A123 batteries
aka LiFe - Lithium Iron Phosphate
last updated 11-16-2008

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Okay these have been out a couple of years but I just recently started using them as a receiver pack on my 50 size helis. I know a lot of people use the Lithium Polymer (LiPo) batteries but I was concerned about these getting too hot while in my truck in the Summer time. So far I really like this batteries! There is a slight disadvantage for use as a receiver pack, that is that the discharge curve is so flat it makes it a little difficult to tell when you need to re-charge. From one flight to the next I am only seeing a 0.02V drop. As you can see in the chart on the right the curve is very flat until it reaches 3.0V per cell. At that point it will drop fast. The best way to treat this is the same as you do for Lipo's. When using a Lipo on an electric heli you time your flight see how many milliamps the charger puts back in the pack. You then take this value and divide it by the pack capacity. If it is less then 80% then you can increase the timer. With the A123's I would suggest only 75%. With the 2300mah batteries I am using that is 1725mah. So far I have only flown eight tanks on a single charge and the charger put back 1521mah. This was a little surprising to me as that is only 190mah per ten minute flight. I really was expecting more.

Regulation - If you are going to use these batteries you need to treat them like you would a Lipo. The voltage for a fully charged two cell pack can be as has as 7.2 volts. This is too much for some of the electronics on the helicopter. You will need to check the operating voltage for every electronic item on your helicopter that will be connected to your 2S a123 pack. Some newer servos are starting to support the higher voltage but do not assume what you have will work... look up the specifications. I am running my regulator between the battery and the receiver. My regulator has the on/off switch built-in but if yours does not then you connect the battery to the on/off switch then connect the switch to the regulator and the regulator to the receiver. If you do have some servos you want to run on the higher voltage it gets a little more complicated. I may cover this later if enough people ask.

Special charger - This is something you need to consider if you are going to start using the a123 batteries. You cannot charge these batteries with any LiPo charger. The charger has to support LiFe (Lithium Iron Phospate). While at IRCHA I bought a G.T. Power A6 and it has worked great. I can balance charge the batteries at 5 amps. I recently saw an advertisement for a Turnigy Accucel-6 that appears to be made by the same company that makes the one I have. This Turnigy is only $40 USD. And the charger does all the other standard battery types in addition to the a123.

a123 vs LiFe - I know some do not like others referring to these type of batteries as a123 instead of calling them lithim iron phosphate. Well the batteries I am using are A123 Racing cells but besides that I still would call LiFe cells that because for one it is easier to say but secondly and most importantly I think it is important to pay homage to the company that created this type of battery. They are the ones that invested the R&D to get the battery to the market. Any others are just copycats.

Poles reversed - This is something I ran into when building my pack. Ordinarily the negative side is the flat side and the positive side has a button type end. When I soldered mine together I had everything done but when I checked the voltage it was backwards. that is when I noticed the little markings for the positive and negative. So I had to re-wire the pack I just made.

Weight - I was using a RX pack 4-cell '4/5FUAPJ' 1950 that I measured at 175.9g. After I made the RX pack 2-cell 'A123' 2300 it came out to 167.6g. That is a little under the NIMH pack but you have to run a regulator so after adding the weight of the regulator (28.5g) that makes it about 20g heavier. Not much and I get to fly a lot longer on a charge.