PD or Iota for my upgrade?

Salvo wrote:
Again, as much as Wayne tried, he can't charge his batteries with 60A. The current tapers before converter voltage gets to 14.4V. If the converter was in regulation, it would increase its output voltage to maintain 60A. That's how converters work. Current should start to taper after 14.4V is reached. Not before!

Let's clarify a point I'm pretty sure we both agree about - relating to remote voltage sensing. The PD and Iota and others that do not have remote voltage sensing will start to taper when the charger is at 14.4 volts, even though the battery is not yet at 14.4 volts. That's why it's so important to have short fat charger cables.

Other than that, we agree. If the charger is tapering below its set current limit, while the voltage is below its max setting (for mine the voltage is 14.8 volts per Trojan recommendations) then something is wrong. It could be an input stage problem - there's not enough voltage to increase the current, or it could be a control issue.

I made some mods I thought would help if it was a control issue. I studied the datasheet for the control chip in the PD series, as well as the PD circuit. There are several interconnections that could have caused premature current tapering.

Unfortunately, my early unmodified tests were at a low voltage, so the tapering could have been due to either problem. Then I tested at higher voltage, after modifications. There was an early increase in current then later tapering. From those two tests, I still don't know where that problem came from. We agree that the properly designed circuit should not taper current until the charger reaches its design voltage limit, or it is simply unable to supply that current.

If it's unable to supply the current, there are some possible fixes. One can boost voltage at the gen. One can boost voltage with a buck/boost autoformer. One can even modify the input stage of the PD. I chose the easiest for me.

AFAICT the UC PWM current mode controller that the PD uses to control the output is designed to work as described above. I don't yet know why the current isn't absolutely flat up to the voltage limit as I would expect from reading about the control chip. It may be an interaction from other parts of the circuit (there is a current limit and a short circuit protection and some other elements that may interact in the control system), or it may be running out of power from the input stage when operated at low voltage.