PD Converters and Water Usage

No, fan isn't the problem. What you see is the signature characteristic of all PD converters. It's a design flaw. As you see it's operating open loop. There's no current regulation, nor is there any voltage regulation. You can improve charging results if the charging cable resistance is reduced and/or if battery resistance is reduced (like AGM), but the signature remains.

All converters have:

1. a peak charge circuit (diode & capacitor) front end that converts ac to 170Vpeak dc.
2. a transformer that drops the 170Vdc to usable levels.
3. a pwm controller (and power fets) that controls transformer switching to achieve the desired output voltage.
4. diodes & inductor/capacitor filter at transformer output to convert pwm waveform to a dc level.

The regulated output voltage is:

Vout = Vpc * Np/Ns * pwm

Where:
Vpc is the peak charge voltage
Np is the number of primary turns on the transformer
Ns are the turns on the secondary
pwm is the percent duty cycle of the controller

Under high loads (in other words in boost mode), the front end peak charge Vpc drops. This is typical for that type of circuit. As Vpc drops, pwm gets bigger to keep Vout constant. So what's the problem? Vpc drops so much that pwm goes to 100% and can't maintain regulation. It's now operating open loop. The design flaw is that the transformer turns ration is incorrect. The secondary doesn't have enough turns.

Here's another plot. Same characteristics. The PD is at 14.1V while outputting 50A. Its regulation point is 14.4V. That's where it should be at (or in current limit). But it can't get there.

DrewE wrote:

Salvo wrote:
If you don't know what you got then you're in the dark.

Here's a 60A PD that only outputs 24A and declines from there. It takes the PD about 100 minutes for it to get to 14.4V.

I wonder if the fan in the converter was not working properly or it otherwise had inadequate cooling. It starts out at 44A or so, but after a very short time (a minute or two, maybe?) is much lower. The curves do suggest that it's neither being voltage nor current limited.

This is a recommendation for Progressive Dynamics converters: The PD 708 deck mount in my trailer is 44 yrs. old and is still performing as expected. It is rated to 30 amps and seems to charge at 13.8V, falling into float at 13.5V after batteries reach a determined acceptance.
I don't use a generator for charging so having more amps to the batteries only gains me time. The few times that I've used the 708, I just get all warm and fuzzy knowing that something was built to last in the good old USA.

smkettner is correct about the graph presented.

There is an extremely high voltage drop between the converter and battery (about 0.8 volts). If the converter were to actually put out 60 amps, the voltage drop would be close to 2 volts. No converter is going to work correctly on such a poor installation. Before evaluating the converter, correct the installation and retest the system.

Doug

Salvo wrote:
If you don't know what you got then you're in the dark.

Here's a 60A PD that only outputs 24A and declines from there. It takes the PD about 100 minutes for it to get to 14.4V.

I wonder if the fan in the converter was not working properly or it otherwise had inadequate cooling. It starts out at 44A or so, but after a very short time (a minute or two, maybe?) is much lower. The curves do suggest that it's neither being voltage nor current limited.

I am saying that graph is from an RV with a poor connection to the battery.
Too long, too thin. Probably both.
ANY converter in that spot will under perform.

WFCO, forgetabout it.
IOTA, steps down to 14.2 in 15 minutes.
Powermax, steps down to 13.6 in 15 minutes.
Paramode, runs a bit low in boost unless near freezing.

What else?

What does better in the same spot?

I'll tell ya. Any converter that does correct voltage regulation. In boost mode, the converter should raise it's output voltage until it either a: reaches max current (60A) or b: reaches max boost voltage (in this case 14.4V). The PD does neither. It's very slow charging.

Salvo wrote:
If you don't know what you got then you're in the dark.

Here's a 60A PD that only outputs 24A and declines from there. It takes the PD about 100 minutes for it to get to 14.4V.

I don't think the primary issue is the converter here.
Or what converter could do better sitting in the exact same spot?

If you don't know what you got then you're in the dark.

Here's a 60A PD that only outputs 24A and declines from there. It takes the PD about 100 minutes for it to get to 14.4V.

Fisherguy posted his results showing the more usual tapering amps of the PD that others have also reported.

Then ah64id posted his results where he has very low resistance wiring between his PD4655 and the batteries where the amps were much better in the Bulk stage with hardly any tapering.

ISTR somebody else (sorry can't remember who right now) managed to get his PD working quite well by doing some special work, but it still had the taper to it, just not very much.

When I say "lame amps" I mean more like what Fisherguy and the others get compared with true constant amps in Bulk (NO tapering) that you get with PowerMax, Iota, and WFCO (when working!), Xantrex, and the rest, without having to go crazy on the wiring or modify its circuit board.

When you only get 40 amps from a "45" amper and then the thing doesn't even hold at 40 but slides down into the 30s, that is "lame"!

The advice to just buy a 55 if you want a 45 equivalent is pathetic.

However PD does have that magic Charge Wizard so you can keep your voltage up, which is a huge advantage over the other brands (except the WFCO 68100)

My solution is to avoid all that by having an adjustable voltage converter of the type that does true constant amps in Bulk. In my case that is a PowerMax as that is the only one on offer AFAIK. It works great! :)

I didn't think RJ would man up.