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Hey guys, i wanted to make a 12v battery level indicator without using an I.C or transistors, so i got the above circuit off the internet and made a few changes to it, but somehow it doesn't work properly; all the LED's are suppose to turn on when the battery voltage reaches 12v, but only three(LED3, LED2, LED4) turn on at this voltage and at 4v led3 is suppose to be the only led on but it stays off. Can someone tell me what's wrong with the circuit. D1, D2, D3, D4 are 3.3v, 6.2v, 9.1v and 11v zener diodes.
Well, since you are never supposed to discharge a lead acid battery below about 11.0V, that circuit, even if it worked is pretty useless.
A fully-charged lead-acid chemistry battery, 12h or so after it comes off the charger is 13.2V to 12.7V. One that is totally discharged is 11.5 to 11.0V. If you are making a bar-graph type display, those should be the end points.
To get any idea about the state of charge of a battery, you need one of these:
Here is what Battery University says about the discharge curve of LiIon:
The specific energy of Li‑ion is twice that of NiCd, and the high nominal cell voltage of 3.60V as compared to 1.20V for nickel systems contributes to this gain. Improvements in the active materials of the electrode have the potential of further increases in energy density. The load characteristics are good, and the flat discharge curve offers effective utilization of the stored energy in a desirable voltage spectrum of 3.70 to 2.80V/cell.
Your battery must be 4 cells, so you you should expect to see 14.8V to 11.2V. Still would be better to use a real voltmeter, rather than a series of idiot lights.
Nope.
A fully charged Lithium-Ion cell is 4.20V so four make 16.8V. A discharged cell is 3.2V when its load should be disconnected so four make 12.8V. The average voltage during a discharge is 3.7V so four make 14.8V.
Three cells make 9.6V to 12.6V, averaging 11.1V during a discharge.
Thanks for your contributions guys. MikeMl the battery is used on an inverter which has no battery level indicator, constantly using a multimeter to check voltage levels will be a hassle.
Thanks for your contributions guys. MikeMl the battery is used on an inverter which has no battery level indicator, constantly using a multimeter to check voltage levels will be a hassle.
Get a Small 50 or 100 uA Meter.
Add a Series Resistor to make it into a Voltmeter with a suitable Voltage Range for your battery.
Than you will have a Good Reference of battery Voltage, Without Excessive current draw.
(A Zener Diode of a Suitable Voltage can also be included to create an Expanded Scale meter.)
The forward voltage drop across the LEDs will be at least 2 volts. If you add that to the 11 volt drop across zener diode D4, you get 13 volts. And depending on what type of LED you're using, the voltage drop could be even higher, preventing it from lighting up until you're above 14 volts.
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