LiPo Batteries

Preamble

An ongoing blog about LiPos, as I feel my way around the topic.

See also Power Up! and LiFePo4 Batteries

The featured image, above, is taken from LiPo battery may have caused shop fire.

Videos

Resurrecting a dead LiPo. Note that this seems very dangerous and the LiPo could burst into flames…

Evidently a better way is to use a NiMh charger:

Restoring/Recharging over-discharged LiPo (Lithium Polymer) batteries!

Which Batteries?

From  KKmulticopter V5.5 Board V2.2 Program + USB Programmer Firmware Loader.

Yeah, I would probably go with at least a 3S battery. I actually haven’t heard of too many people flying a 2S battery on anything over a 330-sized frame; even a lot of the F330 guys fly 4S. 3S is good for all-around flying, 4S will turn your quad into a rocket. I think that if you went 3S 5000mAh, you would get about 12-15 minutes of flight time, maybe more depending on your frame and overall weight of your quad. There’s a max point when battery weight overtakes battery capacity in terms of flight time, but it gets a little complicated, so I won’t attempt to get into that. A battery’s C-rating also comes into play in flight time due to varying rates of discharge. In very basic terms, the mAhs are like the volume of a tank of water, and the C-rating is like the diameter of the hose attached to the tank. Higher mAh means you have more water to spray, and higher C-rating means you can spray a greater amount of water at any given time if you need to. The S part of a battery rating denotes the amount of cells it contains within the battery pack, and is analogous to the water pressure of the hose. I personally fly a couple of 3S 2200mAh with 20-30C because they were (and still are) pretty cheap, I don’t fly very aggressively nor do I fly ACRO (yet), and they offer a good balance of low weight and decent flight time. I get about about 8 mins of flight time per pack. Coupled with 1045 props (I flew 8045s for a few months and liked them a lot, but I strapped a heavy camera on my quad, so I need some more thrust), they offer plenty of grunt when I need it.

From DJI F550 or Tarot FY680

I would say it depends on what you want… honestly I think the best small filming platforms out there right now are quads with three axis gimbals on them. I would get you a zenmuse H3-3D on your 450… I get about 18 minutes of flight on mine with a 2D and still have juice to spare. I use 4S 4500 mah Turnigy nano-tech A Spec 65-85C batteries with the stock motors and 10 inch props.

In my personal opinion it doesn’t make sense to run a “small” (quotes because that’s a relative term) hex over a quad because of the flight times. If you are going to spend the money on a hex you should just go big or a 700-800 size quad with low KV motors. Those guys are reporting flight times of nearly an hour now!

and

The reason why I’m thinking a hex is exactly what Idahobell states about it being less risky about losing a motor or ESC, I’m worried about losing a good chunk of money because of 50 dollars worth of parts failing on me. Currently I have myself an F450 with stock DJI motors, 9×4.5 APC props with a Turnigy Nano tech 5000 mah 4s. Landing gear, tarot t2d as well as a mini 860mah 3s battery on there to run the gimbal and video tx. I’m getting aprox 12 minutes flight time now, with this combo. Originally I thought about just upgrading the motors and putting bigger props on but now I’m slightly worried about losing a motor or ESC. Which brings me to this point, but now you’re making me think twice about going to the hex. I do like the idea of possibly upgrading to a little larger gimbal and maybe a small DSLR which would be good for a hex.

From HMF S550

I have the e300 motors and props with simonk esc’s, and a walkera 3s 5200mAh (they are light) and it works great. Also have a zenmuse h3-3d. I get about 16 mins with this setup with my lipo alarm set to 3.4

and

I have flown two 5000mAh 4s in parallel onto the hmf s550 – now running on sunnysky x2212 980kv on 10×4.5 hq props (apc mr style).

I was doing a test to see if the hex can take a nex-sized gimbal. I loading up 2x 5000mAh battery in parallel, and at the same time strap an addition 500g of weight on top of the quad – bringing the auw of the quad to about 3.3kg. I also increased the gains setting of the naza lite I used.

End result? – It flew great! …I flew for about 6mins and landed with >50% battery left in the lipos. Motors were barely warm. There weren’t as “strained” as I thought they will be and I believe there is still capacity for some additional weight.

and

I’m flying at about 2500 AUW with a 4s lipo 5000 mAh. I get 10 minutes at that weight, put back roughly 3200 mAh and have battery voltage of 15.2.

From Relatively cheap hexacopter for aerial photography?

For the NEX-5n (I had one on a little hexa) I’d get 8 mins flight time with it on board with 1 x 5000 mAh 3s. I was using 10×4.5 props, and small motors like on your list.

and

Most smaller rigs take 3 – 4S, most larger rigs take 6S.
motors are completely different as is ESC’s.

Storing baterries

Never store your batteries at full charge. From Definitive Word on Lipo Storage Mode vs. Full Charge?

This is what Traxxas has to say on the matter, and since this subforum is only for Traxxas-branded batteries…
Traxxas-Battery-Basics

Originally Posted by Traxxas Battery Basics

NiMH, NiCd, LiIon, LiFe, and LiPo
These terms refer to the materials and chemistry within the battery. Nickel batteries (NiMH, NiCd) have cells with the familiar “cylinder with a button on top” construction and a metallic case. Lithium batteries (LiPo, LiIon, LiFe) are usually constructed of flat cells stacked together. The cells may be encased in heat-shrink to form the final pack, or enclosed in a “hard case.” Traxxas Power Cell LiPos use a “semi-rigid” design that is durable and allows greater battery capacity in a pack of a given size.NiMH = Nickel-metal hydride
NiCd = Nickel Cadmium
LiIon = Lithium Ion
LiFe = Lithium Ferrous Oxide
LiPo = Lithium PolymerCapacity
A battery’s capacity refers to the amount of energy the pack can store. Think of capacity as your model’s gas tank; the greater the capacity, the larger the gas tank, and the longer your model can run per charge. In addition to giving your model a longer run time per charge, using a pack with greater capacity also increases “punch,” the feeling of power you get when your accelerating from a standstill or out of turns. The large number (3300, 4000, 5800, etc) on your LiPo battery refers to its capacity in milliamp-hours (mah).One milliamp is a thousandth of an amp, and amps are the measure of load or “current draw” on the battery. To convert milliamps to amps, divide by 1000; for example, 7600mah is equal to 7.6 amps. Milliamp-hours, or amp-hours, refers to the amount of current draw the battery can sustain for one hour. To continue with the example of a 7600mah battery, it would handle a load of 7600 milliamps (or 7.6 amps) for one hour. Since your powerful Traxxas R/C vehicle will likely draw more than 7.6 amps, it will run less than an hour per charge. The important thing to remember is this; the larger the capacity number, the longer your run time.Voltage
The more voltage a battery has, the faster your car will go. Battery voltage is determined by the number of cells in the battery. Power Cell NiMH cells deliver 1.2 volts each; a 6-cell pack has 7.2 volts, a 7-cell pack has 8.4 volts, and an 8-cell pack has 9.6 volts. LiPo cells have higher voltage: 3.7 volts per cell. Because of this, they need fewer cells to provide the voltage needed for high-performance R/C. Power Cell LiPos are available with 2 cells (7.4 volts) and 3 cells (11.1 volts).

C-Rating
C is short for capacity. The load a battery can sustain is indicated as a multiple of capacity. For example, a load of 1C for a 7600mah battery is 7600 milliamps or 7.6 amps. A 2C load would be double the capacity; 15.2 amps (7.6 x 2 = 15.2). All Traxxas LiPo batteries are rated for 25C. For our example of a 7600mah pack, that would be 7.6 x 25 = 190 amps. How much amperage can be used to charge a battery may also be indicated as a “C” value. All Traxxas Power Cell LiPo batteries have a recommended charge rate of 1C, and a maximum charge rate of 2C. For maximum performance and longevity, charge at 1C whenever possible. For example, a 1C charge rate for the 5800mah Power Cell LiPo would be 5.8 amps. A 2C charge rate for the same battery would be 11.6 amps. An important note about C-Rating: Each battery manufacturer has their own formula and methodology for determining the C-Rating they assign to their LiPo batteries. For example, a Traxxas 25C battery evaluated using another brand’s method of calculating C-Rating might be determined to have a 50C rating. For this reason, you should not compare batteries from different manufacturers by their C-Ratings.

2S, 3S
LiPo batteries contain 2 or 3 cells connected in series (S). So, a pack with 2 cells is a “2S” battery, and a pack with 3 cells is a “3S” battery. A 2S battery has 7.4 volts, and a 3S battery has 11.1 volts. If your vehicle or speed control is rated for “6S” and has two battery plugs (such as the E-Revo Brushless Edition), you can plug two 3S packs into it for a total of 6S. Two 2S packs would be “4S.”

“Series” connection means the cells are connected inside the pack so the first cell’s positive tab is connected to the second cell’s negative tab. This combines their voltages; the two 3.7 volt cells deliver 7.4 volts combined. The other way to connect the cells is in parallel (P), which means the cell’s are tabs are connected “positive to positive” and “negative to negative.” This combines their capacities. If you look at the specifications of your Power Cell LiPo, you may see that your 2S pack is actually 2S2P, meaning it has two pairs of cells, each connected in parallel (2P), and the two pairs of cells are then connected in series (2S).

Chargers for RC Batteries
It is critical for the longevity of your batteries and your personal safety that you always use the correct charger or charger settings for your battery, and observe all the precautions outlined in your battery and charger documents. Traxxas offers the #2930 EZ-Peak and #2932 EZ-Peak 2amp chargers exclusively for use with NiMH and NiCd batteries ONLY. NEVER use a NiMH or NiCd charger to charge a Traxxas LiPo battery. Failure to use LiPo balance charger to charge LiPo batteries can result in explosion, fire, and personal injury! The #2933 EZ-Peak Plus can be used with all R/C battery types including Lithium batteries, but you must be sure to select the LiPo, LiIon, or LiFe mode when charging Lithium batteries. Always place your LiPo battery in a fire-retardant bag or case while charging. All rechargeable batteries should be charged in a charging bag or case.

Storing Your Batteries

… LiPo batteries should be stored at 50% capacity. Store LiPo batteries in a charging bag or case. Do NOT store LiPo batteries discharged, as this will reduce battery performance and may lead to over-discharging if the packs are stored discharged for an extended length of time. The Traxxas EZ-Peak Plus makes it easy to store LiPos properly; just recharge the pack using Storage mode and it will charge the pack to 50% capacity.

LiPos and Low Voltage Detection
Over-discharging a LiPo battery will cause irreparable damage and may cause battery failure. To prevent over-discharging, only use Traxxas Power Cell LiPo batteries with an electronic speed control (ESC) that has a low-voltage detection system or alarm. All current Traxxas vehicles equipped with the XL-5, VXL-3s, VXL-3m and Castle Creations ESCs have Low Voltage Detection. Traxxas ESCs will show a green light to indicate Low Voltage Detection is turned on; the Castle Creations ESC will beep once for each LiPo cell it detects (for example, 4 beeps if you have installed two 2-cell packs in your model). The Castle speed control automatically activates its low-voltage detection mode when it detects it is connected to LiPo batteries. If you are uncertain about how to turn on and use Low Voltage Detection, consult your vehicle’s manual or click here for some helpful support instructions. If you need further assistance, feel free to call 888-TRAXXAS. We’re happy to help.

Never Use Damaged Batteries
No matter which type of battery you use, you should discontinue its use if damaged. Never use a battery with frayed or damaged wires, or torn insulation. Never use a nickel battery if it is dented or has other physical damage. Never use a LiPo battery that has visible damage to its outer covering. Never use a LiPo battery that feels soft, or has swollen.

Tips

1) I storage charge/discharge them to 3.85v/cell if they will not be used within 3 days.
2) If cell voltage is between 3.6-3.9v I will leave them if they will be used within 3 days.

The longer they are left at full voltage, the less cycles you will get out of them.

Undercharging to extend life

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Making your LiPo’s last
I will just give an example of how much a small change in how a pack is taken care of can dramatically change how the pack behaves.
Two identical packs were both charged and discharged in the exact same matter…. except one pack was charged to 4.20v/cell and the other to 4.10v/cell. This was done in a very controlled environment… NOT in an RC.
After 500 cycles, the pack that was charged to 4.20v/cell had reached its life expectancy… it would not take more than 65% of its original capacity; meaning the LiPo was no longer able to be used safely.
The pack that was charged to 4.10v/cell was still at 70% capacity after 1,000 cycles… so the .10v/cell difference more than doubled the life expectancy.
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Long term storage

So what happens if you store at 50% and don’t use for a year/ 6 months?? And when you get back to using they are below low voltage?? Wouldn’t you then be better to store at full charge so if storing for a long time they have longer to reach lowest voltage??

and answer

The self discharge rate of LiPo batteries is very low at about 1-2% per month so it’s highly unlikely that you’d fall below critical low cell voltage even at extended periods of storage starting at the 3.85V storage voltage. However it’s always wise to double check on your batteries every couple of month since the self discharge rate will vary with age of the battery, storage temperature and some other factors. Some manufacturers even recommend to cycle the battery every X weeks.
Storing at full charge increases the permanent loss of capacity over the storage period. Some tests showed an five fold increase of permanent loss at room temp storage over a years period of time when stored at full charge vs. 40% charge.
These tests where done on cobalt electrode based LiIo batteries and different LiIo chemistry/electrode make-ups will likely have variances on that loss but it will always be higher at full charge storage.

Posting LiPo batteries

It is not legal to post LiPo batteries in the UK, and it hasn’t been since 2013, see Posting lipo batteries is there any legal way. Note that this is a legal requirement and not a choice of Royal Mail, if they find them then they will destroy them, along with anything else that was in the parcel. There is a caveat though, which is that if the LiPo is included within another electronic device, then it is legal. There are some couriers that will handle them, but you can’t use the usual post.