PD or Iota for my upgrade?

DryCamper11 wrote:


If you are saying that the output voltage of a converter is maxed when the current flow is maxed, you're missing a key point about modern converters - specifically, the PD 9100 and PD9200 series. In those converters, we're talking about a controllable "pump" (to use your metaphor) - controlled by the UC3846, which controls and limits both voltage (pressure) and current (flow).

The control chip increases voltage, which increases current flow, until the current limit programmed into it is reached. (We're assuming an SOC less than about 80% or so so the battery can accept the maximum current rate at a relatively low voltage.) Then the control chip stops increasing the voltage and holds the max current rate.

As the battery charges, its voltage will increase, and the current will drop. The charger control chip will respond by increasing the output voltage some more to hold the max current. Eventually, as this process continues, the max voltage limit set for the control chip will be reached. At that point, the voltage will be held and the current allowed to decrease .

We tend to think of converters as constant voltage sources, having a bulk charging voltage, an acceptance charging voltage, float voltage, etc., but most are far more complex than that.

PowerMax (and others)converters don't do that. They kick right off in bulk at max amps while the converter voltage is fairly low, staying just ahead of rising battery voltage enough to sustain that current.

When a certain converter voltage point is reached (Threshold) then that is when both converter voltage and current are maxed, but it is just for a moment because converter voltage is then regulated , so amps taper. (goes from bulk to absorption)