I apologize in advance for the length of this write up. However, I feel that it is important to have as much factual LiPo information as possible and to have it all in one location. Take it a step at a time and try not to become overwhelmed.
That being said...
LiPo 101
now in session
Rules
1) NEVER discharge below 3v/cell
2) NEVER charge above 4.2v/cell
3) NEVER puncture your pack
4) NEVER short out your pack
5) NEVER use a pack that has puffed
6) NEVER charge unattended
7) NEVER charge at a higher C rate than recommended
8) NEVER use a pack that has been over charged/discharged
9) ALWAYS check cell voltage before connecting your pack to anything
10) ALWAYS keep your LiPo pack well balanced
To calculate the charge rate of your pack
mAh x charge C rate / 1000 = charge amps
For example:
A 2200mah 20-40C pack that states a 2C charge rate.
2,200 x 2 / 1000 = 4.4
This battery pack can be charged at 4.4 amps.
- Please note that if no charge C rate is stated, 1C is standard.
To calculate the constant discharge rate of your pack
mAh x minimum discharge C rate / 1,000 = available amps
For example:
The same 2200mah 20-40C pack.
2,200 x 20 / 1000 = 44
This battery pack can consistently provide up to 44 amps.
To calculate the peak/burst discharge rate of your pack
mAh x maximum discharge C rate / 1,000 = available amps
For example:
Again, the same 2200mah 20-40C pack.
2,200 x 40 / 1000 = 88
This battery pack can provide a peak discharge rate of up to 88 amps.
Peak rates are limited in time... unfortunately, this amount of time does not have an industry standard. This is how a lot of inflated discharge ratings can be claimed. In my experience, honest retailers/manufactures of packs will list the constant discharge rating along with the burst discharge rating and not only the burst rating.
Ratings
When setting up your power system for your RC, make sure that the lower discharge C rate matches or beats the continuous amperage rating of the ESC. I try to beat it by at least 10%. This practice will provide you the most out of your system and it will also keep your batteries from working too hard. A LiPo should NEVER be warm... during use or charging. If it is, you are abusing the pack. Also, the less your pack has to work the longer it will last.
Parallel
Running two LiPo's in parallel will double run time and also your available amperage... which is handy for high demand systems. Some misinformation I have read about the discharge C rating of packs in parallel is that the rating of the pack doubles. This is not the case. The C-rating of a battery pack is a fixed parameter of that pack; well actually it is the cells within the pack that have the C rating. Connecting two packs in parallel does not change either pack as they still have the same specifications, however it does create a battery "system" with twice the effective C rating. The packs are the same, but the parallel system is now theoretically capable of discharging at twice the Amp rate. This is much like the cumulative capacity available when connecting two packs in parallel.
Series
Running two LiPo's in series will double voltage, therefore nearly doubling the speed of your RC. Capacity remains the same. The two packs ran in series MUST have the same capacity and discharge rate. They should be of the same brand as well as have the same amount of cycles on them.
Be prepared to gear down when increasing voltage on your power system.
Charging
There are many charging options out there... it can get really confusing really fast. The best advise I can give is to get the absolute best charger you can afford... your charge system is the backbone of your electric RC hobby, treat it as such. RC's will come and go, but your charge system will remain.
The following features are what I consider to be the absolute bare minimum for a charger... balance charging and a storage charge/discharge feature. Storage voltage is 3.85v/cell. If the charger cannot perform these tasks, look for another charger. If you are going to be charging multiple LiPo's at the same time or 10th scale or larger packs, I recommend getting a charger that is capable of at least 10 amps. Also, ANY half-decent charger can charge multiple LiPo's at a time. It does not require a dual or multi-charger to perform such a task. It only requires the right support equipment... I use a ParaBoard.
Here is what I have done...
this information might help with your decision
I use inexpensive batteries.
I have found them to be very reliable, extremely cost effective, and they have been proven to be under-rated; usually providing more mah and a higher discharge C rate than stated on the pack. SPC is a great brand that under promises and over delivers. There are others that claim extreme discharge ratings that are simply impossible with the technology that is available.
I use an iCharger 206B.
When I purchased the charger, I thought I would never use all 20 amps of its capability. Well, now I rarely charge at anything less than 20 amps lol. I have even considered selling it to get more amperage! I have performed hundreds of charge cycles with this charger and it handles the task without a single issue.
I highly recommend any charger in the iCharger line.
I built my own power supply.
I have ~$30 into my 24v 75a 1800watt power supply.
Sounds complicated, but it really is not that difficult. If you go this route, you are going to want a server power supply as they do not drop voltage when you are pulling amperage like a standard ATX PC power supply.
You can also purchase these pre-built.
I hope this information helps!!
Here are some links to some more:
http://traxxas.com/forums/showthread...rger-vs-cooker
http://traxxas.com/forums/showthread...charging-setup
http://traxxas.com/forums/showthread...ply-Conversion
http://traxxas.com/forums/showthread...ply-Conversion
I typed this up a while ago... not all of it may apply to you, but it is still good info.