Solar controller selection for existing pannels

[All_I_could_aff]

I recently acquired several pieces of road construction type equipment. Each unit was equipted with either five 90 watt solar pannels, or six 75 watt panels (450 watts either way). The charge controller on all of the units is the same model, but seemingly very basic. See attached pictures.
I don't believe the controllers are working properly. In full sun, with my multimeter on the terminals coming from the pannels I am showing about 18 volts, as expected. However, I am showing the exact same voltage on the terminals going to the battery compartment. I would have expected to see output aroun 13 or 14 volts.
I plan on buying a more modern controler at some point, but was hoping to get it working first with the existing parts, but now I'm uncertain.
If anyone has any thoughts on this particular 15 year old controller, or recommendations for a modern controller, I'd appreciate it. Keep in mind I plan on starting with 3 of these panels installed, but I think I want a controller with the ability to handle 5 or six of these panels.

[red31]

Salvo wrote:
That's a great graph. I don't understand why panel voltage is lower when in float. Is that really float?

Actually the battery voltage plot doesn't look right. When charging, it should be ramping up. Outside of a couple of bumps, it's flat. Why is there a bump up around 10:00?

very shaded/low light. low charge current, it was ramping up just slowly, I never figured out how to capture the data and make my own graph with expanded scale. I hooked the controller to a PC and used view star's software and screen capture to get the graph.

[MrWizard]

That increase is when the sun gets high enough to increase output from the panels, the time of morning that happens will depend on your location/ latitude

[Salvo]

That's a great graph. I don't understand why panel voltage is lower when in float. Is that really float?

Actually the battery voltage plot doesn't look right. When charging, it should be ramping up. Outside of a couple of bumps, it's flat. Why is there a bump up around 10:00?

[red31]

Here is a graph of my panel/battery voltage
The batt and panel have the same voltage until the 14.6v batt set pt is reached.
At that time, panel V seems to rise, this is PWM, connecting and disconnecting the panel to limit power to the battery to maintain the set pt V. Connected, the panel voltage = batt V, disconnected, the panel voltage is Voc, the controller's V meter reads this as an average and as more time is spent disconnected, the panel V rises. The lower panel V after it peeks ~20V is due to low light conditions, the controller goes to float (13.4v) ~noon.


Data captured from a View Star 1024BN

Here's my concept of 50% PWM duty cycle, the controller displays 'PV 17.9v, 2A', 'Batt 14.8v, 2A'

[All_I_could_aff]

Thanks everyone, I have panels set up In my yard and 2 hungry batteries standing by for this weekends testing.

[Boon_Docker]

OP - If you are getting 18v from the panels and 18v output from the controller then your controller is more than likely a PWM controller and it may be functional. Hook up the panels to the controller and controller to a battery and see if it will charge the battery and then shut down when the battery is fully charged.

[Almot]

Mr Wiz - right now I have a fainter yet idea of what the OP wanted to know :)... Though it looked a little clearer at the beginning.

OP - if you only have room for one or two panels, then 20A controller is plenty. If your existing 30A works, - keep it. Or get some better 20A PWM model.
Yes, 2*90W panels with small PWM controller and 12V battery should be wired in parallel.

[Ed_Gee]

red31 wrote:

Ed_Gee wrote:

red31 wrote:

All I could afford wrote:

In full sun, with my multimeter on the terminals coming from the pannels I am showing about 18 volts, as expected. However, I am showing the exact same voltage on the terminals going to the battery compartment.

Is this attached to a battery?

attach to a battery and remeasure and re-post results.

New, those panels should measure 21v not connected to a battery, relatively cool, 25C.
connected to a battery while charging, you should measure batt V.

Red31 raises a good point. In all probability that controller needs to be attached to a battery before you can assess whether or not it is working. However, his comment that open circuit panels should show 21VDC is questionable ... that depends quite a bit on the design of the panel ... my new monocrystaline panels show 18VDC open circuit, as yours do so in all probability your panels are OK.

the sticker on the back of the panel shows 21.6 Voc, rated 17v (Vmp).
here's the new panel specs in a different format
http://www.solardirect.com/PDF/SolarElectric/sr90p1n.pdf

Red31 -- I apologize for my misinformation. I was thinking of maximum power point rather than open circuit voltage. My panels also measure about 22 volts when nothing is connected to them - Grape Solar model GS-S-160 monocrystaline.

[red31]

All I could afford wrote:

but was hoping to get it working first with the existing parts,

[MrWizard]

In OP, I don't remember anything about using these on the RV
The panels are on the construction equipment
And the question was what do I need to get it working

I answered that question
Almot answered what you really wanted to know
Maybe he's becoming a mind reader

[pianotuna]

Hook up a hungry battery and retest.

[All_I_could_aff]

Thank you everyone for your valuable advice. I am definitely wanting to purchase equipment ones with an eye toward future capacity increases. I only have room on my roof for one and possibly two of these panels. My plan was to try that first with the existing controller in my backyard and monitor the results.
I understand the differences between PWM and MPPT controllers as well as the price difference, but I am willing to pay more for a more efficient controller which will better utilize the available power of whatever panel is installed, especially considering my limited roof space.
I want a controller that will handle the full power output because on some trips I may choose to bring one or two additional panels which I could locate on the ground near the trailer if desired as well has the two on the roof.
Up until this point in my life my only experience with solar and I camping situation was my 45 W harbor freight "hobby grade" I have gotten through several long weekends dry camping with that kit and my 2 12V batteries, that was with rather frugal energy rationing and I would like to be able to be less worried about power.
By the way for those of you who were asking, my boss and I got all of this used equipment for free, so anything I can salvage is a blessing. Now, about the wire, The way they had it wired from the factory had two of the panels in parallel running down to the controller on one wire pair and then the other three panels in parallel on a separate wire pair. The equipment with the six 75 Watt panels had three in parallel on one wire pair and the other three on a separate wire pair to the controller.
Thanks again.

[red31]

Ed_Gee wrote:

red31 wrote:

All I could afford wrote:

In full sun, with my multimeter on the terminals coming from the pannels I am showing about 18 volts, as expected. However, I am showing the exact same voltage on the terminals going to the battery compartment.

Is this attached to a battery?

attach to a battery and remeasure and re-post results.

New, those panels should measure 21v not connected to a battery, relatively cool, 25C.
connected to a battery while charging, you should measure batt V.

Red31 raises a good point. In all probability that controller needs to be attached to a battery before you can assess whether or not it is working. However, his comment that open circuit panels should show 21VDC is questionable ... that depends quite a bit on the design of the panel ... my new monocrystaline panels show 18VDC open circuit, as yours do so in all probability your panels are OK.

the sticker on the back of the panel shows 21.6 Voc, rated 17v (Vmp).
here's the new panel specs in a different format
http://www.solardirect.com/PDF/SolarElectric/sr90p1n.pdf

[Almot]

MrWizard wrote:

what part about PRE EXISTING did you not see

All of it :)... Because brain wired to my eyes can't process this.

See for yourself: "I plan on buying a more modern controler at some point, but was hoping to get it working first with the existing parts, but now I'm uncertain".

More modern controller is not necessary, strictly speaking, if old PWM works. Though it won't work with 5 and more panels, because 5*6.1>30.

Now, existing panels - if they want to keep those - it's better/easier to use MPPT controller with those, than PWM. There isn't much sense in using existing panels though. It is better/easier to install 2*250W than existing 90W modules.

Now, about "getting it working". Panels - usually - work. They are aging, surface gets milky and scratched, output drops, but they "work". I would not use old panels for a new install unless in dire financial straits, but a purchase of several pieces of road construction equipment somehow doesn't fit in this picture. Existing panels as a temporary setup needed to get some energy right now, leaned against my shack, without mounting them - yes, maybe. Buying a new controller specifically for for old panels - not sure.

Thick wire in the picture is on the "battery" terminal, i.e. was used for a short run from controller to battery. #4 wire from 450W/12V panels wired in parallel is a different thing, this they will have to buy and install IF they want to keep the existing panels. Depending on the length, #4 might not be even thick enough for 450W.

But - yeah, sure, they can keep existing panels and get a new controller.

Sorry Mr Wiz.