bigger one not only for a trolling motor but also to start the petrol motor. The battery expert guy thought it would probably be okay for small to medium motors?
It may also depend on how many starts you want out of it. If you do a lot of drifting, start up move back, drift etc, there won't be enough recovery time between starts. You would need to get big amp hrs to cover for the recharge and recovery time, and then you're talking big bucks.
How I understood it was, okay for small motors, so you can save on space. After that it became cost prohibitive. That was what he said anyway. The 40ah cost $140 and the smart charger $80. cheers Steve.

[Grand_Marlin]

Stick with the higher rate cca lead acid battery.

They are designed for starting and really should be used for starting.

Deep cycle batteries are designed for running lights, tv's, electric motors / bow thrusters etc as a "house battery" bank.

Dont get me wrong, they will start your motor.... but if they are down a bit on charge, you will be in trouble.

Deep Cycle Gel batteries and fibreglass mat batteries are the best, but require a different charger, and as I understand, cant be charged from the motor.
Deep cycle lead acid batteries can.

I recently worked on a 22ft Searay that had a V8 mercruiser in it. It had 2 deep cycle lead acid batteries in it, and it started the motor ok. The owner asked me to check the batteries out, as they were not winding the motor over very quickly.
End result - we replaced one with a Century Marine Pro 600, run off Batt 1 on the isolation switch.
We then linked the two deep cycle batteries together as a house bank, off batt 2 on the isolator switch. This gave a good starting battery, and the back up of the house if needed. House also ran toilet, lights, etc.

Cheers

Pete

[seatime]

dnej, as Grand Marlin says, stick with the cranking battery, winters coming.

that's sounds right about the gel and glass mat batteries needing a smart charger. The 240v charger I have determines the volts required to charge, then "floats" the charge after that, these are sealed batteries. Not sure how this is done charging off the motor, certain rectifier maybe?
How do those Bass boats do it? do they have three batteries.
house AGM or gel + deep cycle lead acid for elec motor + cranking battery.

[dnej]

Thanks for the replies.

The main reason for the question, was to satisfy a debate , over the subject.
I think, a lot of people, do not have a true deep cycle battery, and that is the reason ,for the thought.
We were actually discussing a motor 75 hp, only, and as to why not just have two deep cycle batteries. One as a start battery, to do the job.

As mentioned here, might depend on how many starts, but in this case, it would be probably only, 3 starts a trip.
Great info on the large motor, and that is where they would come into their own.( High CCA Batteries)
I run both, as you would have seen from the other battery post, on this site, and will stick with that, but for smaller motors, I guess you might get away with a deep cycle. Who knows.

Regards David

[PADDLES]

The "cycle" referred to in "deep cycle" is a cycle from full charge to discharged to back to full charge again, and as the name suggests these batteries prefer this cycle to be large ie. battery flattened a fair bit before it gets charged again. They suit camping and stuff where you might use them till they're flat, a normal lead acid battery will die pretty quick if you do this to it. For motor starting uses, ie. a car or boat, the battery might cop a bit of stick on starting and then be trickle charged from the boat/vehicles electrical system. I think that this only affects battery life though, it'll still work fine but not last as long. A standard lead-acid battery doesn't mind being trickle charged for periods of time. That being said though, I wouldn't have a clue what the difference is in construction between the two types of battery. I actually thought that all "marine" batteries were a deep cycle type anyway. Is this correct?

[GBC]

Paddles,

If it's rated at ...CCA, then it's not deep cycle.
If it's rated in A.H. then it is.
We have 2 marine batteries rated in cca, so they are not deep cycle

Anyone reading this with opti's, hpdi's, etecs etc should speak to their dealer about trying to start off deep cyclers. These engines need lots of cca's to kick the computer/fuel pump/starter simultaneously which is plainly stated in the operating manuals. Warranty issues otherwise...

C.J.

[PADDLES]

Thanx mate, didn't know that they marked/rated them differently. But it makes a heap of sense. I'm still wondering though, what it is that makes them different. I mean they're both lead acid style cells. Obviously batteries that are nickel-cadmium, nickel metal hydride etc are a different electrolyte and anode/cathode setup and they have a memory as well so they don't like being trickle charged, but what makes the deep cycle and normal battery different?

[dnej]

Ok, lets examine this issue. Exide,Stowaway, Marine,deep cycle batteries, 12 volt.

an ST 31DC205 Deep Cycle, Has 750 CCA, at 32 deg F ,and 115 Amp hours. Size is 13''X 6 3/4''X 9 7/8"" 24 month warranty.

So you can see, where the question comes from. 750 CCA, should do the trick, I would have thought?
David

[PADDLES]

Yep I agree. But maybe it won't last as long as a "normal" battery for a pure motor starting application where the discharge/charge cycles aren't so huge.

[Grand_Marlin]

I dont know the exact internal differences, but I do know the plate system is different.

Start batteries are designed for short sharp bursts of high current draw. They do not like being drawn right down slowly, then recharged.

Deep Cycle batteries are the opposite. They are designed to be drawn down slowly, with low current draw. They are not designed to take the short sharp spikes of starting motors.

It is sort of like:
You would use a fire hose to put out a fire, but not a soaker hose.
Same as you would use a soaker hose to water your lawn, not a fire hose.
I dunno if it makes sense.

Cheers

Pete

[dnej]

I was told today ,that the new trend from battery companies, is to have one battery, that does both jobs.

I will wait till I see, how long they last, before I change from having two separate type.
Must work I suppose.
David

[Alan_L]

To answer your question on whether or not a deep cycle battery will start a small motor, yes it probably will, would I do it, definitely not. My main concern is when charging a deep cycle battery off an automotive alternator most deep cycle batteries do not like having 20 + odd amps up them, they really should be charged slow, and if you have a dual battery system it's not normally a good idea to connect a deep cycle and a standard battery together, especially if one is fully discharged. I realise that sometimes this cannot be avoided, but try to if possible. It is good to see people using the float chargers to charge their batteries. It's the best way to keep your batteries in good condition.



Just a bit of info on the ratings and different plate set up on batteries.

Standard Lead Acid.

CCA rating is:
the current battery will deliver at the rated CCA (in amps) at -17deg Celcius for 30 seconds without the battery voltage dropping below 7.2 volts.

Amp/Hour rating is :
the current the battery can deliver for 20 hours at 26.7 deg celcius while maintaining a voltage of 10.5 volts. For example, a battery that can deliver 4 amps for 20 hours is rated at 80 A/H.

The plates on a Deep Cycle battery are normally much thicker than a standard CCA rated battery. This is why they can't produce as high a current as a starting type battery, but have the ability to keep producing power for longer at a reduced current.

From what I can gather a marine type battery is a basic CCA rated battery, but the lead material is bonded together stronger on the plates to be able to handle the extra vibration.

Standard Lead Acid batteries do not like to be left in a state of discharge due to the plates becoming sulphated. Sulphation will start when the batteries are approx 1/2 charged. If your batteries are left for a long period in a discharged state it is very common for them to be no longer useful as their current capacity will be greatly reduced, even after charging.


Most 4WD's that have the dual battery setup will have a proper battery isolating control which will only allow the deep cycle battery to charge once the main starting battery has reached approx 13.5 volts. The top of the range types actually disconnect the main battery altogether from the system and just charge the 2nd battery. Even with this system it can still take many hours of engine running to fully charge your batteries, and we still have the problem of too much current being forced into the battery.

Battery technology has come a long way in recent years but there are issues with all types.


Cheers
Alan