My converter dumps an awful lot of heat and I've had to really add substantial cooling capacity so that the thermistors don't shut it down. (It seems that 115F is where they shut the system down). So, as we look around trying to find an alternate DC boost converter, the question of efficiency has come up. I have an August 2010 vintage DC Converter (serial number 201000271). I'm trying to measure its conversion efficiency. Unfortunately, I'm using a Sears DC Clamp Ammeter which I'm not in love with. Here's one datapoint while charging the HV battery in run mode: Vi = 51 volts Ai = 32 amps So Pi = (51)(37) = 1887 watts Vo=256 volts (seems high as under a "light bulb dummy load" I set this at 243 volts. Ao = 7.2 amps So Po = 1843 watts Efficiency Loss = (Pi - Po)/Pi * 100% = 2.3% Given the amount of heat generated, this doesn't seem possible. The current does seem to related to my netted scangauge II reading, so I assume the input side is pretty close too. Does this make sense? Am I doing this the right way? I'd imagine that 15% power loss would be typical.
Could you do something like measure the battery's power with 5 dummy loads with identical resistance wired in parallel (so they take 48V). Then measure the power out after the converter with those things wired in series. If you average it over time it could give the answer.
It might be that efficient at a low current draw. But try when the traction battery is down below 50% SoC, so that you get the full 14 amp hv output on 60 amp input. Ohmic heating is quadratic in current, so your data point above extrapolates to an efficiency of order 90%.
Hmmm, I'm trying to grab data at higher current, but I don't have enough up time to get the 4 readings. I'll try again.
Think about it this way, at 90% efficiency and 3500 Watts total input, that's 350 Watts of waste heat.
Okay, this morning I had a fairly depleted HV, so I let the PHEV recharge it before I went in to work. Vi = 47.7 Ii = 75.8 Pi = 47.7 * 75.8 = 3.6 kW Vo = 243 Io = 15.2 Po = 243 * 15.2 = 3.7 kW So, I have now reconfirmed Pond's and Fleischmen's original "cold fusion" experiment and have determined that Enginer has given us a suitcase cold fusion reactor rather than a PHEV. (Thus, for $3500, it makes the system the best buy on the planet.) Clearly either the inductive coil measuring the current has substantial error either due to the gauge or my technique. Or the time it takes me to switch among the 2 voltage measurements and the 2 current measurements, the system output is changing ever so slightly. This seems like a worthless endeavor. The box is certainly hotter than anything approaching 100% efficiency.
My guess is that DC output has huge ripples and poor power factor, but your meter is not measuring it. Does your meter have RMS function in DC mode? Do you have a scope that can handle 240V to see the shape of the output voltage/current? I bet your power math doesn't add up due to poor power factor of the unit, which would also explain the heat generated.
Good point. I'm moved a while back. This is probably a good excused to dig out the old Tektronix scope. I know the DC does have a very... well... un DC like output. I decided to become part of the DC electrical circuit so as to "feel" how much ripple is on the line (it's as bad as my 60 Hz AC). Also, my AM radio and all the birdies from the converter tell me that the DC is not at all clean.
Manzanita responded: Absolutely we can help you! We have used a modified PFC40 charger to do the DC/DC and the AC/DC conversions for our PHEV kit. This unit can do 12V to 450V. The PFC40PHEV is $3400. Lead time is 7-10 days. There is an alternate!
pbui, you can't compare quality of products; besides the price. It's like matching a kiwi and a watermelon, all in the fruits family thou.
