What Lithium Iron Phosphate batteries are you using?
I'm using a variety. Different tanks, different batteries. Mainly, I use the Hobby King 4500mha matched 2s LiFe. They cost about 23 bucks, and fit in most tanks. For Tiger 1's, I use the Hobby King 2s 8400mha LiFe (38 bucks, and run 7 - 9 hours). For smaller tanks, I've used Hobbico's 2s 3200mha (shorty). The best LiFe I've found so far is the Hyperion 2s 3800mha. They are just a bit smaller, fit into Heng Longs, and are very durable.
As to radios, we've ran some Hobby King 3s 2650mha Li-Pos (I removed those to charge them), and their 3s 1500mha LiFe (also removed to charge). I couldn't use the wall worts to charge with the Lithium batteries in there. This is not really an issue now, as radios are starting to come with Li-Ion batteries as standard equipment (and a wall wort for charging).
Reasons I switched from Nickel based batteries were that I like the facts that LiFe batteries:
1. Are environmentally friendly, (unlike Nickel based battery systems which are hazardous material to dispose of around here). I try to be green when possible.
2. Have no memory (unlike a Nickel based battery). I really don't miss the constant cycling to get batteries to hold their rated charge (we normally tank six or seven tanks to a battle. In my experience, it took 5 cycles (a discharge/recharge) to effectively get the Nickel based battery to hold their rated charge (other than when they were relatively new). In my case, that was 7 tanks x 5 cycles each, plus 4 radios x 5 cycles each, for a grand total of 55 charge/discharges...which needs to begin on a Tuesday night (and continue non-stop) to get everything ready by Friday afternoon's departure time). Even using 4 chargers, it was tedious and time consuming.
3. Are quick charging (I can really push the power into LiFe's fast (10 amps are no problem), which is handy at a battleday if needed. I can full charge any tank during lunchtime.
4. Are relatively unaffected by heat (unlike Nickel batteries which can lose 20-30% of their charge from heat, and additional charge during the first 24 hours after a charge) generated when they stored in parked cars which helps when transporting tanks by car to distant locations (I can leave the equipment in the car at the hotel, instead of dragging it all to the room and charging all night). It's no longer a challenge to show up to a battle with fully charged batteries.
5. Have a long life span. LiFe's will easily take 1000 charges.
6. Are light weight. I'd estimate they weigh about 2/3 of what a Ni-Mh does. I notice it most in my radio.
I went with the LiFe vs the LiPo due to the non-flammablecharacteristics of LiFe and the availability of similarly sized battery packs.
Not to say they don't have drawbacks. If you let them go to zero volts, they are destroyed. You'll never be able to recharge it. If you upgrade, you'll likely need a new charger to charge them, or at minimum, update you current charger's firmware.
They work great for us. Been using them 3 years in many tanks. No issues.