I just picked up an onyx 245 dual port charger. Tho its awesome that it can charge 2 battery's at the same time and also charges about 2 times as fast as the stock charger that comes with the fC40 and is nice that it also can work on ac or dc so I can hook it up to a car battery for field charging. and it gives you data on the charge by showing how many amps its charging at. the cell voltage and time that its been charging for or how long the charge took to complete as well as shows how many Mah the battery took.
But it seems to do a very lousy job at balancing the cells even tho it supposed to be a balancing charger some times my cells on a finished battery will be 4.15 the next 4.18 and 4.20 which is not even close to balanced and it also hardly ever charges more then 12.56v or 12.58v tops and i still end up some times having to throw a battery on to the stock charger for about 2 minutes to finish them And get 12.6 and to properly balance the cells. So they are all the same or .01-.02 volts of each other.
also it comes with 2 of almost every kind of battery plug EXCEPT for the XT60 plugs that the phantoms battery's plug in to. So I had to pick up some XT60 plug ends and solder them on to 2 of the leads that came with it to make my own leads for it.