See also Section 28.12, “Battery care and maintenance” for important information about batteries.
Lipo batteries can ignite if overcharged, or become bloated and damaged if overdischarged. Therefore, it is highly recommended to equalize or "balance" the charge in the cells in the pack either before charging or during charging.
Standalone lipo balancers work in different ways. Some will discharge all cells to a preset voltage, such as 2.75 volts. Some will equalize the cells in the pack by slightly discharging the cells with extra charge. Some balancers work by working with a non-balancing charger to provide
Some lipo balancers currently available are:
Orbit LiPoChecker (1s to 5s packs)
Orbit LiPoChecker pro (1s to 5s packs)
Schulze LiPoBal 8 (1s to 8s packs)
Schulze LiPoBal 14 (1s to 14s packs)
Astro "Blinky" battery balancer (1s to 6s packs)
Thunder Power Smart Balancer TP205 (2s to 5s packs)
Thunder Power Lipo Balancer TP210 (2s to 10s packs)
A lipo balance charger will individually charge the cells in a lipo pack to insure no cells are overcharged.
Some balance chargers currently available are:
Schulze LiPoCard (1s to 4s packs, 3.85 amps max)
Thunder Power High Power Charger (1s to 10s packs, ? amps max, requires optional balancer for balance chargin
Commonsense R/C balancing charger PB-14 (1s to 4s packs cells, 2 amps max)
There is no standard connector for lipo balancing, so you will need to buy balance connectors which are compatible with your balancer or balance charger, and solder these connectors onto your lipo packs.
There are many nice chargers on the market.
Here are the features I recommend you look for:
For micros: able to charge at 500 ma - 1.5 amps
For nonmicros: Able to charge at 3.5 to 5 amps
Delta-peak charge termination (for NiCad/NiMH)
Some type of false peak rejection capability (Sometimes called soft-start, peak delay, etc.) (for NiCad/NiMH)
The soft-start/false peak rejection capability is especially important for Nicad and NiMH charging. Helicopters tend to discharge cells rather deeply, and when these cells are charged, the charger may often "false peak detect". This occurs because the cell chemistry is unstable when deeply discharged and the cell voltage will fluctuate randomly until the cell chemistry stabilizes.
A charger with soft-start or false peak rejection will not require restarting the charging cycle multiple times in the first 5-10 minutes of charging a deeply discharged battery pack.
The chargers which are known to fit these criteria are:
Maha MH-C777 Plus II (surface charge, Nicad, NiMH, Li-ion)
Great Planes Triton (peak delay, NiCad, NiMH, Li-ion, Pb)
Great Planes Triton Jr (peak delay, NiCad, NiMH, Li-ion, Pb)
Great Planes Triton 2 (peak delay, NiCad, NiMH, Li-ion, Pb)
Hitec CG-330 (false peak reject, NiCad)
Hitec CG-335 (false peak reject, NiCad)
Hitec CG-335 Pro (false peak reject, NiCad, NiMH)
Hitec CG-340 (false peak reject, NiCad, NiMH)
Robbe Infinity II (false peak reject, NiCad, NiMH)
Schulze ISL 6-330d (false peak reject, NiCad, NiMH, Li-ion,Pb)
Orbit Microlader (soft-start, NiCad, NiMH, Li-ion, Pb)
Orbit Microlader Pro (soft-start, NiCad, NiMH, Li-ion, Pb)
Orbit Pocketlader (soft-start, NiCad, NiMH, Li-ion, Pb)
The best value in chargers in this list is the Great Planes Triton. It has almost the same features as the high-end Orbit Microlader at about 1/3rd of the price.
Before buying a charger, make sure it can charge the number of cells in your pack! Some chargers can only handle up to 10 or 12 cells, which is insufficient for a Logo 16/20 or ECO 16.
This may be important if you're planning on buying a larger helicopter eventually.
LiPo batteries can ignite and/or explode while charging. Therefore, you should charge LiPo batteries in a metal container (such as a military surplus ammo box) or ceramic container (such as a Battery Bunker).
Most battery charges will require a 12 volt power supply for use at home. Here are some 12 volt power supplies which are suitable:
Samlex America SPS-1206 12 volt 5.5 amp power supply
Samlex America SEC-1212 12 volt 10 amp power supply
Samlex America SEC-1223 12 volt 23 amp power supply
Alinco DM-330MVT 12 volt 30 amp power supply
Maplin XM22Y 13.8 volt 5 amp power supply
Maplin XM21X 13.8 volt 7 amp power supply
Maplin XM19V 13.8 volt 10 amp power supply
Pro Peak 20 amp power supply
A 5 amp power supply is suitable for charging most micro heli batteries. The 12 to 30 amp power supplies are suitable for charging most larger batteries.
A fully charged car battery at rest has a voltage of about 12.6 volts but when the car is running the battery voltage rises to 13.8v because the generator/alternator is running. So therefore all battery chargers designed to work off a car battery will handle 12v to 13.8v of input without problems.
If you must go to a flying field in order to fly, then you will probably need a field battery. It is not recommended to charge larger batteries from your car's battery because automotive batteries are not designed to be discharged on a regular basis.
The steps to calculate the required field battery capacity are:
Calculate the number of watt-hours required per charge
The number of watt-hours required per charge is the voltage of the battery multipled by the amp-hour capacity of the battery.
For example, a ten-cell 2400 maH battery pack has:
(1.2v per cell) x (10 cells) x (2.4 amp-hours) = 28.8 watt-hours of capacity
Multiply by the number of charges
If you want to charge a battery of this size about six times every trip to this field, this will require:
6 * 28.8 = 172.8 watt-hours of capacity
Add fudge factor for charger inefficiency
Battery chargers are not perfect at charging batteries (due to switching power supply and other losses), so add about 20% to account for this.
In this case, this would be:
172.8 watt-hours * 1.2 = 207.36 watt-hours of capacity
Add extra capacity to avoid completely discharging field battery
Lead-acid batteries will last longer if you do not completely discharge them at every use. Therefore I recommend adding at least 20% to your expected required capacity to avoid fully discharging the field battery.
If you anticipate flying extremely frequently (more than twice a week) then you should add at least 50% to your required capacity.
In this case, this would be:
207.36 * 1.2 = 248 watt-hours of capacity
The most common type of field battery is some type of deep-cycle lead-acid battery, due to its low cost and availability. For field battery capacities up to 240 watt-hours, a car "jumpstart" package is a very convenient source of power. One suitable package is the Vector Manufacturing VEC012 jumpstart system. This retails for $50 and includes a 12 volt 19 amp-hour sealed lead-acid battery and a built-in AC charger.
For field battery capacities up to 1440 watt-hours, a marine-style deep-cycle battery is a good solution. These typically cost between $50 and $120 and are available in sizes from 40 amp-hours to 120 amp-hours. Be sure to use a deep-cycle battery as regular lead-acid batteries are not designed for discharge on a regular basis. For field battery capacity up to 2880 watt-hours, the lowest cost solution is to use two 6 volt golf car batteries. These typically cost about $140 for a pair and are rated at 6 volts and 220 amp-hours. The Exide E3600 is one readily available battery of this type.
Note: the higher capacity batteries can weigh up to 70 pounds. For example, Exide E3600 weighs 62 pounds. If anticipate problems moving batteries of this weight, then you may choose to use multiple smaller batteries instead.
I do not recommend connecting field batteries in parallel. If you accidentally connect the batteries incorrectly, it can result in an explosion which will spray sulfuric acid over a wide area. It is safe to connect them in series, however, as a reversed battery will only result in less voltage at the output.
Most high-end battery chargers will also charge a lead-acid battery. Some examples of this are the Great Planes Triton, the Schulzes, and the Orbits. The charge rate is usually limited to about 5 amps on these chargers, so they will take a long time to charge high-capacity field batteries.
A better choice is to use a dedicated lead-acid battery charger. Be sure to select a good quality battery charger which includes an automatic cutoff feature. These battery chargers will avoid overcharging and "boiling" your battery and subsequently causing early battery failure.
Vector Manufacturing makes good battery chargers for this purpose. They use switching power supplies, digital voltage readouts, and a multi-stage charging algorithm for faster charging. The VEC1088 will charge at up to 12 amps, and the VEC1092 will charge at up to 35 amps.
If you fly larger helis, you may want to use a portable generator instead of a field battery and a field battery charger.
Honda manufactures a line of very quiet generators which are ideal for use at flying fields. The Honda EU1000i uses a four-stroke engine, is rated for 1000 watts of AC output, has a noise level of only 53-59 dB and will run from 4-8 hours on a single tank. The older discontinued Honda EX350 and EX650 are also good choices for a portable generator if you can find one. These use two-stroke engines so oil will need to be mixed with the gasoline. These generators output a square wave instead of a sine wave, so some equipment may not work well with it. Be sure to test before you buy one.
Yamaha manufactures the EF1000iS which is rated for 1000 watts of output, and is also a very quiet (47-57db) generator.
The 12 volt output of most portable generators is very weak, so the AC output should always be used for charging batteries. Portable generators should be run at least 30 minutes a month to keep the generator properly lubricated internally.