Cold cranking amps to Amphours?

Chris11 · September 2016

Is there any correlation between the two? I have 2 new marine bats, 225 cca each, for my well pump. They work well (hahaha) for the pump since it's only weekend use, but I'd like the put a charge into my Plug In Prius during the weekdays if I'm there on the property. To fully charge the Prius bat it takes 1000 watts, approximately, for 2.5 hours. Would the marine bats do it? Oh, the panel that keeps the marine bats full is only a 185 watt panel @ 24 volts so wouldn't help to much while charging the Prius.

Thanks for any insight. Chris

Marc Kurth · September 2016

Hi Chris,

No, there really is not a direct correlation.

A battery with 225 CCA is a small battery - likely in the range of 30-40 amp hours each. So in theory you have about 700 to 900 watt hours of total storage. (30 amp hours x 24v = 720 watt hours)

- Your 1000 watt load for 2.5 hours is 2500 watt hours - almost three times your battery bank capacity.

- Putting a 1000 watt load on a 700 to 900 watt hour battery bank even for a few minutes, may cause the voltage to sag to an unusable level. Some batteries are better at this than others.

- If you drain the batteries low in order to get most of that storage capacity, you will destroy them quickly because they are not designed to do that.

So the short answer is that it won't work the way you want it to.

Marc

Chris11 · September 2016

Thanks Marc. I didn't realize those bats were that small in their storage capacity. Oh well...(again hahaha.)

oil pan 4 · September 2016

Short answer is:

No. And any battery that has CCA listed likely shouldn't be used in a off grid power system.

Marc Kurth · September 2016

oil pan 4 said:

Short answer is:
No. And any battery that has CCA listed likely shouldn't be used in a off grid power system.

I will respectfully disagree with the "any" in that statement. Yes, of course your broad point is valid!

More than one true deep cycle battery manufacture publishes everything they know about their batteries - which includes CCA, MCA, HPCA, short circuit current, etc. Remember that deep cycle batteries are also used in all kinds of industrial applications that need full information.

Perspective buyers should read and understand the manufacturers published "DOD vs. Cycles" curves in order to decide if they are suitable for their application.

softdown · September 2016

There is a relationship between the two. Larger, heavier batteries offer more CCA and Ah. The difference is the construction and intended usage. The starting battery is constructed of a large number of thin plates that produce a high number of amps for a short period. Conversely the deep cycle battery is constructed of a smaller number of thick plates that are designed to continually offer usable energy under a long, steady drain.

A deep cycle battery may have ~ half as many plates as the starting battery. The ratio varies of course. My suspicion is that knowing the number of plates vs weight will tell the buyer what the battery is truly made to do.

I have forklift battery cells with only 17 plates per cell....a small number. The forklift battery seems to be the reigning king for deep storage capacity.

FWIW....a person can use solar with nothing but starting batteries. That person would need a much larger amount of batteries to prevent them from draining down and damaging the batteries. In reality, the starting batteries tend to offer short lives because they are doing something they were not built to do. A person may get a year from starting batteries. Two years from deep cycle marine batteries. Four years from golf cart batteries. Six years from solar batteries. Real world results will vary significantly of course.

Johann · September 2016

softdown said:

There is a relationship between the two. Larger, heavier batteries offer more CCA and Ah. The difference is the construction and intended usage. The starting battery is constructed of a large number of thin plates that produce a high number of amps for a short period. Conversely the deep cycle battery is constructed of a smaller number of thick plates that are designed to continually offer usable energy under a long, steady drain.

A deep cycle battery may have ~ half as many plates as the starting battery. The ratio varies of course. My suspicion is that knowing the number of plates vs weight will tell the buyer what the battery is truly made to do.

I have forklift battery cells with only 17 plates per cell....a small number. The forklift battery seems to be the reigning king for deep storage capacity.

FWIW....a person can use solar with nothing but starting batteries. That person would need a much larger amount of batteries to prevent them from draining down and damaging the batteries. In reality, the starting batteries tend to offer short lives because they are doing something they were not built to do. A person may get a year from starting batteries. Two years from deep cycle marine batteries. Four years from golf cart batteries. Six years from solar batteries. Real world results will vary significantly of course.

Real world use of a starter battery here was 1 year use, when i started with solar. And If I remember right, you can use no more than 15% of the starter battery capacity on a daily basis or you shorten the life of the battery.

Cold cranking amps to Amphours?

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