I just did a 2 hour long test, hit CTRl instead of shift and lost all the detailed data I was going to share. Very angry. Fuming mad really, at the loss of data.
And a little dismayed in the performance of the unit.
Here is the short version.
I ran my screwy 31 down 65 amp hours and hooked up the cheapowatt to 118.2vAC, adjusted it to 11.7 volts, same as the battery was reading under a 6.5 amp load, and then connected it to the battery.
It was able to do 38.9 amps according to my gtpower meter and 38.2 according to my clamp on meter with the pot cranked to the max. But it sounded like it did not like the task asked of it. It made an unsettling noise until the voltage trim pot was lowered, and lowered to just barely above the level where it started.
Cheapowatt Terminal voltage would NOT rise to 15.3v when the 31 was this heavily depleted, likely below the 45% range. Max was 14.2v, cranked all the way up and producing 38 amps but making that unsettling noise.
When I dialed the trim pot back down, way back down, it still stayed up in the high 30 amp range and would stop buzzing in the 36 range. I lost the data of voltage readings taken in 3 areas along the circuit as the battery charged, but it was as if trying to get terminal voltage up that high was asking too much from the cheapowatt. like the difference in battery voltage and desired terminal voltage was too great.
On the initial trim pot turning, from 11.7v, lets call the range 1 to 10, at 2.5 the amps were already up in the high 30's and it was quiet, but when turned to 3 or more it started buzzing, kind of like a ticking arcing, and not just a 60HZ buzz perhaps a 30 HZ buzz and not perfectly rhythmic. Lower the trim pot back to 2.5, the amps were still in the high 30's and the buzzing stopped.
As the battery charged, I was able to crank the trim pot up again get 38+ amps but the buzzing was unsettling, and I'd back off after a minute or two, after taking voltage and temperature readings and typing them in to the point the noise stopped, yet the amps were still in the high 30 range.
Every time the amps started tapering and i cranked up the trim pot the amps could easily rise to 38.2, but to get the noise to stop i;d have to dial back the pot and each time for the first 90 minutes, this would be right at 36 amps when the noise stopped.
The temps on the case itself maxed out at 119f, adjacent to the heatsink on the side, the rear heat sink averaged about 10F less. There was a spot inside the unit when I aimed the IR gun through the fan hole that read 135f at one point during the buzzing. That blue thing one can see the corner of in the photo a few posts up. Temps rose quickly during the buzzing at 38.2 amps and settled down at 36 amps.
I don't think that this thing is going to just be able to dial in a preset voltage, slap it on a depleted battery, and let it go until the battery climbs there. I think it might have to be started with a lower voltage setting and then turned up more and more in a few increments as the battery recharges.
The noise it makes when there is a huge voltage difference between the battery and what the trim pot is asking for, is unsettling.
I don't know if I'd trust it to buzz away for 2 hours until the voltage difference was close enough for it to stop. it was not the amount of amps it was able to delivers. they maxed out at 38 something, but the buzzing would stop when the trim pot was lowered a good amount but the amps were still at 36. I could leave the trim pot there and the amps would taper, and then I could crank the trim pot, get 38.2 amps listen to the buzz, back off until the buzz stopped and see 36 amps again.
When it was buzzing, maxed out at 38.2 amps, the temperature readings were increasing pretty rapidly, when backed off to 36 amps they dropped off a bit and leveled out.
I don't know how well of a 30 amp bulk charger this thing is going to make, or how long it will last as one, unless the voltage pot is just moved up higher, a little at a time as the battery charges. It is as if though it can make 38 amps, anything beyond 36 and it protests.
Also when dialing the voltage back down when the battery in nearing full, it makes a Slight, but high pitched noise until battery voltage drops to the apparent trim pot setting.
Still happy with the purchase, but I don't think it is the end all be all of manual chargers. I think it will require lots of babysitting if used to charge a depleted batttery, but should be fine as a top charger or a float charger.
I also have no idea how detrimental the noise is. It was much less noticeable when the original fan was making 5 times the noise, but now that the fan is quiet, the noise just seems wrong and damaging and confidence sapping.
Any ideas what the noise is? And how detrimental it is? The temp increases were quite noticeable when it was making noise and quit rising soon as i backed off the trim pot. then the amps would begin to taper, and i'd turn the voltage pot up again and the cycle would repeat. if pushed beyond 36 amps by turning the voltage pot too high, it would make the unsettling noise and temps would rise fairly quickly.
I never let it buzz for too long, 3 or 4 minutes max, so I do not know how hot it would eventually get, but i figure i could have smoked it if i cranked the trim pot to the max in the beginning and left it for 90 minutes.
i dont think all the heatsinks and air one could move around it would keep it from smoking something eventually.
