THere is only 1 TRULY safe rechargeable battery. The A123 LIFEPO4 chemistry.
NOT LIFE. It is not as reliable. It does have a sloped discharge curve. The A123 cells / batteries NEVER explode or catch on fire when crashed, over discharged or overcharged Turbines are flying gas tanks. They do not need a LIPO or LIFE battery crunched & setting fire to the field & storage buildings. A123 do have a good / bad discharge curve. I know it well because I have put A123 cells in every rechargeable battery powered tool I own. Every week I run my 4 cell A123 B & D vacuum cleaner to less than 5% left. It slows down a little bit at about 10 %. But I go to 1/2 speed under load. Recharges to 95% right off the FMA Cell Pro 4 chargers. I have 2 of them.
Been using that B & D for decades like that. The cells put out a FLAT line discharge. But DAM IT .......... When you get to the drop off at the end ??? It might be seconds at 10 c or greater. So you have little warning the end is near. Recharge after or before every flight. They can not be killed. I have run them to 0 % in boats. No change in capacity . BUUTT a charger will not charge those dead cells You need to NOT use the tiny balancing plug I use a car charger on ONLY the 6 vdc setting about 2 minutes of a 10 amp charger brings the cells up to the R C charger range. Their round metal cases are TOUGH.
Your call . Get a custom pack with the connector you use & long enough leads.. Tried LIPOs I screwed them up too easily They got very puffy in months. The fear of a fire pushed me back to A123.