Deep cycle vs deep cycle/starting

[dh]

What is the difference between a deep cycle battery and a startin/deep cycle battery? I saw one said 625 CCA 125 reserve. Would I get more AH for my buck to go with a strictly deep cycle battery?

[eamarquardt]

Batteries are constructed differently for different purposes. Starting batteries are designed to provide very high current for short periods of time (so they have lots of plates and a lot of surface area). At the other end of the spectrum there are deep discharge batteries that are designed to provide much lower currents for extended periods of time (fewer but much thicker plates). There are "compromise" batteries with characteristics in between the two extremes.

"Marine" batteries are kinda in the middle and will tolerate a discharge of 50% of their rated capacity repeatedly. Golf cart batteries are much more robust and can tolerate up to an 80% discharge of their rated capacity w/o degraded service. So, for good service in a trailer a starting battery is a bad choice. Marine batteries are moderately sized and priced and can be a reasonable compromise. A true deep cycle is gonna be bigger, heavier, but provide more capacity and a longer life.

"Choose wisely".

Hope this helps.

Cheers,

Gus

[Wobbly Wheels]

First off, ignore the labels - batteries are 95% marketing.

Pick up a 'deep cycle' and then lift a 'starting' battery of the same size. If the deep cycle isn't significantly heavier, then the sticker is the only part of that battery that's 'deep cycle'.

A true 'deep cycle' battery has more lead in the plates and the plates themselves are thicker and heavier. A start battery has more plates but they're thinner. The former tolerates deep discharges and full charge cycles better, whereas the latter has more reactive surface area to provide more current for a shorter duration, as Gus mentioned above.

A 'marine' battery simply has its CCA rated at zero degC instead of zero degF. Typically, they also have threaded terminals instead of automotive posts.

For RV refits, I usually spec only deep cycle batteries unless the customer specifically requests otherwise.

[Larry C]

Good info......
Where does the cheap little lawn tractor batteries fall? They are used for starting small engines, but are left to discharge for sometimes weeks or even months. Are they some type of deep cycle?
The reason I ask is I would like a very light battery for my Ultralight build. My needs would just be LED lights and a Fantastic fan. If the Fantastic is too much draw, I would try computer fans instead. Weekend use only or charge from vehicle while traveling.
Any thoughts/issues with this idea?

Thanks,
Larry C

[caseydog]

Batteries are constructed differently for different purposes. Starting batteries are designed to provide very high current for short periods of time (so they have lots of plates and a lot of surface area). At the other end of the spectrum there are deep discharge batteries that are designed to provide much lower currents for extended periods of time (fewer but much thicker plates). There are "compromise" batteries with characteristics in between the two extremes.

"Marine" batteries are kinda in the middle and will tolerate a discharge of 50% of their rated capacity repeatedly. Golf cart batteries are much more robust and can tolerate up to an 80% discharge of their rated capacity w/o degraded service. So, for good service in a trailer a starting battery is a bad choice. Marine batteries are moderately sized and priced and can be a reasonable compromise. A true deep cycle is gonna be bigger, heavier, but provide more capacity and a longer life.

"Choose wisely".

Hope this helps.

Cheers,

Gus

I got nothing to add to this. Good description, Gus.

CD

[48Rob]

Where does the cheap little lawn tractor batteries fall? They are used for starting small engines, but are left to discharge for sometimes weeks or even months. Are they some type of deep cycle?
The reason I ask is I would like a very light battery for my Ultralight build. My needs would just be LED lights and a Fantastic fan. If the Fantastic is too much draw, I would try computer fans instead. Weekend use only or charge from vehicle while traveling.
Any thoughts/issues with this idea?

Hi Larry,

Lawn mower batteries are simply a smaller version of a standard starting battery.
Will it work? Yes, it just won't last as long because of the wear and tear of being discharged more that it was designed for and for being exposed to so many more charging cycles than it was designed for.

If weight is an issue, you can buy deep cycle scooter and wheelchair batteries that are designed for your intended purpose.
They're about the same cost, and smaller.
Here's a link;
http://www.partsforscooters.com/Battery-12V-12AH-104-9

Rob

[dh]

Thanks for the replies, that help Gus(s). Now, anybody willing to tackle the latter half of the question, how do pure deep cycle batteries compare in price to marine batteries?