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How To Install a Battery Level Indicator in a Charging Station

How To Install a Battery Level Indicator in a Charging Station

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Old 11-25-19, 09:38 PM
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How To Install a Battery Level Indicator in a Charging Station

I have a battery level indicator (5-segment) that I am trying to incorporate into a charging station. The indicator just has + and - terminals to connect the battery. But when I try to incorporate this into a 5V charging station, the indicator displays the correct battery level until I apply the 5V charging source. Then the indicator displays the battery is full. How should I make this work as expected--always display the battery's actual level, even when charging? Thanks!
 
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Old 11-26-19, 05:51 AM
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You need electronics between the charging power source, the battery, and the meter. I am not an expert here so I do not know what that electronics has to consist of.

All battery charging involves connecting a DC source with voltage higher than what the battery is delivering so as to "push" electricity into the battery :"backwards" namely positive of the charging source to positive terminal of the battery.

The electronics should vary the charging voltage depending on the level of charge in the battery so far. The electronics is supposed to provide a voltage from separate terminals (not the battery terminals) to apply to the charge meter that depends on the amperes flowing in the charging circuit and the voltage across the battery terminals.
 
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Old 11-26-19, 06:01 AM
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Most battery level indicators work simply off the voltage. It works when only your battery is connected because the display only sees that voltage. When you plug in a charger the battery level indicator sees the voltage of the charger which is always high/full. The easiest solution is to purchase a battery level indicator. They are only $5 with everything needed ready to go.
 
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Old 11-26-19, 06:44 AM
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This is not a job for a simple voltmeter, like the display you have. It requires a state of charge computer, which knows the history of the battery (its capacity) and the power (Volts and Amps) of the charger, and a time reference. Far more complex than what you have now.
 
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Old 11-27-19, 10:43 AM
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Thanks for the responses. I figured this was not going to be as simple as it seemed. The charging module I am using has 4 LEDs on it that show the battery level while the battery is being charged, but they are tiny and have no intrinsic way to connect them to external LEDs. Guess I'll have to figure out how to do that now.
 
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Old 11-27-19, 11:17 AM
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You also haven't said what battery chemistry you are trying to monitor. Lead based batteries are easier to measure charge level based on their voltage while the lithium technologies are much more difficult because their voltage curve is almost flat through much of it's range.


Don't pay attention to the actual voltage numbers. The important thing is the curve and how it relates voltage to percentage of charge.
 
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Old 11-27-19, 01:15 PM
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Oh, sorry. This is a set of two 3.7V LiPo batteries connected in parallel.
 
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Old 11-27-19, 01:32 PM
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Get a LiPo checker. It will plug into your pack's balance lead and checks the pack's overall voltage and also allows you to look at the voltage of each cell which is very important when monitoring LiPo's. Keep in mind that you should balance charge your pack or charge each cell individually. You need to keep both cells as closely matched as possible.
 
 

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