Thor Forums

[FW28z]

I think you actually mean a converter not an inverter. An inverter's input is 12VDC and supplies 120VAC when not on shorepower, while a converter is simply a DC power supply that provides 12VDC from 120VAC and intrinsically includes a battery charger.

While this might seem a matter of semantics, some RVs have both an inverter and converter, so it can be confusing in the discussion if meaning the other.

Most of the modern converters these days are capable of multiple stage charging (including a trickle charging "float mode") a battery.

In normal operation, you should always run both the converter and battery when on shorepower. When the converter is connected to the battery and you use 12VDC, energy is being supplied by both the converter and battery. Lead acid batteries charge by a voltage, and the converter voltage will always be slightly higher than a battery's voltage.

Converters may not be capable of supplying all of the 12VDC power needs for the RV. Thor normally installs (made in China) WFCO converters. The last two digits of the converter is usually the DC rating. My WFCO is a 8955 (89 series - 55Amps DC output).

For example (if you have not changed over to LED interior lighting), each lamp consumes 2A, and if you turn on half or all of them, you could easily draw a 30A load (@12VDC); the water pump may use 20A when running, and so on. If the converter cannot supply this load, the battery supplies it.

In actual operation, keeping the battery connected means the battery supplies the energy needed by the house, and the converter/charger keeps the battery charged.

The WFCO converters are three stage; Absorption (normal operation supplying 13.6VDC), which is active whenever you have a load on the system. The other two modes are Bulk and Float. Bulk mode is essentially a "fast charger" (14.4VDC for 4 hours max), while Float mode is the trickle charge mode (13.2VDC) when there is no load on the system.

So essentially, the converter supplies 13.6VDC when it and the battery are supplying power to the system. But then, if you turn all of the 12V loads off, the converter goes to 14.4VDC "fast charge" for 4 hours (or less, depending on the state of charge on the battery), and then switches to "trickle" charge (13.2VDC) indefinitely.

A fully charged lead acid battery supplies 12.6VDC (12.8VDC for AGM), and since the converter always supplies a higher voltage, the battery will always be under some state of charge by the converter (the higher the voltage difference, the faster the charge rate).

It's always possible you have a bad converter/charger. I still have the two original house batteries (also Harris) in my 2011 coach and they are still working OK.

Some people have replaced the converter section of the WFCO 8955 with the Progressive Dynamics 4655 (made in USA) as the charger is a 4 stage (equalization charge), and is a more robust charger. That is always an option as well.