1994 International 4700 Conversion Begins

Ozrockrat

Expedition Leader
Ye I agree with DWH a lot of controllers are positive ground. Make sure that the panels and the controller are not earthed except through the battery lead.
 
Ye I agree with DWH a lot of controllers are positive ground. Make sure that the panels and the controller are not earthed except through the battery lead.
I'm going to try that when I get home tonight and see what happens.

Scooter...

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I've been reading more about the positive ground and I am grasping it....I think. It certainly sounds like that is my issue. I am really surprised at the limited amount of information accessible via Google regarding this topic. Solar has been around for a very long time as has positive grounding. I get there is an issue with two different "grounds" and differing pontentials causing issues with eachother. I guess the terminology is the confusing part. Looking at circuit flow and ignoring the "ground" verbiage it makes more sense. I'm looking forward to getting home and hooking up the negative side to the controller and see what happens.

The hard part to digest or visualize is that the "ground" from the battery is connected to chassis so why can't the panel be as well? If I am actually understanding it correctly, it's not actually the "ground."

Scooter...

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Spoke to an old Navy guy at work who explained it some more. It's interesting and I'm learning a lot of information about 12 volt systems that I never knew existed.

Scooter...

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dwh

Tail-End Charlie
Yea, it's the use of the word "ground" that leads to confusion. Technically it means planet, but we normally don't connect vehicles to the planet, except for incoming mains power which should already be grounded.

In vehicles, solar panels and charge controllers, what it means is, "the unswitched side".

In a "negative-ground" system, like a (non-British :) ) vehicle, the unswitched side is negative. All the switches that do stuff are in the positive lines.

In a "positive-ground" system it's the opposite.

So, in a "positive-ground" charge controller, all the positives (solar, battery, load) are hard-wired together, and it's the negatives which have the switches to do stuff. (In a solar panel it means the pos is hard-wired and the bypass diodes switch the negs.)

So with a positive-ground charge controller, by connecting the battery and solar pos to the charge controller they become hard-wired together. Then when you connect the solar panel neg to the chassis, where the battery neg is already connected, you create a bypass (full or partial) around the controller because now the solar +/- and the battery +/- are both hard-wired together.
 

Ozrockrat

Expedition Leader
In general just connect as per the wiring instructions and never ground anything unless the instructions tell you to. Also it is good practice to never rely on the body/chassis to be a conductor. Try to run a negative cable wherever it’s needed.
 

dwh

Tail-End Charlie
And for what it's worth, the Brits are right. Ben Franklin got it wrong when he figured that power flows from pos to neg. It actually flows from neg to pos.

In practical real-world use it doesn't really matter which way you do it as long as you remain consistent. It's mixing the two that gets tricky.
 
It's all coming together in my head. Thanks for the clarification both of you. As for the wiring diagram; yes, it does show one + and - going to the controller but it does not say you can't connect to chassis ground. So, without understanding the circuit flow for this application a chassis ground seemed like a normal connection. The instructions for the first charge controller were horrible and the second one was better but not that great. Neither instructions mention whether the controller was neg or pos grounded. At least now I know some of the symptoms created on a positively grounded system when wired wrong and I still have the capacity to learn something new! Well, I will as soon as I get home and it all starts working correctly.

Scooter...

Sent from my LGMP260 using Tapatalk
 
Yea, it's the use of the word "ground" that leads to confusion. Technically it means planet, but we normally don't connect vehicles to the planet, except for incoming mains power which should already be grounded.

In vehicles, solar panels and charge controllers, what it means is, "the unswitched side".

In a "negative-ground" system, like a (non-British :) ) vehicle, the unswitched side is negative. All the switches that do stuff are in the positive lines.

In a "positive-ground" system it's the opposite.

So, in a "positive-ground" charge controller, all the positives (solar, battery, load) are hard-wired together, and it's the negatives which have the switches to do stuff. (In a solar panel it means the pos is hard-wired and the bypass diodes switch the negs.)

So with a positive-ground charge controller, by connecting the battery and solar pos to the charge controller they become hard-wired together. Then when you connect the solar panel neg to the chassis, where the battery neg is already connected, you create a bypass (full or partial) around the controller because now the solar +/- and the battery +/- are both hard-wired together.
This might explain why the ambulance wiring has had me baffled more than once since the beginning. Almost all the switches have been on the negative side. I did not get why, I just went with it. Or, I'm reading too much into the problems I've had with the truck wiring.

Not sure if that would make sense though. I've wired plenty of things up on the truck using the negative side as "ground." I would think I would have all sorts of problems if the truck was positively grounded?

Scooter...

Sent from my LGMP260 using Tapatalk
 
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Ozrockrat

Expedition Leader
This might explain why the ambulance wiring has had me baffled more than once since the beginning. Almost all the switches have been on the negative side. I did not get why, I just went with it. Or, I'm reading too much into the problems I've had with the truck wiring.


Scooter...
This is sometimes used to make the wiring more failsafe. If the switch wire gets grounded (in an automotive system) it fails to the on position the same as if the switch wire is switched to the negative.
 
Yup, that was it. The charger is in "boost" mode and sending power to the batteries. It figures, the day I get it connected correctly (a big thanks to the help) it's cloudy! I'm in a desert and the sun shines almost the entire year!

Now, off to run more wires for my CB radio and PA speaker. This project should be pretty straight forward...

Scooter...

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patoz

Expedition Leader
I don't have any solar stuff yet, but I've paid particular attention to this situation, and even saved the thread for future reference. I learned something here, and I'm glad that solved your problem. Hopefully, this will prevent me from making the same mistake when I do my install.

My thanks to the 'help' also! 👍
 
I don't have any solar stuff yet, but I've paid particular attention to this situation, and even saved the thread for future reference. I learned something here, and I'm glad that solved your problem. Hopefully, this will prevent me from making the same mistake when I do my install.

My thanks to the 'help' also!
You and me both!

It's been interesting trying to understand it. I asked some electrician friends I know trying to grasp the concept. A couple of them had heard of the positive ground but not seen it in use. A couple folks have seen it in vehicles but not since the 40's!

Now that it's working, I'll be able to check the power output tomorrow. It is highly likely there will be plenty of sunshine.

Scooter...

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Ok, thank you.

I'm still trying to wrap my head around the concept but I think I get why they wire panels this way.

If wired straight from the panel, controller to the battery it's a single path of electrical flow between the negative and positive. With the solar is part of that circle it adds power to the circuit to which the battery absorbs the power as needed.

Now, connecting the negative to chassis ground as I did changes that path and begins to try and charge the entire truck? This is what confuses the controller as the chassis becomes charged to Output Voltage from the solar panels it sees the batteries as fully charged.

Is this remotely close to what's happening? If not I'll delete the post as not to confuse anyone else!

Adding panels is not the same as adding a new light or device to the truck, it"s an in-line charger.

Scooter...

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