Spektrum DX3r Battery Mod

[BrianG]

Well, the tray (with the "box" removed) fits 6 AA cells. The thickness of the cells may give you some trouble though. There is a little room above the tray, but not sure how much, or enough for the A123 cells.

Then, what about the voltage? Peaked, 2s A123 cells are 7.2v (a bit high), nominal at 6.6v (probably ok, but still a teeny bit high), and LVC at ~5v. A UBEC (or even a linear regulator) has too much drop-out voltage to use it effectively (esp at LVC), and besides, a switching BEC would be wasted here due to the low differential voltage and relatively low current. If I were to use 2s A123s or lipos, I'd probably use a diode in series with the + line to drop a consitent ~0.7v. True, at LVC, that will be quite low, but A123's drop fast though. Just set the radio voltage alert for ~5.6-5.8v.

[jhautz]

Originally Posted by BrianG

Well, the tray (with the "box" removed) fits 6 AA cells. The thickness of the cells may give you some trouble though. There is a little room above the tray, but not sure how much, or enough for the A123 cells.

Then, what about the voltage? Peaked, 2s A123 cells are 7.2v (a bit high), nominal at 6.6v (probably ok, but still a teeny bit high), and LVC at ~5v. A UBEC (or even a linear regulator) has too much drop-out voltage to use it effectively (esp at LVC), and besides, a switching BEC would be wasted here due to the low differential voltage and relatively low current. If I were to use 2s A123s or lipos, I'd probably use a diode in series with the + line to drop a consitent ~0.7v. True, at LVC, that will be quite low, but A123's drop fast though. Just set the radio voltage alert for ~5.6-5.8v.

Just thinking about this again. If you are using 5 NiMH cells they are 1.4 to 1.5v peaked so 5 of them is 7.0 to 7.5v and 2 x a123 cells are only 7.3v peaked (3.65 x 2) I might try hooking upa 2s a123 pack to the radio just using aligator clips on the inputs just to make sure I dont toast the thing before I tear it apart and make any modifications.

[lincpimp]

I guess that a 2s2p pack of the 1100 a123 cells would fit in there? Just an observation...