Solar panels only provide trickle charge

[kalli]

Hey, 

bought a T25 maybe 4 years ago. It came with a solar panel on the back of a high roof (will attach pics later). 
Inside there's also a charge controller. but no matter what weather or what battery state, I never see the display show more than 1.1A charging, never more than lets say 15W

it looks very similar to this model: https://www.amazon.co.uk/ECO-WORTHY-Pan ... id-Battery 
So i expect best case scenario 100W 

I've tried cleaning the panel of course, but is there any electrical troubleshooting yo,u think I should do before I replace? 
Also I've noticed something odd:
- when I measure directly at the battery (in line amp measure betweeen battery minus and the disconnected battery minus cable), then I only measure 0.5A charge (meter is accurate, so I rather trust this than the charge controller). so where is the rest? when I measured in the night (no charge, I only have 100mA discharge (clock or radio)) - so I think I can exclude any other load?
- it never displays anything on output (usage). no matter if I switch on the stereo, or plug in anything in the USB port of charge controller (although the USB works)
- i also have a VSR (split charge relay) and noticed when leisure battery is empty, the solar panel will charge leisure (+500mA), but after 5 secs the relay kicks in and it tries to charge both, but i see -200mA (not charging! discharging) for a couple of seconds and then it clicks off again. 


Any ideas really appreciated, I'm very confident with cable tracing and multimeter, so ... shoot
 

[shepster]

See whats coming out of the panel on a sunny day (difficult this time of year I know) for starters and take it from there.

If you're getting a decent voltage from the panel then maybe the controller is shagged?

[sarran1955]

Hello,

I have had flexy solar panels on my van for about 10 years.
I find they last about 5 to 7 years.
The test voltage comes up alright at 18 volts, but only 500 ma instead of between 8-10 amperes under load. 
I changed the latest 1 by cutting the cables off the old panel and splicing in the new panel ones. This saves dismantling inside the vehicle.
The new panel was as powerful (200 Chinese watts=120 real watts), a bit smaller and 1/2 the price.
Hope this helps,
Cordialement,

[Mocki]

The key in your question is where you tell us the charge controller has a usb outlet….   It’s chineasium "pooh" !
It’s a cheap token controller . Swap it out for a MPPT controller , but first 
Disconnect the panel from it and read the voltage on the panel down leads in just day light . If you have 18v ish put a 21w brake light bulb across it and measure the voltage with a load , if it’s family steady , the panel is working g albeit maybe not the best , but it working 

[cobblers]

As Mocki says, if your charge controller has a USB port its a shoddy token chinese one and is best replaced - they're cheaply made and unreliable.
With a half decent charge controller, you'll be able to see the solar voltage and current directly on it's display (or via app) which makes diagnosis much easier.

If you just put the leads of your meter across the solar panel and measure the dead short current, in decent sun you should get 5 or 6 amps out of a 100w panel. But now is not a good time of year to try and troubleshoot this - my 150w panel peaked at about 12w today. The half an amp you're getting at the moment is actually about all you can expect this time of year.