Imagine having your car towed to the garage because of a dead battery. You couldn’t get the car going even with a jump-start. Your mechanic hooks the battery up to a charger/maintainer for diagnostic purposes. The unit flags your battery as defective. What does that mean? Is the battery really fully dead?
It could be that the battery has reached end-of-life. But it could also be that the battery just needs to be put through a gradual restoration cycle to bring it back to life. But if a battery can be revived, why would your mechanic’s charger/maintainer flag it as defective?
It is All in the Safety Logic
Clore Automotive, a manufacturer of several leading brands of battery maintainers and chargers, explains that it is all in the safety logic. They say that battery maintainers and chargers need to be safe above all else. Unfortunately, some units flag a dead battery as defective because the built-in safety logic refuses to charge any battery below a certain voltage threshold.
The interesting thing is that one battery charger could flag a battery as defective while another has no problem fully recharging it. Clore Automotive knows this all too well. Their battery chargers are known throughout the industry for their ability to revive seemingly dead batteries.
How a Battery Is Deemed Defective
For the record, all of this applies only when a mechanic or consumer is using a smart battery charger. Traditional dumb chargers don’t have the ability to effectively determine when a battery is defective. With that out of the way, let us talk about how a battery is deemed defective by a smart charger.
Modern smart maintainers and chargers depend on a minimum battery voltage to do what they do. As long as that minimum voltage exists, a unit will turn on and begin output. But if the measured voltage is too low, the unit will do nothing.
Some battery chargers require 9-10V on a 12V battery in order to recognize it as a valid load. Anything lower assumes reversed polarity, a shorted cell, or a disconnected battery. The unit will shut down for safety purposes.
In addition, some brands explicitly state that their chargers and maintainers are built with features that prevent sulfation and overcharging. Their units are not designed to address existing sulfation or a deeply discharged state. As a result, the built-in safety logic errs on the side of caution and flags a questionable battery as being defective.
How Other Chargers Revive Dead Batteries
If it is possible to design safety logic to flag a dead battery as defective, additional logic programmed to overcome sulfation and other curable conditions is also possible. That’s how some brands of battery chargers go about reviving seemingly dead batteries.
For example, a battery charger might be designed to ignore the traditional low voltage cutoff. The same charger might also utilize pulse/high-frequency or higher-voltage algorithms that break up sulfate crystals slowly and gradually, thus restoring the battery to a level above the smart-charger’s threshold.
Though not recommended, some DIY users go so far as to bootstrap a dead battery by temporarily joining it with a good battery and parallel. The smart charger recognizes an acceptable voltage from the good battery and begins charging. The dead battery is restored by piggybacking off the good battery.
Here is the bottom line: a battery flagged as defective by a battery charger/maintainer could very well be restorable. Flagging it as defective might be nothing more than the result of a brand’s safety logic. Another brand of charger could actually revive the battery.