Inverter Drains Van Battery

[tnmarm]

Alright! So I went tracing and found something "odd". The house battery is behind the inverter. What i mean is that the house battery connects to the inverter, and the 12V power is connected into the inverter as well (at the positive and negative terminals).

So House Battery -> Inverter Terminals -> Junction Thing -> One wire to Sportsmobile Relays and House Power, Another to Battery Isolator

Still confused? Here is a rough diagram.
Note on the inverter, i have the red and black coming in and out at different points but really it comes in and out at the terminals.

(Thick black is conduit)



From the Sportsmobile book, it seems the Inverter actually should be directly connected to the house battery, but that all the house power stuff is ALSO connected to the house battery. Rather than everything connected to the Inverter.

Whats weird is why the isolator stops house items from draining its battery (fridge, lights) but didnt stop the inverter?

Thoughts or ideas?

[tnmarm]

Also. In the process I found that I dont have a second van battery. There is a sticker under the hood that says there is an additional battery under the frame.

However, there is no battery there on mine. The platform is gone and the connections are just covered and not connected to anything. Is that normal?

[Scalf77]

What engine does your van have? Diesels typically had two, gas had an option for a second battery

Does the inverter have a fuse, typically they require or recommend a Class T Fuse between inverter and house battery. This is where they normally distribute a wire to another circuit, sound like they just went off of the terminals on inverter. Nothing inherently wrong with that other than some possible fusing issues.

I suspect that your always consuming power from your start battery, even with just the 12 volt items. You never really stated the duration of time for this event. So maybe with the inverter enabled you increase the current a little more so that it is actually noticeable. Or that you need a slightly higher current to short out isolator. To validate I would remove house battery from the isolator. And run the same test again.

If it does not drain the starter than the isolator has probably gone bad, it would be worth checking all the connections, making sure they are clean, and the case is grounded.


happy hunting.

-greg

[tnmarm]

7.3L Diesel. And the van seems to show diagrams for two, but the second one isnt there.
This is the van btw: http://www.sportsmobileforum.com/for...ile-23506.html

The inverter did not have a fuse between it and the battery. There is a fuse between the inverter and "Sportsmobile Stuff" in the diagram. Its a big fuse, couldnt get the cover off to fully read what it was rated, but it said fuse for sure.

The duration last week during my testing was Monday to Friday. I left the fridge running the whole time. I noticed in the Solar panel control panel the house battery would be down a bit in the morning, and then come back up by the evening.

The inverter was turned on Wednesday till Friday. The control panel was on the whole time, and the inverter was only on, not set to invert or charge. Nothing ever stopped working (inverter, panel, fridge, lights) but the van wouldnt start on Friday. A quick jump from another car got it going.

We camped in it last weekend as well, ran the fridge the whole time and ran all the lights for several hours on Saturday. Van started just fine when we left on Sunday.

The house battery does appear to charge with the van running (solar panel controller with battery status goes to full quicker than solar alone).

Ill test removing the house battery at the isolator. Wouldnt the starter battery draining be a sign the isolator was bad? (your post says opposite)

But what makes you think the 12V system is always pulling from the starter? From the diagram i made, it seems to match the diagram in my Sportsmobile book aside from the inverter being in the wrong place. But again, seems the isolator would have stopped all that.

[Scalf77]

Originally Posted by tnmarm

Wouldnt the starter battery draining be a sign the isolator was bad? (your post says opposite)

But what makes you think the 12V system is always pulling from the starter? From the diagram i made, it seems to match the diagram in my Sportsmobile book aside from the inverter being in the wrong place. But again, seems the isolator would have stopped all that.

Yes, it is a sign that the isolator is bad, if my post said otherwise I apologize. It could be possible that one of the diodes in the isolator is bad, the one that would normally block current flow from house to starter. The alternator could still charge the house.

I don't own a 7.3 but my assumption would be that it should have two batteries. This could also be adding to your problem.

-greg

[tnmarm]

I have emailed the previous owner (im the third owner) to see if they know anything about the missing second battery.

Also hopefully some 7.3L owners are lurking around and can chime in.

[tnmarm]

So I went and did a quick test.
Turned Inverter ON. Set to Inverting ON. Turned AC Breakers ON.

I watched the Solar Controller (battery showed fully charged), and when I did the above, the battery level dropped a little (solar showed charging starting) and voltage went up. Which leads me to believe that the Inverter actually started pulling from the house battery as it started showing load on the house battery.

Which leads me to think your comment about the isolator being bad might be true. Which means Im probably pulling from the starter battery at all times. Will still test the isolator. Also went through your stickie on isolators. I have the blue Surepower block. Its probably the original from SMB which means its 16 years old lol.

[86Scotty]

Get rid of it. They are trouble. Try a Blue Sea or anything but that blue Sure Power. They all go bad.

[shadetreevanman]

Originally Posted by tnmarm

So I went and did a quick test.
Turned Inverter ON. Set to Inverting ON. Turned AC Breakers ON.

During this quick test did you meter the effect of the inverter status on the start battery? Reading your post I see you metered the house battery, but no mention of the start battery voltage during your test. Your assumption the inverter had anything to do with the start battery not starting the van on ONE occasion is flawed without testing. In your case, so far, I haven't read conclusive proof the isolator is bad. Not saying the isolator shouldn't be upgraded to a Blue Seas unit, just that it may not be the culprit this time.

I've never owned a 7.3 diesel van, but the two I've been around both have dual start batteries. Listening to my buddies try and start their vans on cold days, I don't think they would have been successful running a single battery. And I would be inclined to add the second battery for future peace of mind.

I always equate diagnosing automotive and/or electrical issues to being a detective. In that state of mind I try to isolate and observe. As Sherlock Holmes famously said, "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth".

Facts as we know them;
Starter Battery did not start van on one occasion

Causes?
1) Isolator could be allowing Starter Battery drain from invertor usage. Easily proven with a meter on start battery as you turn inverter on/off with ignition off.

2) Some other battery drain on Starter Battery from devices normally wired to it, such as leaving on interior lights (non LED) or the radio for lengthy period. Or some other undiscovered drain.

3) Starter Battery is failing to hold charge.

4) 2nd Battery required because it's a Diesel.

5) All of the above

Keep testing and evaluating. Good luck. Regardless of the resolution, you are learning more about your van through this.

[Dbark]

Mine is doing this too. My house battery is dead. So confused by this system. I just posted this near same question on Facebook.