Help me figure out my house battery system...

[HoboJen]

Hey guys,

So as you might have seen I recently purchased a new to me van! It's a ford cargo that already has an auxiliary battery system set up, and I have a few questions about it. I've already looked through some related threads here and it's been helpful... but I still have some questions.

I drained my starter a few days ago so I want to understand how all of this works so I don't strand myself. It sat for a couple of days and I used some house power, but I thought the solenoid isolated the starter battery? I jumped from another car, but I am reading that you can jump from the house (but also hearing it's not so good?).

I have a Die Hard Platinum house battery(31M) and tripp-lite 1250W inverter (with a plug for shore power). It has a solenoid but I'm not sure what kind it is - looks like an 80A, a silver one without any markings on it that i can see. how do I know if it's still working properly?

My system is hooked up like this (sorry no diagram):
-house battery connects to inverter.
-house battery connects to solenoid - connects two wires going to front - starter and "on"? (i don't know what that means in the diagrams i've been looking at)
-house battery connects to a switch - connects to LED lights, roof vent, sink pump
-house battery connects to a fuse panel - connects to LED lights, roof vent, sink pump

What is the switch for? Is that just to turn off everything at once? does it prevent the house battery from charging? I don't think it's that kind of switch is it?

My big questions are these: how do I know if the solenoid is working? Is there a way to know if the house battery is charged or working? I just don't want to drain the starter when i'm out camping without another vehicle.

One final much less important question... how difficult is it to hook up the radio into this system? there is a spot for one more fuse and I think it would be easy to hook it up the same as the lights, vent, and sink. Except how do I hook it up to the radio itself? I just installed it so I'm familiar with the wiring behind it (just the simple part of connecting it to the wiring harness).

Thanks everyone

 

[maelgwn]

The way I would check would be with a multi meter. I would set to it to measure voltage.

1st with the engine off measure the voltage of the two wires from the front at the solenoid. One (the fatter cable) should measure between 12 and 13 V and the other (the thinner one) should measure 0V.

2nd start the engine - the thinner cable should now measure 12V or so. The voltage of the house battery should be very similar the starting battery now (say 13.5V). If this is all ok then the solenoid seems to be switching on ok with the ignition.

3rd turn the engine off again and measure the resistance across the solenoid between the cable from the house battery and the fat cable from the front. If this is 0 then your solenoid has failed - it is effectively stuck on (closed).

Don't worry about jump starting from the house battery - easiest way is to use your jumper cables from the house to the starter batteries otherwise your would need to upgrade your solenoid and fuses to a higher current capacity.

Lastly - someone else would have a better answer about the radio. You would need to change the power supply to the radio to a new wire from the fuse box from house battery. But I think you also need to alter the "ignition" wire to the radio so that you can switch it on with the engine off.

Hope that all made sense!

 

[HoboJen]

Thanks! Most of that makes sense... this part below sounds a little confusing but I think it will make more sense when i have a multimeter in hand. I'm going to pick one up tomorrow.

3rd turn the engine off again and measure the resistance across the solenoid between the cable from the house battery and the fat cable from the front. If this is 0 then your solenoid has failed - it is effectively stuck on (closed).

 

[DiploStrat]

Shooting the Trouble

First thing you need to know: How did you drain the starter battery? If you killed the starter battery, but not the house battery, then the problem may have nothing to do with the house side. The usual case would be putting so big a load on the house battery that BOTH batteries were drained. If your house battery still held a charge while the starter battery was dead, I would worry about parasitic loads on the starter side. Something in the camper wired back to the starter battery? A starter battery at the end of its life? Etc.

It is REALLY hard to diagnose at a distance, but here are some thoughts on how to trouble shoot the house side.

-- The good news is that none of this is hard (it is just a bunch of circuits) but it can be complex -lots of switches, fuses, etc.

-- I tend to be really skeptical of old dual battery systems, so I would start by disconnecting EVERYTHING and then reconnecting step by step, assuring yourself that each part works as planned.

So, ignoring for the moment everything connected with your starter battery (but only for the moment, if this vehicle is old but new-to-you, then the death of the starter battery may have nothing to do with the camper/house battery at all), start by tracing the heavy, load wire from the starter battery to the house battery via the solenoid (aka, relay). Also trace the control wire(s) for the solenoid to be sure that you know what energizes the solenoid - ignition key, toggle switch, other?

Generally,

-- There is a larger wire running from the positive terminal of the starter battery to the solenoid and then to the positive terminal of the house battery. This carries the load.

-- There is a smaller wire running from a fuse block or somewhere else under the hood to a terminal on the solenoid. Usually, this comes from some source that is only live when the engine is running (as opposed to off or starting). There may be a second wire that runs from the solenoid to ground. N.B. There are a few variations of this that work by switching the ground or negative leg of the solenoid, but this is less common.

Now you test or reconnect everything. This thread shows almost all of the variations on a key controlled circuit and has great diagrams.
http://www.expeditionportal.com/for...ke-a-cheap-isolated-dual-battery-setup-for-50

If this is confusing, then you will probably need professional help. I tend to prefer electrical shops that cater to ambulances and other such vehicles over the usual RV shops, mostly because so many RV's are poorly wired.

Good luck!

 

[DiploStrat]

My system is hooked up like this (sorry no diagram):

-house battery connects to inverter.
-house battery connects to solenoid - connects two wires going to front - starter and "on"? (i don't know what that means in the diagrams i've been looking at)
-house battery connects to a switch - connects to LED lights, roof vent, sink pump
-house battery connects to a fuse panel - connects to LED lights, roof vent, sink pump

What is the switch for? Is that just to turn off everything at once? does it prevent the house battery from charging? I don't think it's that kind of switch is it?

To your specific questions:

-- House battery to inverter - Normal. From the inverter I would expect that it runs on to some form of fuse box for your 110v AC loads.

-- House battery to solenoid - I would guess that the wire running to the "starter" runs to the positive terminal of the starter battery. If it actually runs to the starter motor, then it is a bit odd. The wire marked "on" probably runs to a fuse block somewhere, to a terminal that is live when the ignition key is in the "on" or "run" position, as opposed to "off", "start", or "accessory" positions. As noted, this is normally what you want to do.

-- House battery connects to a switch - This sounds like a master house battery load kill switch. (Especially if it has a funky red toggle on it.) Very common in RV wiring, used to assure that there are no parasitic loads on the camper batteries. Turn it "off" and everything should be dead on the camper side.

-- House battery connects to a fuse panel - This would normally be downstream of the kill switch. If not, then I don't know how the wired things.

Again, with an old beast, you are better off redoing all of the wiring to be sure that you know exactly what is going on. This also allows you to clean things up, check that you have good grounds, and upgrade the wires where needed.

 

[mtnbike28]

I just installed it so I'm familiar with the wiring behind it (just the simple part of connecting it to the wiring harness).

Thanks everyone

I am not good with electronic stuff BUT I read a lot about aftermarket radio installs and killing the starting battery - I would look at this install closely, I wonder if your house battery set-up is fine and when you did this install something is draining your starting battery!

hth

 

[HoboJen]

Thanks guys.

I have no idea how i drained the starter. the only thing i used in the van were lights, vent, and minimal sink pump, just while i was out there working and it also sat for a few days without being started. i did not have on the front lights, radio, or anything in the 12v factory plug-ins. the house battery never seemed dead or near dead. i noticed the starter was dead when i came back the next morning and was going kayaking. i just did a jump without testing too much since I needed to be there by a certain time. this was also before i did the radio. also, the radio had already been upgraded from factory. but it worked 10% of the time and didn't have aux, so I updated it and it was an easy install since it had already been done. but you could be onto something here with the radio causing an issue.

this whole system is fairly new, only a year or two old. and IIRC, the starter battery is stamped 12/13, so I don't think it's that.

So, ignoring for the moment everything connected with your starter battery (but only for the moment, if this vehicle is old but new-to-you, then the death of the starter battery may have nothing to do with the camper/house battery at all), start by tracing the heavy, load wire from the starter battery to the house battery via the solenoid (aka, relay). Also trace the control wire(s) for the solenoid to be sure that you know what energizes the solenoid - ignition key, toggle switch, other?

yeah i have only noticed that the big wire and small wire go to the front of the vehicle, but i have no idea what the control wire connects to. I'll try to figure that out today as well.

i kind of also want to go watch a movie out there, just to see if i can kill the house and see if the starter also dies. maybe the starter dying was just a fluke... though i'm leaning to some kind of parasitic load... OR the solenoid being burnt out. hopefully not faulty wiring (my bulleted list is how the wiring is actually done.. a diagram would be much easier to follow though)...

and yeah, that's the thread i've been reading!

 

[DiploStrat]

OR the solenoid being burnt out.

Remember these "rules." You have described only one charge source, the engine alternator.

-- If the engine alternator is your only charge source, then a key controlled relay is your best option. (If you have alternate charge sources, like solar or shore power attached to your house battery, then, for reasons that I have posted ad infinitum [ad nauseam?], some form of automatic relay is much better.)

-- If you have only one charge source, connected to the starter battery, then the most common failures are A) dead house battery because of too much load and too little charge, or B) both batteries dead because the relay isn't opening and is thus allowing the house load to draw down the starter battery.

-- A dead starter battery and a charged house battery would indicate that your relay is successfully isolating the two batteries when one is being discharged. (You didn't specify how charged the house battery was, only that it had enough charge to start the truck.)

All of this leads me to believe that you have a problem with the starter battery circuit.

-- If the house battery is getting a charge, then that means that the alternator, etc., is working.

-- If the alternator is charging and the starter battery is dying, then you have some (big) load that you don't know about or a bad battery.

Best I can do from a distance, but it does not sound like the solenoid is the problem.

 

[Joe917]

You probably should load test the starter battery, just because its new does not mean its good. A weak battery and a small draw could be all it is.

 

[HoboJen]

there are two charge sources, one is the alternator and the other is shore power - the inverter has a plug. I have not yet used the shore power, only the alternator.

is there a way to tell how charged the batteries are? i'm not sure how charged the house battery was... and I jumped from my other car, not the house.... and if the relay/solenoid isn't working, could the house stuff be on but really running through the starter?

thanks again for helping me with remedial van electronics... hah. I'm determined to understand this. Then I want to add solar... after a few trips, of course... and after i can learn about what i already have.

so today's homework:
- emissions retest and change of ownership
- drain the house battery by watching a movie or something, and see if the starter is also drained.
- figure out what the wires going to the front are actually connected to... better understanding of starter battery circuit.
- buy a multimeter to do some tests from the first reply

i still have a question about that switch... is that only to kill house power? or does that make an incomplete circuit so that the house battery doesn't charge either? the switch is connected to a wire coming out of the battery. the switch goes to a connector which then splits to the lights, pump, fan.

 

[HoboJen]

Thanks Joe... Looks like a load tester is also not too expensive a tool. nor is the multimeter. and maybe i can borrow them from someone.

 

[dwh]

there are two charge sources, one is the alternator and the other is shore power - the inverter has a plug. I have not yet used the shore power, only the alternator.

Are you sure the inverter is an inverter/charger? Could be that the inverter has a shore power connection to feed the 120v receptacles when there is shore power - but it might not be a battery charger as well. You should verify that.

is there a way to tell how charged the batteries are?

Disconnect them, let them sit a couple hours to stabilize, then check the voltage. A fully charged "12v nominal" battery should have a "resting voltage" of between 12.7v - 12.8v. 10.5v is considered a "dead" battery, but a lot of times, stuff like lights will still be working even below that - dim, but working.

Here's a pic from Google:

i'm not sure how charged the house battery was... and I jumped from my other car, not the house.... and if the relay/solenoid isn't working, could the house stuff be on but really running through the starter?

The solenoid (relay) is dead simple. There are two basic types - one has 3 terminals (2 large, 1 small) and the other has 4 terminals (2 large, 2 small). The small terminals are to power the thing. If it has one small terminal it would get 12v hot (usually ignition switched) and will ground through the case/mounting strap. If it haas two small terminals it would get 12v hot to one terminal, and ground to the other (doesn't matter which is which).

When 12v power is applied to the small terminals, it activates an electromagnet which pulls contacts together to tie the two big terminals together.

To check it, disconnect both batteries, then figure out which of the small terminals is ground, and apply 12v power to the other one. Then see if there is continuity between the big terminals. Then disconnect the 12v power to the small terminal and see if there is NO continuity between the big terminals. If that's what you get, then it's working. You should hear it click when you apply and remove power to the small terminal and the solenoid moves.

i still have a question about that switch... is that only to kill house power? or does that make an incomplete circuit so that the house battery doesn't charge either? the switch is connected to a wire coming out of the battery. the switch goes to a connector which then splits to the lights, pump, fan.

Yea, dunno. Not really descriptive enough. My truck does have a switch between the house battery and the house fuse block, which kills ALL loads from the house battery.

Yours sounds like something else. You've described an aux fuse block, but also just said the wire from the switch splits and goes to all sorts of things. Track it down and come up with an accurate description of exactly what it runs to.

 

[dwh]

Someone gave me a 5 dollar multi-meter from Harbor Freight. It worked fine, except that the + and - were wired backwards. If I want a cheapo, I usually get 'em from Radio Shack. Decent quality for the money.

 

[HoboJen]

thanks again guys.

i will look into the inverter... the plug may just power the 120V outlets.. I am not sure if it is also a charger.

The solenoid has three terminals.

The starter battery was very weak today but did still start. I passed my emissions retest and picked up a multimeter at radio shack. So next up is figuring out how to use it and taking the measurements you described. I'm also going to dig into the wiring and make a better diagram which i can take a picture of and post (don't have visio). i had the switch off while i was driving around (didn't think about it), so we'll see. starter battery was strong the other times i started it after driving around.

 

[dwh]

I have Visio around here somewhere. I don't use it for quickie wiring diagrams. I normally use either MS Paint or Paint.NET (an excellent freebie Photoshop clone).

With 3 terminals, the small one is for power to the solenoid and the ground is though the strap.

If you have the batteries disconnected (just the positives is good enough, leave the grounds hooked up), you'll need to rig a test wire to go from the battery + to the small terminal on the solenoid.

Is your meter digital? If so, it will have a continuity setting which will beep when you touch the two probes together. That's how you'll test the big terminals on the solenoid. It should have continuity between the big terminals when you apply power to the small terminal, and no continuity between the big terminals when you don't apply power to the small terminal.