battery maintenance - matthias-schulze
Contents
1. any fuller schulze elektronik gmbh page 1 4 1 3 Memory effect of Ni Cd amp Ni MH cells If cells are repeatedly stored partially discharged or are recharged from a half discharged state what is known as the memory effect sets in The cells note that their full capacity is not required and react by refusing to make it available One aspect of this is that the crystalline chemical structure inside the cell changes the cell s resistance rises and its voltage collaps es under load with the result that full capacity can no longer be exploited at normal discharge currents Even if reflex charging were to eliminate the memory effect there is no denying the necessity to store your cells in the discharged state this applies to Ni Cd cells and also to Ni MH cells A characteristic fact of these cells is that they self discharge and the rate of self discharge is different for each individual cell in a battery pack If a fully charged pack is left for a considerable time it will eventually consist of cells of widely varying states of charge If at this point you a give the pack a full charge the cell with the highest charge will be overcharged heat up and be ruined while the cell with the least charge will still not be full after the same period of charging b discharge the pack the cell with the least charge will be com pletely flat first then reverse polarity and often suffer an internal short2. circuit At the point when this happens the cell with the most charge is still not yet completely discharged This is a reliable method of wrecking your most valuable packs and rest assured that reflex charging will make absolutely no difference However there is one method of avoiding the prob lem discharge cells after use and recharge them just before use 4 2 Nickel Cadmium baitteries Ni Cd Nominal voltage level 1 2 V cells Selecting the fast charge current manual setting Charge current 2 C never less C nominal battery capacity Maximum continous discharge current Currents of 10 C to 30 C are possible depending on cell type Long time storage Empty i e discharged to the discharge voltage cut off level see maintenance at low temperature 20 C to 10 C Maintenance Charging The automatic current setting circuitry patent applied for provides optimum protection to your Ni Cd bat teries during charging The reduced current towards the end of the charge ensures a completely full pack combined with only a slight temperature rise as you will easily see in comparison with conven tional constant current techniques Do not use the automatic charge current calculation of the Ni Cd batteries when charging Ni MH batteries Discharging To prevent your cells from memory effect and to keep the full capacity you have to discharge it after use even when you store it over night select Auto D program to dis
3. Never charge fully charged Ni MH batteries with the Auto C or CD programs Over heating and danger of explosion The cut off automatic is disabled for about the first 5 minutes of charging this could lead to a minimum charge time of about 10 minutes Amongst model car operators it is standard practice to erase any memory effect by discharging each cell individually via a resistor of approx 10 Ohms in series to a 1 amp silicon diode 1N4001 Warning At lower cell counts 1 6 and low charge currents below 2 C the battery makes only a very low voltage peak when fully charged Under those conditions the cut off automatic works less reliable then with higher currents and or higher number of cells Typical for Sanyo Twicell and RC3000H cells High maximum load capacity and voltage level Typical for Panasonic P3000NIMH cells High maximum charge capacity and voltage level Typical for GP GT3000 3300 cells Extremely high charge capacity good voltage level Can be discharged with medium currents about 40 45 A 4 3 Lead acid batteries Pb and VRLA valve regulated lead acid batteries Nominal voltage level 2 0 V cell Charge voltage level 2 3 V cell 2 42 V cell for 3 hours Min discharge voltage 1 7 V cell this reduces lifetime Number of cells to be selected on the isl 6 Nominal voltage of the battery to be charged divided by the nominal voltage level of lead acid battery cells cell count Example 12 V Lead aci
4. Useful information about batteries and maintenance Extract from our operating instructions Issue 22 NOV 2003 3 Commonly used Terms Final charge voltage the voltage at which the battery s charge limit capac ity limit is reached The charge process switches from a high current to a low maintenance rate trickle charge at this point From this point on further high current charging would cause overheating and eventual ter minal damage to the pack Final discharge voltage the voltage at which the battery s discharge limit is reached The chemical composition of the batteries determines the level of this voltage Below this voltage the battery enters the deep dis charge zone Individual cells within the pack may become reverse po larised in this condition and this can cause permanent damage Memory effect The real memory effect has been recorded by Nasa caused by repeated charge discharge cycles Nasa has found that full capacity can be regained by overcharging the cells In modelling applica tions different effects are responsible for the reduction in cell capacity The problem can be cured by balancing the cells see below and pre vented by the measures described in Chapter 4 1 3 Balancing a method of regaining full nominal capacity by alternately charging and discharging the pack sometimes several times This pro cess is especially useful after a long period of non usage e g after pur chase or after several weeks wi
5. acturers can safely be charged at a higher rate of up to 1 6 C Panasonic 3000 3 5 4A GP 3000 3300 3 A Saft 3000 3 A not if battery is charged inside a transmit ter Sanyo 3000 3300 4 5A Maximum continous discharge current Currents of 5 C to 15 C are possible depending on cell type Long time storage Empty i e discharged to the discharge voltage cut off level see mainte nance at low temperature 20 C to 10 C Maintenance To protect your Ni MH batteries from the memory effect and keep the full capacity discharge the cells after use down to the discharge voltage limit even when you store it over night Never discharge by car bulbs or the drive motor premature charge termination but use only the Auto D programm when the battery type Ni MH is selected The cut off voltage is 1 volt cell This eliminates the danger of deep discharge ter mination and polarity reversal over discharge It is important that you take the trouble to give Ni MH cells when storing at 10 30 C a charge discharge cycle around every four weeks other wise they become tired and have to be pampered to restore them to full vigour This involves going through the tiresome business of many re peated charge discharge cycles The automatic current setting circuitry patent applied for provides optimum protection to your Ni MH batteries during charging Do not use the Ni Cd automatic current selection for Ni MH batteries Warning
6. charge down to 0 85V cell If a battery is brand new or used irregularly it is often only possible to balance it completely by carrying out several discharge charge cycles Amongst model car operators it is standard practice to erase any memory effect by completely discharging each cell indi vidually via a resistor approx 68 Ohm This deliberately unbal ances the pack but it can cause the automatic charge termination circuitry to switch off the current prematurely during the charge process For receiver batteries special types such as the Sanyo KR500AAEC N500AC lower resistance are a good choice Warning The reduced charge current with 1 6 cells makes the volt age peak in the charge curve very slight especially with batteries of high nominal capacity In this situation the charger is sometimes unable to detect the full condition due to the ill defined peak schulze elektronik gmbh prenzlauer weg 6 64331 weiterstadt germany fon 49 6150 1306 5 fax 1306 99 homepage http www schulze elektronik gmbh com eMail hotline schulze elektronik gmbh com page 2 4 3 Nickel Metal Hydride batteries NiMH Voltage level 1 2 V cell Selecting the fast charge current no automatic program Charge current typical 1 C never less set a fixed current of for exam ple 1 2 A with 1100 mAh batteries or 3 A with 3 Ah cells Some modern high current Ni MH cells made by particular manuf
7. d battery divided by 2 0 V gt 6 cells Selecting the fast charge current Charge current 0 4 C C nominal battery capacity Maximum continous discharge current Typically 0 2 C short time load up to 1 C Long time storage Full at low temperature more precise at 10 C up to 12 month at 10 20 max 9 month at 20 30 C max 6 month at 30 40 C 3 month Charge again after this period Maintenance In contrast to Ni Cd Ni MH batteries lead acid batteries must be fully recharged after use in order to maintain full capacity The nominal capacity can be reduced very quickly by incorrect handling overloading repeated 100 discharges and especially deep discharg es Please observe the battery manufacturer s recommendations Useful information about batteries and maintenance Extract from our operating instructions of the chargers Typical The characteristics of lead acid batteries are quite different to those of the Ni Cd sealed cell packs which are used as the pow er source in model aircraft cars and hydro boats They can only tolerate relatively low currents relative to their capacity if their full capacity is to be exploited and or the voltage is not to collapse too far Used as single cell glowplug energiser batteries and power source in some scale boats Very low self discharge rate 4 5 Lithium Manganese Oxide batteries LiMnO Nominal voltage level 3 0 V cell Selecting the fast charge curren
8. ls 4 of 2050mAnh are connected parallel 4p gt 4 2 05 Ah 8200mAh 3 of the parallel cells are connected in series 3s gt 3 3 7V 11 1 V Selecting the fitting cell type Select that battery type from the is 6 menue which characteristics match best with the data sheet of the battery manufacturer Selecting the fast charge current Charge current 1 C SANYO KOKAM or less 0 7 C PANA SONIC C nominal battery capacity Maximum continous discharge current Up to 4 C very new types more depending on cell type Long time storage Empty i e discharged to the discharge voltage cut off level see maintenance at low temperature 20 C bis 10 C Maintenance Discharge with 1 C down to above listed discharge voltages Always store these cells in the discharged state if stored fully charged the result can be a permanent reduction in capacity When stored at 40 C or more charge additional every two months Typical They are very popular as power supplies for sail winches 2 cells Their limited ability to supply high currents means that they are only suitable as flight packs with more than 20 minutes flight time slow flyers Piccolo Hornet Logo10 Very good energy weight ratio Hint Many manufacturers direct how many cells are allowed to use in series and or parallel use The exact technical term of a Li Po cell is Lithium lon Polymer bat tery the true Lithium Polymer cells work only with higher
9. must expect differences in charge characteris tics if you use fully automatic charge current calculation in Winter the charging properties will be worse than in Summer The best working temperature for a Ni MH cell is 40 60 C At lower tem peratures the cell can not supply higher currents Caution when us ing those cells a a receiver battery in a helicopter in the wintertime The lower the internal resistance of the battery the higher the charg er can increase the charge current for that battery For a battery charger which sets the current automatically the resistance of the cable is added to the internal resistance For this reason use heavy cable large cross section even for receiver batter ies and keep them short Do not charge via a switch or switch harness If you wish to measure battery capacity accurately a suitable dis charge current is usually 1 10 C 4 1 2 Reflex charging Charging processes which include a brief discharge pulse definitely have the effect that the battery is several degrees cooler at the end of the process However from the point of view of the compe tition operator this is an undesirable effect as the cell chemistry can only supply high currents if its temperature is raised to a cer tain extent All these effects whether they actually occur or are simply hear say have no practical significance if batteries are correctly handled in the first place When a battery is full you can t fill it
10. t Up to 0 35 C dep on cell type Maximum continous discharge current Up to 1 5 C Maintenance Always store these cells in the charged state Typical These cells are particularly recommended as receiver bat teries 2 cells required although correct charging and storage are very important However we do not recommend them as slow fly flight packs since they have a limited ability to supply high cur rents and their useful life varies greatly according to the discharge current and the extent to which they are discharged Very good weight energy ratio Hint The most common form of this cell type is the Tadiran cell Tip Ideally all single cells in a pack should be charged separately alternatively charge all cells in parallel 4 6 Lithium ion batteries Li lo amp Li Po Nominal voltage Lilo 3 6 V cell SAFT Nominal voltage Lilo LiPo 3 7 V cell SANYO KOKAM Max charge voltage Lilo is 6 4 1 V 40mV cell SAFT absolute limit 4 3 V cell LiPo is 6 4 2 V 50mV cell MoliCel Min discharge voltage Lilois 6 2 5 V Z MoliCel 2 7V Z SANYO absolute limit 2 3 V cell LiPo is 6 3 0 V cell KOKAM Number of cells to be selected on the isl 6 Nominal voltage of LiPo pack div by nominal cell voltage cell count gt 11 1 V LiPo pack divided by 3 7 V gt select 3 cells If you would select more the pack would explode during charging Example The Kokam TP8200 3s4p pack consists of 12 cel
11. temper atures of more than 60 C schulze elektronik gmbh prenzlauer weg 6 64331 weiterstadt germany fon 49 6150 1306 5 fax 1306 99 homepage http www schulze elektronik gmbh com eMail hotline schulze elektronik gmbh com
12. thout flying and is also used to disperse the memory effect see below The effect of balancing is to break down the coarse crystaline structure low capacity inside the cell and convert it into a fine crystaline one high capacity Power On reset the status of the is 6 after it has been connected to the car battery Ready message charger ready to run the program you have just selected batteries not connected The display shows GO C Coulomb or capacity Unit of measurement relating to the quantity of charged energy In conjunction with charge current data this unit is used to determine the recommended prescribed charge current of a battery of a given capacity Example if the charge or discharge current of a 500 mAh battery is 50 mA we refer to this as a charge or discharge at one tenth C C 10 or 1 10 C A mA unit of measurement relating to charge or dis charge current 1000 mA 1 A A Ampere mA Milliampere Ah mAh unit of measurement for the capacity of a battery Amperes x time unit h hour If a pack is charged for one hour at a current of 2 A it has been fed 2 Ah of energy It receives the same quantity of charge 2 Ah if it is charged for 4 hours at 0 5 A or 15 minutes 1 4 h at 8 A 4 Useful information about batteries and 4 1 1General information maintenance Do not charge below 0 C optimum is 10 30 C A cold cell is not capable of accepting as much current as a warm one For this reason you
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