Checking 12V solar system for obvious errors

**sensij** · 01-22-2015, 10:43 AM

It looks ok, depending on your grounding. Can you add some green lines to your drawing to indicate ground writes?

**thastinger** · 01-22-2015, 10:45 AM

You'll want a fuse between the panel and CC, should be fine other than that.

Be sure you properly size all of the wires for the Amps and distance

**Sunking** · 01-22-2015, 11:04 AM

Originally posted by thastinger

You'll want a fuse between the panel and CC, should be fine other than that.

No need or requirement for a fuse between panel and CC in this application. Wouldn't work even if he left it in there like the rest of the fuses because it is a Floating system.

OK a few issues, which you can remedy or keep, makes me no difference.

1. Cigarette lighter ports are rated at 10 amps max. If you look at any vehicle that has them is why they are fused with 10 amp fuses

2. You should use fuses to the cigarette lighters, but what you have now will not work because the system is Floating vs Grounded. Floating is fine, but if you use a Floating system you have to put fuses on both polarities, not just one as you have done. .

**antobag** · 01-22-2015, 12:09 PM

Many thanks for the help everyone.

Originally posted by Sunking

No need or requirement for a fuse between panel and CC in this application. Wouldn't work even if he left it in there like the rest of the fuses because it is a Floating system.

OK a few issues, which you can remedy or keep, makes me no difference.

1. Cigarette lighter ports are rated at 10 amps max. If you look at any vehicle that has them is why they are fused with 10 amp fuses

2. You should use fuses to the cigarette lighters, but what you have now will not work because the system is Floating vs Grounded. Floating is fine, but if you use a Floating system you have to put fuses on both polarities, not just one as you have done. .

1. I managed to buy a port rated at 20A: http://www.ebay.co.uk/itm/360643893924. Maybe they over-estimated on the rating, but I plan to use 10A max on all my devices so I shouldn't have a problem there.

2. I do intend to keep it Floating as it will only be a 12V system. In terms of having fuses on both polarities, would this mean I need to have them in two additional positions (indicated by the stars in the edited circuit diagram below), or just one of them? What fuse rating would you recommend putting there?

Solar Power System edited.jpg

**sensij** · 01-22-2015, 01:05 PM

That is a pretty inexpensive charge controller. The MPPT mode is for bulk charging only, it runs in PWM for absorb and float. Better than a straight PWM for sure, but not quite true MPPT. Anyway, before you commit to floating the DC, do some continuity checks between the terminals, and the terminals and the case. With no obvious chassis ground terminal, they may be relying on the DC- to be grounded to provide the equipment ground.

Even if you leave it floating, your panels and anything else with a metal surface will need an equipment ground. The green lines still need to be added to the drawing.

**Sunking** · 01-22-2015, 01:14 PM

Originally posted by antobag

2. I do intend to keep it Floating as it will only be a 12V system. In terms of having fuses on both polarities, would this mean I need to have them in two additional positions (indicated by the stars in the edited circuit diagram below), or just one of them? What fuse rating would you recommend putting there?

Yes Sir that is exactly what I mean. Although the drawing does not specify where those fuses actually are, you want them as close to the battery post as possible. In fact if you select the right ones they bolt directly on the battery Term post called MRB like this available from Blue Sea. One is a single, and the other is a double unit which would work for you. Don't forget to buy the fuses.

**antobag** · 01-22-2015, 02:03 PM

Originally posted by Sunking

Yes Sir that is exactly what I mean. Although the drawing does not specify where those fuses actually are, you want them as close to the battery post as possible. In fact if you select the right ones they bolt directly on the battery Term post called MRB like this available from Blue Sea. One is a single, and the other is a double unit which would work for you. Don't forget to buy the fuses.

Thanks Sunking, another highly informative answer.

Originally posted by sensij

That is a pretty inexpensive charge controller. The MPPT mode is for bulk charging only, it runs in PWM for absorb and float. Better than a straight PWM for sure, but not quite true MPPT. Anyway, before you commit to floating the DC, do some continuity checks between the terminals, and the terminals and the case. With no obvious chassis ground terminal, they may be relying on the DC- to be grounded to provide the equipment ground.

Even if you leave it floating, your panels and anything else with a metal surface will need an equipment ground. The green lines still need to be added to the drawing.

Thanks for the info sensij. Would grounding the panels be as simple as using thick copper wire to connect the frame(s) to a grounding rod that's been rammed into the earth? Apologies for the newbie-ness, my experience with this is limited.

**Sunking** · 01-22-2015, 03:09 PM

Originally posted by antobag

Thanks Sunking, another highly informative answer.

Thanks for the info sensij. Would grounding the panels be as simple as using thick copper wire to connect the frame(s) to a grounding rod that's been rammed into the earth? Apologies for the newbie-ness, my experience with this is limited.

Would be a waste of time and money, and if you did greatly increases your risk of a lightning strike.

**inetdog** · 01-22-2015, 03:25 PM

Originally posted by antobag

Many thanks for the help everyone.

...

1. I managed to buy a port rated at 20A: http://www.ebay.co.uk/itm/360643893924. Maybe they over-estimated on the rating, but I plan to use 10A max on all my devices so I shouldn't have a problem there.

Even if the port is rated at 20A, whatever male plug you connect into it will probably not be rated that high. I have seen a lot more melted male DC power ports than melted sockets.

**paulcheung** · 01-22-2015, 04:01 PM

Originally posted by Sunking

Yes Sir that is exactly what I mean. Although the drawing does not specify where those fuses actually are, you want them as close to the battery post as possible. In fact if you select the right ones they bolt directly on the battery Term post called MRB like this available from Blue Sea. One is a single, and the other is a double unit which would work for you. Don't forget to buy the fuses.

Dereck, There is a problem for we off grid folks, the fuse is only rated 58 volts DC Maximum. We absorb at 60 and equalize at 64 volts DC. can we still use it?

**Sunking** · 01-22-2015, 05:20 PM

Originally posted by paulcheung

Dereck, There is a problem for we off grid folks, the fuse is only rated 58 volts DC Maximum. We absorb at 60 and equalize at 64 volts DC. can we still use it?

Absolutely.

**Sunking** · 01-22-2015, 05:22 PM

Originally posted by inetdog

Even if the port is rated at 20A, whatever male plug you connect into it will probably not be rated that high. I have seen a lot more melted male DC power ports than melted sockets.

The issue is the center pin. Not much surface area or pressure to make contact.

If you know how to solder, or a small torch use what RC models use like a EC3 or EC5 connectors. EC3 is good for 40 amps, and EC5 for 120 amps. If interest let me know and I will show you a video on how to solder them on correctly.

**sensij** · 01-22-2015, 05:52 PM

Originally posted by Sunking

Would be a waste of time and money, and if you did greatly increases your risk of a lightning strike.

Just to be clear, for the sake of the OP. If it turns out that either of these conditions are true:

1) Continuity between Solar DC- and Battery DC- terminals

2) Continuity between the charge controller case and any of the DC - terminals

would you advise grounding any part of the system?

**antobag** · 01-22-2015, 06:03 PM

Originally posted by inetdog

Even if the port is rated at 20A, whatever male plug you connect into it will probably not be rated that high. I have seen a lot more melted male DC power ports than melted sockets.

Originally posted by Sunking

The issue is the center pin. Not much surface area or pressure to make contact.

If you know how to solder, or a small torch use what RC models use like a EC3 or EC5 connectors. EC3 is good for 40 amps, and EC5 for 120 amps. If interest let me know and I will show you a video on how to solder them on correctly.

If I have a 10A or 5A fuse in the positive polarity before the cigarette socket (as shown in my diagram), will melted ports still be an issue?

In any case, I would very much like to see that video. It'd be great to be able to use 40 or 120 amps - I'm quite limited with my current (no pun intended) 10 or 20 amps.

Checking 12V solar system for obvious errors

Checking 12V solar system for obvious errors

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