Unfortunately there are to many different types of cells refered to as A123 with different voltages and cut offs which is why it is hard to find good chargers and few if any on board voltage displays. I believe the engineers are trying to work on an answer but it could be a while.
Just two examples of cut off / loaded voltage measurement problems,regarding A123,availableon the net:
A123 Battery FAQ for Giant Scale and IMAC
"Here’s the biggest issue.. load testing. The beasties just don’t react like we expect.. a 1 amp load for 10 seconds will convince somebody not familiar with them that there’s something wrong with the load tester.. the needle won’t sag! I’ve even had guys start melting switch ports and connector housings trying to get enough load on the pack to use an ESV in the tried and true sense. Just doesn’t work. Because of the incredibly flat discharge curve and the ability of the cell to hold voltage while doing 'heavy lifting', using a standing voltage level under load to decide when to recharge can lead to a disaster because when the cells go flat they do so remarkably fast. So, we go to the next question.."
A123 battery Information - SinCity Jets.
"The battery's only downside is that you can not tell how much energy is left in the pack by reading the voltage. Because the discharge curve of the pack is so flat, the voltage will be almost the same throught its cycle, and then "cliff dive" at the end of its cycle. Because of this, it is important to become familiar with how much energy your vehicle uses during each use. For planes, I advise people to fully charge their batteries and then fly 2-3 flights. Then, fully charge the packs again and see how much energy (Mah) you put back in to the packs. Then simply divide the amount of energy by the number of flights and come up with your average Mah per flight. This will allow you to set your safe cut-off. It is advisable to only use 1800-2000 of the pack's 2300 Mah's. "

Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links