LongGo Batteries

Lithium polymer cells have already been used for years in palmtops, handheld computers, notebooks, digital cameras and cell phones. They are now making their entrance in model building. For the medium term, nickel-cadmium (NiCd) and nickel metal hydride (NiMH) batteries are being driven out by the new lithium polymer cells. These batteries offer enormous advantages with respect to capacity in proportion to weight. Only specially selected cells are used for LongGo batteries - never cheap merchandise from the Far East. Starting with the manufacturer, only the best cells from current production (in terms of internal resistance and voltage) are selected exclusively for LongGo. Only these cells carry the LongGo quality feature and are then made into high-quality receiver batteries. This type of cell assembling is utility patented by EMCOTEC GmbH.

LongGo batteries hold UL approval (approval regulations for the U.S., inspected by Underwriter Laboratories (UL) in the USA). Elaborate tests are needed to obtain this approval, which guarantees the safety of the batteries. Thus, with proper handling, LongGo batteries will not explode. Reports have been printed in various magazines and forums regarding burning down or exploding lithium cells. The cause of these hazardous properties lies in the use of cheap cells, offered at dumping prices in the Far East. These cells cannot be compared to the quality of LongGo cells. The integrated safety electronics of the new LongGo S series means no more fear of risks even if they are handled incorrectly. Intensive trials and tests at EMCOTEC GmbH have also provided proof of the dependability of LongGo batteries.

Based on numerous tests (even under peak current conditions) only slight capacity losses could be observed after about 300 charging cycles of the lithium polymer cells. The manufacturers themselves indicate a capacity loss of about 15% after 500 charging cycles. 500 charging cycles of a receiver battery correspond to about 1500-2500 flights, at any rate. This provides an extremely high level of dependability, which in no way takes second place to the traditional cells.

LongGo Flight Batteries:

The newest flight batteries of the SBC series (Special Balancing Connector) allow the balancing of the single cells during charging using the LongGo Balancer through a special integrated connector- see accessories/charging or E-Shop). Here too, EMCOTEC is pioneer in this domain. Since flight batteries are heavily used, rebalancing plays a major role. Due to high currents (up to and over 100 amps) the cells hold different voltages after some flights. Therefore, cells with the highest voltages are overcharged during "normal" charging. In the long run, this leads to decreasing capacity - the battery gets worse and life time shrinks. The cell voltages of the LongGo flight batteries of the SBC series are being charged to equal voltages thanks to the connected balancer. The batteries therefore hold their full power even after many flights and they live longer. First prototypes were already being used very successfully during the F3A European Championship 2004. Positions 1, 3 and 5 were placed with products from EMCOTEC. A great success!

KOKAM Lithium-Polymer Batteries:

The Lithium-Polymer cells of the Korean manufacturer KOKAM are the best acknowledged cells on the market today. Low internal resistance, high current carrying capacity, best voltage stability and long life cycles mark these cells. KOKAM is the leader in LiPo technology and possess many patents worldwide for manufacturing of the cells. Due to best contacts to KOKAM, these cells are available from EMCOTEC through our E-Shop. For electrical flight, for low cost receiver power supplies or other applications in daily life, were light weighted energy is necessary - with LiPo batteries from KOKAM one is always on the right side.

OEM-Batteries:

We can provide special solutions for batteries in the field of OEM applications. No matter whether with or without monitoring electronics, whether with or without integrated charger circuitry - we elaborate a concept for each application. Due to the manufacturing capabilities in Far East cost can be kept low, what is a major aspect for a high quantity of cells. Ask us without obligation - we can help!

General Information on Lithium Polymer Cells:

Further development of the previously well-known lithium ion batteries entails new, advanced battery technology, which exhibits 25% higher energy density. This easier and - more importantly - safer further development of lithium ion batteries entails the lithium polymer batteries (for short " Pli" or "LiPo"). In the lithium polymer batteries, a less aggressive paste replaced the highly toxic fluid electrolyte. Because of this, the customary sheet steel housing of the Lilon cells can be eliminated in the LiPo cells, which saves on weight and prevents the danger of explosion from excess pressure. Flexible packaging made of thin aluminium foil is sufficient. Due to the mould ability of the aluminium casing, the battery can be brought into virtually any desired shape, which makes it ideal for use in PDA's, notebooks, digital cameras and cell phones.

The paste electrolyte is only chemically stable within a certain "voltage window". Thus, the batteries are extremely sensitive to excess or low voltage. The maximum cell voltage of 4.2 volts (to be exact: 4.235 volts) may in no way be exceeded, even for a short time! For this reason, lithium polymer cells require special battery chargers. The lowest cut-off voltage, on the other hand, is 2.5 volts. With a discharge below 2.5 volts per cell, permanent damage can be expected. In practice, the batteries should already be charged for cell voltage of 3.0 volts. When discharging, the jump from 3.0 volts to 2.5 volts is quickly reached, since the voltage of the cell breaks down very quickly when discharge is complete. Monitoring the cell voltage is thus very important in order to prevent destruction of the battery from total discharge. The DPSI RV systems used in conjunction with LongGo batteries thus have an integrated voltage monitor.

One big advantage of the lithium polymer batteries is that they do not have any memory effect and only a very slight self-discharge. Fully charged, the batteries continue to provide 95% of their capacity after a period of six months (assuming proper storage).

On the other hand, the poor solder ability of the thin terminal lugs for individual cells can create a problem. The seal of the cell can easily be damaged during soldering, which can then result in permanent damage. A special soldering process is used in LongGo batteries, which spares the cell, rules out damage and protects the warranty. The ready-made LongGo batteries thus offer a high quality, dependable power supply without risk to the user.

Another advantage of the lithium polymer cells is the conditional quick-charge capability. LiPo cells can be charged with 1C (i.e. with 1.2 amps for a 1.2 amp/h battery). Since charging is first power controlled and then voltage controlled, the battery is fully charged after about 1½ hours. One disadvantage is the de-balancing in cells connected in series. If one cell becomes full or empty BEFORE the other, the total capacity of the battery is reduced sooner or later. To compensate for this, you would actually need to charge in-series cells separately (individually), which leads to high costs in charging technology. Therefore, LongGo batteries are selected, matched exactly according to voltage, and only then made into a battery. Since the currents for supplying the receiver station are not as high as in electro-flights, for example, the de-balancing does not have as strong an effect. Nevertheless, soon there will also be small electronics that can be plugged to the 2100 and 3300 series batteries from time to time, which will then enable fully automatic balancing. After 1-2 hours, the cells will again be in "harmony". That ensures the valuableness of the batteries over a long period of time.



Safety tips for the LongGo receiver batteries:

  • Operate as a receiver power supply only in connection with the DPSI family (RV, TWIN, LR)
  • Use only battery chargers approved by EMCOTEC GmbH
  • Observe the charging current (max. 1C) and the charging voltage when charging
  • Observe the maximum admissible current of the batteries
  • Protect from mechanical forces (crushing, squeezing, bending, drilling)
  • Do not under any circumstances open or cut open the batteries, do not throw into a fire, keep away from children
  • Do not short circuit the batteries under any circumstances
  • Do not discharge receiver batteries below 5.0 volts (2.5 volts per cell), or they will be completely defective! The batteries should already be charged with a voltage of 6.0 volts.
  • Do not operate the batteries below -5°C, since the capacity decreases sharply at minus temperatures.
  • Protect the batteries from the effects of heat (install away from hot components (e.g. exhaust)
  • Charge the batteries before storing (e.g. during winter break) – do not store in discharged state!
  • Where possible, do not leave the batteries unattended when charging.
  • If lithium polymer batteries become involved in a fire (e.g. a crashed burning jet), NEVER extinguish with water; use a powder extinguisher instead!
Because of the high energy density (up to 190Wh/kg), the cells are not safe and require special care! EMCOTEC GmbH shall therefore assume absolutely no liability for damages that arise from incorrect handling of the lithium polymer cells.
   
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