PD or Iota for my upgrade?

BFL13 wrote:
"I completely agree with you that the output current should not be tapering down at the same time the output voltage is creeping up"

Vector (B&D) chargers do that all the time as normal.(but only for the absorption stage)

As it happens, I've got a Vector (B&D) VEC-1093DBD charger.

I have posted graphs of this many times,

When I get some time, I'll try to look them up.

Vectors are programmed to taper the amps when battery voltage reaches 13.9v but voltage continues to rise throughout the absorption stage to approx 14.6 or for the newer models 14.8 temp compensated by the time amps are down to about 5amps.

The PD has two monitors - voltage and current. The input to the control chip from the voltage monitor is modified to control the output voltage. Basically, the chip is told to hold different specific output voltages, if possible, but it is varied only in steps. One voltage is for float, one is for boost, etc.

AFAICT, the current monitor is just a limit, which is not varied. At least I don't recall any discussion of it being varied. I'll look at the circuit again (or anyone else here can do it - it's posted) to see if the output current is limited differently based on the output voltage, or if the output voltage is varied based on the current output.

Something must be causing that behavior. I'm confident that it's not in the firmware programmed into the microcontroller (the "Charge Wizard") as it can only change the output voltage and then only in one of three different voltage steps. It can select those steps based on time, measured output voltage or manual selection inputs from the pendant, but it can't do continuous output current control (and the patent on the CW doesn't describe that type of control).

That means it's got to be in the circuit diagrams - either an intentional design choice or a byproduct.

This is an alternative but very effective charging profile to the other type where voltage rises to a threshold before amps taper when voltage is then held constant at the threshold Vabs. Some converters actually drop the level of voltage below threshold to a lower constant Vabs such as the Iota dropping to 14.2 from 14.8.

IIRC, one of the PD patents describes the PD as using 14.4 (boost), 13.6 (normal)and 13.2 (float). I believe the patent says it cuts off boost after 8 hours (4 hours if entered manually) or after 4 hours from the time the battery exceeds 14 volts.

I must admit, a profile that decreases current immediately seems odd to me. Below a certain voltage, one can be reasonably certain the battery is not fully charged. Why not supply more current, which it is clearly capable of supplying? The additional current will charge a large capacity battery as needed, and for a smaller capacity, the voltage should quickly rise to the trigger, causing a switch to the next lower step voltage.

I wonder if it relates to the dual use of a converter as a power source for the RV and a battery charger? Well it should eventually become clear from the circuit and/or by looking at the device in operation with a scope and meter.

My PowerMax 100amper dropped to 13.6 for absorption after reaching 14.6 for bulk as built, but I modified it so it stays constant at 14.6 after reaching that during bulk. I now love my PowerMax but need to use another charger or converter for float charging/maintaining. .

If you have posted that mod anywhere, I'd like to see it. I always enjoy seeing what others have done.