Batteries 101

There seems to be some issues about batteries and charging issues that keep coming up. First off the lead /acid i.e. wet batteries are really storage batteries. The charging system is designed to recharge the batteries back up after starting. The charging system is not designed to charge dead or even really low batteries.
Wet batteries self discharge at a rate of about 4.5% a month. And that rate goes up when the temperature goes up. So as one can see just leaving a truck sit for a few months a battery will loose quite a lot of capacity. This is one of the reasons 6TLs with over 200 minutes reserve are so forgiving.
One reason a battery will discharge is if the battery is dirty. If one has a dirty battery and places a probe from a meter on the top of the case and the other probe on a terminal there will be a slight reading. Another cause is a bad diode in the regulator. Poor connections on the terminals will also cause problems. And there can be some device that is left on.
So how do we get the most life out of a battery? First off keep them charged. That means after starting the vehicle is has to run long enough for the charging system to recharge what was used to start the vehicle. Keep the batteries clean, use some kind of anti corrosion coating on the terminals, I use plain grease. Lastly check the batteries for charge condition when they aren’t used, and even when used check the batteries to make sure they are being charged enough. I use a Duo-Chek refractor type unit to check the charge on the batteries, I don’t like the hydrometer types because they are usually to temperature sensitive, and hook them up to a charger when needed.
Some use Solargizer chargers and trickle chargers for there needs. Those work, however there isn’t enough sun where I keep the fleet for Solargizers to work and I have too many batteries to have trickle chargers.

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So what is the best way to "revive" a dead battery? I get volts on it but when I hook up my battery charger, no charge. the liquid level is correct but I have not check the PH on it yet.

A battery is filled with electrolyte that is sulfuric acid. When a battery discharges the sulfuric acid breaks down into among other things sulfates. The sulfates coat the plates and eventually the battery “shorts” out, actually it insulates the plates so they can no longer accept a charge. The 6TLs have a deep sump so when the sulfates collect in the bottom of the case it takes some time before is does truly short out the battery. There are pulse type chargers that will help and can even reverse the sulfating of a battery. There are chemicals that are supposed to work in de-sulfating a battery, I haven’t tried them. As far as reviving a battery, the 6TLs are a large battery and it takes a lot of time to bring them up. I have had some that I would put on a 20 amp charge every other day for a week to bring them back up. And even then they only will last so long. Unfortunately once a battery is damaged/ discharged severely its life is reduced. If you have a severely discharged battery I would check the electrolyte level and charge it every other day for a week checking the electrolyte daily. Don’t ever allow the plates to go dry. As far as what to put in it, distilled water is what is best, however usually the cheapest bottled water in the grocery store in the gallon is distilled water. After a week allow the battery to rest for one day then test it. Testing it right after charging may only tell what the surface charge is and not whether the battery took a charge.

What about adding more electrolyte (not straight acid) instead of distilled water?

I have always been told and have added straight water. And since electrolyte is simply sulfuric acid and water and when a battery is being charged the water is broken down into hydrogen and oxygen there is no reason to add acid since none is lost.