Please monitor the Schumacher automatic chargers. They are known to take a battery to way too high a voltage. This is not good for the battery and not good for the vehicle if one leaves battery connected during this overvoltage situation. Do not trust the built in Voltmeter, as it reads 0.25 too low, and do not trust the state of charge indicator, as it just guesses at state of charge by the voltage when first connected. It does not magically go in and analyze battery condition and state of charge, as the marketers would have you believe
NO flooded 12v battery should ever be taken above 16V, and my schumacher and others I have seen will do 16.4v
This is not a more is better situation.
16V is an 'equalization' charge, an intentional overcharge to make all cells in the battery reach their maximum specific gravity. it will restore a battery to its maximum remaining capacity but it is also hard on a battery and will degrade the positive plates to some degree, and a starter battery has such thin plates to begine with.
An EQ charge at 16v should only be performed after a regular "full" charge and it should not require more amperage than 5% of the battery capacity measured at the 20 hour rate. When specific gravity, compensated for the rising temperature, no longer rises, terminate EQ charge. If battery temperature rapidly rises, terminate charging. Do not let the battery get above 120F. Do not EQ charge a battery while still connected to vehicle
How well an alternator can handle bulk charging a depleted battery is very platform specific. Usually the charging circuit is way too thin to support massive currents at higher voltages.
I often max out my alternator often charging a large well depleted deep cycle battery over a highly upgraded( fat) copper circuit and the alternator is now in its eighth year, and this is an old design alternator.
Newer vehicles can( not necessarily do) have more robust alternators able to dissipate the tremendous heat they can generate when maxed out
While one can recharge a depleted battery to ~ 80% state of charge pretty quickly with a charging source capable of high amperage and cableing capable of passing it with minimal voltage drop, that last 20% takes time. 2 to 4 hours, no matter the charging source.
It is best to let a plug in charging source take care of that last 20%. However the charging source will need to hold mid 14.x voltage for those 2 to 4 hours.
If the automatic charger sees over 12.8 volts( surface charge) from a recently driven vehicle, it will not seek 14.5 +/- 0.4V, and just try and hold float voltage of 13.2v.
Not many amps are required to hold 13.2 and very little charging then takes place on a battery which requires it.
Trick the charger by removing surface charge by turning on headlamps until voltage falls below 12.6v, then start the automatic charger.
When the green light/ full charge indicator lights up, do not believe it. A hydrometer will prove it to be a liar 19 times out of 20.
Do the same thing, apply a load until battery voltage falls below 12.6v and restart charger at the lowest amp setting. One can keep doing this until specific gravity rises in all cells to 1.270 or higher. I had to do this 8 times with the Schumacher linked to above before a battery SG maxed out and two cells were still 'fair' at 1.255 while the rest were 1.270 or higher.
Do not believe the charger, the green full charge indicator is a supreme liar. yet oh so soothing for the human seeing it.
A happy battery is one which gets to spend as much of its life as close to 100% charged as possible. When a battery is under 80% state of charge it is losing capacity. the lower it goes and the longer it stays there, the faster the battery capacity is lost.
Think of it like a gas tank which keeps getting smaller. You can still fill it up, it just has less to give than it did when new and fully charged.
You can slow the rate at which the gas tank contracts by keeping it full at all times and returning it as close as possible to a true 100% charge ASAP.
Relying on the alternator return a sub 80% battery to 100% is a fool's errand. If your vehicle needs a jump start, drive it home, bleed off the surface charge, and plug in the charger, and don't screw around with a 1.5amp maintainer on a depleted battery. The battery needs to spend 2 to 4 hours in the mid 14v range, and it might take several hours before the mid 14 range is reached, depending on the capability of the charger and the level of battery depletion, as well as the battery health.
Proper Lead acid battery charging can be taken to ridiculous levels. I have the tools and interest and experience to achieve the ridiculous.
Right now, I have brand spanking new a 410$ lifeline AGM group31 125 AH deep cycle battery top charging. Once the Amps required to hold it at 14.4v drop below 0.625a, I will terminate the charging.
I use an adjustable voltage 40 amp power supply as a battery charger. It has a meter on the output leads which show voltage, amperage and counts cumulative current. Watt hours and Amp hours. Peak amps/watts, and minimum voltage.
The Lifeline AGM is now only taking 1.34 amps at 14.4v. It will likely take another hour or more before I terminate charging.
NO flooded 12v battery should ever be taken above 16V, and my schumacher and others I have seen will do 16.4v
This is not a more is better situation.
16V is an 'equalization' charge, an intentional overcharge to make all cells in the battery reach their maximum specific gravity. it will restore a battery to its maximum remaining capacity but it is also hard on a battery and will degrade the positive plates to some degree, and a starter battery has such thin plates to begine with.
An EQ charge at 16v should only be performed after a regular "full" charge and it should not require more amperage than 5% of the battery capacity measured at the 20 hour rate. When specific gravity, compensated for the rising temperature, no longer rises, terminate EQ charge. If battery temperature rapidly rises, terminate charging. Do not let the battery get above 120F. Do not EQ charge a battery while still connected to vehicle
How well an alternator can handle bulk charging a depleted battery is very platform specific. Usually the charging circuit is way too thin to support massive currents at higher voltages.
I often max out my alternator often charging a large well depleted deep cycle battery over a highly upgraded( fat) copper circuit and the alternator is now in its eighth year, and this is an old design alternator.
Newer vehicles can( not necessarily do) have more robust alternators able to dissipate the tremendous heat they can generate when maxed out
While one can recharge a depleted battery to ~ 80% state of charge pretty quickly with a charging source capable of high amperage and cableing capable of passing it with minimal voltage drop, that last 20% takes time. 2 to 4 hours, no matter the charging source.
It is best to let a plug in charging source take care of that last 20%. However the charging source will need to hold mid 14.x voltage for those 2 to 4 hours.
If the automatic charger sees over 12.8 volts( surface charge) from a recently driven vehicle, it will not seek 14.5 +/- 0.4V, and just try and hold float voltage of 13.2v.
Not many amps are required to hold 13.2 and very little charging then takes place on a battery which requires it.
Trick the charger by removing surface charge by turning on headlamps until voltage falls below 12.6v, then start the automatic charger.
When the green light/ full charge indicator lights up, do not believe it. A hydrometer will prove it to be a liar 19 times out of 20.
Do the same thing, apply a load until battery voltage falls below 12.6v and restart charger at the lowest amp setting. One can keep doing this until specific gravity rises in all cells to 1.270 or higher. I had to do this 8 times with the Schumacher linked to above before a battery SG maxed out and two cells were still 'fair' at 1.255 while the rest were 1.270 or higher.
Do not believe the charger, the green full charge indicator is a supreme liar. yet oh so soothing for the human seeing it.
A happy battery is one which gets to spend as much of its life as close to 100% charged as possible. When a battery is under 80% state of charge it is losing capacity. the lower it goes and the longer it stays there, the faster the battery capacity is lost.
Think of it like a gas tank which keeps getting smaller. You can still fill it up, it just has less to give than it did when new and fully charged.
You can slow the rate at which the gas tank contracts by keeping it full at all times and returning it as close as possible to a true 100% charge ASAP.
Relying on the alternator return a sub 80% battery to 100% is a fool's errand. If your vehicle needs a jump start, drive it home, bleed off the surface charge, and plug in the charger, and don't screw around with a 1.5amp maintainer on a depleted battery. The battery needs to spend 2 to 4 hours in the mid 14v range, and it might take several hours before the mid 14 range is reached, depending on the capability of the charger and the level of battery depletion, as well as the battery health.
Proper Lead acid battery charging can be taken to ridiculous levels. I have the tools and interest and experience to achieve the ridiculous.
Right now, I have brand spanking new a 410$ lifeline AGM group31 125 AH deep cycle battery top charging. Once the Amps required to hold it at 14.4v drop below 0.625a, I will terminate the charging.
I use an adjustable voltage 40 amp power supply as a battery charger. It has a meter on the output leads which show voltage, amperage and counts cumulative current. Watt hours and Amp hours. Peak amps/watts, and minimum voltage.
The Lifeline AGM is now only taking 1.34 amps at 14.4v. It will likely take another hour or more before I terminate charging.
