Is this solar panel worht keeping?

[Ostinato]

I have a 30 yr old solar panel that given the obvious deterioration I would discard but the output voltage is on or slightly above spec. Should I keep it or am I missing something?

[Shrew]

Is it outputting the appropriate amperage? IMHO that is what really matters.

[BlackHeron]

If it ain't broke...

Are you planning on a long passage where the failure of this panel may become an issue?

Are you a bit short on power where replacing this older panel with a newer more-efficient higher-wattage panel with the same or similar footprint might make a significant difference?

Or could you wait another year or two where maybe an even more efficient panel of this same size may come out and yield an even greater power increase over one bought today?

If this is the biggest boat problem you have to deal with at the moment count yourself lucky.

[Jim Cate]

there are two simple tests to run: At near noon on a sunny day, with the panel set square to the sun, measure t he open circuit voltage and the short circuit current. If they are anywhere near original specs the panel is serviceable.

I've had some that looked equally "bad" that worked on our boat for long periods.

Jim

[BugzyCan]

Personally I would turf it and get a new one. 30 yrs old, it is bound to contain something that will kill you or cause cancer, and new things just feel so much better. You can probably double the output with a new one of the same size too, or more.

[Ostinato]

Originally Posted by Jim Cate

there are two simple tests to run: At near noon on a sunny day, with the panel set square to the sun, measure t he open circuit voltage and the short circuit current. If they are anywhere near original specs the panel is serviceable.

I've had some that looked equally "bad" that worked on our boat for long periods.

Jim

Thanks everyone - just what I needed to know. I should have checked the amperage. Will do it in the next day or so and then if it’s good decide how I going to use it.

[ozsailer]

Gday Ostinato,
OK the panel may be working BUT, 1) the panel is 30 years old, 2) the efficiceny by build must be on the lower end of its life, 3) Efficiencties of panels have increased remarkedly over this time 4) For the same size panel or close to it I think you will find that you can purchase a unit the same size with two to three times more output. 5) the cost per watt has dropped significantly and you will get more bang for your buck. 6) I am guessing here but I would suspect you have a solar controller of the same vintage - upgrade to a MPPT controller at the same time - these have also come down in price for far far greater effeciencies.


Greg H
Lagoon 440

[Cliffhanger]

I recently replaced two 80W panels that were nearly 30 years old with a single, high efficiency panel of 415W. The new panel is only slightly bigger that the old ones. Now I never have to run an engine to charge the batteries.

On the one hand "if it ain't broke don't fix it" If you don't need the extra power, I'd just leave it.

[hzcruiser]

Originally Posted by BugzyCan

[...] 30 yrs old, it is bound to contain something that will kill you or cause cancer, and new things just feel so much better.

Pretty sad attitude, isn't it?

A lot of people 'swear' by their old stuff, as it is reliable and easy to service rather than new devices that are mostly made to a price point, which means not for longevity. Once a part breaks, it's often difficult or impossible to get spares or manufacture intricate plastic parts yourself.

Even with a 3D printer I wasn't able to produce a plastic replacement of the same dimensions than the old one that would hold up well enough to work.

Re the solar panels, as Jim mentioned, just measure open voltage and short current to see if the panel is electrically up to snuff.

Some people might not know how to do this: open circuit is easy: disconnect the leads and measure the voltage. For a 12V panel it's usually above 18V.

Short circuit is not so easy, depending on our meter: If your meter has a 10A setting you can measure panels up to about 120W (10 A * 12V) directly by putting the meter across the panel leads, again with nothing else connected. If your panel is bigger or meter is smaller, you need a shunt resistor which has printed on it the capacity in Amps and voltage it would drop if that current is being passed: e.g. 100A/100mV meaning you can measure 100 mV across the shunt leads if the panel puts out 100A. In other words, the voltage on short circuit is going to be very low.

[Jim Cate]

^^^^^^

Heinz, it seems to be a 50 W panel and the short circuit current around 3+ amps, so most DVMs should be able to measure directly.

Jim

[barnakiel]

Measure Amps. Keep if fine. Dispose responsibly, if expired.


One of our panels has similar damage but works well anyway.



b.

[Jim Cate]

so. it appears that we are not alone in having panels with similar appearance that still work more or less normally. Does anyone know what causes this appearance change, and why it seems to have little effect?

Just curious...

Jim

[BlackHeron]

If you have a decent solar controller it'll tell you exactly how much power the panels are making and at what voltage. If you have multiple panels just unplug the others for a few seconds while you read them to check each one out individually.

I can tell at a glance if I have the panels articulated well or not by how many watts they are all putting out. When there is a problem with a panel or the wiring it shoes up immediately in the displayed numbers being lower than expected for a given level of sunshine, angle of the sun, and factoring in any shading issues.

[RaymondR]

The wattage rating of the panel is the output current at a certain voltage not the short circuit output. It's usually at the voltage where the wattage output is the highest, which is what is exploited by your MPPT controller to maximize battery charging.

So to find out the amount of output deterioration you need the measure the ampage with sufficient resistance in the circuit to force the voltage up to the rated voltage. Measure the current at this voltage and multiply the two.

[hzcruiser]

Originally Posted by RaymondR

[...]

So to find out the amount of output deterioration you need the measure the ampage with sufficient resistance in the circuit to force the voltage up to the rated voltage. Measure the current at this voltage and multiply the two.

Well, the "rated" voltage would not be the one where the panel delivers the maximum power. The max power varies a little bit all the time, that's where MPPT comes in.
Apart from that, not many people would have the knowledge nor tools to "dial in" a variable resistance that can consume the power of today's panels.
Hence why other options were suggested above.