CGRetired makes a good point about charging high capacity batteries with a wall wart. However, on the other side of the coin you can cause yourself problems by charging for too long or at too high a rate. Check out the warning at [link]http://www.hangtimes.com/txpacks.html[/link] four items down the page. It seems that the high capacity Sanyo packs are sensitive to overcharging and mechanical shock and these failures are not covered by warranty.

Generally speaking, if the wall wart charger was the one that came with the radio, and you stick with the voltage battery (RX) that came with the receiver, the wall wart charger won't overcharge. But, normally speaking, you don't normally leave a charger on for multiple days, usually, guys just put the thing on the night before and let it charge overnight. This is fine for a typical 700 mah battery, or the standard TX 9.6 volt battery of about 700 mah or so. They will usually charge in about 14 hours or less, or overnight.

When people increase the capacity of those batteries, say to what I have, 1650 mah, then the wall wart charger will also work ok, but for a fully depleted battery, 1650/50=33 hours. That is ideal time. Add about 10% for overhead and you now have almost 37 hours of charge for a fully depleted battery.

Fast chargers, field chargers if you wish, will charge at much higher rates, the Sirius, for instance has three settings, 250, 500, and 1000 mah. But, as said, the batteries must be able to handle this higher rate of charge or they will be damaged.

If a battery states a 1C charge rate, then the maximum rate of charge is 1650 mah (for my battery). But, most batteries say that .1 C is a good rate or 1/10th C or 165 mah is a good safe charge rate, so charging will take 10 hours at that rate for a fully discharged pack.

Most of us don't deplete these batteries fully, so the charge time will be totally dependent on what is remaining in the battery and what it takes to full charge it. For instance, a 1650 mah battery depleted to 950 mah, has depleted 700 mah and will take about 7 hours at 1/10th C to fully charge, or, depending on the safe charge rate for the battery, will take somewhat less.

Moral to the story? Read your battery specs and see what the capacity is, what the charge rate, and what the discharge rate is (less important for TX/RX operation, but very important for batteries used for propulsion power). Determine what the charge rate and the rate your charger will provide and do the math. You can't go wrong.

If you are uncertain, then get a discharger and run it through the discharger to depletion and recharge to full capacity. Siruis, again, sells a battery discharger with a digital display. You hook it up and discharge the battery through the discharger, and it will show what the total current flow was through the discharger. That will tell you what was left. For instance, a 700 mah battery, discharged through the discharger, the indication shows 300 mah. That means that 300 mah was left and you obviously used 400 mah during your flying time. This can give you some idea, for the future, how much you used and how long your batteries will last under normal conditions.

Hope this helps.

CGr.

for my receiver after experimenting with couple of NiCD and NiMH i have installed a 2cell LiPO 2100 mah and a regulator to bring the voltage down to 4.8v. It takes approx. 1.5 hours to charge (imax balance charges. Works with wall outlet and car battery) and gives me 4~5 days of flight (3~6 flights a day). Infact never brought the charge to 25% so do not really know how much more time it will give me. Also the weight of the whole setup is less than other battery packs .
I wish i could get the same setup for my 9Cap transmitter also.