If I use a charge controller for a 12v battery that limits the voltage and Amps would my battery die?

Question

If I use a charge controller for a 12v battery that limits the voltage and Amps would my battery die if I am using more volts and amps than the charge controller is allowing to run into the battery? Basically I want to run applications of the battery through an inverter but the applications use a lot of volts and amps. I want to charge the battery with a simple generator that creates plenty of energy but I have been told just running it into the battery would damage it so I need a charge controller that limits the voltage to 14-15 volts and 20amps but my applications use more than that. So would my battery go dead or would it take more energy the lower the battery level is?

So even though my generator is creating enough energy to supply the applications but the controller is limiting how much energy from the generator is going into the battery it will still go dead?

Answer 1

Yes and Yes. The battery can only put back what was given to it, so if you use more current than you supply to the battery, it will eventually go dead. The lower the battery voltage became the more current the charger would have to supply, BUT modern controlled battery chargers are usually current limited such that they may not ever allow the full current your system would require. There's no such thing as a free lunch. You cannot pull more current out of a battery than you put in on a sustained basis. For very short times, yes, however the average must be such that you are recharging during the low load times sufficient to make up for the high load times, and then the battery must be capable of supplying the larger current when it's needed.

Answer 2

What would work best is a charge controller that provides a constant voltage (CV) characteristic. These limit voltage but not current. Most battery manufacturers prefer this charging method. Your generator would still be able to supply all the current your inverter requires, but the battery would never overcharge. The battery would furnish power during surges, and when the generator was off.

Many of these type chargers have a floate mode. They will switch to a slightly lower voltage, when, they sense the battery has reached a certain current level. This maximises the life span of your battery. As soon as a load is sensed, they switch back to the charge mode.

If you want to know everything you've ever wanted to about storage batteries, try the book. "Storage Batteries" by George Wood Vinal. Large libraries or college libraries usually have it. An old book, but the bible on the subject.

Good luck.

Answer 3

In addition to Bill's response.

I hope that you are using a sealed lead-acid (SLA) battery, other types are far less forgiving, and will explode if mistreated.

For decent battery life, you need to control the charge current to battery based on the battery's charge level. For a 12V (nominal) SLA battery, you want to make sure that the battery's voltage does not drop below 10.8 volts (prefer 11.0V), and charge at no more than 20% of the amp-hour capacity of the battery.