Subscribe Contribute Advertise Facebook Twitter Instagram Forums Newsletter
Modular Waterproof Solar Panel System
Display Avatars Sort By:
Matthew Naylor
(mrnlegato)

Locale: Mid-Atlantic
Re: Re: Re: Re: Re: troubleshooting on 05/31/2012 13:13:26 MDT Print View

Is there a special technique for applying heatshrink on T-shaped (3-way) splices?

What don't you like about the liquid electrical tape (said as a complete novice)? I've certainly noticed the messiness, difficulty of removal, and apparent difficulty in providing complete insulation.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Re: Re: Re: troubleshooting on 05/31/2012 13:29:24 MDT Print View

Twist the three wire ends together, solder, and then apply the heatshrink over the single end.

Liquid electrical tape isn't much good except for the case where you can barely reach the spot with one hand, so you just paint the stuff on as best you reach. For any normal project on a work bench, there are many better electrical insulators like heatshrink, tape, and fish paper.

--B.G.--

Matthew Naylor
(mrnlegato)

Locale: Mid-Atlantic
Re: Voltage drop on 06/06/2012 09:00:50 MDT Print View

I have the two LX2400s, and will be installing them in the next few days. I fixed my wiring, and the panels seem to be OK (despite fearing shorting them with bad wiring, or burning one of them out without the diodes...), although /i haven't seen them produce the peak 400mA total; they're at something like 340mA in full sun.

I do have a question though; if I wanted to experiment with the cheaper Schottkey diodes--this is after all just a big experiment--which kind should I get? These?:
BAT54: 30 V Schottky Diode
http://www.onsemi.com/PowerSolutions/product.do?id=BAT54
NSR0230: 30 V, 0.2 A Low VF Schottky Diode
http://www.onsemi.com/PowerSolutions/product.do?id=NSR0230

Thanks

Matthew Naylor
(mrnlegato)

Locale: Mid-Atlantic
Re: Re: Goal Zero / backup batteries on 06/06/2012 09:06:44 MDT Print View

Another product (Suntastics sCharger-5) I noticed on a PCT blog this year seems to have decent power output with low weight. I would add a backup battery to their system even though it apparently has enough current to charge a smartphone. I wonder the performance after a few cloudy/overcast days...
Product:
http://www.suntactics.com/USBSolarChargerMoreDetails.html
Blog:
http://mexicotocanada.com/2012/06/05/day-42-45-renewing-energy/

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Voltage drop on 06/06/2012 09:23:54 MDT Print View

BAT54: 30 V Schottky Diode

NSR0230: 30 V, 0.2 A Low VF Schottky Diode

These two have very similar forward voltage drop ratings.

--B.G.--

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Modular Waterproof Solar Panel System on 06/06/2012 10:02:48 MDT Print View

By now you have figured out that the specifications on many solar panels are complicated, and many are overstated. It would be nice if the manufacturers could get together and standardize some test conditions. Well, they probably have already, but the weaker manufacturers may not mention their product's results that way. That leaves the average consumer holding the bag, so to speak.

Some friends of mine have large permanent solar systems on their houses. In two cases, they each said that they almost bought a "pig in a poke" with systems that would not meet specifications... and those are systems costing upwards of $30K.

For your small portable system, I guess you just have to experiment. Put up two different panels side by side in the sun for a month and see what you get.

--B.G.--

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Voltage drop on 06/06/2012 10:47:49 MDT Print View

What would happen if you had no Schottky diode? Then the "voltage drop" would be zero

You would have to disconnect it at night, maybe, to prevent discharge

I have a solar panel on my RV that I just put directly onto battery, but that's a different situation

If you had a home installation, you would have to have the diode because you wouldn't always remember to disconnect at night

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Voltage drop on 06/06/2012 11:10:00 MDT Print View

Jerry, the other situation happens in the portable case. If you have two separate panels in parallel feeding to one battery or charger, you get into a funny situation with shade. One panel might be in direct sun, and the other panel might be in shade. Then the power of the sunny one might dissipate in the shady one. Since the backpacker is not always watching his own panels for this, it can happen any time. That's why the blocking diodes are a very good thing to have.

If the diodes had a very large forward voltage drop, then it might not be worthwhile. If the diodes were enormously expensive, then it might not be worthwhile. If you had only a single panel, then it might not be worthwhile.

I use a charge controller on my solar system, and it has the blocking diode built-in.

--B.G.--

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Re: Re: Voltage drop on 06/06/2012 15:02:02 MDT Print View

With anything I use, I like to minimize maintenance and the "futzing" factor. Same goes for solar. My RV system has a charge controller and the built-in diode too. I also have a sophisticated battery monitoring system that actually tracks amps in and amps out, and it is programmed to display the usable amps remaining in the battery bank in amps or as a percentage of the total... it also does a whole bunch of other stuff that I have never bothered to learn, because that becomes a futz-factor too. So the solar system just sits and does its job. I wash the panels a couple times a year and check the battery water level once every couple of months.

If I were to use solar for backpacking, I would want the same ease of use. Just keep it in the sun and no futzing with anything. But then to me, bringing electronic gadgets to too much fuss in itself :)

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: Re: Re: Voltage drop on 06/06/2012 15:33:14 MDT Print View

Nick, it sounds like you have a good permanent solar system for home. I guess you get a real charge out of it.

--B.G.--

Matthew Naylor
(mrnlegato)

Locale: Mid-Atlantic
performance tests: panels + smartphone on 09/23/2012 09:41:18 MDT Print View

Performance update:
I experimented with this setup on a short labor day overnight trip in Harriman State Park from the Elk Pen parking lot @ NY-17 along the Appalachian Trail to spend the night at West Mountain Shelter overlooking the Hudson River. The day was very sunny, but the trail was nearly constantly covered in shade. Our lunch / rehydration spot was modestly sunny, but I was lazy about putting keeping the panels in the sun.

I tested this by starting with the backup battery at zero charge. I tested the resulting charge by powering my phone off, and recording the phone charge state before charging and after charging overnight.

Verdict:
After 7.5 hrs of heavy shade hiking (some of that did have direct sun), my phone only gained 42 mAh of charge overnight! That's 5.6 mAh/hr in shade.
Caveats: this does not account for the phone battery power consumed in shutdown and startup, and the solar battery might charge my phone less efficiently when it's near-zero charge?

In the next few days, I'll repeat this experiment hanging the panels out my apartment window to see what the maximum charge comes out to.

Smartphone experiment:
Droid Incredible 2
Airplane Mode on 95% of the time (turned off briefly to check Google Maps for an AT hiker, and at the end of the hike to text family)
Backcountry Navigator checked several times for GPS/map guidance
Backcountry Navigator set to track @ 1min interval, 20m min distance, 300m gps accuracy
This "heavy" use consumed 535 mAh over 7.5hr; 71 mAh/hr

On the return trip, I used no BC Navigator tracking, but still used it for guidance. (I'm not certain, but I think BC Navigator my keep the GPS on constantly unless you tell it to turn off the GPS... I might have been able to save more power)
This "light" use consumed about 45 mAh/hr

Clearly there is still a bit of a gulf between what the phone consumes and what the panels produce... thankfully the 6000mAh battery will store 10+ days of 12hr "light" use... so that's good.

Edited by mrnlegato on 09/23/2012 09:45:34 MDT.

Matthew Naylor
(mrnlegato)

Locale: Mid-Atlantic
Re: Re: Re: Re: Voltage drop on 09/24/2012 07:53:39 MDT Print View

Another question for the electrical whizzes on the forum; am I right in thinking that I would not need a shunt to install this 0-1A ammeter inline with my solar panels?:
http://www.ebay.com/itm/Red-LED-DC-0-1000mA-0-1A-Digital-display-ammeter-Ampere-Meter-/150897948069?pt=LH_DefaultDomain_0&hash=item232237f5a5

I'm planning on putting this inline with the panels on the top of my pack (prob. no waterproofing or switch... just easily removable if the weather gets bad)...

Thanks!

Wizard of Oz
(wizardofoz)

Locale: New England
Re: Re: Re: Re: Re: Voltage drop on 09/24/2012 10:17:29 MDT Print View

Directions on that Ebay sale site are very sketchy. it doesn't look like you need a shunt for this (meaning it's internal on the board). But it definitely seems to say that you want the two - wires (black wires) connected together to ground. i.e. they don't want the in- above GND or too much current will drive the sense circuit. I would find a spec sheet on the part when you get it in hand and take a careful look before power it.

Take a look at a few alternatives too like this one, http://www.newark.com/murata-power-solutions/dca-20pc-5-dc4-rl-c/current-meter/dp/87K3619 just so you get a feel for how they should work.

Hope that helps. DON'T LET THE SMOKE OUT! :)

Matthew Naylor
(mrnlegato)

Locale: Mid-Atlantic
lightened case, ammeter on 10/08/2012 11:36:15 MDT Print View

Found an alternate casing in the form of a gian Tic-Tac case. Used Sugru to affix the DC connector on the case opening, and made a new hole for a USB cable. Assuming the Sugru and plastic holds out, one ring of electrical tape will make this waterproof.
The change saves almost 6 oz... most of the weight is just from the USB cable!

Electronics in Tictac: 6.2oz (mostly from the battery... previously 11.6 oz)
Solar panels: 4oz
(add a few oz extra for extension cable, battery charger)

tictac outer
tictac inner

The ammeter listed above actually works great, and I fixed it up with Sugru, a battery case (w/ on/off switch) and breakout cable to bring on test hikes. 1.5 oz

ammeter

PS Tests in full sunlight were way better than shade, but I lost the results - will post another time.

Edited by mrnlegato on 10/08/2012 11:38:14 MDT.