Damn it TCK, quit asking questions I can answer.:lmao:2s or 3s is the number of cells. a 2s pack is 2 cell and a 3 cell is 3 cells. The more cells the more volts. 3 cell is 11.1 volts and I believe the 2 cell is 7.6.
I used to run a 2 cell lipo on my Axial with a 55 turn. Then I tried my 3 cell for a short time. Wow, you will be surprised how much difference "volting up" will make.
Duratrax 230 charger... I have one of these and I love it. I have 7 different batteries that I charge on it (everything from really old 1000 mah nimh - 3000 Nimh to 2s and 3s Lipos.) I never have a problem with it, I can use it on a car battery (for scale running) or I can plug it into 110 for club events. I have tried to charge a 2s pack on 3s setting and vice a versa and the charger is smarter than the operator. :roll: I think it is a great way to get into Lipos.
I use the Common Sence Blinky balancer too. I balance the lipos as they charge. That way it makes sure all 2 or 3 cells get an equal charge.
Have fun!
To expand on what you posted:
Each LiPo cell is 3.7V nominal. When it is fully charged, the cell is usually around 4.2V. The lowest voltage that a cell can be safely discharged to is usually 3.0V. That is what most Low Voltage Cutoffs (LVC) are set to, but some people like to set theirs to a slightly higher voltage (3.2 maybe?) If the cell's voltage falls below 3.0V, it can become permanently damaged and unable to charge again.
When you see a LiPo Listed as: 2S2P 4000mAh 20C-25C, here's what that means:
2S means 2 Cells in Series. When you wire cells in series, you increase the output voltage, but mAh and C rating stay the same. This pack is a 7.4V nominal pack, with a total voltage range of 6.0V at LVC, and 8.4V fully charged.
2P means 2 Cells in Parallel. When you wire cells in parallel, you increase mAh and C rating, but voltage stays the same. This pack actually has 4 total cells, which can be a little confusing at first, but if you think of this pack as two 2S packs, it makes a little more sense.
You want to balance the cells because over time an unbalanced cell can become a very unbalanced cell and either over-charge or over-discharge a pack, as well as reduce the overall capacity of the pack. Balancers are cheap, and easy enough to be used each time you charge the pack, but some people only balance every few times they charge it.
4000mAh is the capacity of the battery. 1Ah = 1000mAh, 3600mAh = 3.6Ah. Capacity equates to run time, but in a slightly more complex manner. This battery would take one hour at a rate of 4 amps to discharge. That is if there was a constant 4A load being applied to the battery. That is almost impossible in the real world. In reality the vehicle sees varying amounts of load, sometimes a lot more than 4 amps, and almost nothing when it is sitting still.
20C-25C is the constant discharge and maximum or burst discharge rate. 1C equals the number of amps to discharge the cells in one hour. For this battery 1C is 4 amps. So if you multiply that by 20, you get 80A. This means that the battery can stand a constant rate of 80A if needed. Burst rating is usually 5C higher than the constant discharge rating. This is the maximum amount the battery can withstand for a short period of time as in 15 seconds or so. This is helpful if you need a little more power to get over a rock or something. This battery can handle 100A of maximum short term load.
C rating is also very important to know when charging. Most LiPos are rated for 1C charge rate, but the batteries you are looking for can handle 2C, however, The onyx (and most basic chargers) isn't capable of 10A charge. You never want to charge the battery at more than what it is rated at, otherwise you will have some nasty issues.
LiPos have a lot of warnings on them because they can be very dangerous. If you aren't comfortable with making sure you can follow the rules, then don't get LiPos. What's the worst that can happen? An extremely violent fire, that can burn down your car, your house, etc. (Just go onto YouTube and search LiPo fire.) What happens is if the battery is subjected to over-voltage, over-current, under-voltage, high-heat, internal or external short, reverse voltage, punctures or shock damage, the chemicals inside the cells react against each other and cause the violent fires. This usually shows as "puffing" first, but can quickly turn into a fire. If you notice your cells getting a little puffy, it's probably safer to just dispose of it properly than risk a fire.
Having said that, it's not hard to take care of LiPos, and once you know the basics, you shouldn't have a problem with them. I won't go back to Nickel cells. Ever. LiPo is just better technology. Most chargers have dummy safety features to help prevent you from burning down the neighborhood, but I do recommend a "LiPo Fire Safe Bag" to store and charge the batteries in. Better safe than sorry.
Phew, now that that's all typed up, I hope this helps!