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I would like to upgrade my RC project, changing from common AA batteries to li-poly. I've chosen them because I always see them in RC planes/cars. My model would require 7.2/9V and a max instantaneous dran of 1A, the capacity depends on the cost.

I've searched over Google, but I can't get my head around what's needed to use such batteries. Most guides I've found refer to batteries for arduinos or don't mention chargers/vendors, but since I'm not in the circle, I can't distinguish good from scam, cheap for dangerous.

What are the full set of components needed and any possible risks in mishandling litium polymer batteries? (beside most oblivious ones like overcharge or puncture).

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    \$\begingroup\$ obvious shopping question, try rcgroups rcgroups.com/forums/… \$\endgroup\$ – Sunnyskyguy EE75 Mar 28 '17 at 23:03
  • \$\begingroup\$ Removed the shopping part, this is a solid design question. \$\endgroup\$ – Passerby Mar 29 '17 at 3:50
  • \$\begingroup\$ What is it "common AA battery"? You mean alkaline, or li-ion or nimh? Every of those has different voltage. \$\endgroup\$ – Chupacabras Mar 29 '17 at 7:24
  • \$\begingroup\$ @Chupacabras nimh 1.2V \$\endgroup\$ – sassoPera Mar 29 '17 at 7:25
  • \$\begingroup\$ @sassoPera, I asked because "common AA battery" is alkaline for me ;) \$\endgroup\$ – Chupacabras Mar 29 '17 at 7:42
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Lipoly batteries are good because of their high energy density. There are some alternate chemistries that are worth considering as well, but the idea will be the same.

  1. Battery maintenance:
    Maintenance is relatively simple. Do not let the battery die all the way and make sure to buy a balancer/charger. Most lipoly batteries have an extra header used for balancing. Yiu can buy a battery monitor to connect to this. It will beep and flash red when the battery is low.

  2. Battery charging
    Lipo batteries will have a "c" rating for charging and discharging. Be mindful of this number because exceeding this number will increase the likelihood of a "thermal event." How do you use the c rating? If a battery is rated at 1Amp-hour and 1C (charging), then the max charge current should be 1amp-hour*1C =1A. Do not overcharge. Typically a battery is 4.2V is per cell, but there are higher voltage batteries. LiFePO4 is 3.3/cell nominal. I think 3.6 charged. For your needs a 2S (2-series) would work well.

  3. Brands?
    There are many, but I really like Turnigy from hobbyking.com. I've had good like with Zippy as well.

  4. Safety
    Lipoly batteries CAN overheat and result in FIRE. There are some countermeasures to this:

    1. Use fireproof/fire resistant containers when charging and storing batteries
    2. take swollen batteries to your nearest battery store for safe disposal.
    3. Add fuses to all devices (uncommon). This is done in cars for the same reason.
    4. Check LiFePo4 batteries. Slightly lower energy density, but they are less likely to catch on fire.
    5. Keep a class D fire extinguisher around. This is both a chemical and electrical fire.
    6. There are "hard case" batteries that reduce the likelihood of a puncture. I've only ever owned one, but I did really like it.
    7. Always monitor your charging batteries. If there's a fire, you want to be there.

I would provide links for you, but my computer died and I'm on my phone.

Edit: I have this charger and like it a lot

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  • \$\begingroup\$ There are bags you can buy that help contain a failure if a battery goes up in flames (charge/store in the bag). Also, you should not leave LiPos charging unattended. \$\endgroup\$ – Steve Mar 29 '17 at 15:21
  • \$\begingroup\$ Yup! That's why I added the containers. I've used the bags in the past, but now I use ammunition cases. I did forget to discuss unattended charging. Good point. Adding it. \$\endgroup\$ – amwalker707 Mar 29 '17 at 17:12

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