Donn Lee's blog

RC Groups Discussion - 2100mAh lipo and SS: "I just put a 2s 2100 thunder power pack in my slow stick. I have yet to time it officially but I am getting between 40-60 minutes with it. it is also lighter than the 6cell 600mah nicad pack I was running before. on a fresh charge she will hover for about 5sec. before she falls out. I am very impressed with it. I let three other people fly my plane on one charge last time out. performance and duration were impressive."

RC Groups Discussion - 400 vs. 300-350 motors with 3S lipos: "[T]he 400 motors are a lot more robust than the 300-350 motors and will survive 3S much better. Many last an entire season or more.

The brushes will eventually wear out, though, and it's important to replace the motor before they completely go. Otherwise, you stand a chance of the motor taking out your speed controller when it does.

You can typically tell when it's time to replace the motor. A fresh battery pack will perform like it's almost discharged. Then you slap a new motor in it and it's like a whole new plane."

RC Groups Discussion - 2S2P lipos, more info: "If you buy a 2s2p pack ready made in that configuration, soldered and shrinkwrapped you don't need to separate them to charge them. The manufacturer of the packs should have balanced the cells allready when they manufactured the packs. All you need to do is charge it correctly on your charger.

I have packs which are in 2s1p configuration, which I use with a Y-cable in 2s2p configuration. As long as both packs are each individually FULLY charged when I first connect them, there's no need to disconnect them between each charge-discharge cykle. I just treat them as if they were a ready made 2s2p pack, for as long as I use them in my planes which need 2s2p packs. Then when I disconnect them to use as separate 2s1p packs in my smaller models I charge them individually. When it's time to use them in 2s2p again, I just make sure that they are both freshly and fully charged, connect them with the y-cable, and continue using them like that for as long as I want to. The bonus about this is that these packs gives me greater versatility, since I can use them in both bigger (more amp-hungry) planes and smaller ones.

Just to repeat my main point, for you 2s2p pack which is ready made and soldered to a PCB, there's no NEED to separately charge the cells, as they will be balanced by the manufacturer. You treat them as a unit, set the Amps and Voltage correctly, charge and fly!"

RC Groups Discussion - Using two 2S1P lipos: "The most flexible way to achieve 2S2P is build 2ea 2S1P packs (7.4v ea) and connect the packs in parallel with a Y harness. This gives you the additional options of using the individual 7.4v packs by themselves (2 @ 2S1P) or connecting them in series to make 14.8v (4S1P).

There is no rational reason I can think of to make 3.7v (1S2P) packs unless it was to power one of the micro motors used in the tiny indoor flyers.

I personally think you're on the wrong track. Regardless of how you construct the packs (2S1P or 1S2P), you're going to have to charge the packs individually unless you want to risk wrecking some cells and at the recommended 1C charge rate, that could take as long as an hour per pack for a total of 2 hours unless you want to buy more than one charger.

A single 2000-2100 mAh 2S1P pack will give you the same capacity, weigh less, and you can charge it with -one- battery charger in about an hour."

RC Groups Discussion - Slow Stik Li-Poly pack: "A stock 300 SS will be a bit lethargic on a 2S LiPo and a 3S will kill the motor in short order. A good compromise is to replace the EPS300 motor and gearbox with with an EPS350C in either C or D gearing. They run as good or better on 7.4v as the 300 does on 8.4v and you won't be taxing either the battery or the motor.

That was the last brushed system I ran on my SS: 350C w/ C gearing, 11x8 prop, TP2100-2S LiPo. It flew great and 3 or 4 10-minute flights per charge were the norm. On several occasions I flew for 50-60 minutes with a little throttle management. "

Make Sense of the Jargon - Jeff's RC Airplanes: "Making Sense of the [RC] Jargon"

MotoCalc: "Balancing cells in a pack: If a battery of cells is not matched, repeated charging and discharging will result in some cells being at a different percentage of charge than others. The cure for this is to equalize the pack by slow charging it. When the first few cells become full, the remainder will keep charging while the already full cells are overcharged (which doesn't actually put any more power in; it just heats them slightly). Once all the cells are full, the pack is equalized. By equalizing the battery occasionally, you also reduce the risk of cell reversal."

MotoCalc: "Li-Po battery info: The newest electric-flight cell technology, really a specific type of Lithium Ion cell. LiPoly cells have a much higher power to weight ratio, although they cannot (at the time of this writing) deliver the high currents that NiCd cells are capable of. However, unlike NiCd or NiMH cells, they can be wired in parallel, increasing their current output capability. LiPoly cells have a nominal voltage of 3.7V, as opposed to the 1.2V of a NiCd or NiMH cell. LiPoly cells cannot be charged on a NiCd/NiMH charger."

RC Groups Discussion - Complete Guide to Lithium Polymer Batteries and LiPo Failure Reports

Difference between Li-Ion and Li-Polymer batteries: The charge process of a lithium-ion-polymer is similar to lithium-ion. These batteries use a gelled electrolyte to improve conductivity. In most cases, lithium-ion and lithium-ion-polymer share the same charger. [http://www.batteryuniversity.com/partone-12.htm]