On Mon, Jul 15, 2024 at 09:25 PM, Steve T wrote:
I have a button on my converter to force it into boost mode, which takes the voltage from around 13.6 to 14.4.? ?That increases the current going into the battery by almost 50%.? The voltage drop for 30 ft of 10 awg wire is .43 volts.? If the drop is proportional to voltage, that would mean a 25% power loss.? That's a pretty big hit.
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If the battery is still in bulk charging mode, the converter will automatically compensate for the voltage drop of the wire, unless it is really large. When the voltage at the charger reaches the preset limit, it goes into absorption mode, at constant voltage. True, at the beginning of this mode, the current is still high, so there will be slightly less voltage at the battery, However, as the battery charges, the current drops and the battery voltage approaches the charger output voltage. All this means is that absorption mode takes a bit longer, but the battery will still get fully charged. Boosting the charger voltage in this mode can overcharge the battery, which is not good. Once the charger goes into float mode, you definitely don't want to boost the voltage.
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There certainly is no harm in mounting the charger close to the battery and/or using larger wire to minimize voltage drop, which will improve charging efficiency. However, if you don't need the absolute lowest charging time or highest efficiency, it isn't necessary.
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Note that both the absorption voltage and float voltage are temperature dependent for lead acid batteries. Some chargers include a temperature sensor at the battery and automatically compensate for temperature.
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All the above applies only to lead acid batteries. Li-ion batteries require different charging conditions.
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Scott Ellington
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