DC Voltage Readout or Bad Voltage

[sealevel_ram]

I have an 04 Winnebago Ultimate Freedom Diesel pusher.

When I look at the voltage readout on the inside wall, it starts out at 11+ volts. I turn on some lights and the reading rapidly drops, and soon the fridge is flashing "LOW DC".

It happens with the unit plugged in (30 AMPS), or not, or running on generator. Don't know about 50 Amps.

Doesn't happen with the engine running.

My battery bank is new and good. Took them all out and tested them.
In the last year or so I have replace the inverter/charger and the transfer switch and the EMS board.

Don't know if it is related, but the EMS readout is not correct for 30 AMPS. Couldn't believe it is part of the problem, since the EMS is for AC only, I think.

Please help if you know about this problem.
Thanks.

[sealevel_ram]

Problem Solved.......

Cleaned up connections thoroughly to and from batteries and between batteries and inverter/charger.

Got good voltage.

Important lesson I should have already learned.

Thanks to all who replied.

[time2roll]

Yes you need to walk your voltmeter from the battery terminal to the panel checking each connection. At some point you will find a drop in voltage. Fix that connection.

[sealevel_ram]

Here is a summary so far:

Voltage on panel readout and battery voltage do NOT agree. Battery stays full voltage. So problem is downstream of batteries?

With disconnect switch off (disconnected), panel reads 0. Disconnect solenoid works. Problem is between disconnect solenoid and panel, which could be anywhere in the 12 Volt system? Comments?

Ran out of time. Will make more checks tomorrow.

Thanks for all the replies so far.

[DrewE]

sealevel ram wrote:

DrewE wrote:
One possible place to start checking--not the only possible culprit, of course--is the shutoff latching relay for the "salesman switch".



One way to verify is to see if the voltage at the battery, measured with a trustworthy multimeter, goes down along with the displayed voltages in the RV. If the display goes down but the battery stays pretty much level, the problem has to be between the two somewhere.

Is this the House ON/OFF switch by the entrance door?
Display goes down, battery voltage stays up.

Sorry, I jumped around a bit and wasn't clear. The control switch by the door is for the disconnect and is what I was talking about--or rather, the thing that the switch connects to that does the actual switching.

With the disconnect disconnected/turned off, the house voltage should be zero (if no AC power is present or the converter/charger is connected to the battery and not the house side of things) or the converter/charger output voltage (if it's connected on the house side) and the battery voltage something else.

With it connected/turned on, the voltage at the battery should agree with the voltage shown inside. If it does not agree, there is a bad or broken connection somewhere, which might be at the actual solenoid switch that the button by the door controls but might be elsewhere. If they agree and are both low, then the battery is not being charged properly and/or is bad, as others have suggested. Basically, the idea is to measure the voltage drop between the battery terminals and the interior voltmeter indirectly by comparing the two voltages.

[BFL13]

You are not measuring "battery voltage staying up" You already said when not plugged in you still see 11 volts on the "inside display"

With no 120 from being plugged in, the inverter- charger cannot make any DC, so all you have left is battery for DC--that s your 11 volts (batteries near dead!) Your alternator charging is working though.

You need a multi-meter to check voltage in different places. Battery posts (the real battery voltage) and at the DC terminals of the inverter/charger.

Some inverter -chargers need to have the charger "enabled" while others seem to enable themselves automatically. If you have 120v in the rig and no voltage at the charger terminals, it is not "enabled"

[sealevel_ram]

DrewE wrote:
One possible place to start checking--not the only possible culprit, of course--is the shutoff latching relay for the "salesman switch".



One way to verify is to see if the voltage at the battery, measured with a trustworthy multimeter, goes down along with the displayed voltages in the RV. If the display goes down but the battery stays pretty much level, the problem has to be between the two somewhere.

Is this the House ON/OFF switch by the entrance door?

Display voltage goes down, the battery voltage stays up. In other words, when the display shows low voltage, the batteries are still 12+.

[DrewE]

Maybe there's a poor, high-resistance connection between the battery (and converter/charger) and the rest of the DC system. One possible place to start checking--not the only possible culprit, of course--is the shutoff latching relay for the "salesman switch". Ground and battery cable connections, etc. should also be inspected and cleaned/repaired as needed.

One way to verify is to see if the voltage at the battery, measured with a trustworthy multimeter, goes down along with the displayed voltages in the RV. If the display goes down but the battery stays pretty much level, the problem has to be between the two somewhere.

[time2roll]

Need to verify the inverter/charger has 120vac on the input and about 13.6vdc on the output terminals to verify function. Post the equipment model numbers for best answers.

BTW 11 volts is overly discharged and the batteries are desperate. If you have or can borrow a 10+ amp portable charger it would really help the batteries while you figure this out.