Is a fully discharged battery now junk?

[CalG]

Not a certain death, but there are things to be aware of.

Sulfation is one. The battery plates combine with the acid irreversibly and a solid precipitate of lead sulfate forms and drops to the bottom of the battery case. That material is lost to ever being part of the "battery" function again. If it builds up to a level where it touches the plates, it will short them out. That is the nature of "a dead cell" . Some "deep cycle" batteries merely give extra room under the plates to allow the sulfate to accumulate. Sulfation begins whenever the battery is less than fully charged, and accelerates in formation the more deeply the battery is discharged. Time at a discharge state is the death. Mean while, a fully charged battery sulfates so slowly as to be a non-issue. Lead acid batteries , properly serviced and charged, will maintain charge "on the shelf" for a VERY LONG TIME. That is why they are popular in emergency back up applications.

Recharging.

High rate recharge encourages the formation of "gassing bubbles" and assures circulation. The electrolyte will "stratify" without such circulation. This causes a chemistry imbalance in the acid and is harmful to the plates.

A fully (or even partially) discharged battery wants high rate recharge at first, with a taper off in amperage at something like 80%, then a fine "finish charge rate" as the battery approaches full capacity.

A trickle charge from dead will kill a battery in short order. Typical alternator systems EASILY can charge at 30 amps and more. And that is GOOD! A Good automatic controlled battery charger is a worth while investment. But costs over $100. But then the last battery I bought cost over $250 Whew! They went up!

A 3 amp "automatic maintainer" is not the same!

There are many very good explanations about the ins and outs of lead acid batteries on the net. Look for some, and READ the various suggestions. ....

Anecdote is not evidence.

ONLY use distilled water $2 a gallon at the drug store.

 

[newbury]

Careful on charger choices. Some of the newer slightly smart chargers will not recharge a really dead battery. I keep a couple of older inexpensive Schumakers on hand hand to kick the battery. Than I can use my "smart" battery charger.

 

[Diggin It]

I've been told (you know how that goes) that a dead battery should be jumped from a running vehicle to the point the dead vehicle will start, then charged further by operating the vehicle.

Maintainers and float charges are to maintain a charged battery.

On charger I have will not even begin to charge a really dead battery. It has to sense voltage to even start the cycle.

 

[RandyT]

. I never understood boiling the cr*p out of them with a high amp fast charger.

Alternators will basically high amp charge a battery for a few seconds to several minutes depending on discharge. No different hooking a high amp automatic battery charger to the battery than it is connecting a dead battery to a high amp alternator.

 

[wolc123]

I bought an old Farmall Cub at a silent auction at work last fall. It had sat unused for 17 years. The 6 volt battery in it was shot. They gave me a second, 18 year old 6 volt battery, along with it. The second battery had been purchased new, but never installed.

I had a very difficult time locating a new 6 volt battery, so I took the (6) year old one out of my Ford 8n, and put that on the cub.

I filled the (3) cells with distilled water (each took a cup or so) and placed the “spare” 18 year old battery on my 6 volt charger. I was able to start the 8n with it, the first time, even though it only showed 5 volts on a meter.

The second time I had to jump it with the Cub. I then ran it hard for about (4) hours plowing a field, allowing the old Ford tractor’s generator to charge it fully.

Since then, Ive been using that old battery in the 8n all year, and it has started it good every time. Apparently, a 6-volt lead-acid battery can be left dead on a shelf and half dried up for quite a few years, and still be good.

 

[mrmikey]

I left the radio on on my Kawi Voyager, the battery, a 2 yr old AGM was dead to the point that it wouldn't even turn on my maintainer. Hooked it up to my booster pack with the maintainer on it to give it a nudge to start charging which it did. Battery finally gave up the ghost this year 4-5 years after killing it.

 

[Hay Dude]

Take care of your batteries.
The price of batteries is up 50-100% in the last few years (3.8% inflation my ass).
I just bought a battery for a small Kubota diesel and the “mid grade” battery was $159.
Large farm tractor batteries are now $300.

 

[ArlyA]

I thought running a battery down will desulfate the plates and harm it. We use Schumacher chargers that is suppose to help with that.

 

[scootr]

I needed the tractor so put a spare in and the discharged battery is on a 3 amp slow charge "smart" modern charger. I never understood boiling the cr*p out of them with a high amp fast charger.

I'll let it slow charge longer and then see what happens. All good to know.

High amp charge is what gets all the heavy elements off the plates and bottom of each cell and back into the water. So do charge it now with amperage equal to 10% of it's capacity. And bring and hold that battery in the 14v range for a day to ensure proper charging. Then let it rest 12 hrs and check how much voltage it is able to hold. 12.7-12.8v is full
Your car & tractor fast charges it's battery immediately after each use. The key long battery life is to never leave the battery in a state of discharge.

 

[scootr]

Just paid $159 for a gas truck battery after we left it plugged into the RV too long while idle.