Battery half dead (550CCA now at 270 CCA)

[JEDI]

2005 Mazda3 Automatic

I had a load test done on my battery this week.
Original: 550cca
Load test: 270 cca

it starts fine unless the temp= 0F, at which point the engine wont turn over the 1st time. I had to crank the engine a 2nd time to start. but i dont expect any 0F weather in DC till next winter (Nov 2009).

So i plan on replacing the battery at the beginning of fall.

That got me thinking about how weak (cca wise) before i start having problems cranking the engine at 60F?

 

[boomerang]

The thing about batteries is that they often work one day and not the next.

You've got a failing battery on your hands. You can replace it whenever you desire, but you shouldn't be surprised if it leaves you stranded.

IMO, it would be a miracle if it lasted until fall.

 

[LTC8K6]

I'd just go ahead and get it replaced. It's unlikely to last until fall if the load test is accurate.

Is it still under it's pro-rated warranty? Those are usually 5 years or more.

Probably the only reason your car is starting is because it's fuel-injected. If you had an old fashioned carb, you'd have been stranded already.

 

[Muadib]

You might not hit 0, but you will be close. Is it really worth the risk?

 

[Zenmervolt]

That's not how you do a load test...

You load test a battery by applying a load of half the rated CCA for 15 seconds and then checking the lowest voltage level measured during that 15 seconds period against a table of minimum voltage levels for temperature level. A load test at 50 degrees should show a voltage of not less than 9.4 volts (40 degrees would be not less than 9.3 volts). You don't get an amp rating result from a load test, you get a minimum voltage result. The shop that load tested your battery is feeding you BS.

Load Test Description

ZV

 

[JEDI]

Originally posted by: Zenmervolt
That's not how you do a load test...

You load test a battery by applying a load of half the rated CCA for 15 seconds and then checking the lowest voltage level measured during that 15 seconds period against a table of minimum voltage levels for temperature level. A load test at 50 degrees should show a voltage of not less than 9.4 volts (40 degrees would be not less than 9.3 volts). You don't get an amp rating result from a load test, you get a minimum voltage result. The shop that load tested your battery is feeding you BS.

Load Test Description

ZV

i have the printout.

12.8v
270cca

edit:
why does your link say 9.6v for a good battery?

 

[StageLeft]

Originally posted by: JEDI

Originally posted by: Zenmervolt
That's not how you do a load test...

You load test a battery by applying a load of half the rated CCA for 15 seconds and then checking the lowest voltage level measured during that 15 seconds period against a table of minimum voltage levels for temperature level. A load test at 50 degrees should show a voltage of not less than 9.4 volts (40 degrees would be not less than 9.3 volts). You don't get an amp rating result from a load test, you get a minimum voltage result. The shop that load tested your battery is feeding you BS.

Load Test Description

ZV

i have the printout.

12.8v
270cca

edit:
why does your link say 9.6v for a good battery?

12.8 has to be your resting voltage, which doesn't mean much because even a completely obliterated battery can be taken up to its desired initial voltage with charging, but as soon as it hits a load its volts will be floored. That's why his link is talking about 9.6 while under duress. If you take any battery, even one in perfect condition, if it's, say, a 12V battery at rest, as soon as you put it under load the volts will drop with stress--the more you try and pull from it, the lower the volts will be. Also, batteries invariably perform worse when cold, so the colder it is the less overall power it can put out. This is a key reason cars have a problem starting in the cold.

If your battery is as bad a you say I'd scrap it now. They are not expensive and being stranded will be a pain in the ass.

 

[LTC8K6]

9.6V would be while the test load is applied.

My local Ford dealer has been reporting battery strength in CCA for a long time now.

 

[Zenmervolt]

Originally posted by: JEDI

Originally posted by: Zenmervolt
That's not how you do a load test...

You load test a battery by applying a load of half the rated CCA for 15 seconds and then checking the lowest voltage level measured during that 15 seconds period against a table of minimum voltage levels for temperature level. A load test at 50 degrees should show a voltage of not less than 9.4 volts (40 degrees would be not less than 9.3 volts). You don't get an amp rating result from a load test, you get a minimum voltage result. The shop that load tested your battery is feeding you BS.

Load Test Description

ZV

i have the printout.

12.8v
270cca

edit:
why does your link say 9.6v for a good battery?

12.8 volts is the resting voltage which is useless for determining battery health. In fact, 12.8 volts is higher than a battery normally stabilizes at (normal resting voltage is 12.7 volts) which means it's likely that the shop failed to allow the surface charge to dissipate before testing. Batteries will often show higher than normal voltage values for a few hours after being fully charged; this "surface charge" dissipates after sitting for a bit and is not an accurate reading of the battery's true voltage.

The link shows 9.6 volts for a good battery (at 70 degrees Fahrenheit, acceptable voltage is lower at lower temperatures) because there is a voltage drop under load.

CCA is determined by the number of amps a battery can supply for 30 seconds at 0 degrees Fahrenheit without falling below 7.2 volts. For example, a 12 volt battery rated at 550 CCA can supply 550 amps at 0 degrees Fahrenheit for 30 seconds before the voltage falls below 7.2 volts.

Yes, it's possible to back-calculate CCA from a load test using mathematical formulae, but giving just the new CCA number really does not provide a sufficient amount of useful information. Frankly, it seems designed mostly to convince consumers that they need a new battery prematurely. ("Oh, sir, you're 100 amps below your car's CCA spec, you need a new battery right now!") Auto makers specify a certain CCA rating knowing that even after a year the battery will drop lower than its rated capacity. There is some leeway built into the specification to account for CCA drop as the battery ages, if there wasn't we'd be replacing batteries every year, or even more frequently.

As far as starter draw, a good starter will draw between 130 and 250 amps. For a modestly-sized 4-cylinder you're probably looking at a total amp draw from the starter of 150 amps depending on temperature. Purely theoretically, a healthy battery with 175 CCA should be able to start the car even at 0 degrees Fahrenheit if you have all accessories turned off.

ZV

 

[Jabbernyx]

Originally posted by: Skoorb
If your battery is as bad a you say I'd scrap it now. They are not expensive and being stranded will be a pain in the ass.

QFT. Even a battery for the Lincoln LS (rear mounted with vents), which is a royal PITA to find (used to be a dealer-only item) isn't that expensive. ~$120 after tax and core for a NAPA LEGEND 750CCA battery. Of course, you could also splash $200+ for an 800CCA Optima