Add panels to existing system?

[Bob Van Go]

I bought a van that already has 2 panels on top. They're the flexible kind and are probably old. I understand these wear out quicker than their rigid counterparts. I'm wondering if I can add a couple more panels in line with them, or would it be better to just replace them since I don't know the specs or anything on the ones up there so can't match them. Judging by the size they're probably 2 100W panels, but according to the controller I'm only getting 2.5 amps out of them maximum. I drained the battery down to 12.7V to see what I could get and the controller read 21V and only 2.5A for the PV. I should be getting a lot more. Are my panels shot?

 

[Rocketman]

Was it a bright sunny summer day at noon?

21v * 2.5a = 52watts - so you were getting at least a quarter of the power out of them (assuming 100w each). Now if it is the middle of winter with a low sun angle, you will get more power come summer.

You need to look up the specs of the panels to know if they really are 100w each. How are they hooked up series or parallel?

Is your Solar charge controller a mppt style? Or a pwm? If it is a pwm you can gain more power by switching to a mppt - like a Victron 75/15.

They might be good - one could be bad.

Can you get more solar watts on the roof if you replace them?

Good Luck

 

[sunshine_eggo]

Flexible panels generally don't last. It sounds like they should just be replaced.

What is your charge controller?

 

[Bob Van Go]

It's an EPEVER Tracer 40A MPPT controller. I'd have to unmount the panels to see what they are. Yeah, it's winter so sun wasn't directly above. Can't just add a couple more? I have some room.

 

[sunshine_eggo]

It's an EPEVER Tracer 40A MPPT controller. I'd have to unmount the panels to see what they are. Yeah, it's winter so sun wasn't directly above. Can't just add a couple more? I have some room.

They're probably just 100W. You should be able to produce about 50-60% in full unshaded solar exposure at high noon.

You could add more, but you definitely don't want to put them in series with them.

 

[Rocketman]

Yes you can add more panels - if more than three in parallel - each will need a fuse - there are MC4 fuses.
It is best if all the panels have the same electric specs:Vmp & Imp.

If the Vmp & Imp are not the same there will be a penalty- how much depends on how different they are. If you get the Vmp and Imp we can help figure it out.

 

[HarryN]

Most vans can easily have 2 or 3 each, 150 - 200 watt panels on top.

Just mount them cross wise.

 

[0truck0]

As said, rare to get 100% of the rated wattage. Need to be aimed directly at sun to get most available light possible.
No, they do not last as long, but until they go bad they are the same as any other 100 watt panel. How are they attached? Danger is they lay on the van roof and trap water and that caused van damage.

If you are $$ able to replace them, then I would replace them with glass panels. Just redo it all from the start, do it right.

If you know what your power needs will be that is a really good starting point. Maybe you only need 50 watts, maybe you need 500 watts, you tell us...