Charging car batteries (Lead Acid) at 0F

[bob_ninja]

Is there a temperature limit for charging car batteries (Lead Acid)?
I was using a smart charger from CTek on my cars last night. The temperature was around -15C or 0F. It is a small charger, 3.3A.
It only workes for about 1-3 hours then indicated battery is full.

It has a setting for cold when it uses a slightly higher volatge, 14.7V I think, not sure. One of the batteries is older and I am sure has a diminished capacity. It was deep discharged couple of times this fall (left the lights on). I expected the charger to charge that one for much longer as I couldn't start the car previous morning.

Anyway, at what temperature charging Lead Acid is not effective?

thanks

P.S.: Took a quick look at Battery University, but found no reference to temperatures.

 

[Flash_Gordon]

You can charge a lead acid battery at low temps as long as it is not frozen. This should not be a concern at 0°F. There are some characteristics worth noting.

The charge acceptance rate a 0° and below is much lower. It will take longer to get to a fully charged state. The full charge voltage is higher-about 1V higher at 32° than at 75°F. Higher by about 1.8V at 0°F.

Battery capacity at lower temps is greatly reduced. At 0°F the capacity is about 50% of rated. Battery specs are typically given for 75°F.

These factors make low temps much tougher on the demands you put on your starting battery. Since you know one of your batteries is weak, it is probably a good move to replace it now. Every over discharge can reduce capacity and battery life by up to 25%.

Mark

 

[Nubo]

If you run into deep-discharge situations (and who hasn't!), a deep-cycle battery makes a lot of sense. In fact, most modern cars have a considerable current draw even when parked ("dark current"), and can drain a battery substantially in just a couple of weeks.

There are various AGM type deep-cycle batteries which also serve well as starting batteries. Optima and Odyssey(Hawker) are examples. Another beautiful benefit of AGM is that the batteries are practically leakproof -- no corrosion to deal with. In fact, I think the Odyssey site used to have a video where they cut one in half with a bandsaw. No leaks!

 

[bob_ninja]

...
The charge acceptance rate a 0° and below is much lower. It will take longer to get to a fully charged state. The full charge voltage is higher-about 1V higher at 32° than at 75°F. Higher by about 1.8V at 0°F.
...

Aha, good info
So the charger using winter mode tries to compensate by increasing voltage little bit (much less than 1V) whereas I actually need much more, 1V+

I guess I shouldn't even try until 32F+

thanks

 

[bob_ninja]

If you run into deep-discharge situations (and who hasn't!), a deep-cycle battery makes a lot of sense. ...

Well it is not much of a problem as most newer cars sound an alarm when you leave a light on. This only happens on my older car. In general I find the standard car batteries to be fairly reliable, so no need for deep cycle.
Also I drive a lot of highway which regularly recharges them and keeps them near full, so deep cycle battery would be wasted.