![]() ![]() Even flashlights are following this trend, with incandescent bulbs being displaced by brighter, less power-hungry LED-based flashlights.įor our testing, we set out to compare battery chemistries in different applications to see which types are best suited for which applications. Not only can manufacturers cram more stuff into smaller spaces, but the integrated circuits in the devices require ever less wattage to operate, thus increasing battery life. ![]() Modern portable electronics are power conservative and growing more so by the day. With so many choices, is it worth the trouble and expense to seek out other battery types or will you do as well with off-the-shelf alkalines? And if the latter is true, which alkaline is the best buy? In addition to the ubiquitous disposable alkaline, there are also rechargeable alkalines, lithium manganese dioxide, nickel-cadmium (Ni-Cd), nickel-metal hydride (Ni-MH) and lithium ion (Li Ion) cells. These days, there are more battery chemistries to choose from than just alkaline. Redundancy or not, you still buy lots of batteries. Even so, youre sure to carry plenty of battery powered devices in the airplane: several flashlights, a back-up portable GPS, a VHF radio. You probably have dual alternators and perhaps even dual batteries, so electrical redundancy is all but a done deal. ![]() then.I will be confused too.If you fly a state-of-the-art single-engine airplane, lucky you. If you will find out that the charger keeps charging for any value of R_ext and the charger signals an error even if the battery under charge has a nominal voltage. Please note that the charger will see now the sum R_bat + R_ext. The value of the resistor is likely small (we can start with 1Ω for example) and find out from which value the charger starts to complain and signals it is a bad battery. Then we insert externally a resistor R_ext (as if it were internal) in series between one terminal of the charger and the corresponding pole of the battery. On the other hand, perhaps we can check the validity of this 'internal resistance' idea for a charger by doing just the opposite as it follows:įirst, we find a good battery that the charger can charge it normally. Then we remove the resistor and notice how much the battery voltage drops (Vbat1-Vbat2): ![]() We measure the two voltages V_res on the resistor (R_ch) and V_bat1 on the battery. One easy method is to wire the battery as if we like to charge it via a resistor. If the charger refuses to continue charging the battery though its voltage is nominal then we can conclude that it detects its internal resistance (R_bat) first which usually increases with time. But if dissipation is not a problem (by using a power resistor or many resistors in parallel, series or both, to get R_ch), using 12V for example can let the charging current be rather constant while V_bat is increasing with time. R_ch = (Vcc - V_bat) / I_ch (worst case is when V_bat=0)įrom the formulas above it is better to choose a low Vcc to decrease dissipation (not higher than 5V). The charging current (I_ch) doesn't have to be high since we are not in a hurry :wink: This can be done via a resistor and a DC supply. If its voltage is too low then we should try charging it with a simple method till it restores its nominal voltage. Sorry, I couldn't get your point on how to let the charger see the battery as having internal low impedance.īy the way, I supposed that measuring the voltage of the old battery gives a nominal value (for example like 1.2V or a bit less). ![]()
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