AT WHAT VOLTAGE DO BATTERIES PRODUCE CURRENT?

Someone had posted asking "At what voltage do batteries start to produce current when an alternator is charging at 14.5?"...... so I made a very quick and crude video of at what voltage your battery actually starts to produce current instead of receiving "charging current" compared to when a load is applied and voltage starts to drop... because current can’t go IN and come OUT of a battery at the same time.

I basically had an alt turned on putting current into a battery "charging current" then ramped up a load slowly. You'll see that voltage starts to drop but same amount of current is going into the battery, (When current meter reads Negative that means current is going INTO the battery and when it reads Positive its PRODUCING current going to the load)... then as voltage approaches "battery voltage" the "charging current" gets less and less then as more load is applied the battery starts producing current and current flow reverses out of the battery instead of going INTO the battery.

 

At the beginning of the test you'll see the Voltage is 14.4 and roughly 15 amps is going INTO the battery. So, at this point the battery is doing nothing but sucking up 15 amps of alt power and supplying NOTHING to the load present. ... which in your case would be your amplifier.

 

If you pause at "23 seconds" (Which is when around 230 amps of current is being pulled total), you'll see that the voltage is 13.3 and current is neither going in nor coming out of the battery. (0 amps) It is nonexistent at this point.... BUT the alternator is maxed out at 230 amps and the battery is just chilling' doing nothing at all... YET...

I keep applying more load and you will see that the Voltage continues to fall, and the battery starts producing current. (notice how the current meter on the right starts to read Positive instead of Negative) The whole time the alt is still doing its 230 amps, but the load applied is more than that, so the balance comes from the battery. I ended up applying 350 amps total of load on a 230-amp alternator and one battery. You'll see that the current meter, which is reading ONLY the amount of current going in or out of the alternator, goes up to 120 amps. I could not get the camera on all 3 meters, so I just focused on what the battery was doing.

 

After I stopped applying more load I slowly backed off and reversed the process slowly back to no load other than battery charging. ... This time the battery stopped producing current at around 12.2 instead of 13.3. That is because I drained the battery during the process and had less surface charge. When I removed the load completely the "charging current" was all the way up to 60amps! So, from just that tiny dip into the battery for less than 10 seconds charging current went from 15 amps to 60 amps. So, imagine how much load that is on a multi-thousand-watt system and a dozen batteries.

 

That is why keeping your batteries charged periodically on a charger is mandatory in keeping a healthy alternator.

 

I think It is pretty cool and a good piece of information to help people understand what’s really going on in a way they can visualize.