I learned today that the freezing point of a freshly charged battery is -75F! 75% charged, about -17F, so trick is to definitely keep it charged!
Most home garages, even unheated ones, in most places don't see much below freezing (if they are ATTACHED garages). I live in Michigan and my storage garage "up north" only sees below freezing (that is, below 0C or 32F) when there is extended periods of temperatures 10 degrees F or below. That isn't that often, and has not happened every year. The battery freezing, even on partially discharged batteries, happens in temperatures not often seen where we live...right Chan??
My own personal opionion is I would NOT want anything "plugged in" like a trickle charger, that is
unattended such as in a storage garage or someplace remote from where you are living. While rare, any number of things can happen to something plugged in and unattended, the worst of course, being a fire. I have a Mercedes-Benz battery (n.b. not known for longevity compared to many others) purchased in 2004/2005 I believe, and it gets stored (in the car) unattended and with no trickle charger on it every winter. I charge the battery to full before storage; and it rarely drains itself below 75% over the long winter. I charge it to full again in April when I fetch the car. I have not had an issue with ithis battery (save for the time this year that the mechanic drained it by leaving the door open all day with the courtesy light on...) and would expect I will need replacement as a simple matter of course in the next year or two. Most people who have "failed" batteries discover their problem in winter (CCA: does that parameter ring a bell?). BTW, it took JA17's "big-a#@" battery charger an hour at PUB to bring mine back after the mechanic nearly did it in!!!
If you store your car
remotely where nobody (like yourself!) will be "attending it" regularly, and you are very interested in the very best battery protection, it is probably best to remove the battery from the car and take it with you to a place where you CAN look after it. Store it fully charged, and if you want, put a trickle charger on it.
DO YOUR HOMEWORK. Note that even the "brand name" battery tenders, while claiming "UL
Compliance" are NOT UL
TESTED or CE rated. I wonder why? Unless you fuse them specifically, it is quite possible that a low-voltage condition (I've had this at my home and business many times in the past) could cause a high current condition and cause a short. Rare, but it could happen. If you look at how these things
generally connect (with spring-loaded clamps like a set of mini-jumper cables) you can understand that it is possible for these clamps to spring off--and possibly causing a short too. You can hard wire them with certain models or options. The thought of even the possibility of an electrical fire really frightens me. I'd rather buy batteries a little more often.
Just my opinion. Here's some information from a battery manufacturer:
NOTE: Storing, charging or operating batteries on concrete is perfectly OK. The most important things to avoid:
Freezing. Avoid locations where freezing temperature is expected. Keeping battery at a high state of charge will also prevent freezing. Freezing results in irreparable damage to battery's plates and container. [Freezing can happen between -19 F (40% charge) and -98 F (fully charged)]
Heat. Avoid direct exposure to heat sources, such as radiators or space heaters. Temperatures above 80° F accelerate the battery's self-discharge characteristics.
Step by step storage procedure: 1. Completely charge the battery before storing. 2. Store the battery in a cool, dry location, protected from the elements. 3. During storage, monitor the specific gravity (flooded) or voltage. Batteries in storage should be given a boost charge when they show a 70% charge or less. Completely charge the battery before re-activating.
So what THAT says is the battery will freeze, at a 40% charge, at -19F. Well, let me say this about that. First, if you are storing your car at
-19F, you should find a better storage location, something that is a little warmer than that!. If your battery is at
40% charge, you have a battery issue to begin with! Correct both of those situations, and you'll be better off!
