More solar questions

[GATJcampers]

New to solar, trying to figure it out and have some questions. I have 2 brand new 6 volt golf cart batteries from sams club wired in series. I have a new 100 watt solar panel kit that came with the panel, wiring and charge controller. I'm not getting the correct voltage at the batteries. I've run a bunch of tests and suspect the charge controller is bad. So I plugged the panel directly to the batteries. open circuit test show I'm getting about 20 volts from the panel. Then hooked up to the batteries it shows 12.1 and holding for the past hour. It is all hooked up properly. Could the batteries be bad? I have a newer better charge controller on the way but now I don't know if that's the problem. I have a previous post named understanding solar that has a little more back ground info. Any help is appreciated. Thank you

[grizzzman]

I tested every panel "before" they got hung on the roof of several M/H and trailers. shorting will not hurt a panel.

[time2roll]

I did mean exactly what I said to short the panel wires together to measure the Isc.
Use a wire nut if you like. Then measure the current with the clamp-on ammeter.
Not a big deal and no harm to anything.

[BFL13]

ajriding wrote:

time2roll wrote:

GATJcampers wrote:
With no load on the rv and the batteries still connected I set clamp to DC amps and got .45. Batteries still at 12.1. I understand you say it can take days but I've done that and they are just not charging. I'm sure some of that is my lack of understanding but it just doesn't seem like the panel is any help.
I do have a volt meter also.

If you remove the panel from the battery and short the panel terminals together then what is the amp reading on the meter? s/b close to 5 amps at noon or the Isc rating.

MrWizard pointed this out.
DO NOT SHORT THE SOLAR PANEL WIRES OUT. Do not connect the solar panel positive to the panel negative, this will destroy the panel. The guy did not mean to "short" anything, rather to put a multi-meter on it, and "short" is not the correct term…. But if you just measure the voltage straight off the solar panel you should see 20 volts in good sun. If less than 18 then you probably have a bad panel. If less than 12 then it is trash.
Always use a good charge controller, not the $12 ones. You will spend $80 or more. Sun Saver makes one I have been happy with, and it has some heft to it.

The batteries from an auto parts store are almost always decently charged, not sure about Sam's Club, probably they were charged at the factory and never again.

Always get the newest batteries that you can find. Always get ones of the same age if you are running in parallel (for 12 volts systems), for 6 volt in series this is not an issue.

One 100 watt panel is enough to keep batteries charged, but not a lot to boondock. If you plan to use DC power off just the solar consider at least 200 watts, 300-350 if far north, cloudy/rainy a lot, or in the winter (low sun angle), or have kids that constantly charge devices.
If you plan to use an inverter and run a lot of household things then you need more…

Some solar controllers operate by shorting the panel, so how could that destroy the panel?

Scroll down to page 4 of 24 "ASC For Non-Solar Applications"
http://specialtyconcepts.com/SPECIALTY_CONCEPTS_PDF_FILES/ASC_INSTRUC_MANUAL.PDF

[ajriding]

time2roll wrote:

GATJcampers wrote:
With no load on the rv and the batteries still connected I set clamp to DC amps and got .45. Batteries still at 12.1. I understand you say it can take days but I've done that and they are just not charging. I'm sure some of that is my lack of understanding but it just doesn't seem like the panel is any help.
I do have a volt meter also.

If you remove the panel from the battery and short the panel terminals together then what is the amp reading on the meter? s/b close to 5 amps at noon or the Isc rating.

MrWizard pointed this out.
DO NOT SHORT THE SOLAR PANEL WIRES OUT. Do not connect the solar panel positive to the panel negative, this will destroy the panel. The guy did not mean to "short" anything, rather to put a multi-meter on it, and "short" is not the correct term…. But if you just measure the voltage straight off the solar panel you should see 20 volts in good sun. If less than 18 then you probably have a bad panel. If less than 12 then it is trash.
Always use a good charge controller, not the $12 ones. You will spend $80 or more. Sun Saver makes one I have been happy with, and it has some heft to it.

The batteries from an auto parts store are almost always decently charged, not sure about Sam's Club, probably they were charged at the factory and never again.

Always get the newest batteries that you can find. Always get ones of the same age if you are running in parallel (for 12 volts systems), for 6 volt in series this is not an issue.

One 100 watt panel is enough to keep batteries charged, but not a lot to boondock. If you plan to use DC power off just the solar consider at least 200 watts, 300-350 if far north, cloudy/rainy a lot, or in the winter (low sun angle), or have kids that constantly charge devices.
If you plan to use an inverter and run a lot of household things then you need more…

[time2roll]

GATJcampers wrote:
Did some test today
Voc 19.75 (label says 21.6)

Isc test with leads in the plug 0.0 amps
test by short circuit with clamp meter 2.85 (5.74 on the label)
not sure what it means. panel bad?

Clean panel with NO shade pointed direct at the bright sun on a clear day around 1 pm seems weak. Very weak.
I would be contacting the seller.

[BFL13]

GATJcampers wrote:
Did some test today
Voc 19.75 (label says 21.6)

Isc test with leads in the plug 0.0 amps
test by short circuit with clamp meter 2.85 (5.74 on the label)
not sure what it means. panel bad?

The panel heats up when the sun is on it, so it has lower Voc, like the 20 you are getting.

Amps depends on brightness of sun and you get less with sun off angle, most with panel aimed right at the sun. The 2.85 could be right for the conditions.

Not sure what you are getting there with plug vs clamp-on readings. Might be wrong setting on the multimeter in the plug? Or a bad plug is the reason you are not getting amps through to the battery?

It is possible to get the voltage but have trouble with the amps if there is something wrong with the wiring ISTR

[GATJcampers]

Did some test today
Voc 19.75 (label says 21.6)

Isc test with leads in the plug 0.0 amps
test by short circuit with clamp meter 2.85 (5.74 on the label)
not sure what it means. panel bad?

[Wild_Bill_888]

“Your small solar system may not be able to reach bulk voltage but it will still be able to charge.”

Certainly true if the battery is disconnected from the rv and the battery self discharge current is low. But, if the rv loads average 0.8 amps or more in the example, the batteries will die.

[2oldman]

GATJcampers wrote:
Is it possible to be defective and show 20 + volts? Maybe it's giving hardly any amps? Thoughts?

It's possible, but it's more likely to show lower voltage as well due to damage to parts of the panel.

[red31]

GATJcampers wrote:
Unfortunately that last test wasn't at noon, it was more like 3 pm. When I open circuit tested the panel it was giving 20 + volts. Is it possible to be defective and show 20 + volts? Maybe it's giving hardly any amps? Thoughts?

Yes.

BTW you controller 'turns on' anytime the battery is below 13v. panel and batt v should be very close when actually charging but if the panel can only make .7A then that is an issue, be sure to set you clamp on to DC and only clamp one around one wire.

[CA_Traveler]

2oldman wrote:

GATJcampers wrote:
The charge controller has a cut in of 13 volts and a cut out at 14.2 volts. I expected it to be in between those numbers. Not the battery volts(I understand 12.7 is full) but during the charge I expected it to be between those numbers..

My experience is that's not how it works.

Discharged batteries will see a slow rise in voltage to the numbers you expect.

X2

It MAY rise to bulk/absorb charge voltage of 14.8V. It will not cut out but as the battery becomes charged it will drop to float voltage of 13.4V. OK the controller will cut off at night during the multi day charging.

Your small solar system may not be able to reach bulk voltage but it will still be able to charge.

[2oldman]

GATJcampers wrote:
The charge controller has a cut in of 13 volts and a cut out at 14.2 volts. I expected it to be in between those numbers. Not the battery volts(I understand 12.7 is full) but during the charge I expected it to be between those numbers..

My experience is that's not how it works.

Discharged batteries will see a slow rise in voltage to the numbers you expect.

[MrWizard]

Note
The short circuit test is with a digital multimeter on the 10 amp setting
Connected between the positive and negative wires

The wires are not connected together without the meter
You can not read the amps flow that way
Unless you have a DC amps clamp on meter

[CA_Traveler]

For my flat mounted panels I use 2/3 panel power for 5 hours to adjust for losses.

Hence for a day with flat mounted you would get 5.7A*2/3*5 hours = 19Ah. For 220Ah batteries for example at 50% charge it takes 110/19 = 5.8 days to charge.

Agreed with above. Discharged batteries result in shorter life. Get them charged.

Consider at least a 3 stage automatic charger for $40 and 30A ($70) is better.

Typo correction.