New to solar. questions on fuses, breakers, and grounding

[SunEagle]

I have an 88 amp hour battery. If I wanted to connect another panel in the 30-50 watt range with the 100 watt that I already have and use my single battery would this be a problem?

Again. Unless the panels Vmp & Imp are very close to one another you will not get them to work well together. Wiring them in parallel or in series will result in less than the total amp output.

[njp6x6]

I have an 88 amp hour battery. If I wanted to connect another panel in the 30-50 watt range with the 100 watt that I already have and use my single battery would this be a problem?

[SunEagle]

Is there an issue connecting a 100 amp hour and an 80 amp hour battery in parallel ( if they are both in good condition)? I am starting with just one battery but looking ahead to the future. I am guessing I should not connect an old battery that has been cycled below 50 percent many times with a new battery

Yes. If the batteries are not the same Ah rating and age then you will get unequal charging and discharging. That will kill the weakest battery first.

[njp6x6]

Is there an issue connecting a 100 amp hour and an 80 amp hour battery in parallel ( if they are both in good condition)? I am starting with just one battery but looking ahead to the future. I am guessing I should not connect an old battery that has been cycled below 50 percent many times with a new battery

[Sunking]

I have only been asking about the ground post on the metal case for the CC and inverter which I understand is just to keep current from flowing though the housing.

Wrong. If you use that terminal will force current to flow through the chassis. It puts the grounding conductor in parallel with the battery return (negative polarity) conductor. Most charge controllers and cheap automotive Inverters people buy, internally have the Negative Battery circuit bonded to the equipment chassis. . Huge flaw in design that wreaks havoc.

What are you opinions on using 4 of these from Amazon http://www.amazon.com/gp/aw/d/B01765...0XL&ref=plSrch they just seem appealling because they are inline and don't require the 45 dollar breaker housing that Raj suggested at the top of this tread. But is there is so e reason not to use them I won't

Stay far away form them. They are used by Auto Mobile Stereo Installers and very cheaply made. 12 volt only application and use mechanical pressure to connect wiring. Last thing in the world you want to use.

You want a OCPD (over current protection device) that mounts directly on the Battery Term Post. In this type of system the source of power is the battery, not the solar panels. Solar panels are current sources. You can short their output all day long and nothing happens. In fact that is exactly how you test a solar panel known as Isc test. Short a battery out and you have an explosion and vaporized copper wire.

This is why you install the OCPD on the battery post from the wires coming from the Controller instead of on the controller output. If you put the fuses on the controller output, you leave all that wire back to the battery unprotected.

One of the best OCPD I know of for battery systems is made by Blue Sea part numbers 2151 duals, and 5191 single. You would use a pair (2) of the 2151, one on each battery post. Then use 4 MRB fuses

[SunEagle]

Ok, so I think understand this. A negative ground, such as in a car, actually has a connection from the negative battery terminal to the frame work of the vehicle. So that's why in a car audio system you only need to put a fuse on the positive cable. I hadn't even thought of that until now. I have only been asking about the ground post on the metal case for the CC and inverter which I understand is just to keep current from flowing though the housing. What are you opinions on using 4 of these from Amazon http://www.amazon.com/gp/aw/d/B01765...0XL&ref=plSrch they just seem appealling because they are inline and don't require the 45 dollar breaker housing that Raj suggested at the top of this tread. But is there is so e reason not to use them I won't

Those fuses are only rated for 12volts DC and used for DC loads so they might not work when the battery is being charged at a higher voltage.

[njp6x6]

Ok, so I think understand this. A negative ground, such as in a car, actually has a connection from the negative battery terminal to the frame work of the vehicle. So that's why in a car audio system you only need to put a fuse on the positive cable. I hadn't even thought of that until now. I have only been asking about the ground post on the metal case for the CC and inverter which I understand is just to keep current from flowing though the housing. What are you opinions on using 4 of these from Amazon http://www.amazon.com/gp/aw/d/B01765...0XL&ref=plSrch they just seem appealling because they are inline and don't require the 45 dollar breaker housing that Raj suggested at the top of this tread. But is there is so e reason not to use them I won't

[Amy@altE]

Thanks a lot everyone! I feel like the fog has almost lifted. In the little diagram above you show fuses on both the positive and the negative. I always thought you only needed fuses or breakers on the positive side? Also, I just want to make sure that even though all the equipment I have, has grounding wire posts, I can just ignore that?

Sunking is describing an ungrounded system. For ungrounded systems, you need to break both the plus and the minus. Negative grounded systems should not have the minus broken as it is the path to ground.

[Mike90250]

the pigtails are likely tin plated copper strands. Aluminum would be a poor choice of wire for that application. (but I got a set of cheap jumper cables made of copper plate aluminum wire)

[njp6x6]

One more question, my panel has MC4 (I think that's what they are called) connections wired to the panel and came with a pair of 12 inch pigtails that's plug into them. That wire is aluminum I assume (definitely not copper). Is there any reason not to solder my 6 or 8awg wire to those pigtail? I don't really see how else you would connect it

[njp6x6]

Thanks a lot everyone! I feel like the fog has almost lifted. In the little diagram above you show fuses on both the positive and the negative. I always thought you only needed fuses or breakers on the positive side? Also, I just want to make sure that even though all the equipment I have, has grounding wire posts, I can just ignore that?

[SunEagle]

The Charge controller you have is capable of handling a lot of power and can be used in a fairly large 24 or 48 volt system in a permanent structure so it will describe the use of ground fault breakers but for a small 12 volt system I wouldn't bother, but it is your choice. Again, for grounding, it is a small system, I would use the chassis. Lightning is looking for a way to ground. Your camper is on rubber tires is it not. I also agree with Amy, that a Midnite SPD would help better than anything else if you are concerned about lightning. Concerning the battery cable, I based the AWG 4 on the inverter. At 1000 watts it would draw about 83 amps. I think a #4 can handle about 105 amps. Use what ever the inverter manual calls for, thats probably best.

Rick

Just a little data concerning lightning and rubber tires. To get enough insulation between the vehicle and ground to stop the flow of electricity those tires need to much bigger (none currently made big enough) and consist of very high insulating properties.

The reason lightning does not "enter" a vehicle is because it acts like a "cage" and lets the the electrical charge go around the outside (across the tires) to the ground.

[Sunking]

OK no ground of any kind is required or needed in your application anywhere. If you buy the right type of charge controller, MPPT, use grid tied panels wired in series, no fuses are needed or required between the panels and controller period.

All you need is 4 fuses installed directly on the battery term post. One pair facing the controller, and one pair facing the Inverter. The fuse sizes depend on Charge Controller Amp Output, and Inverter input current requirement. Size the fuses to 125% of device requirement. Just make sure the wire is rated for the fuse current. That is all you need for maximum protection. Anything else is just a waste of money. DO NOT CONNECT anything to the vehicle chassis.

[Sunking]

You could look at using a Midnite Solar SPD for lightning protection. Although nothing will protect against a direct hit, it is good protection against a nearby hit

What? Lightning hit a RV, or nearby strike? Are you joking?.

[Raj]

The Charge controller you have is capable of handling a lot of power and can be used in a fairly large 24 or 48 volt system in a permanent structure so it will describe the use of ground fault breakers but for a small 12 volt system I wouldn't bother, but it is your choice. Again, for grounding, it is a small system, I would use the chassis. Lightning is looking for a way to ground. Your camper is on rubber tires is it not. I also agree with Amy, that a Midnite SPD would help better than anything else if you are concerned about lightning. Concerning the battery cable, I based the AWG 4 on the inverter. At 1000 watts it would draw about 83 amps. I think a #4 can handle about 105 amps. Use what ever the inverter manual calls for, thats probably best.

Rick