OK, have to admit I embarked on this experiment without doing my own research--just relying on the MO article--and my German isn't so good. Did some more research on my own and this is what I came up with:
1) The rated Ah on the stock battery is 10Ah versus 2.3Ah for one A123 pack and 4.6Ah for 2 packs. However, the A123 packs keep up their voltage when discharged better than the lead acid and don't suffer like lead acids do when you deep discharge.
2) Based upon ratings for similar batteries, the stock lead acid battery probably provides around 170 cranking amps vs 120 (10 seconds) for one A123 packs and 240 for 2...glad I went for two packs.
3) Charging batteries seems to be based upon two variables: max amperage and max voltage. When initially charging a discharged battery, you want to limit the amount of current it absorbs (constant current phase). The A123s are rated at 3A per pack for standard charge and 10A in fast charge mode. I am not sure about the lead acid, but I believe they are rated for far less (anybody know this for a fact?).
After a while of charging in constant current mode, the voltage of the battery rises and you want to keep it from going higher than a max voltage (constant voltage). For lead acid batteries, this voltage is 13.6volts, but more sophisticated charges will provide 14.4V for a while, then reduce to 13.6V for charge maintenance. The A123s are rated at 14.4V (4 in series) constant voltage charging. I measured the voltage being provided to the batteries by the motorcycle and it came in at 14.2V--just about perfect. One thing I don't know is if it is OK to continuously charge the A123s at 14.4V. The positive, though, is I haven't read anything that says it shouldn't be done. Plus it's not like I ride my motorcycle continuously.
The tricky bit with charging the A123s seems to be cell balancing--although you may have 14.4 volts in total across the 4 cells, it is possible to have one cell at 5.1 volts and the other cells at 3.1V--for example. Although the A123s seem to be tolerant of some overcharging, if it's too much you will lose a cell. The good news here is that when the cells fail they don't explode/catch on fire. The cell packs have individual leads to each cell so that you could build a balancing circuit to avoid this. A123 systems actually sells lead acid replacement batteries with built in balancing circuits:
http://www.gyllingteknik.se/a123/ALM...nfidential.pdf
I'm going to try my luck without the balancing circuit. Reading the Radio Control web sites, there seem to be a lot of people going without balancing circuits without trouble. The tricky bit seems to be initially charging the batteries from a deep discharge--I don't plan on encountering that too often. If they are already fully charged and in balance, then they seem to stay that way--fingers crossed. BTW my batteries came fully charged. Will let you know if I lose a battery.
So to sum up, still don't know everything, but they seem to OK with the addition of a balancing circuit. Time will tell how they do without one.
regards
oh, here is the spec cheet:
http://a123systems.textdriven.com/pr...UGUST_2008.pdf
if overcharged/overheated.
Linear Mode
