New to Wind-Sun

lysol

I am new here and didn't see an introduction section. Leaving from Solarplanetalk and coming here, I'm hoping to see a more "friendlier" forum.

I'm building a portable Pelican Case generator and I have 1 thing I'm not 100% certain on. The solar panel input is going to be limited at 10 amps with 12V panels. The wire feeding it to the box will be less than 10' long. I'm wanting to use 16 gauge wire. I can't find out if this will be dangerous or not or I'll just lose a little amperage. Most wire charts only go up to 14 AWG for reference. Thanks!

Cariboocoot

Re: New to Wind-Sun

Welcome to the forum.

We try to be friendly here. If anyone isn't, we sick the dogs on them. And the cats.

What you're wonder is can you put 10 Amps through 16 AWG wire without serious heating going on?
And you're wondering it because the sixty-eleven wire charts out there give sixty-eleven different answers.

Actually 16 AWG can handle 10 Amps without frying. It's pretty near its peak capacity, so it will get warm especially if it goes on for too long.

Now about that power loss issue. Yes, there will be some. There always is. In this case over 10 feet about 7%. That's rather high. I'd recommend using 12 AWG instead; no issues for current handling or V-drop then.

BB.

Re: New to Wind-Sun

Welcome to the forum Lysol.

We try to keep the forums on topic, professional, and family friendly.

There is some "fun here", but mostly we try to keep to the subject to make it easier for people to find what they need.

Your question... There are several things you need to address when wiring a system.

First is safety--Batteries can have very high output current into a short circuit. So, you should have a fuse/breaker on each wire that leaves the battery positive bus.

You can use this NEC table--Which is pretty conservative (and if you use the NEC code book, there are further deratings for conduit fill, ambient temperature, etc.). Also, for wire used on in the sun (solar panels)--Long term UV exposure can degrade insulation in months to a couple of years. If long term exposure, use UV rated wiring and/or conduit.

There are less stringent codes (like Boating) that will let you carry more current for wiring... Many times, wire is exposed in boating applications, so it gets better cooling. Your choice.

Wire Current Ampacities NEC Table 310-16
ABYC Wiring Standards

For 16 AWG wire, the ABYC allows 21-25 amps... The NEC would allow 18 amps (usually, for NEC, we use 14 or 12 AWG as the minimum cable size--Note that 14 AWG in NEC is 15 amps maximum (see notes below chart) and 18 amps for 16 awg--a smaller wire size).

NEC wiring and breaker/fuses use a 80% or 1.25x derating factor for wiring... For example a 10 amp load should have a minimum of 12.5 amp rating (round up to 15 amp fuse/breaker/wiring).

Next, voltage drop... Many times, with solar power systems, you use much larger diameter cable to send the (relatively) low 12 volts (or 24/48 ) volts any distance and not have too much drop. We usually use 3% to 1% as a recommended maximum voltage drop.

So, for your standard Vmp~17.5 volts, that would be 3% or 0.525 volt drop maximum. Using a generic voltage drop calculator:

• 16 AWG wire @ 10 amps and 0.5 volt drop => 5' (one way wire run) of 16 AWG wire will give you 0.5 volt drop

I would suggest that 5' of 16 awg wire with a 15 amp breaker/fuse would be the longest run I would suggest.

Note that with charge controllers, they are most accurate with 0.1 to 0.05 volt maximum drop between the controller and the battery bank (for a 12 volt bank)... So a 0.05 volt drop with 16 awg wire would be 1/2 foot maximum run.

For a small system, 16 awg for solar panel+charge controller wiring will just barely work (at these maximum lengths).

Personally, I would probably get heavy duty extension cord from the hardware store (16-10 awg cord sets are available)--The can be UV rated and the outer jacket+internal structure would give you a more rugged installation. You should use strain relief on the cable ends--Or even use a "non-standard" plug and socket to make the unit portable/easy to setup-breakdown).

Twist lock plugs have their advantages (won't fall out) and disadvantages (somebody trips, the plug will not fall out and may pull over panels/equipment and break). For DC circuits, Anderson connectors are popular and both ends are "shrouded" against easy short circuits.

-Bill

NorthGuy

Re: New to Wind-Sun

IMHO, when it comes to 10' distances, you cannot save much money on wires. #16 wire will give you 0.8V drop and 8W loss on max production. If I were you I would go with #10 wire.

I hope that was friendly

lysol

Re: New to Wind-Sun

Amazing!!! I had figured I would be at the limit of the 16 gauge wire. That's my fault because I had purchased a mil spec 5015 16AWG connector/plug for my solar panel input. I will have to repurchase a different set in 12 or 14 gauge. I mean, I won't be running near the maximum 10A limit though. With my kit, I would only need to replace at maximum 8Ah as the battery in my kit is a 15Ah battery and I don't see using more than 5Ah overnight anyway. So let's say I want to replace the entire 8Ah in a 4 hour period the next day, I would only need to really push at minimum of 2 Amps. Then maybe an extra 2 on top of that to charge my phone while charging the battery as well. So I'm guessing I won't be pushing more than 5A through the solar panel cable.

Here's my schematic I made on MS Paint. I'm definitely feeling more welcome here. Thanks guys. I'll try to give you guys as much information as I can think of. The wire sizes I guess are tentative.

This picture only contains the components that are inside the case. The solar panel socket is what my solar panel cable will plug into. Also, the A/C battery charger only puts out .8A

Cariboocoot

Re: New to Wind-Sun

Whoops! Time to put the brakes on.

You have a 15 Amp hour battery? You definitely do not want to feed 10 Amps to that. You also definitely do not want to draw 8 Amp hours out of it.

Let's just check everything twice and make sure the numbers and terms are correct before proceeding.

lysol

Re: New to Wind-Sun

It's an AGM battery. I figure at .3C(not sure if that is the limit or not), I could pump up to 5 amps into it max. 8Ah would be the 50% limit.

Cariboocoot

Re: New to Wind-Sun

By my calculations 10 Amps would be 66% of the Amp hour capacity, which is high even for an AGM. And 50% of 15 Amp hours is 7.5. You may think 1/2 an Amp hour doesn't mean much, but it can.

On the up side you may not need as much panel as you think to recharge that battery. 3 Amps would be a 20% rate, and on 12 Volts that's only 52.5 Watts +/- a bit.

Your schematic is fairly straight-forward. I have to ask what the two non-specified meters are for? They seem to be wired together in some way as well. You probably do not need that momentary switch on the Voltmeter either. Perhaps you might want one of MidNite's battery meters there instead: http://www.solar-electric.com/mnbcm.html It would keep track of the battery SOC fairly well, without the added expense of a true battery monitor.

So far, so good.

lysol

Re: New to Wind-Sun

Cariboocoot wrote: »

By my calculations 10 Amps would be 66% of the Amp hour capacity, which is high even for an AGM. And 50% of 15 Amp hours is 7.5. You may think 1/2 an Amp hour doesn't mean much, but it can.

On the up side you may not need as much panel as you think to recharge that battery. 3 Amps would be a 20% rate, and on 12 Volts that's only 52.5 Watts +/- a bit.

Your schematic is fairly straight-forward. I have to ask what the two non-specified meters are for? They seem to be wired together in some way as well. You probably do not need that momentary switch on the Voltmeter either. Perhaps you might want one of MidNite's battery meters there instead: http://www.solar-electric.com/mnbcm.html It would keep track of the battery SOC fairly well, without the added expense of a true battery monitor.

So far, so good.

Thanks Cariboocoot.

Just to confirm, you said that 3 Amps would be a 20% rate. You could express that as .2C as well, correct?

I'm actually using 1 meter right now. It's a Watt's Up meter from RC Electronics USA

Meter Animation:
http://www.rc-electronics-usa.com/watts-up-screen.html

I'm still new to this all so my portable power pack is also an experiment/learning deal as well. I want to monitor incoming and outgoing power to get a better hands-on understanding. At the same time, I can use this generator to power (3) 3 Watt LED camping lights at night.

I did leave out an explanation as to what those smaller wires are for. While they aren't really needed for the meter to work, they are needed to power the meter when the voltage on the main lines drops below 3 Volts. When I got home from work, the meter was off and I lost all of my day's data. This way, they run off the battery when needed and no data is lost. There is a 3rd wire I didn't show that when touched to the negative of the battery, it resets the meter's stats. I could put a switch on it or something. The volt meter will be flush mounted to the outside of the case with a momentary on switch so it's not always running. Just push the button to check the voltage. I do like that meter you posted however that gives me a nice percentage SOC.

The meter has helped me learn the efficiency of a solar panel behind a window + metal screen. I'm only able to get about 0.4Ah per day from my 20W monocrystalline panel in my condo. It doesn't help that my window faces SE and I wish I had a balcony, but I make do. I think this will make a decent test kit.

lysol

Re: New to Wind-Sun

Also, I guess I would be safe to assume that 16 AWG wire would be safe for my solar input as I'll only be using up to 5 Amps. I completely forgot about the battery's limitation.

Cariboocoot

Re: New to Wind-Sun

It's all the same math, just expressed differently: 20% of C is the same as C * 0.20 or C/5.

A couple of 'powered' Watts Up meters to watch what's going in and out is a good, cheap solution.

lysol

Re: New to Wind-Sun

Just wanted to stop by and say thanks everyone. I have some more wiring to do still, but it has been a great learning experience. I won't be using this style meter again as a shunt/meter would have been a whole lot more practical. Either way, it's fun and I'm learning from my mistakes. Once it's all wired up, I'll make it nice and neat.

lysol

Re: New to Wind-Sun

And one more...