RC-Monster Forums - View Single Post

BrianG · 05.17.2007, 12:20 AM

1: From what I've read, you can charge them to 4.2v because after a certain point, they simply won't accept any more charge. So they are saying you can't overcharge them. Still, I would either use a A123 charger, a lipodaptor, or a charger with a settable 3.6v/cell CC/CV threshold voltage.

2: I have also read you can charge at more than 1C on the A123 cells. However, I don't know what this does to the life of the cells. I wouldn't go much more than that just to protect the investment. If time is that critical, I'd just get an extra pack or two.

3: Any balancer should work as most will simply equalize cells whatever their voltage. Some balancers may not function if it sees the cells lower than a certain value. Since the A123's LVC is about 2.2v (IIRC), this might cause some balancers to not work until the cell gets to a minimum value. Can the 205 work? I dunno. I'm sure someone here has used one before and could explain further.

4: Most cells use the "can" as the - terminal so the sleeves ARE ABSOLUTELY NECESSARY. Otherwise the metal "can" would touch the adjacent cell causing a short circuit. The sleeve is the insulator. I suppose you could remove the cardboard and replace with decent heatshrink if you were worried about water deteriorating the cardboard. If you are paralleling two cells, then the - terminals are touching anyway, so it shouldn't be an issue.

Just remember that these cells are 3.3v/cell nominal, 3.6v/cell CC/CV threshold, and 2.2v/cell low V cutoff. This means that LVC units may not function right with certain cell counts. People say that the dropoff is quite abrupt so a LVC isn't really needed anyway.

As always, runtime depends on the setup, driving style, terrain, etc. As long as you aren't pushing the current limits of these cells where you start losing Ah, you should get as much runtime as a similar capacity lipo.

6s A123 is 22.2v at a 3.6v/cell full charge. 5s lipo is 21v at a 4.2v/cell full charge. 6s lipo is 25.2v at full charge. So, 6s A123 is sorta like 5s lipo.

	(#2)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	05.17.2007, 12:20 AM 1: From what I've read, you can charge them to 4.2v because after a certain point, they simply won't accept any more charge. So they are saying you can't overcharge them. Still, I would either use a A123 charger, a lipodaptor, or a charger with a settable 3.6v/cell CC/CV threshold voltage. 2: I have also read you can charge at more than 1C on the A123 cells. However, I don't know what this does to the life of the cells. I wouldn't go much more than that just to protect the investment. If time is that critical, I'd just get an extra pack or two. 3: Any balancer should work as most will simply equalize cells whatever their voltage. Some balancers may not function if it sees the cells lower than a certain value. Since the A123's LVC is about 2.2v (IIRC), this might cause some balancers to not work until the cell gets to a minimum value. Can the 205 work? I dunno. I'm sure someone here has used one before and could explain further. 4: Most cells use the "can" as the - terminal so the sleeves ARE ABSOLUTELY NECESSARY. Otherwise the metal "can" would touch the adjacent cell causing a short circuit. The sleeve is the insulator. I suppose you could remove the cardboard and replace with decent heatshrink if you were worried about water deteriorating the cardboard. If you are paralleling two cells, then the - terminals are touching anyway, so it shouldn't be an issue. Just remember that these cells are 3.3v/cell nominal, 3.6v/cell CC/CV threshold, and 2.2v/cell low V cutoff. This means that LVC units may not function right with certain cell counts. People say that the dropoff is quite abrupt so a LVC isn't really needed anyway. As always, runtime depends on the setup, driving style, terrain, etc. As long as you aren't pushing the current limits of these cells where you start losing Ah, you should get as much runtime as a similar capacity lipo. 6s A123 is 22.2v at a 3.6v/cell full charge. 5s lipo is 21v at a 4.2v/cell full charge. 6s lipo is 25.2v at full charge. So, 6s A123 is sorta like 5s lipo.