I have used small solar panels for 15 years to keep batteries charged when toys are not use. I bought two new panels to hook up to other toys (motorcycles). These are just 2.5 watts. They have a built in controller even though one is not really needed for this application.I fully charged both motorcycle batteries on the normal battery tender and then hooked up the solar panels for use while the bikes are in storage. I have done this in the past but I needed to use my other solar panels for a different use this time so that's why I bought new ones now.Both of these panels seem to be pulling energy OUT of the batteries to the tune of 0.2 volts per day. The panels output the right amps and volts when hooked up to my multimeter but they are pulling juice out of the battery instead of putting juice in.Today I rechecked the panels with the multimeter and they output correctly when in the sun in terms of volts and milliamps. I then hooked them up each to their respective motorcycle and aimed the panels at the bright sun. The voltage on the batteries actually goes down right away by .05 volts in .01 volt increments once you hook up the panels. It only takes about 5 seconds to go down .05 volts. When you turn the panel away from the sun or unhook the panels the voltage on the battery goes back up right away by .05 volts. This can be replicated multiple times. This makes no sense. This is the same on two separate motorcycles with two separate batteries and two separate solar panels that are brand new.Why would this happen?Thanks.

Sounds like you have your positives and negatives switched hooking up to the batteries. Is everything labeled well?

The normal plug in battery tender charges these batteries correctly which proves that the leads are indeed hooked up to the battery correctly. If the leads were not correct then the plug in battery tender would have blinking lights and not charge the batteries. There is an sae connector at the end of the lead coming from the battery that plugs into the sae connector from the solar panel. So the leads are definitely arranged correctly. Thanks for asking.

I'm sure your battery is hooked up correctly based on the maintainer working just like you said. I'd be suspicious that the connectors from the solar panel are reversed (from the factory) except you said you checked them for voltage and output which was fine so it makes no sense.I'd just do a quick check on polarity of the solar connectors with a DVM if it were me just to make sure. Otherwise I have no idea why you are seeing the conditions you report. Good luck and let us know if you figure it out.

I just checked the panels again and there is no minus sign on the DVM reading so the solar panel wires and connectors seem to be arranged correctly. Thanks for the idea to double check that. :)

I would check the voltage of the panels while in the sun. Watch your multimeter. It should indicate + and -. Then check the battery. Both should be the same potential, such as reading +12 on the battery and solar panel. However if you read +12 on the battery and -12 on the solar panel, it would indicate it being hooked up backwards. Or you might be reading something like 8 volts in full sunshine. Indicating that you will need to wire more solar panels in series to get to something like 15 volts, so that voltage will flow into the battery, not away from it.Fred.

Solar panel problem | Good Sam Community

jefffoxsr
Explorer
Jul 13, 2014
rottidawg wrote:
It appears Battery Tenders and solar hook ups are wired backwards from each other! .

Yes that is what I finally figured out. So I have two connector leads on each battery. One for use with my battery tender and one for use with my solar panels. One of those connectors has the red to the negative battery terminal.
rottidawg
Explorer
Jul 13, 2014
I have been having the exact same problem.

It appears Battery Tenders and solar hook ups are wired backwards from each other! The following is a cut and paste from: http://www.sae2pin.com

Polarity being which side of a particular connector is “hot” (+) positive, and which side is (-) negative.
In the case of Battery Tenders, the connector polarity is driven by the necessity for it to be the “protected” female side of the SAE 2 Pole connector at the end of the assembly connected to a vehicle battery to be the “hot” (+) positive side. Therefore, the exposed pin side of the SAE 2 Pin on the end of a Battery Tender output must be “hot” (+) positve.
Portable Solar Chargers are a different situation, since the solar cells are a power source. Their output connection must therefore be of the polarity which will have the “protected” female side of the SAE 2 Pin connection being the “hot” (+) positive. Accessory assemblies must then be of a polarity in which the exposed male pin of the SAE 2 Pin meant to be plugged into the output connection of a portable solar charger must be the “hot” (+) positve.
Anyone connecting leads in circuits such as those discribed above must be carefully mindful of polarity. There may even be times when it is necessary to use a multi-tester to confirm polarity. The continuity test function of a multi-tester can be employed to determine which contact (or pin) on the connector at one end of a lead is mapped to (leads to) which contact on the connector at the other end.
westend
Explorer
Apr 11, 2014
Voltage drop when placed in direct sun may be due to heat. Battery discharging when module is not producing power is a lack of diodes.

I think you would be better served by upgrading to a larger, more robust solar module. 2.5W at typical Michigan insolation probably won't keep up with the battery's inherent discharge rate.
wa8yxm
Explorer III
Apr 11, 2014
hmknightnc wrote:
Sounds like you have your positives and negatives switched hooking up to the batteries. Is everything labeled well?

Second.

Another issue with many low cost panels (This is not your problem) is that in sun they generate power but in dark they suck it.

Solution is to install diode, yours (With built in controllers) should already have that feature.
big_buford
Explorer
Apr 11, 2014
jefffoxsr wrote:
I just checked the panels again and there is no minus sign on the DVM reading so the solar panel wires and connectors seem to be arranged correctly.

Thanks for the idea to double check that. :)

I also have a battery tender. Friend gave a 15w panel with same connector and aligator clips. When i use the clips from panel on the tender I have to reverse connection, put pos clip on neg.
1492
Moderator
Apr 11, 2014
Moved from Forum Technical Support
Golden_HVAC
Explorer
Apr 11, 2014
I would check the voltage of the panels while in the sun. Watch your multimeter. It should indicate + and -.

Then check the battery. Both should be the same potential, such as reading +12 on the battery and solar panel. However if you read +12 on the battery and -12 on the solar panel, it would indicate it being hooked up backwards. Or you might be reading something like 8 volts in full sunshine. Indicating that you will need to wire more solar panels in series to get to something like 15 volts, so that voltage will flow into the battery, not away from it.

Fred.
jefffoxsr
Explorer
Apr 11, 2014
I just checked the panels again and there is no minus sign on the DVM reading so the solar panel wires and connectors seem to be arranged correctly.

Thanks for the idea to double check that. :)
hmknightnc
Explorer
Apr 11, 2014
I'm sure your battery is hooked up correctly based on the maintainer working just like you said. I'd be suspicious that the connectors from the solar panel are reversed (from the factory) except you said you checked them for voltage and output which was fine so it makes no sense.

I'd just do a quick check on polarity of the solar connectors with a DVM if it were me just to make sure. Otherwise I have no idea why you are seeing the conditions you report. Good luck and let us know if you figure it out.
jefffoxsr
Explorer
Apr 11, 2014
The normal plug in battery tender charges these batteries correctly which proves that the leads are indeed hooked up to the battery correctly. If the leads were not correct then the plug in battery tender would have blinking lights and not charge the batteries. There is an sae connector at the end of the lead coming from the battery that plugs into the sae connector from the solar panel. So the leads are definitely arranged correctly.

Thanks for asking.

Forum Discussion

Solar panel problem

About Technical Issues

Related Content

Solar Panel

Solar panels

Solar panel identification

Attaching a solar panel

Solar Panel Expansion