Last year I upgraded my single stage converter to a four stage unit, PowerMax PM4-55. My original converter put out a constant 13.6 volts. The new three stage converter would provide faster charging of batteries with higher voltage (14.6 volts), yet not boil the batteries when the unit switched to a maintenance mode (13.2 volts). After installing, the unit appeared to be working fine and would switch modes as advertised.
This year I noticed two problems:
- My original Magnadyne dash radio would stop working after a day on shore power. The AM/FM bands quit, but the weather band continued to work.
- The isolator solenoid that connects the chassis battery to the coach battery would drop out, and not allow the chassis battery to be charged while on shore power.
The Radio – Magnadyne M9850
In 1999, the Southwind was a high end Fleetwood coach that included a lot of state of the art features, including an “Entertainment Center”, the dash radio. The dash radio could be turned on/off remotely and was powered by the coach battery when on shore power.
While troubleshooting, I discovered as the supply voltage (coach power) dropped below about 13.1 volts, the AM/FM portion of the radio would fade away and stop working. The weather band would continue to work. I could toggle the converter power to reset it and force it into high mode (14.6 volts) and the radio would come back to life. HUM……
I removed the radio from the dash and opened it up. I didn’t see anything obvious, except a filter capacitor had swollen and was bad. Its possible this could cause some weird issues, so I replaced it (2200uf @ 16 volts).
After installing the new capacitor, I rechecked the radio, It helped, but the AM/FM would still cut out around 13.0 volts.
Chassis battery not charging while on shore power
A couple years ago I had a similar problem and discovered that the isolator solenoid was bad. That didn’t appear to be the problem this time.
The Battery Control Center (BCC) controls the solenoid and energizes it when it senses that either the chassis or the coach battery has over 13.2 volts. This should happen when the engine is running, or the coach is plugged into shore power (or generator power). The BCC de-energizes the solenoid if the voltage on both batteries drops below 13.2 volts..
THE SOLUTION
The four stage converter I installed varies the output voltage to provide different voltages and charging rates. When 110 volts is applied to the converter, it starts out in a high voltage mode, 14.7 volts. This mode lasts about 30 minutes and provides for an initial fast charge at high current. After 30 minutes, it switches into a run mode, 13.8 volts.This mode lasts about 12 hours and provides a top off charge for the batteries. After 12 hours, it switches into a maintenance mode, 13.2 volts. This keeps the batteries charged, but doesn’t boil them.
Last year I installed a shunt and monitor so I could monitor the coach batteries. What I discovered was that the voltages were about 0.1 volts low, so when the converter switched to maintenance mode, it was only putting out 13.1 instead of 13.2 volts. This voltage (13.1) was below the BCCs threshold and would cause the isolator solenoid to de-energize, The 13.1 volts was also at the threshold that would cause the AM/FM bands on the dash radio to stop working.
The solution was to make a minor adjustment to the PowerMax voltage so when it switched into the maintenance mode, the voltage would be high enough so the BCC wouldn’t disconnect the isolator solenoid, and the converter would keep both sets of batteries (coach and chassis) fully charged while on shore or generator power.
My converter is buried under the refrigerator, but fortunately, I had enough room to reach in with a small screwdriver and make the adjustment. I read the voltage on my monitor, then adjusted it up a small amount (0.1 volts) .
SUCCESS – I let the converter cycle through its modes and the next morning it was reading 13.20 – 13.28 volts in maintenance mode. The radio was still working and the isolator was still energized, YES… 🙂