At 09:48 PM 9/9/02 -0500, you wrote: >I was charging my new set of US-125's after the second break-in run (2.5 >miles), and like the first and second charge, it isn't coming up to the >voltage recommended by the manufacturers. As you know, the USB >recommendation is rather high. The typical recommendation (and that >endore\sed by Trojan) is 2.4 vpc, USB's is 2.583. > >So correcting for temperature, for a 114V nominal pack, I should see 136.8 >(based on 2.4 vpc)to 147.2 (based on 2.583 vpc) volts at 80 degrees.
Temperature is the key, the charging recommendation would probably assume that the battery is in open air and can dissapate the waste heat of charging. I bet that with your batteries in blocks, that the center ones get slowly hotter until they are 110deg. or so at the end of charge! I think that their charging voltage is a bit high anyway! >It made it to 138, and I caught a whiff of sulfur at that point, so I >stopped. Am I bordering on cooking them? The current was never more than >10A, and was around 5 when I quit. Yes at high temperature the hydrogen from overcharge combines with some of the sulfuric acid to form hydrogen sulfide or rotten egg gas. I don't think you did it long enough to cause much damage! >If this is an indication of overcharging, I need to revise my list of >voltages down, but how far? I need to make sure I have this nailed before >I try to go any great distances. I think you will end up somewhere between 133 and 137 volts for an 8 to 10 hour charge. This will need a bit of trial and error, the way to go is to tune the end of charge voltage until that you get the finish current you want. This will be a different value depending on the length of time you have for charge.( try for 2 amps or less ) It will also need to be a lot lower for a day or two of float, perhaps only 0.25 amps. Watch out for thermal increase! Happy tuning, and let us know how you get on! Regards Steve
