Input voltage from panels stays at 5vdc regardless of solar panel voltage

[wa_desert_rat]

I just completed the installation of my solar array on our motor home. 640 watts. First connected two 68-watt Unisolar panels and let that run for a day with no problems. Then added one 240-watt (24v) panel and that was ok. Added the second 240-watt panel on a cloudy day with little voltage and the Classic 150 input voltage was all over the place. This is to be expected.

But this morning the 150 showed 5vdc input when the panels at the combiner box showed 70vdc. Voltage at the input of the 150 shows the same. Yet, even with zero solar panel voltage the 150 shows that same 5vdc.

Battery bank voltage looks about right. The 150 says it's "resting".

No kidding!

Don't know the SW version.

Any ideas?

Craig

[Westbranch]

you will need to tell us HOW those panels are connected, series, Parallel. of some other combo before we can understand your setup...

I agree something is very strange.  Are there any error messages?

I seem to remember something about a  low voltage reading when resting, ie like a remnant.

For FW version press the left most < button repeatedly (6 or 7 ?) to find RFR reason for resting and FW version..

[tecnodave]

Craig,

It is normal for a Classic to have about 1/2 battery voltage at the input when no voltage from the panels are present. I am thinking check your connections between the combiner box and the input of the Classic. If you have an open connection there it would just as you describe.

When posting it will make it easier to understand problems if you will describe your system as fully as possible to aid in diagnosis. Panel voltage, amps , way wired , battery volts , type , amp hour rating
Every little bit of data will help everyone helping with problem.

td

[wa_desert_rat]

Panels are all in series... two 12vdc (nominal) and two 24vdc (nominal).

There is 5vdc showing when there is NO PANELS CONNECTED.

It's not an open connection. I can measure voltage at the input pins with the cover off.

Is there some sort of reboot or reset to factory?

Craig

[vtmaps]

There is 5vdc showing when there is NO PANELS CONNECTED.

That's normal (and is a frequently asked question).  Technodave explained it in the 2nd reply to your question.

--vtMaps

[wa_desert_rat]

Thanks for that. I missed the implications. My bad.

I have a place in the cabling right behind the 150 where I can measure solar panel voltage and that's all showing appropriate readings. I'll take the cover off in the morning and see what's up.

Craig

[zoneblue]

Panels are all in series... two 12vdc (nominal) and two 24vdc (nominal).

That sounds a bit nasty. Whats the Imp of all those panels, hopefully not too far off?

[Westbranch]

Panels are all in series... two 12vdc (nominal) and two 24vdc (nominal).

That means that you have 2 series arrangements: 2 panels  @ 12 V = 24 volts and 2 panels @ 24V = 48 volts...  That is not going to work.

You can not combine a 24V array with a 48V array and expect to get any thing from that arrangement. 

First connected two 68-watt Unisolar panels and let that run for a day with no problems. Then added one 240-watt (24v) panel and that was ok

This is probably why you did get something from 2 old panels  and 1 new panel as they were all 24V

[tecnodave]

Craig,

The real problem here is these two panel types are pretty incompatable, the Uni-Solar are about 4.1 amps where the larger panels are 8 amps or so. A series setup with different currents will not work well or not at all.  A parallel setup will be difficult as well as the real voltage (Volts at max power) must be within 1 volt or better for good results. Most of the large "24 volt" panels are 60 cell about 29-30 volts where your Uni-Solar are equivalent to a 36 cell panel at 18.7 volts times two in series is 37-38 volts. Now if yor had or bought 72 cell panels at 36-37 volts you could use two Uni-Solar panels in one string and the 72 cell panels in parallel with that.

I am doing that with Siemens (36 cell) mono panels with Suntech (72 cell) poly panels, that said I am an electrician and would not recommend such for a person who does not have experience with electrical circuitry.

td

[wa_desert_rat]

I'm not sure why any of these suggestions would solve the problem of 5 volts indicated as input when there are 50 volts on a DVM measured right behind it. I can understand that there might be issues of how efficient the system is in this configuration (or another configuration) but according to the information above 5 volts is pretty much indicative of zero input from the solar panels. I would have thought that at least it would show the voltage.

It was working great... and it's now back in the configuration it was in when it was working great. I suspect that there is something else going on...

Craig

[Resthome]

I'm not sure why any of these suggestions would solve the problem of 5 volts indicated as input when there are 50 volts on a DVM measured right behind it. I can understand that there might be issues of how efficient the system is in this configuration (or another configuration) but according to the information above 5 volts is pretty much indicative of zero input from the solar panels. I would have thought that at least it would show the voltage.

It was working great... and it's now back in the configuration it was in when it was working great. I suspect that there is something else going on...

Craig

You keep indicating "measured right behind it". Not sure what that means. Shut the Classic Battery and PV breakers on and take the front cover of the CL150 off ) be careful if this has a MNGP with the attached cable. Turn the Breakers back on. Measure the voltage at the PV terminals inside the Classic and tell us what it reads at the PV terminals.

[tecnodave]

Craig,

The 5 v. In would be normal for a 12 volt system. It is battery power coming back through the controller that you are seeing.

One issue that might have come up by tying all these panels in series is that there are series bypass diodes and sometimes reverse flow diodes in the junction boxes of the panels. It is possible that the larger panels have overloaded the smaller panels bypass capability and blown the diodes. Next step would be to check each panel separately and verify power out of each. Just a voltmeter will verify voltage only, try a small load on each panel to verify operation. A 12 volt light bulb for example will be a good indicator that the panel is producing.

I am pretty sure that the thin film panels do have reverse flow diodes and they are buried in the sealed junction boxes. Next to impossible to get to.

The easiest way to use panels that are not compatable with each other is to use two charge controllers each with their own array and connected to the same battery bank.

td

[boB]

Craig, are you measuring 70 volts at the input terminals of the classic with your multi meter while at the same time you are seeing 5 volts on the classic display ?

At one time you mentioned that you saw 5 volts on the display with no panels connected which may be normal for your battery voltage if it is a 12 volt battery system.

What is your battery voltage and is that voltage agreeing fairly close with your multimeter ?

Just for grins, try wiggling the classics' terminal block to make sure it is in there right.

Needed a bit more clarification here and there but we should be able to figure this out.

The mismatch of PV may be a secondary concern but quite different than the 5 volt issue.

boB

[tecnodave]

Craig,

If your series stack of panels has only 50 volts here is where your problemlies.  If all wired in series as you have described  I would expect to see  18.9  plus  18.9  Plus  30  Plus 30 volts for a total of approximately 98 volts. If you have damaged one panel the voltage will not equal the total open circuit voltages of all the panels .  VOC  is volts open circuit ( no load ) where VMP or V@MP is the voltage when the panel is loaded to maximum power.

Again at this point I would suggest that you verify each peice by itself then try connecting to charge controller.

You need to collect data on these panels and verify the volts and amps of the panels are compatable.

Panels in parallel must have the Voltage the same within a few percent.
Panels in series must have the Current at max power the same within a few percent

td

[wa_desert_rat]

Just for grins, try wiggling the classics' terminal block to make sure it is in there right.

Finally! A suggestion that addresses my problem. Regardless of the voltage coming from the panels (and it makes no difference how they are wired... we're just talking voltage here) the 150 does not indicate it. And I can measure the voltage from the panels at the busbar behind where I have mounted the 150.

Tomorrow I'll check that connector block.

But what I really want to know is if there is an easy way to reset the 150 to zero other than taking the battery out and disconnecting all power input. Will that bring me back to initial settings?

As far as the conneciton sequence goes, this is an experiment to see how the system works in various configurations. If I have to I'll simply put the two Unisoloar panels on another MPPT controller I have and let that one and the 150 work together. It's not as configurable as the 150 though.

First I need to find out why the 150 is not seeing input voltage.

Craig