Chassis Batteries won't charge

[Alpine Road Warrior]

I know this is a subject that has come up many times before. I have run out of options on what to do. I have 6-6 volt house batteries and 2- 12 volt chassis batteries and all are AGM's and less than 6 months old. I replaced the solenoid also at the time of battery swap. At first they seem to charge ok but now the chassis batteries won't charge at all unless I stick a portable charger on them. When running the engine the batteries stay charged. I have watched the lights on the Vansco in battery compartment and when the solenoid snaps #19 comes on for about a half second then goes out. Could there be anything else wrong besides the solenoid? The solenoid is only a couple months old. It is the Trombetta Fatboy. My next option will be to replace the solenoid again unless someone comes up with something else to check.

[EngineerMike]

ARW- are you plugged into shore power when this happens?

I get the same thing when the coach is setting unplugged & house batt's are down a ways. I think the solar panel is giving enough charge volts to light #19 but not enough amps to keep voltage up once chassis discharged batt's are connected and drawing big time. This pulls volts down, shuts #19 off, up comes volts again, #19 on then volts down, repeat. This can burn the contacts on the solenoid over time, adding resistance and exacerbating the problem. I don't have the same problem when plugged in.

Nick Escamilla has an idea on adding two relays to the #19 circuit so it cuts the solar volts out of the loop. The circuit would interrupt the #19 positive wire w/the relays in parallel so either alternator charge or Xantrex charge signal would close a relay and complete the #19 signal to connect house & chassis for charging. Solar volts would still light #19 but no relay would be closed so the Trombetta would not connect. I haven't looked for a location to take Xantrex charge signal to do this myself. Maybe Nick is listening?

[dgerstel]

If 19 is lighting, then going out and not flashing, then it sounds like the solenoid is probably OK. The 19 light should be staying on if either bank of batteries are being charged. What is your power source when the light comes on then goes off?

[Alpine Road Warrior]

I am hooked up to shore power and using the inverter to charge batteries and the coach is inside a building. Another question would a bad battery cause this? I just noticed it looks like something has leaked from one of the batteries by the neg. post. The batteries were down to 4.2 volts so I disconnected the batteries and trying to charge batteries separately. I watch the charger and it slowly moved up in volts with a 30 amp charge. I watched it for about 30 minutes and it only got up to 11.2 volts. So I left it on and will go back and check in a few hours.

[jerry davis]

I installed an echo charger which seemed to solve all my solenoid and assorted problems.

[EngineerMike]

ARW- sounds like the heavy draw of the offending battery is drawing the charge volts down substantially so it drops below the threshold to keep #19 lit & the Trombetta connected. Once disconnected, volts go back up, 19 lites & batteries connect, volts go back down...
Time for a new battery.

[Alpine Road Warrior]

I disconnected the batteries and charged separately with portable charger and sure enough I have a bad battery. It won't take a charge. Thanks for all the help guys.

[Nick Escamilla]

E Mike, I did add the circuit that you described to prevent the solenoid from working itself to death.

I install 2 relays, a 12 Volt DC relay and a 120 Volt AC relay inside the battery compartment.

1. 12 VDC relay coil hooked up to a output wire from Xantrax marked Ignition. Relay energized when Ignition Key Switch is ON. The other side of the coil to ground.
2. 120 VAC coil hooked up to a non-inverted source. I used the Washer/Dryer plug. (2 wires, 16 gauge lamp cord)
3. Wire both relay contacts to normally open, in parallel.
4. Remove hot wire (#19) from the solenoid and connect to relay contacts.
5. Add jumper from other relay contacts to the solenoid.

Solenoid can now energize only if either relay is energized.

12 VDC RELAY - Energized with ignition switch ON. This will charge batteries while engine is running. It will also allow the Boost Switch to operate as intended.

120 VAC RELAY - Energized only on shore power or generator power; allowing batteries to charge.

Like E Mike said, this solenoid cycling condition only happens with solar panels. Solar panels will still operate as designed and are not be effected by this change.