Battery confusion question

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drum23

Seaman Apprentice
Joined
Nov 25, 2008
Messages
37
Been having a problem starting my 25 Merc lately. I bought a new Duralast battery 1000 CCA's. After 2 trips on the water, the battery will only recharge to ~90% (12.5VDC). A friend of a friend who claims extensive mechanical knowledge told me that that number was kinda low for a brand new battery. So I got the battery tested under load at one place (not the store where I bought it) and it came back 879A/1000A and the printout said to "replace battery".
When I took the battery to Autozone where i bought it, they hooked it up and it read 12.8V, but they didn't tell me how many amps it was reaching. The tech there said the first place tested it wrong because they compared the read out to the max CCA's. He told me something about you are supposed to base a marine battery on 75% of its max CCA's. I think he was saying that if a marine battery only stores 75% power or less than it should be replaced? I know 1000 CCA's is overkill for a 25 hp motor, but I plan to use this battery with a trolling motor this summer, so I am more worried about getting the max amp-hours. Does it sound like this battery is normal or not? Sorry for the long post.
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
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28,765
Re: Battery confusion question

If the battery is rated at 1000 CCA it should deliver 1000 CCA or very close to it. The "879" number would represent that battery with one bad cell (there are six cells in a 12 volt battery). But as was mentioned, take it to a different store for testing.
 
pvanv

pvanv

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Apr 20, 2008
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6,511
Re: Battery confusion question

And if you do want to go trolling with an electric trolling motor on the battery, be sure that it is a deep cycle battery. Yours may not be that type. If only a starting type, draining it down for trolling will wreck it quickly.
 
J

jhebert

Ensign
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Jul 24, 2005
Messages
902
Re: Battery Cranking Ampere Rating and Measurement

Re: Battery Cranking Ampere Rating and Measurement

A battery with a rating of 1,000-CCA (Cold Cranking Amperes) seems astonishingly large. Perhaps the battery is rated at 1,000-MCA, Marine Cranking Amperes. In general the rating for MCA will be higher than the rating for CCA. A battery rated for 1,000-MCA might only be rated for 800-CCA. This dual rating system may be the source of your confusion with regard to the measured capacity.

The open terminal voltage gives an index to the state of charge, but it does not reveal the amount of energy stored in the battery or how many amperes it can deliver. An open terminal voltage of 12.5 Vdc corresponds to about 30-percent discharged. Cf.: http://continuouswave.com/whaler/reference/chargeBattery.html

The usual charging voltage for "12-volt" batteries is around 14.5-volts. During charging the battery terminal voltage can only rise as high as the charger voltage. Be sure your charger is producing enough voltage to fully charge the battery. If you have a small charger, it could take the charger a long time to bring a battery as large as a 1,000-CCA battery to full voltage.

It is common in retail stores that a battery tester is used which tries to assess the capacity of the battery and determine its cranking ampere rating. These devices do not actually place a load on the battery that is anywhere near the measured cranking amperes they are rating. Instead, they typically try to infer the cranking amperes from an indirect measurement of the battery's internal resistance. The lower the internal resistance, the more cranking amperes the battery will be able to deliver.

If you bought a battery that is supposed to have a rating of 1,000 cranking amperes, and it only measures 879-Amperes on the retailer's own test equipment, then you did not get a 1,000-Ampere battery. You should discuss this discrepancy with your retailer. If the battery label says "1,000" the test meter should, too, and counter salesman advice to the contrary about marine derating should be ignored. Just be certain you are both talking the same units. The test may be measuring CCA and your rating may be MCA.

Using the same battery for engine starting and for running an electric trolling motor is not a good idea, but that is the topic for another discussion.
 
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tx1961whaler

Vice Admiral
Joined
May 31, 2008
Messages
5,197
Re: Battery confusion question

...and don't confuse CCA and amp-hours. Totally different parameters, and usually inversely related. A traditional deep-cycle battery has a high amp-hour rating, and low CCA rating, while a high CCA starting battery has a low amp-hour rating.
 
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Ridemywideglide

Petty Officer 2nd Class
Joined
Jan 13, 2009
Messages
166
Re: Battery confusion question

tx1961whaler said:
...and don't confuse CCA and amp-hours. Totally different parameters, and usually inversely related. A traditional deep-cycle battery has a high amp-hour rating, and low CCA rating, while a high CCA starting battery has a low amp-hour rating.
Click to expand...

Sorry for the hijack, but reading this made me realize, I put a deep-cycle 1000 (I think 1000, close either way) battery in my I/O for starting/running. It cranks slowly. I this a place I should just run a regular car battery instead of the deep cycle?
 
Barnacle_Bill

Barnacle_Bill

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Feb 8, 2004
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6,469
Re: Battery confusion question

Ridemywideglide said:
Sorry for the hijack, but reading this made me realize, I put a deep-cycle 1000 (I think 1000, close either way) battery in my I/O for starting/running. It cranks slowly. I this a place I should just run a regular car battery instead of the deep cycle?
Click to expand...


No, use a marine starting battery.
 
D

drum23

Seaman Apprentice
Joined
Nov 25, 2008
Messages
37
Re: Battery Cranking Ampere Rating and Measurement

Re: Battery Cranking Ampere Rating and Measurement

jhebert said:
A battery with a rating of 1,000-CCA (Cold Cranking Amperes) seems astonishingly large. Perhaps the battery is rated at 1,000-MCA, Marine Cranking Amperes. In general the rating for MCA will be higher than the rating for CCA. A battery rated for 1,000-MCA might only be rated for 800-CCA. This dual rating system may be the source of your confusion with regard to the measured capacity.

It turns you were right about it being MCA's instead of CCA's. It does clear up what the salesman was talking about with the battery being derated about 75%.

I still think the battery wasn't charging right because I left the battery on the 15 amp charge setting overnight and it stayed at 90% which was the same reading before I went to sleep.

Autozone did swap out batteries for me so it's not problem now.
Click to expand...
 
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tx1961whaler

Vice Admiral
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May 31, 2008
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5,197
Re: Battery confusion question

bhile said:
No, use a marine starting battery.
Click to expand...

Ridemywideglide said:
Sorry for the hijack, but reading this made me realize, I put a deep-cycle 1000 (I think 1000, close either way) battery in my I/O for starting/running. It cranks slowly. I this a place I should just run a regular car battery instead of the deep cycle?
Click to expand...
)

Agreed, us a starting battery for an I/O. It's a car motor, and potentially needs alot of cranking amps. They also have a high output alternator that is not designed to properly charge a deep cycle battery. I tend to use deep cycles for my small (40 hp max, old 2 stroke) outboards, since they require much less starting current. Plus I don't run an alternator to charge them.
 
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Ridemywideglide

Petty Officer 2nd Class
Joined
Jan 13, 2009
Messages
166
Re: Battery confusion question

Well I got the walmart battery.. Maxx-29 if I remember right.. 875(825?) MCA.. I'll verify tomorrow.
But it is a trolling/starting/deep cycle...
As far as I can find, there are either deep cycle, or there are car batteries (starting)..
I've yet to find this mysterious "marine starting" battery.
 
F

fire831

Petty Officer 1st Class
Joined
Aug 26, 2002
Messages
373
Re: Battery confusion question

Ridemywideglide said:
Well I got the walmart battery.. Maxx-29 if I remember right.. 875(825?) MCA.. I'll verify tomorrow.
But it is a trolling/starting/deep cycle...
As far as I can find, there are either deep cycle, or there are car batteries (starting)..
I've yet to find this mysterious "marine starting" battery.
Click to expand...

I see the Marine Starting Batteries all the time at Wally World.
 
dingbat

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,567
Re: Battery confusion question

For starting I'd go with a dual purpose marine instead of a starting battery.

Having said that, I run a pair of Grp. 27 AC Delco Voyager Deep cycles. Never had a issue with charging or starting the boat. Usually get 5-6 years out of them.
 
S

sschefer

Rear Admiral
Joined
Nov 13, 2008
Messages
4,530
Re: Battery confusion question

I can see the advantage to using combo style batteries. I guess I'm just a little hard headed when it comes to using my starting battery for anything other than starting.
 
642mx

642mx

Lieutenant Commander
Joined
Apr 19, 2008
Messages
1,588
Re: Battery confusion question

I've got the Duralast battery thats a dual purpose. I think its rated at 1000CA. (its freaking huge! I had to modify my battery box for it to work). I bought it mid-summer and its done great. I run 3 amps and it doesn't seem to affect it at all... it always starts the boat with ease. I do however, throw a charger on it when I have time or if the boat has sat for two or three weeks.
 
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