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

[nobb]

I have one of those electronic battery testers that give out a battery SOH (state of health %) value to estimate how much usable CCA is left. It basically takes the usable CCA over the rated CCA as a percentage. I'm thinking it would be good practice to do a quick battery health check every fall before the winter hits.

In the summer, I could probably run a battery that's only got 20-30% SOH and it would still start the vehicle just fine. However, since our winters get to -45C around here, I'm wondering if anyone knows typically how much SOH % would be a good cutoff guideline to start considering a battery replacement? Or would you look at it from an engine size perspective? eg. I have a 2.0 on my Hyundai and it came with a 600 CCA battery, so in the winter, how many CCA do I need at minimum?

 

[Rand]

If I have to worry about it I replace it.

 

[JimPghPA]

That is a difficult one to nail down an exact cut-off percentage. I also have one of those electronic battery analyzers. For my area (Pittsburgh PA) the coldest day we ever had here in the past 50 or so years was -22 F. And I consider 75 % of the factory rated value as the lowest acceptable level I will use in the future, though I would be thinking of replacing it if it read 80%. But at -45C you might want to increase that considerably. Maybe 85 % or 90 %. In areas that it gets that cold, you probably would not be wasting money to upgrade to a larger size battery with more CCA if it will fit, even if you have to buy a different battery tray.

Maybe what it boils down to is how willing are you to spend to maintain reliability?

 

[Snagglefoot]

Here is something you might like. It follows my effort to find the answer to the same question you have.

https://bobistheoilguy.com/forums/threads/tracking-an-aging-battery.336304/

 

[samven]

I used my battery in a 1.6l Fiesta until it fell about 1/3. It was a 590 CCA and was still working 10 years later but at only 450 CCA according to the meter. But I did notice it was slower to start and I put a voltmeter on the lighter plug and noticed the voltage was dropping to 7V during the crank so I replaced it this fall. I am not sure I trust their estimate of CCA since that is a rating at 0F and if your testing your battery at 50F I think you get an over optimistic reading. The best you can do is look at the milliohm reading it gives and compare that to what it was new. If you dont have a reading from new most auto batteries start at somewhere around 3 milliohms but each one is a bit different. Once that number has increased 60-70% its time to replace or at least evaluate it. If your in a warm climate it will probably continue to work just fine but I would not chance it in real cold weather and I would be carrying one of those lithium jumper packs.

 

[Snagglefoot]

To the OP. What voltage and state of charge is your battery at on these cold mornings. Also tell us the actual temperature. We are hovering at just below freezing right now in SE BC. (Not to be confused with the lower mainland. )

 

[WobblyElvis]

How good your battery is at -45C is really not going to be the issue because at those temps you are going to be using external help like a battery warmer, block heater and or an oil pan heater. Repeatedly starting [if possible] a vehicle without these devices at -45C is just inviting trouble. I would not count on any vehicle starting at -45C without assistance.

 

[eljefino]

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.

 

[JHZR2]

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.

 

[JMJNet]

Depends on how bady you want to find out??
How detrimental it will be when it happens in the middle of nowhere?

 

[skyactiv]

Hyundai has been installing AGM in some models and trims like the Elantra for the past several years. So don't downgrade to a flooded battery if it came new with AGM.

 

[wpod]

Load test it the only test.

 

[andyd]

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.

I was told that a dead battery can freeze and split, but a charged battery won't freeze. Molecular motion or something

 

[nobb]

To the OP. What voltage and state of charge is your battery at on these cold mornings. Also tell us the actual temperature. We are hovering at just below freezing right now in SE BC. (Not to be confused with the lower mainland. )

Still probably a few months away from hitting those temperatures, hence there's no real way to accurately test. I'm moreso using the electronic meter as a gauge to see how the battery may be expected to perform.

 

[Snagglefoot]

Still probably a few months away from hitting those temperatures, hence there's no real way to accurately test. I'm moreso using the electronic meter as a gauge to see how the battery may be expected to perform.

Although everyone is accurate that that the battery testers are better than voltage, may I suggest you pop your hood open just a bit so you don't have to disturb your electronics by opening a door. Leave the vehicle over night. In the morning open the hood fully. Use a simple voltmeter to check the voltage of the battery. If it’s still over 12 V, you are still good. If you see anything under 12, chances are it’s not going to start at -40. Just an old Saskatchewan farmer trick. Mine read 12.05 V this morning. Still going.

 

[nobb]

Although everyone is accurate that that the battery testers are better than voltage, may I suggest you pop your hood open just a bit so you don't have to disturb your electronics by opening a door. Leave the vehicle over night. In the morning open the hood fully. Use a simple voltmeter to check the voltage of the battery. If it’s still over 12 V, you are still good. If you see anything under 12, chances are it’s not going to start at -40. Just an old Saskatchewan farmer trick. Mine read 12.05 V this morning. Still going.

My battery sits at about 12.6V. During cranking today (warm 10C outside) it drops to 7.5V which seems to be a bit low, always thought 9-10V during crank was better.

 

[Snagglefoot]

No expert but 12.6 is strong. I would think the cranking voltage is highly dependent on the design etc. Keep us posted. I’m thinking you’ll be fine for this winter.

 

[javacontour]

While not as cold as your area, I just keep one of those small jump start packs in each car and check that it's charged up.

I showed oilBabe how to use it. If we have to use it without any contributing cause like leaving the headlights on, it's time to replace the battery.

Just went through this on my Mazda3 last weekend. I was parked waiting for oilBabe and didn't realize I had both my headlights and fog lights on. So drawing about 220w 4 H11 bulbs at 55w each, not to mention the other lights that were on. Fog lights must have been turned on by the carwash when they did the interior clean. I don't normally have them on.

Drained a battery with a reserve capacity of 160 minutes at 25w in about 20 minutes of engine off lights on.

Jumped it with one of those pocket sized packs and drove home. Charged it overnight and tested it with a carbon pile tester. It didn't go down to the weak zone until the 3rd or 4th hit with the tester. So I think the 4 year old battery is still good. Topped it off again after the test of course.

Bottom line, if you don't trust it, either replace it or carry a jump pack to help it out.

 

[Snagglefoot]

Here’s an example of the voltage drop when you open the car door and the interior light comes on and the electronics wake up. The 12.06 volt dropped to 11.95 when I opened the door. The battery still tests at 650 CCA.

 

[nobb]

Here’s an example of the voltage drop when you open the car door and the interior light comes on and the electronics wake up. The 12.06 volt dropped to 11.95 when I opened the door. The battery still tests at 650 CCA.

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.