regular auto "starting" battery versus true "deep-cycle" battery
i've noticed this question asked-stated-discussed in a number of threads on a lot of different forum sites, maybe i can shed a bit-o-light here,
yes, you CAN interchange them SOMEWHAT - however - as with most things, IF they truly were the SAME, there would have been no reason to do the research - developement - manufacturing to market the two DIFFERENT types to begin with!!!
from this thread:
the "pros-cons-well, it-worked" were pretty well said, the complete thread is a good read in that a real-world person can understand the language, no "gob-i-lee-gook" type "fur-inner-speekin" degree required
a couple things in particular do stand out and deserve a bit more attention:
Cariboocoot - June 2012
...none of that changes the manufacturers' recommendations of cycling a deep cycle a few times to reach its maximum capacity and cycling it regularly thereafter, or giving it the Absorb stage or occasionally equalizing it as needed (assuming it isn't sealed).
That is to say, the charging profile of a vehicle's system does not match the recommended charging profile for deep cycle batteries...
Blackcherry04 - March 2014
...The only issue you run into with a deep cycle is they are self limiting on the amount of current available.
A starting battery is designed for high current of short duration.
A deep cycle, a lower current release over a long period of time.
On a V8 where the amp demand is high ( 300 + amps ) you'll definitely see a lower cranking speed and voltage sag...
Cariboocoot - March 2014
And here's me living in a place with -35C Winter temps ... for the job just because it happens to be able to do it.
(the whole post)
Cariboocoot - March 2014
...You can see the difference in the ratings: true deep cycle batteries don't have cold cranking Amps associated with them and automotive batteries don't give you Amp hours capacity.
the thread even touches on ups, wheel-chair, elec-vehicles, and so on...
also, from here:
...What are the differences between a starting and deep cycle battery?
Generally speaking there are two different types of lead acid battery, Starting and Deep Cycle. If a starting battery is routinely deep cycled (discharged below 20%-50% of max capacity) it will generally fail after 30-150 cycles. The same starting battery will last for thousands of cycles if it is just used normally (2% - 5% discharge).
A starting battery is generally designed to start some form of internal combustion engine (car, truck, boat etc). In a starting battery you will find more lead plates, thinner and often made of a lead "sponge" similar looking to a foam sponge. This sort of arrangement means that the plates have much more surface are in the solution than a Deep Cycle battery and allow them to draw larger currents much quicker than a Deep Cycle battery.
A deep cycle battery on the other hand has much thicker plates and they are solid, not sponge. These thicker plates have less surface area and thus less of the instant power that a starting battery needs. They are designed to be discharged down to 20% of their maximum charge repetitively. The thicker lead plates allow for this as they are much sturdier than their sponge counterparts.
Cold Cranking Amps (CCA) is an indicator of the amount of current a battery can deliver for 30 seconds at zero degrees Fahrenheit without dropping below a specified cutoff voltage (normally 10.5 volts). The cranking amps a battery can produce changes with temperature. The warmer it is the more Cranking Amps a battery will produce.
You can use a Deep Cycle battery as a starting battery provided that you take into account the lower CCA of a Deep Cycle battery. As a rule of thumb it's a good idea to upsize the battery by about 20% to deliver the same amount of cranking amps from a deep cycle battery. Also the self discharge rate of Sealed batteries is a lot less than flooded lead acid types.
How long will my battery last?
How long a battery will last depends hugely upon the way it is used and how well the battery is maintained. Both overcharging and undercharging will have serious adverse effects on the lifespan of a deep cycle battery.
In particular you can seriously shorten the lifespan of a battery if it is used in a deep cycle application that it was not designed for. An example of this would if you were to use an automotive starting battery as a deep cycle battery.
General expectations for batteries if deep cycled (these are just approximate guidelines):
Starting battery (Automotive battery etc) : 3-13 months
Marine Battery : 1-6 years
AGM Deep cycle: 4-7 years
Gel Cell Deep Cycle: 2-5 years
Flooded Lead Acid Deep Cycle Battery (L16-RE etc): 4-8 years