Resistance is Futile.
Can someone that's in the Battery business quantify for me with numbers the type and measurement of Wet Cell lead acid battery recharging resistance, for the various types... sealed, AGM, etc. I am...
Forum Discussion
Bordercollie wrote:
Not saying you EE's are wrong, but high cell resistance when discharged does not make sense based on my observations. When I start to charge a discharged battery, the amp meter shows a higher number of amps/rate of charge whch diminishes as battery becomes charged and tapers off to a very low rate as battery becomes fully charged. ???
There are two components that limit the current. First is voltage potential and the second is internal resistance.
On a 50% discharged battery resistance is high but battery voltage potential is low. The charger voltage easily overcomes the voltage potential and is limited by the resistance or charger max output.
As a LA battery becomes charged the voltage potential of the battery increases so the differential to push a charge into the battery drops. You may start with a 2.5 volt differential (12.0 vs 14.5) and as charging approaches 100%, the voltage differential approaches zero. All the while during charging the resistance is dropping as shown on the graph I posted above.
One of the largest factors in resistance is the ability of the electrolyte to conduct the electricity. As the battery becomes charged there are more ions in suspension to conduct. When the battery is super discharged the electrolyte is nearly just water and a fairly poor conductor.
The change in resistance can be observed in an over discharged battery when initially charging. At a fixed voltage the amps will be very restricted at the start and increase once you have 10%/20% charge in the battery. Then of course taper off again as the charge goes over 80%.
