posted
i see that most starting batteries are rated in cranking amps and most deep cycles are in amp hours. about what would the ratio from cca to amp/hr be? like say if i had a 115 amp/hr battery what kinda cranking amp rating would be equivalent? is a 115 amp/hr battery a decent sized one? would it compare to the rating of a yellow top or similar?
thanks
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posted
cranking batteries are designed for instant bursts of large current. Thus, you want to know how much current it can put out for say... 10 seconds. This is your Cold Cranking Amp spec (CCA).
A deep cycle is designed to slowly discharge its entire charge, in an application such as a trolling motor etc. Thus yo uwant to know how long it will last.
1 amp hour = 1 amp for 1 hour 2 amp hours = 2 amps for 1 hour, or 1 amp for 2 hours or... well you get the point
Ok NOW im going to bed
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posted
so would there be any differance in the output of the batteries? like when my amps draw hard would a cranking battery supply them better than a deep cycle?
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quote:Originally posted by PimpDaddy: so would there be any differance in the output of the batteries? like when my amps draw hard would a cranking battery supply them better than a deep cycle?
For the most part, yes. However as I said, if your going to go with cranking batteries, just make sure that you do not discharge them too much, or they will be damaged.
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~
posted
Unfortunately neither CCA or Ah is a perfect rating to go by for car audio use, and there is no conversion between the two.
As stated in the first reply CCA is how much current the battery can produce for a certain amount of time. The actual test is done for 30 seconds at -17.8 degrees C. The battery is discharged to 1.2V per cell. Most amps don't run below 10 Volts and normally are at higher temperatures so this number doesn't tell us much without seeing a graph of what the voltage is for the entire test. Ah rating is also as stated earlier, how many amps for how many hours. The SAE test for Ah rating is 25A discharge down to 1.75V/cell or 10.5V. This is a more interesting number for car audio but still doesn't tell the whole story. Because you will get much more capacity at low discharge rates than you will at high rates. Say you can draw 25A for 4 hours, which is a 100Ah rating. You won't be able to draw 100A for 1 hour, probably more like 3/4 of that.
The main difference between a regular battery designed for normal automotive use and a deep cycle is how it reacts to full discharges. A regular battery will only allow maybe 40-50 cycles down to 10.5V, this is at a low discharge rate (25A or so). Where a deep cycle will allow up to 200, and actually get better between the 40-140 cycles. So they are better for applications where you run 'em till they're dead and charge 'em back up. In SPL applications you generally will be discharging at a higher rate and will be charging them right away so I don't see the benefit of a deep cycle if all other specs are the same. But don't let them go down to low voltage or you will lose capacity, and the further down they go the worse it gets.
If you really want to know which battery is best for you, ask the manufacturer for discharge voltage curves at different rates. Then by knowing how much current your stereo draws you can compare batteries and actually see which one gives you more usable power for your situation.
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