Overnight Discharge in Disconnect

[caseydogmusi]

I have a FC 2017 which I have had only a few months. The relatively new (last October) Interstate batteries are discharging overnight when the disconnect switch is in the store position. Interstate tested the batteries and said they are OK. I measured parasitic drain with a DVM and only one lead (fat red one without the terminal clamps) showed any drain and it was only 20ma. I did not test the "charging" lead for drain.

The converter seems to be working though it did not go automatically into boost this morning even though the batteries were very low (like 1.7V). I manually put it in boost mode and that seemed to work. I am aware that the store switch needs to be in the use position for the batteries to charge.

The batteries were fully charged last night, I unplugged from shore power and set the store switch to store and had very dead batteries this morning.

Any ideas appreciated.

[Vantair]

Clearly at 1—- volt both seem shot (taken down far below 50% discharge. A lesser possibility the converter is not charging them fully.

At the battery’s terminal connections, separate them to test voltage each individually. If less than 10-11 volts in either you likely have a bad or gone dry wet cell. Replace them both matching models/production date.

If you can fit Newer AGM type, that’s a superior choice in life cycles and discharge abuse (thus 2.5 x more expensive) to flooded wet cell technology.

[azflycaster]

I would have the batteries checked. When you said they were fully charged when you unplugged power, did you wait an hour and then check the voltage? Batteries will always look great when the converter is running.

[caseydogmusi]

It does seem like it might be the batteries but I took them to Interstate Friday and they charged them overnight and checked them before I picked them up. They said they looked OK and they were charged to 12.5V which I checked when I got home. I suppose they could still be bad.

Another piece of information is that the converter is currently putting 13.2V on the batteries but the boost mode is supposed to be higher. I put it in boost manually, it did not go there automatically.

[caseydogmusi]

I found that the one lead I did not previously check has a large drain on it. Its the red one that looks like a car battery connector and it provides the charging voltage when on shore power. When the shore power is connected and the batteries are connected about 1.5A is going to the batteries. However, with the disconnect switch in "Store" a large current is flowing into the unit. Everything is off inside as far as I can tell.

Bad converter? Or is there some power use I am missing?

[Adventure.AS]

Do you have the inverter on? Even if you aren't running anything from the inverter plugs there is a substantial draw on the batteries.

[caseydogmusi]

Yes, I just checked and the inverter is off. There is a green led that come on when it is on and it is off. If I press it the green light comes on and I can hear the fan on the inverter running.

[Al and Missy]

Follow the red wire. If it only goes to the converter, the converter is bad. The converter should never pull current from the batteries. If it goes somewhere else, that is where your problem is. So in store mode, you had no lights or anything else using 12 volts?

Al

[caseydogmusi]

Right. Nothing on that I know about. As far as the draw, it doesn't seem to matter if it's in store or use.If the converter is on the battery receives some current, about 1.5A.

[wulfraat]

In a 2017 the converter is not wired to the batteries in an isolated manner, it is wired to the pos / neg bus bars, which are removed from the circuit when the use/store relay is set to store mode.

There are a few different potential draws in the 2017 when the use/store switch is off.

1. Inverter. The switch in the wall doesn’t actually turn it off, just puts into standby mode with lower draw. Use the switch on the front of the inverter itself to actually turn off.

2. LP detector. This bypasses the battery disconnect relay and goes direct to the battery. Always on.

3. Trailer brakes. These are wired directly but will not draw unless there is a faulty trailer disconnect switch.

4. 12v lead to power jack. Likely not the issue.