Portable (suitcase) solar "install" question

[johnm1]

I've gone back and forth on solar panels on the roof or portable. Well, due to a tight budget, portable is the only way I'm going to get solar for now and it makes sense for me to try it out 1st as we camp in shade a lot.

I'm looking at the 100-160w "suitcase" styles that are out there and the size/brand don't matter for my question ... unless someone has a real concern about a particular brand or company. Some, like Zamp, are not in the running due to cost.

Most of the kits come with a charge controller (which except Zamp is not water proof) and it's mounted to the back of the panel(s). I want to move it to inside the rv nearer the batteries.

- Using alligator clips to the batteries would be a pain in the backside for my setup. What kind of disconnect plug/connector should I use when I set up and take down the panels?

- I have the "Zamp Solar ready" outlet on the outside of the rv. Can I use that? Is it big enough wire for 100-160 watts of solar?

- Do I need to worry about arcing while connecting/disconnecting?

- Should I install a power cut-off on the wire right near the panels? Which one and I assume it should be water-proof?

- No system that I've seen has any fusing/circuit protection. I assume I should? And where does it go ... between the panels and CC or between the CC and the batteries?

Thanks,
John

[ktmrfs]

johnm1 wrote:
Would it be acceptable to use extension cords for the wire runs from panel to CC? I saw in other threads that suggest soldering the neutral and ground together to effectively increase the wire size. It might have been ktmrfs who posted it.

My thought was to use off the shelf 10 gauge extension cords (whatever length(s) make sense) and then make a short adapter cord with ground and neutral connected which would plug into both ends of the off the chelf extension cord. This would allow me to use the extension cords for other 120VAC needs. Since one of these adapters would be permanently attached to the panels and the other would be permanently attached to the CC, it should be safe for the normal schmuck like me.

Since I don't know how to draw or add a pix to this forum I'll use words to describe what I'm thinking ...

Solar panel with permanently attached adapter / off the shelf extension cord / adapter that's permanently attached to the charge controller / battery.

It makes sense in my mind anyway!

you could do this, but I'd make sure to have a tag at both ends when it is connected to the solar panels so you or someone doesn't accidentally plug it into 120V. A big label velcro'd to each end that says warning do not connect to 120V or something that catches attention.

Also, connect the male end to the panel, female to the charge controller. that way your less likely to plug it into 120V. And if the cable becomes disconnected you don't have an exposed 12V hot and ground that can short to anything.

Also, by paralleling ground and neutral you basically end up making one leg a wire size larger. 2 10ga in parallel = 8 ga. 2 12's = 10 ga.

so as long has you have the extra wire it's worth using it.

[johnm1]

2oldman - I don't have a good answer for you on that.

But, since I wouldn't have to alter the extension cords, it allows me to use them for other purposes when they're not being used for the solar setup.

So I guess my answer is ... why not? Why not try to gain as much efficiency as I can for the little effort that this would take?

[2oldman]

How does increasing the effective wire size for such a short distance help? Perhaps I'm not understanding what you're saying.

[johnm1]

2oldman - yes. This way the extension cords can be used for normal 120vac things when they aren't being used for the solar (like when we're at home).

I'd probably get a couple of cord covers/protectors for while they are in use with solar.

[Tom_M1]

johnm1 wrote:
Would it be acceptable to use extension cords for the wire runs from panel to CC? I saw in other threads that suggest soldering the neutral and ground together to effectively increase the wire size. It might have been ktmrfs who posted it.

This would work very well. Just don't plug the cord into a 120 volt outlet. I know a couple of people doing this.

[2oldman]

johnm1 wrote:
use off the shelf 10 gauge extension cords (whatever length(s) make sense) and then make a short adapter cord with ground and neutral connected which would plug into both ends of the off the chelf extension cord. This would allow me to use the extension cords for other 120VAC needs.

You mean the ground and neutral would be connected only at these shorter adapters?

[johnm1]

Would it be acceptable to use extension cords for the wire runs from panel to CC? I saw in other threads that suggest soldering the neutral and ground together to effectively increase the wire size. It might have been ktmrfs who posted it.

My thought was to use off the shelf 10 gauge extension cords (whatever length(s) make sense) and then make a short adapter cord with ground and neutral connected which would plug into both ends of the off the chelf extension cord. This would allow me to use the extension cords for other 120VAC needs. Since one of these adapters would be permanently attached to the panels and the other would be permanently attached to the CC, it should be safe for the normal schmuck like me.

Since I don't know how to draw or add a pix to this forum I'll use words to describe what I'm thinking ...

Solar panel with permanently attached adapter / off the shelf extension cord / adapter that's permanently attached to the charge controller / battery.

It makes sense in my mind anyway!

[BFL13]

"Do I use the 17.8vpm instead of 12v for the drop calculations? If yes, then I'm guessing I'd be well above the 12-14+ volts needed? "

With 12v PWM, panel voltage is the same as battery voltage except for a bit of voltage drop, so figure between 12 and 15 as it rises during the day. Use total panel rated Isc as your "expected amps" to go with the voltage in the tables to pick your wire gauge.

Eg a 100w panel will be 6 amps so two in parallel will get you 12 amps (and more of a voltage drop with the higher amps) You might add a panel later so get wire now to allow for that, and also a high enough amp controller--That Grape 40 is an excellent choice with its high amps, features, and costing no more than many lower amp ones.

Again, Vmp is only for MPPT controller calculations.

[ktmrfs]

johnm1 wrote:
Is the 0.6 - 1.2 volt drop going to kill my recharging ability with solar or is this where the CC comes in and somehow makes it work?

My wiring thoughts ...
- 50-100ft (1 direction) of 10 gauge wire with Anderson type connectors between the panels and the CC.
- CC within 5 ft of the battery (either inside the RV or inside a waterproof box).
- 10 gauge wire from CC to battery? I don't know what's biggest wire that I can use on the CC.

Keep in mind, I have a generator to (hopefully) do the heavy lifting charging every few days and (again hopefully) the solar will just hum along and finish it up.

edit: just saw red31's post.

Do I use the 17.8vpm instead of 12v for the drop calculations? If yes, then I'm guessing I'd be well above the 12-14+ volts needed?

your configuration of wire size is similar to mine. good choice IMHO. One suggestion. Break the 100ft of wire into 3 sections, a 50ft, and two 25ft sections. that way you can pick and choose what fits the camping situation.

for voltage drop calculations, you need to know current. drop is Amps x Resistance.

For your configuration and wire guage, if your using a PWM controller, don't worry about voltage drop. with a 160W panel, and around 9A max current with 10ga wire, it's a non issue. it won't affect the charging current at all, nor the float voltage. you'll see a max drop of around 2V which is still keeps you above battery voltage.

If your using a MPPT controller, you'll loose a few watts of bulk charging power. 100ft of 10 ga has 0.2ohms resistance. at 10A thats 20 watts of lost charging power, or 1.5A max. out of around 15A max current available with MPPT controller. again don't worry about it.

Now if you had 500W of solar or so, and a MPPT controller with panels in parallel, voltage drop will have noticeable effect on your max current at 100Ft of 10ga

[johnm1]

red31 wrote:
how about 2 sets of 10g 50' each?

IMO, 12g would be too small @ 100'. But 12g landscape is readily available.

yes, 10 gauge is what I wrote. I could do 2 sets of 50 ft though. That makes sense.

Would the voltage drop be acceptable?

[red31]

mike-s wrote:
By the time you get to the late absorption stage (say, <0.5 A), the voltage drop will be <0.1 V.

Let me ask? PWM doesn't taper it just turns on/off and as the off time increases there is less ON time charging.

If ON is 5A, Off 0.0A that results in 0.5A over some time frame, is the voltage drop during the ON time still based on 5A?

[red31]

how about 2 sets of 10g 50' each?

IMO, 12g would be too small @ 100'. But 12g landscape is readily available.

[johnm1]

Is the 0.6 - 1.2 volt drop going to kill my recharging ability with solar or is this where the CC comes in and somehow makes it work?

My wiring thoughts ...
- 50-100ft (1 direction) of 10 gauge wire with Anderson type connectors between the panels and the CC.
- CC within 5 ft of the battery (either inside the RV or inside a waterproof box).
- 10 gauge wire from CC to battery? I don't know what's biggest wire that I can use on the CC.

Keep in mind, I have a generator to (hopefully) do the heavy lifting charging every few days and (again hopefully) the solar will just hum along and finish it up.

edit: just saw red31's post.

Do I use the 17.8vpm instead of 12v for the drop calculations? If yes, then I'm guessing I'd be well above the 12-14+ volts needed?

[red31]

With PWM, I want the panel to operate left of Vmp due to the radical drop in power to the right of Vmp (IV/power curves).

So I look at a kyocera panel specs NOCT (real life conditions), the 17.7Vmp spec is now 16.0v @ NOCT.

It gets hotter here than 20C NOCT.

So what battery voltage do ya want to use to determine max voltage drop NOCT?

I want to be able to do monthly 15.5v so with 0.5v voltage drop I'd be @ NOCT Vmp. 0.5v of 15.5v is just over 3%.

Of course the rest of the month 16v-14.8 = 1.2v of drop.

https://pdf.wholesalesolar.com/module%20pdf%20folder/KD135GX-LFBS.pdf?_ga=2.225155162.157547657.1498...