Art and Gary,
Thanks for both of your comments. I just got a reply from Mastek and they gave me a slightly, but importantly, different way to adjust the output of the power supply. I will try that later this morning. I believe it will work.
Just to recap though. I received my cells and they were all exactly 3.29v as best as I can measure with my DVM. They had been in transit for at least two months so I would think they were as "balanced" at that level as I could ever achieve. But they need to be top balanced higher.
I am starting with two cells, one at a time, only so I can work out the process of doing it in a reasonable amount of time. To bring up 4 cells at one time would take days let alone hours if done in a carefully observed manner. I won't leave this first set of cells on the charger for longer than 10-15 minutes at a time. I make a note of voltages (power supply display and my DVM on the cell) and the amperages (power supply display and my Fluke clamp-on on the charging
wires). I am trying to get to a reliable and repeatable process to make the remaining cells easier, faster and still safe.
I intend to bring each individual cell up to close to 3.60v, intending to go to 3.65v with 4 cells in parallel. After that I will put all 16 cells in parallel. If the total set is still at 3.65v I will just leave them hooked up for a few weeks while I do more prep work on the boat
. I believe this follows what Maine
Sail and what you have said basically.
Yesterday afternoon, I reset the power supply so that it was doing more of what I wanted to see. It was still not operating the way I expected as it was still putting out 6 amps at a displayed 3.7v. Per the manual, it should have already reached the overvoltage limit and stopped charging completely and it did not. I had set the overvoltage limit at 3.7v and the charging voltage at 3.6. I have verified that the amp readings on the power supply are reasonably accurate compared to my DVM but that the voltage readings are not necessarily so.
With the setup and adjustments I had, I got the one cell up to 3.65v with about 5-6 amps still flowing. I did not want to go to 3.7v so I disconnected at that point. Ideally, I want to get to 0.1-1.0 amp at 3.6v for an extended time for each cell. And then I will put all cells together and let them sit as noted above.
My issues seem to be mostly with getting used to the power supply. It is not what I would call a precision instrument and is awkward to adjust for the overvoltage limit in particular. It only displays and is set to 0.1 volt increments which is not very precise for what I am doing, especially for one cell. It will be better for four or more cells provided I watch it carefully. The reason I say that is because a low amperage will not quickly change the cell pack voltage and I will be able to react if there is a problem at the knees.
Based on what I have seen so far I believe the real exponential voltage increase (upper knee) is 3.7v or higher. The Sinopoly specs call for 3.7v as a maximum charge. If that is correct that should be well below the actual knee but I don't want to experiment
with that on my own cells.
I will know more today as I continue to fine tune the operation of the power supply. I think I was putting too much credence as to how manageable the power supply is. I take all voltage measurements only at the tops of the cells (not the stainless bolts). I am using a couple of my copper cell straps which I lightly sanded and put on the lightly sanded cell terminals. I hook up m charging terminals to those straps rather than connecting them to the bolts in the terminals.
Short of putting ring terminals under the bolts to the terminals I can't get a better connection. I don't want to use rings under the bolts since I may have to quickly disconnect the power supply and you can't just turn off the power supply before disconnecting the load (per manual).
I think today I will get to where I need to be. In a couple of days I should have my first set of four cells done. I don't have 8 hour stretches to be at the operation so it will just be several days before I get done.
Again, I appreciate your comments. I am trying to implement your thoughts using the new adjustment process I just got from the vendor, living with the imprecision of the controls even with that. I can see why Maine Sail prefers a fancier power supply.