A few more questions about solar panels...

[Qwazert]

As you may recall...I had some issues with my solar panels/batteries a few weeks ago.
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/30348700.cfm

I've since bought a new controller (because the old one would show the batteries as Charged even though they obviously weren't) and I've come across another puzzle....
The controller is a RENOGY Voyager, rated at 20 amps which should be sufficient for my 100W panels.

Here are the details of my solar panels: The first is an offshore-made flexible type...


and the second is a rigid style, like the type you get mounted to a roof...


As you can see, the specs are fairly close and do NOT exceed the ratings on the controller.

Here's the interesting part; when I connect only ONE panel I get a charging current of around 2-3A.
If I connect the second one in parallel, the charging current either stays the same or decreases slightly.

The controller has built in reverse polarity protection and it gives no errors, so I'm 99.9% certain that the panels are connected properly.
So why am I getting LESS current with the second panel connected?
Does the controller sense that less is required because the batteries are fully charged (still connected to shore power)?

[Qwazert]

Another update...

Spent the past two weeks "dry camping" and we brought along our "spare" 100W rigid solar panel.
With the new charge-controller in action, we had ZERO issues with the batteries this time.
By the end of the second week, I put away the rigid panel and just used the flexi-panel on the roof. Controller was drawing between 5 and 7 amps first thing in the morning and was down to 1 or 2 by noon...into fractions by dinner time.

I call it a success.

[Qwazert]

CA Traveler wrote:

Qwazert wrote:
Everything appears to be working as it should...but I need AT LEAST another 100W of solar-grabbing capacity.

Absolutely and then you'll need another 100W and then another... :B

Well, as I mentioned a few weeks back...my buddy has two 95W panels on his roof, the same batteries and never has an issue.
We have similar camping "styles" and similar RV's. If I get another 100W flexi-panel...I'll be 10W up on him. 😄

[2112]

You can turn off the converter at the circuit breaker panel and continue evaluating your solar panels with shore power plugged in.

Run the fridge on propane to better simulate boondocking if you wish.

[CA_Traveler]

Qwazert wrote:
Everything appears to be working as it should...but I need AT LEAST another 100W of solar-grabbing capacity.

Absolutely and then you'll need another 100W and then another... :B

[Qwazert]

So this morning (before it got too hot) I unplugged shore power and let the RV sit for over an hour while I mowed the lawn and did a few other chores. Granted there was only parasitic loads (fridge sensor...USB outlets...etc) in play at this time.
After my work was done, I connected the flexi-panel first and tossed it up onto the roof like I usually do. The Controller showed 3 – 4 amps of charging current. Disconnected that one and then connected the rigid mono-crystalline panel...showed about 5 amps.
Battery voltage was about 14.5 in both cases.
Next, I connected both panels in parallel...controller current showed between 7 - 8 amps at first. Within 15 minutes, this dropped to around 4....then to about 2 (about 15 mins later).
Battery voltage was steady14.3 – 14.5
Solar-panel voltage fluctuated from about 19 volts at the beginning, to around 16 near the end (when controller-current dropped to 2 amps).
I went inside and turned on every light and fan there was...controller current jumped back up to about 5 amps and solar-panel voltage increased as well.
Left everything on for about 10 minutes then turned it all back off...within three to five minutes, the controller-current dropped to 2 amps and solar-panel voltage to about 16.


So it looks to me, that the problem I had in the very beginning (3 weeks ago) was that my single 100W solar panel just didn’t have enough “juice” to keep these heavy-duty batteries topped up.
Everything appears to be working as it should...but I need AT LEAST another 100W of solar-grabbing capacity.

[Qwazert]

red31 wrote:

Qwazert wrote:

I don't believe I have any way of forcing this controller into BULK mode...it does that part automatically.
And I don't have any little lights...just an LCD readout.

Which exact Voyager do you have? Is it the waterproof one or ?

This one...

[CA_Traveler]

Add a 20A load to the battery and that will cause maximum amps from your controller and confirm both panels are working.

[red31]

Qwazert wrote:

I don't believe I have any way of forcing this controller into BULK mode...it does that part automatically.
And I don't have any little lights...just an LCD readout.

Which exact Voyager do you have? Is it the waterproof one or ?

[Qwazert]

red31 wrote:
the little lights on the controller indicate when the controller is in BULK mode.
Bulk mode is the only mode where the panels full power goes to the battery. The panels should operate at approx battery voltage during BULK mode. As the battery voltage rises, panel operating voltage will rise to match that of the battery.

Other modes, power is limited to maintain a constant voltage. The panel is turned on/off to keep the voltage at a certain set point.

So the controller needs to be in BULK mode for your test!

I don't believe I have any way of forcing this controller into BULK mode...it does that part automatically.
And I don't have any little lights...just an LCD readout.

[2oldman]

Qwazert wrote:
As I understand things, connecting them in series will not be much of a benefit, since I need more charging CURRENT, as opposed to higher voltage.

An MPPT controller will sort that out for you regardless of how they're connected.

[CA_Traveler]

Qwazert wrote:

As I understand things, connecting them in series will not be much of a benefit, since I need more charging CURRENT, as opposed to higher voltage.

In fact the amps would be the lower Imp panel.

Serial panels with a MPPT controller can be a better option depending upon a number of parameters. MPPT converts the higher voltage power to the battery voltage and increased amps. Basically the OP would get about the same amount of battery V and A for charging as the PWM controller with parallel panels.

[CA_Traveler]

As stated remove any other charging source and add 10A+ load (lights etc) and see what you get with 2 panels.

But be aware that the contoller amp output FIRST is used by any house loads and any excess then charges the batteries. ie With a 8A output 2A may be house loads and 6A battery charging.

[CA_Traveler]

I have two 12V panels...not a 20.8 and a 22.6...they are both considered as 12V panels.

That's Voc (open circuit) which is useful for testing panels. Vmp (maximum power) is used for power along with Imp. Voc and Isc (short circuit) are useful for testing a panel.

12V panels are generally 36 cells and Vmp is 18-20V. They are used as one or in parallel to charge 12V batteries with a PWM controller. The wiring loss is much less of a factor as long as the maximum battery charging voltage is maintained which is usually 14.4-14.8V. Panel temperature is another consideration.

72 cell panels can charge a 24V battery. 60 cell panels provide very limited voltage drop for 24V batteries.

[red31]

the little lights on the controller indicate when the controller is in BULK mode.
Bulk mode is the only mode where the panels full power goes to the battery. The panels should operate at approx battery voltage during BULK mode. As the battery voltage rises, panel operating voltage will rise to match that of the battery.

Other modes, power is limited to maintain a constant voltage. The panel is turned on/off to keep the voltage at a certain set point.

So the controller needs to be in BULK mode for your test!