I have a battery that has drained completely in a car I rarely used over the past year. No problem… I just need to replace it.
However, if I had the ability to recharge it (with something like a battery tender - and no, I don’t have anything like this, so don’t say “try it!”), would the battery a) hold a charge? b) hold enough of a charge that the car would start and the battery would charge over the course of driving it around town or c) never charge and therefore be useful.
If memory serves, once the battery drains down to the point where it won’t even crank the engine, it’s dead and cannot be saved. If this is so, why? I don’t understand why a battery that could take a charge when there was some juice left in it can no longer do so when it has been completely drained.
if this battery can be saved, what would be the best way to charge it?
Long ago lead acid batteries could be recharged from zero ten or twelve times without any problem. In those far off times the plates were about three times the thickness of the current plates in auto batteries. Now the plates are thin. Not a big deal even with hard use the lead is redeposited as the battery charges. But, with thin plates the complete discharge will leave small holes through the plate. Every discharge after that will make the holes grow. You might get six months use of a battery recharged from totally flat, but you might not.
it depends why it’s “dead.” if it’s sulfated plates, then a “boost” charge might break the sulfation and let you regain usable capacity. if the plates are sulfated badly enough, you’re hosed. If the battery is dead because the plates in one or more cells are damaged, you’re hosed.
so based on the responses, I am hosed? I don’t mean to sound confused, but since I don’t know exactly why this battery drained (I assume it was because of a lack of use. It literally sat for months), there is no way to know for sure if the plates are an issue or not. Since I can’t see the plates, I will never know unless I buy a charger and let it run and see what happens.
I think you’re pretty much hosed and due for a new battery. One of the worst things you can do to a battery is to let it sit, especially drawn down, or being slowly drawn down via all the small electrical draws in a modern vehicle.
Get a jump, run the car for a while, and see if it will restart. No sense giving up without giving it a chance. Just don’t get into a spot where you count on it until you have some successful experience.
The old battery may be salvageable for a bit more life if properly charged. How long that is depends on the damage and how old it is already. If you only need to move the vehicle from A to B, maybe a quick charge or jump would work. If you plan to use the vehicle regularly for some time and the battery is over three years old, just replace it now.
PS> Owning a VOM and a battery charger is a good way to start life.
Marine batteries are designed to be deeply discharged, and will take and keep recharges over an appreciable lifetime (of the battery). Automotive batteries are not designed to do this, and each incidence of significant discharge shortens the battery’s life. How often and how deeply discharged are key factors, so there is variation from case to case. I would guess that most likely, the battery could be recharged (SLOWLY – a rapid recharge will likely worsen things) and hold enough charge to start the car for a little while, but will not hold a charge long enough to be practically useful.
If you plan to use the car regularly now, get a new battery and that should be it. If you plan to use it rarely but want it to start with no fuss, get a new battery and get a tender-type charger that will keep it up without overcharging it. I would not rely on the current battery to give normal service – even if you charge it, you could still drive somewhere then come out to find it won’t start for the trip home.
taking it to an auto service place then they could put it on a charger and try to recharge it for you. their rechargers, if a good place, will have modes to charge slowly so as to not damage the battery and modes that could desulfate the battery (if that is needed and not too far gone). ask the price and determine if it is worth it.
jumping a dead battery may work, may not work, might kill the dead battery. it is an all depends.
borrow a charger that does the slow charge and desulfating. take it to someone that has that type of good charger.
I think the best course of action is to buy a new battery. As someone upthread mentioned, even if I get the car running after a jump, there is no guarantee it will start again after I get to my first destination. I wouldn’t want to be stuck somewhere.
I will also buy a battery tender type device, as I will not be increasing significantly the amount of time I will be driving the car in the immediate future.
How old is the battery? I would estimate that the average life of a battery is about 3-4 years depending upon how many cranks (starts) you have done on it. If the battery was relatively new when you stored your car, then I would say have it charged and move on.
Also, the next time you store your car. Unhook the battery. The clock, etc. runs the battery down over time.
Do **not **jump start the car. Doing so will put a huge burden on the alternator/regulator in both cars. If you’re going to do anything at all, take **Gary T’s **advice and try slowly recharging it. The best thing to do, of course, is to replace the battery.
My advice is based on the theory that few things are more incomvenient than a car that won’t start.
Any decent auto repair shop will be able to test the battery by putting a load on it to see if it can handle normal operational loads. They will also test the alternator to see if there is a problem there. Then you can decide what steps to take - and batteries, for what you get, are very reasonable.
If your car normally sits for months; if it is outside in the sun, you can get a solar trickle charger from someplace like NAPA or O’Reilly for around 40 bucks. If inside, a regular trickle charger can be had for about the same amount.