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Educate a Noob: How do the batteries work?


notbadbutgood

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Hey Friends, 

My last topic was looking for an original owner's manual to hopefully answer this question myself. However, I was informed that owner's manuals were more or less expanded brochures, and not of much use. (By the way, I have a '78 Dolphin Micro Mini.)

This question is sort of related to the truck, but it's mostly related to the coach...I'm wondering how the batteries work? Or specifically, how the power works. 

I have a regular car battery, and a deep cycle battery. At least that's how I understand it. The gentleman who sold me the camper said that the main battery is dead (it totally is), and that the car itself is running off of the deep cycle battery (which, will likely also need replaced). 

So...how does all this work? I imagine both batteries must be charged by the alternator, but like, which battery powers what, currently? And did these campers come with a generator, originally? I can't find one, so I'm guessing no.

How does shore power factor into this? Those wires are janky, and I'll likely have to replace it, but like, on the campers little grid, where does everything fit in? 

A primer would be nice, if someone would like to take the time to educate a noob. Or, if you prefer to point me toward a resource where this information would be found. I've looked through here and found lots of awesome resources about troubleshooting, repair, and enhancement/addition...but nothing that really gives me a primer on how the system worked out of the factory. 

Thanks in advance! 

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Wish I could draw on this computer the wiring is a simple diagram, but lots of words. First thing you need a voltmeter.

You have 5 parts in an RV 12v system The engine alternator, the isolator, truck battery, house battery and the 12v power distribution system.

The alternator is the power source 14v+ with the engine running

The isolator charges both batteries when the engine is running. When the engine is off the isolator separates the batteries so you don't drain the truck battery down.when you party all night.

Truck battery , just what it says

House battery this is what powers all the 12v stuff in the RV

The power panel takes one 12v lead and divides it up and feeds it through fuses to power stuff in the RV. The fuses protect things. There should be/may be two 12v auto reset circuit breakers. One between the isolator and house battery. One between the 12v house battery and the power panel.

Second thing you need a voltmeter

 

 

Edited by WME
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Both of these things are SUPER helpful. (Especially yours, @WME!)

Point taken, @Derek up North :P

I guess I should have been more specific, that I'm looking for someone with specific knowledge of 70's Micro Minis, in the absence of an owner's manual; it seems like maybe your '86 is probably similar to mine, @WME?

Anyway, in retrospect, I probably should have dug a little deeper in Google before asking the community. My bad. I'll be looking for the isolator tomorrow. I do know that even though the truck battery is disconnected, the house battery will start the truck, so it appears that when the ignition is turned, it'll pull from either battery to start?

At any rate, I'm going to do a bunch of studying about electrical before doing any rewiring or mods. 

Thanks, guys! (And if anyone here has a 70's Micro Mini and would like to further this discussion, let's do it!)

Edited by notbadbutgood
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There's not going to be too much difference in the house wiring. Alternator goes to isolator and isolator has separate wires that go to truck battery and house battery. House battery is connected to the power center. Power center is also connected to the plug to hook up to shore power. Find your power center and see if there are any markings on it. maybe show us a pic and we could give you some more detail on it. Possible the previous owner jumped the isolator because he knew the truck battery was bad. Wouldn't hurt to show us how the batteries are hooked up too.

Sunrader wiring diagram is pretty simple and same one used since at least the very early 80's, maybe before that. Ignore all the holding tank stuff for now.

http://toyotamotorhome.org/forums/index.php?/gallery/image/996-sunrader-wiring-diagram/

Linda S

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The 70's micros had pretty basic wiring. You will have two systems, 12 volt and 120 volt. It helps if you educate yourself on how each of these systems work.

Most older rigs have a fuse panel for 12V located somewhere in the coach. Much like the fuse panel under the dash, it takes power from the coach battery and "distributes" it to the 12 volt systems. The 120 volt system is similar to the one you have in your house.

These are two separate systems. You need a basic understanding on how each system works. It's impossible for members here to walk you through your particular rig. Over the years owners make changes to each system to suit their individual needs. A factory wiring diagram probably wouldn't be much help.

In addition to the voltmeter you should also have a continuity tester to identify different wire runs. Once you know what wires go where you can start to reassemble your rig.

It's a time consuming project. Good luck.

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If you're able to start with only a 'house' battery installed, it sounds like someone has done some creative wiring. Isolator eliminated or ''jumped'? There was no real revolution in the wiring of these. '70s, '80s or '90s.

I'll just add to what Linda said. Instead of the 12v going from the isolator to the coach battery, you might find it going to the power center 1st, then to the house battery. Whichever allowed the builder to use the shortest cable runs. Both will work.

Make a note that it seems to be universal in the motorhome world that 'Black is positive, White is negative.'.

 

 

93 Dolphin - Converter and Monitor Wiring 2.jpg

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Another tip. So often there are posts by people who disconnect the multiple wires from the house battery without labeling which one goes to which terminal. It then becomes a big guessing game, especially if there's DPO wiring involved! :)

EDIT:  Some early models have both cab and house batteries installed under the hood. Where's your house battery? Post a couple of pictures under the hood. We should be able to spot the isolator pretty easily for you, IF there's one still there. One installed and wired as original, shouldn't let you start the engine with no cab battery installed.

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You can't rely on "standard colors" there are none. I kind of remember older converter/chargers having a switch not an automatic system of drawing power from the coach battery and plug in. It's possible to start the truck with the house battery but highly unlikely unless it is under the hood and there is a mix up as to the one actually doing the deed. If it's in the coach there is not a large enough wire to handle the load of starting an engine. Think of the isolator as an electric switch instead of throwing a switch it is done electrically with an isolator. The ideal is to disconnect the coach battery from the truck when it's not running, the reason is to allow you to start the truck in the morning after running the lights etc in the coach after partying all night otherwise you would have two dead batteries. You can charge the truck battery as you would a normal car with the engine running as long as it starts so that's why you have an isolator once it's running the isolator also allows the truck to charge the coach battery. Pretty clever device but ridiculously simple.  

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12 hours ago, Derek up North said:

Post a couple of pictures under the hood. We should be able to spot the isolator pretty easily for you, IF there's one still there. One installed and wired as original, shouldn't let you start the engine with no cab battery installed.

So...I went a little crazy, and took a GRIP of photos under the hood. Just a heads up, I'm not really new to doing basic care and maintenance on cars, so I know what most things under the hood are; I'm just completely new to motorhomes, and the extra components and different configurations that come along with them. 
 

This should be most angles of what's under the hood. I'm pretty sure I caught everything, for the curious.

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WOW, by the time WE get this mess cleaned up and working, YOU will be a qualified Electrical Engineer

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OK first things first. Label all the wires on each battery, remove the wires, remove the batteries. CLEAN batteries and battery trays. Use a baking soda water mix, keep cleaning until the foam stops.

Charge the batteries out of the truck and see whats good.

P.S. I see a lot of pulleys with out fan belts including the alternator, whats going on???

Edited by WME
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35 minutes ago, WME said:

P.S. I see a lot of pulleys with out fan belts including the alternator, whats going on???

@WME Ha...yes, it's missing two belts that I pulled off. ;) They were bad, and I have the new ones. I'm in the process of replacing belts, doing a fluids flush, changing brake pads, etc. I have some new plugs and wires and filters, as well. 

Do you think, based on visuals alone, that I should clean up the electrical, or should I just...clean house? I do have a charger, but the cells are dry in the car battery, and it's heavily corroded, so I assumed I should just recycle it and get a new one. The deep cycle takes and holds a charge (but I agree, needs cleaned.)

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35 minutes ago, Derek up North said:

It looks like the deep cycle battery is installed on the passenger side. Isn't that where the truck starter battery usually lives? I don't own that year, but ...

BTW, I wouldn't be trying to sort this out without a multimeter. Got one?

@Derek up North I do have a multimeter, yes, though I'm relying on my dad's knowledge, regarding how to use it. So I will, in fact, be learning a lot about electronics while working on this. 

As for the position of the deep cycle and truck batteries, It looks like there is welded original housing that the batteries fit in, so I think they're where they were originally designed to be. (Another factoid I was hoping to learn with an original owner's manual, back when I thought those were relevant. Oh the things you learn in two days!)

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Nothing like battery location will be in a factory manual. That's what we are for. You might call us RV historians. Mostly cause were old but we still know a thing or two. I hate electric just as much as Derek but I taught myself how to use a multimeter. Ya just have to dive in there. Need to see pic of everything you can show us.

Linda S

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Basic hookup for a 3 pole isolator.  https://www.etrailer.com/question-100433.html

You will need to check the isolator with the meter ...

If the truck  battery is dry then it needs replacement.

Edited by WME
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12 hours ago, Derek up North said:

Looking at other pictures you posted, I don't see 4 posts, but only 3. Anyway, see if you can find a make and model on yours and Google to find instructions for it.

It has an external regulator they only require a 3 pole isolator. Good posting by WRE can also be done with a volt meter while in place. With both batteries connected and engine off there should be no voltage on the "A" post and voltage on both 1 and 2 once the engine is running there should   be razing voltage on all 3 posts to somewhere in the 13+  to 14 volt range.

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So on your other post you mention that you bought your rig from a friend who is a collector. If so he would already know this stuff and he could at least tell you what wiring he's done to it. You just bought it. He's a friend. Make him fix it. Don't understand why he didn't go over all this with you first

Linda S

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