Featured solar panels: where to buy

[DrewSTNY]

Yes, any wet cell battery.

They also make a battery maintenance solution, but I have always used distilled water.

If I remember right, we read around 1.300 for a fully charged L16RE-2V Trojan 2 Volt, but those batteries read really high. I think normal is somewhere around 1.26 or 1.27 for fully charged.

 

[todd]

you cant check AGM's with a hydrometer

 

[todd]

AGM = absorbed glass mat.... the sulfuric solution is absorbed into a glass mat separating the plates. most of the time even if you tip it over very little solution will spill.... *edit* my AGMs wont spill. but I looked online and it seems some cheaper AGMs are considered a wet type battery.
A good voltmeter is best. A fully charged 12 volt battery will have an open circuit voltage of around 12.6 volts depending on the type, and a battery is considered fully discharged when the voltage drops to 10.5 volts at the 20 hour discharge rate

a hydrometer is best for wet cell batteries. A fully charged cell has a specific gravity of around 1.27 to 1.28 depending on the battery manufacturer. A discharged cell will have a specific gravity of about 1.1 To be fully accurate the battery has to have been at rest for a period of 24 hours before the reading is takes to ensure homogeneity of the electrolyte.

There's some new meters using capacitance to judge batteries charge but I have no knowledge of how they work and they are expensive.

 

[DrewSTNY]

Gotcha, wasn't paying attention.

Best cheap thing then is to make sure the batteries stay about the same voltage when fully charged. I am not sure, but it's probably within 10% of each other's voltage.

 

[freegander]

so i bought 10-12 gauge butt connectors to splice the 10 wire with the 16...is this safe or will it be too loose? i figured since its heat shrink, it could shrink enough to fit a 16.

 

[DrewSTNY]

so i bought 10-12 gauge butt connectors to splice the 10 wire with the 16...is this safe or will it be too loose? i figured since its heat shrink, it could shrink enough to fit a 16.

Yes, it will be loose, unless you fold the 16 gauge wire over once or twice so that there is something for the splice to crimp onto. You can do just the 16 gauge, but you have to smash the crimpdown so much that it just about destroys it. At least, that is my experience.

+++++++]-===

+ is the wire with insulation
] is the end of the insulation
= is the bare wire doubled over

Hopefully, that makes sense. I don't have a good picture to show you.

 

[freegander]

Wow, for not having a picture that is a very useful and creative diagram. Thank you so much!

How do i figure out which fuses to use where? i read somewhere that it is based on wire size, but won't it also be affected by the load or the components i want to protect?

 

[DrewSTNY]

The wire does have a maximum capacity; however, for what you are doing, I think you will put in the sizes recommended by specification or by maths.

Since you are DC all the way, life is good. If you have volts and power, the equation is

Current = Power / Voltage

I would use 12V for your voltage even from the panel. If you find that the panel fuse is blowing often on really sunny days, I would go up to the next size fuse.

If you are lucky you might have an "IV" curve for the panel which will tell you what it's maximum current is across all voltages. I would make the fuse at that point for the panel since your charge controller can do some black magic to charge your batteries at partial panel power.

I would fuse your charge controller at whatever it is rated for plus a little bit. So a 10A charge controller probably should have a 15A fuse between it and the batteries.

Hopefully, everything you are buying will have recommended fuses in either the specification sheets or installation manuals.

For reference, here are some wire sizes and their maximum current recommendations:

18 AWG = 14 AMPS
16 AWG = 18 AMPS
14 AWG = 25 AMPS
12 AWG = 30 AMPS

I have seen cars from the factory with higher fusing than what is above, but they are going for cheap, not for what's right. The problem you run into is heat, smaller wire with higher current means more heat.

 

[freegander]

woooooo! i got the cheap charge controller to light up!

not completely sure what most of this means or how to manipulate it to work efficiently (or at all?) but at least it lights up.

another question: on the battery, it says cycle use is 14.5-14.9V and standby use is 13.6-13.8V. my readings have been around 12.8V. what does this mean?

 

[todd]

"Standby" use – using batteries as backup power: Batteries used in standby applications are predominately used to supply emergency power, helping prevent any damage that may be caused by sudden loss of mains power. For standby power applications, so-called stationary or standby batteries are often used. These batteries are rarely discharged and their charge is constantly maintained

"Deep-cycle" use – using the battery as a direct power source: 14 volts is a common voltage for charging a 12 volt battery.

those voltages you stated are probably charging voltages depending on use patterns.

12.8 volts is the standing voltage for a fully charged 12 volt battery.

EDIT BTW congrats on getting lights to work! your doing a great job and I for one am proud of you

 

[freegander]

okay, so, translation for me: 12.8V is the most voltage I should expect to read from this battery?

I currently have everything wired up and I just made a smoothie and charged my phone using energy from the sun!

I've been double checking the voltage with a multimeter as well, but I'm worried something isn't working right. it seems too good to be true. lol.

i have the solar panel faced towards a wall in my house, so it's reading some ambient light, but no direct sunlight. i'm still getting 11.5V from it, while full sunlight read is about 21V. When I plug my laptop into the inverter, the voltage in the battery goes down from 12.8 to around 12.5 and stays there. (I think because the battery is charging at the same rate it's discharging? could that be?)

I am still getting no read on current (which is the bottom LED display on the charge controller). The green light on the charge controller is always on, which is supposed to signify that the battery is at full charge. Am I just not discharging it enough?

thank you for your help and encouragement!

 

[todd]

the voltage will almost always drop a bit when your pulling a load from it.
12.8 volts at a rest.. if its being charged you will see more.. most charge controllers put 12.8 -16 volts into the battery depending on depth od discharge. as the battery gets fuller the voltage and amperage put in gets smaller.

so yes if your battery is full your charge controller shouldn't be putting a lot of voltage into your battery. maybe 12.6 to 13 volts. and a few milliamps

when your testing the battery to determine how full it is remember to disconnect the charger and let the battery rest a bit. ( minimum 15 minutes, a few hours is best but not practical). you want to read the battery level not the amount of charge the panels are producing.

 

[DrewSTNY]

Any update? Were you able to get this installed and tested on more sunny days?

 

[freegander]

Thanks for asking. I've been living in my van since last Sunday (the 9th). The solar panel was mounted that day and we've been tweaking the configuration since.

Today, I figured out how to adjust the output voltage on the charge controller. I set it to 12.8 volts (Previously it had been set to 5 volts) and now it actually shows a red light when the battery is under charged and a green light when it's charged and it displays around 1.3amps or less for current (in my previous picture that was the LED that showed all 0s).

So, I think it's working? It seems to discharge and charge fairly quickly. But it's also been super cloudy and rainy here (the panel still reads pretty well even with clouds though).

All I know is we've been using the battery for a week and have been able to charge our phones, laptops, and run a small fan pretty well.

Should I set the charging voltage for 12.8 or something higher?

 

[DrewSTNY]

You could go higher. Does the battery manufacturer have a float voltage recommendation? Barring that, I would probably go between 13.5 to 14.5. It's more important to not let it go below 11 or 10.5.

 

[freegander]

You could go higher. Does the battery manufacturer have a float voltage recommendation? Barring that, I would probably go between 13.5 to 14.5. It's more important to not let it go below 11 or 10.5.

the battery came with no instructions. : \
on the battery itself it says cycle use is 14.5-14.9V and standby use is 13.6-13.8V. what is float voltage?

 

[DrewSTNY]

It's basically where the battery is fully charged and the solar panel is just maintaining a steady voltage.

I would probably go to the cycle voltage since you are using it all the time.

 

[DrewSTNY]

That's pretty sweet that the charge controller can handle such a wide range!

 

[freegander]

yeah, i set the charge controller to 14volts. we'll see if it works and doesn't blow up!

having solar is really magical. being able to watch movies in the middle of a national forest, completely disconnected from civilization...there's nothing like it ; )

 

[freegander]

i just found this site that auctions off items the government no longer needs. maybe stealing panels is a lot cooler, but it looks like this is a complete setup and the bid is currently only $300?
https://www.publicsurplus.com/sms/auction/view?auc=1831778