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Old 08-03-2015, 05:55 PM   #1
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Renogy Solar systems

I just spent the last half hour chatting with one of their salesmen. I had a couple of questions about this kit:

Amazon.com: RENOGY® Solar Panel Starter Kit 400W Mono: Four 100W Mono Solar Panel UL 1703 Listed+One 30Amp PWM Charge Controller+Three Pair of MC4 Branch Connector+One Pair of 20Ft Adaptor Kit with Male and Female MC4 Connector+ Four Sets of Z Bracke

I want to hook it up to two 100 amp/hour batteries. According to him this kit should work fine but... There is always a but isn't there, LOL! To quote him:

"
RepresentativeThat 400W system should be fine, just keep in mind that that charge controller is positively grounded so if your vehicles batteries are negatively gounded then make sure not to use the DC load out terminal directly from the charge controller because it can cause some problem"
He then told me if I didn't want to worry about that problem I could use this system

400 Watts 12 Volts Monocrystalline Solar RV Kit | Renogy Solar

This system uses a negative ground but costs $155.00 more.

My question is it worth the extra cost? Seems both will do the same thing and both come with 20 feet of wire so the panels can be moved around.

Jim
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Old 08-04-2015, 07:52 AM   #2
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Save your money, The Positive ground will work just fine.

Its not really a "Positive Ground", i.e. when you and I read this, we immediately think " OMG, if we hook this up, we'll short out the battery". Wrong.

Most Solar controllers have the ability to not only charge the battery, but they can also turn loads on/off. The "LOAD" terminals on the controller can be programmed to turn on/off by time-of-day and/or battery voltage. This is great if your off grid and unattended. i.e. If its 11pm or the battery voltage is getting low, the controller can open the "LOAD" s terminal to disconnect the loads and keep from discharging the battery.

The "Positive" or "Negative" ground refers to how a particular controller switches the "LOAD" terminals on/off.

Negative Common system - Automobiles, RVs, etc.
The on/off switch is on the positive side of the load and applies the PLUS to the load. The negative side of the loads are all common and connected together, and they all connect to the batteries negative terminal all the time.

Positive Common System - The on/off switch is on the negative side of the load and applies the MINUS to the device to turn it on. The plus sides are common and connected together and they are connected to the batteries plus terminal all the time.


SO, WILL a POSITIVE GROUND CONTROLLER SHORT OUT THE BATTERY??

Answer, NO. If you did connect something to the LOADS terminal, the worst that will happen is that the controller will not be able to turn the load off, because the vehicles common ground will be supplying the negative side of the battery instead of the controller.

Odds are, you will not be connecting anything to the "LOAD" terminals on the controller. I've been trying to think of what someone would use the "LOAD"s terminals for in a MH, I can't come up with any.

However, if you decide to use the "LOAD" feature for something in your MH, use a small relay, i.e. the LOAD terminals will energize the relay, then use the relays contacts to apply the "positive" to your load.
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Old 08-04-2015, 10:47 AM   #3
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Quote:
Originally Posted by waiter21 View Post
Save your money, The Positive ground will work just fine.

Its not really a "Positive Ground", i.e. when you and I read this, we immediately think " OMG, if we hook this up, we'll short out the battery". Wrong.

Most Solar controllers have the ability to not only charge the battery, but they can also turn loads on/off. The "LOAD" terminals on the controller can be programmed to turn on/off by time-of-day and/or battery voltage. This is great if your off grid and unattended. i.e. If its 11pm or the battery voltage is getting low, the controller can open the "LOAD" s terminal to disconnect the loads and keep from discharging the battery.

The "Positive" or "Negative" ground refers to how a particular controller switches the "LOAD" terminals on/off.

Negative Common system - Automobiles, RVs, etc.
The on/off switch is on the positive side of the load and applies the PLUS to the load. The negative side of the loads are all common and connected together, and they all connect to the batteries negative terminal all the time.

Positive Common System - The on/off switch is on the negative side of the load and applies the MINUS to the device to turn it on. The plus sides are common and connected together and they are connected to the batteries plus terminal all the time.


SO, WILL a POSITIVE GROUND CONTROLLER SHORT OUT THE BATTERY??

Answer, NO. If you did connect something to the LOADS terminal, the worst that will happen is that the controller will not be able to turn the load off, because the vehicles common ground will be supplying the negative side of the battery instead of the controller.

Odds are, you will not be connecting anything to the "LOAD" terminals on the controller. I've been trying to think of what someone would use the "LOAD"s terminals for in a MH, I can't come up with any.

However, if you decide to use the "LOAD" feature for something in your MH, use a small relay, i.e. the LOAD terminals will energize the relay, then use the relays contacts to apply the "positive" to your load.
Thank you for your quick reply. I was under the impression that the "load' terminals is where you would connect the battery to. After all, that is the "load" isn't it? The reason I, we, buy these panels is to maintain the charge in the batteries so I considered that the "load". I now understand that they are a separate set of terminals that I will not be using. Their salesman did not make that clear when I asked him about it. He just stated that if I was concerned about the system being positive grounded I should but their "RV" system. He did say though that their standard system would work if wired properly. Not much of an explanation is it?

I now understand that I do not use those terminals thanks to your explanation and I appreciate that.

I do have another question. How heavy is the four panel system? I am guessing but figure around 75 pounds? Their web site gives a weight of 16.5 pounds and I figure that is for each panel, correct?

I will give them credit for their kits, they seem to be complete. The only thing I think I will need to add is a rack to hold the panels. From what I have read here that is easily done using 3/4 inch pvc pipe. That might add another 10 pounds of weight.

I may need to add a third battery, another 60 to 70 pounds, but time will tell me if that is really needed. I know that it couldn't hurt but this system is starting to get expensive. That might have to wait till next year.

Jim
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