What battery SOH% is it time to replace? Winter -45C

Hmm so what's the conclusion for that? Is your battery just low on charge? If it's still doing 650 CCA that seems like it would still be strong enough to start in the winter?

I just re-tested my battery after doing a full charge. It's rated at 600 CCA, but only tested 370 CCA and it has a resting voltage of 12.6V.
Check the voltage again in a couple days. I tested the voltage a couple weeks ago because it was cranking slow and it was 11.81 but started ok, slow but got er done. Put my Ctek on it for 15ish hours and the voltage was 12.4 for a couple days but by the weekend it was back down to 11.8. New battery will be here Wednesday.
 
Midtronics and the battery makers agree that 60% is the yellow zone and 50% of original capacity is worth a warranty replacement.

I prefer tracking the voltage during cranking, it's a more realistic scenario for one's own particular car. It's not good for the starter motor to give it too little power.

I might appreciate a bad Midtronics result giving me an early warning because some batteries quit "unexpectedly," but slow cranking also means it's time.

PS How often to you "really" need to start at -45C? I've seen -23F outside but my garage hovers in the positive teens. I have a magnetic oil pan heater and little space heater I set up to blow fan forced air under the engine compartment when it's stupid cold.
What cranking voltage do you recommend?
 
Typically one might condemn a battery when capacity drops to 80% of nameplate, and/or impedance doubles.

You don’t have any real way to know capacity, and a state of health metric based upon a non-time trended data set is dubious at best. The best bet is to load test it and see how it performs.

If it provides suitable output (in terms of current and voltage drop), then you have an answer. If not, especially if you can test it in relatively cold conditions,then change it.

At -45 one has to be concerned with batteries not being at 100% SOC as well, as electrolyte can freeze And crack the case.
Impedance? AC voltage at battery? Now I'm really confused...
 
Impedance? AC voltage at battery? Now I'm really confused...
Who said anything about ac voltage?

The term impedance is used for batteries to define the variety of effects that oppose current flow, not just the esr.

It has generally been found that a 1kHz waveform is a good and fast way to identify practical valuation for impedance and forecast how the battery will perform.

Just substitute ESR or resistance in there and you shouldn’t be confused.
 
Who said anything about ac voltage?

The term impedance is used for batteries to define the variety of effects that oppose current flow, not just the esr.

It has generally been found that a 1kHz waveform is a good and fast way to identify practical valuation for impedance and forecast how the battery will perform.

Just substitute ESR or resistance in there and you shouldn’t be confused.
Thanks- I looked it up. Fluke has a very good explanation, too. Did not realize you were using a specialized tester. Got "confused" by the impedance term, since its AC resistance and varies with frequency- so I assumed you were talking AC.
 
Message to Nobb. If you really want to get to the bottom of this, take the battery in and have it checked on a second tester. I find it strange it has a strong sitting voltage and such a low CCA.
 
What cranking voltage do you recommend?
I recall seeing here >9.5 V being "good" but some cars draw more than others from the same rated batteries. It would be a good thing to monitor, trend-wise, so one has early warning of problems.

Gear reduction starters are easier on electricity than direct-drive ones, so a battery on the decline curve will be on a steeper, nearer to death, portion if little is asked of it.
 
I replaced my wife 2014 JEEP GC battery prematurely due to the difficulty in changing it out. It's underneath the passenger seat and it takes me about an hour change it. A battery can quit without any warning.
 
SOH from a conductance tester is only handy if your battery dies in the most ideal way: Losing capacity gradually over time. The last battery I had fail died suddenly and was testing at near 60% SOH a week earlier. I didn't even get a slow-crank warning. It was fine one day, dead the next. Any others I've tested long term that died in a more ideal way, you really didn't even need the conductance tester to predict failure. Those always exhibited the slower-than-normal starts when it was time for replacement.
 
Message to Nobb. If you really want to get to the bottom of this, take the battery in and have it checked on a second tester. I find it strange it has a strong sitting voltage and such a low CCA.

Yea, weird indeed. I wish this battery was more serviceable, but the top and caps are literally plastic welded on. I prefer batteries where you can somewhat access the caps to check water level and such. Sometimes you can restore a bit of capacity (assuming there's no mechanical damage) by adding in a saturated mixture of water and Epsom salt.
 
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