All RV converter chargers fail at charging your batteries correctly

Even high end RV’s come with inadequate converter chargers that can not charge your battery to 100%.

ATC RV Converter ChargerThe most common reason for short battery life is not charging the battery to 100%. The second most common is overcharging the battery. Converter chargers (what comes with most RV’s) do not have the ability to change voltages or provide temperature compensation to the charging voltage. There needs to be a way to adjust the Absorption and Float voltages independently for your battery’s requirements and adjust for wire size. Many RVs come with a thin gauge wire between the charger and the battery. This will give you voltage loss that needs to be accounted for. I have found where the charger is putting out 13.8 volts and the battery was only getting 13.3 volts at 18 amps with factory 8 gauge wiring. There are many converters that only put out 13.6 volts! All deep cycle battery manufactures require 14.2-14.8 volts to charge a battery.

 

Lifeline Charging Voltage at Different Temperatures for a 12 Volt Battery*

Temp °F Absorption Voltage Float Voltage Temp °F Absorption Voltage Float Voltage
-40 16.88 15.86 70 14.41 13.39
-30 16.58 15.56 77 14.30 13.30
-20 16.30 15.28 80 14.27 13.25
-10 16.03 15.01 90 14.15 13.13
0 15.78 14.76 100 14.04 13.02
10 15.54 14.52 110 13.95 13.00
20 15.31 14.29 120 13.87 13.00
30 15.10 14.08 130 13.81 13.00
40 14.90 13.88 140 13.76 13.00
50 14.72 13.70 150 13.73 13.00
60 14.56 13.54 160 13.71 13.00

 

To correctly charge any deep cycle battery there needs to be some form of temperature compensation. I am sure you can imagine the temperature swing on an average day in the sun when a battery is in the black box of death (on the tongue of your trailer). You can see from Lifeline’s chart above, the only way to fully charge their battery at 30 degrees F is with 15.1 volts. This same voltage setting will give an extra 1.05 volts at 90 degrees F and dramatically shorten the lifespan of the battery.

Most RV converter chargers combine 3 stage battery charging into a dual stage hybrid process. This will lead to shorter life expectancy.

Next read “The four stages of RV battery charging

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