Johnny L

It looks fine to me from the photos. Nothing charred, nice 1% metal film resistors (or copies thereof). The mounting of the three transistors looks a little strange though. It looks like the main PCB (phenolic, loses points for that) was wave soldered, and the three transistors soldered on later by hand.
Good old through hole components! Ah, those were the days.
I wonder if it might be repairable.
Yes, overvoltage is bad. It's just that solar panels are current sources with a voltage clamp, so they are inherently current limiting.
So the battery had 20+ volts across it? That doesn't sound right. Is it possible that the battery was disconnected somehow? Is there a fuse that could have blown? Though usually the panel doesn't have enough current capability to blow a fuse. Maybe the fuse or wiring was loose? You mentioned a tap; could the tap have disturbed the wiring rather than the charge controller?
It may even be that the charge controller is still working (if you can get it back together successfully).

If the battery modules are from a motorised scooter, I would hope that they are not actually starter batteries, but rather deep cycle ones (but that can hopefully dish out decent current as well).
Bubbling means that water has been dissociated into hydrogen and oxygen. Are the battery modules sealed or flooded? If flooded, you may need to add water a little sooner than would otherwise have been the case. If sealed, that's not great, but some dissociation can be tolerated; as long as the vent didn't have to release pressure, the gases can combine back to water, and no great harm would be done.
I'm surprised that 6.5 A of charge current (just over 0.1 C) doesn't sound like too much charge current to me, so I'm surprised that the voltage rose to over 20 V, or sceptical that the current was only 6.5 A. With your 10 A solar charge controller (when it was working), you might have delivered more than 6 A, perhaps as much as 10 A. I would expect 60 × 0.15 = 9 A to be safe for almost any lead acid battery, and one designed for a scooter might possibly take even more charge current.
I hope your life comes together soon, and that you don't have any more electrical accidents.

Bummer 😞 your "home battery" should be ok, I think, but you should certainly refrain from trying that again 🙂. Good luck with the controller to come next week...

Just to chime in. PWM is always inferior to MPPT, except in perhaps a very specific case, and will only be so for a small part of the year (or day). PWM has no storage component - it really is just what it says PWM. It will connect the solar panel to the battery with a mosfet until the battery voltage exceeds a setpoint and then disconnect until it goes below setpoint minus hysteresis. So it also cannot output more current than the panel current. The big loss in efficiency is the fact that you lose all the power in the voltage mismatch between panel and battery. So if you have a panel that delivers 20V and 5A (at peak power in this example case), and a 12V battery, you will only be able to deliver 12V@5A to the battery, which means you lost out on 40W.

That could be a dual diode, and would have failed shorted. Most semiconductors fail shorted when they overheat like that.
I finally figured out why you thought it was so messy under there, with what looks like bare solder over some PCB tracks. That's actually a standard technique for increasing the current carrying capacity of printed circuit tracks. It's easy to do with standard wave soldering, where a wave of molten solder is passed at a carefully controlled speed over the bottom of the board.
It wouldn't have been the knock, but the reverse connection. It obviously doesn't have reverse protection, or if it does, it relied on a fuse that wasn't there, between the MPPT output and the battery.
Ah. No, the 21.2 V is probably you somehow reading the open circuit voltage of the panel, which will fall with load. The bubbling was probably the battery being short circuited by the MPPT, with no fuse to limit the current. 
It might be short circuiting the panels as well, which would cause the extra current. But short circuit current for a panel is usually only a little higher than MPP current, so that's a little weird. Maybe you have thin cables or a high resistance connection somewhere. Worth checking after the new unit is installed.
LEDs commonly fail either at high age, or very low age (first week or so of operation; the "bathtub curve"). Cheaper parts are not burn-in tested.
That is lucky. I note that PWM controllers are generally inferior to MPPT ones, but with single panel 12V systems, they can perform well. Some people even claim that they are more efficient than MPPT controllers for that situation.
If you mean the low battery voltage cut off, yes, that's good for battery life. See if you can set it as high as 12V. This will affect run-time. The ideal is about 50% SOC for lead acid batteries. This is a little over 12V no load and rested, which is often roughly 12.0 V under load (depending on many factors).
 

Hi all
Firstly, I must mention that I am not in the same league as the other members on this forum. Sometimes three really bad things can happen at once and it can take everything from you.
I'll spare you the details, but I ended up living in a caravan in the Karoo, isolated and helping on the farm in return for food and shelter. To be honest, I prefer this to society, but once covid is under control, I'll have to fight my way back.
For now, I have NO money, so what I have, I have to look after. No use suggesting I buy anything at this stage even if you mean well.
Someone donated a few rands so I can at least run my laptop, sound system, lights, be able to solder and keep a bunch of things charged, etc. I don't need more.
60A SLA (3x 20A motorized scooter batteries) 12mm X 300mm connector cables. I don't know the current rating, but it's overkill for sure. As thick as 300A jumper wire.
120W Panel (poly of course)
200W dinky "Alibaba quality" inverter (the only time I come near that output is when I use my 180W coffee grinder for 5 seconds in the morning) it's actually really okay for R550.
A now busted 10A PWM charge controller. The cheapest piece of cr*p on the market, but it worked well until I reverse polarised it on a starter battery this morning because I couldn't find my glasses. (I am middle aged and used to be middle class and understand electricity. I am livid with myself for this idiocy)
The controller started smoking immediately and was disconnected and the cranking battery is fine at least. Yet the controller still seemed alive. I took it back to my "home battery", connected negative and only touched the positive. The battery immediately started bubbling and I removed it within a second.
It was pumping 21.2v into the battery (the panel maximum short circuit current is of course about 6.5A). Idiocy #2, should've tested the battery out terminals first.
Could this have seriously damaged my SLA's within a second? They didn't get warm and the multimeter reading was still 13.2v as before the incident (I hardly manage to drop to 80% SOC and that's only after an evening of binge watching series with the sound system loud and using my soldering iron, AC and 12v lights on and recharging stuff)
The best load test I could do was the 180W grinder and the drop was down to 12.64v after 15 seconds and stabilised there. It has since recovered to 13v and slowly dropping to resting voltage as usual.
I'm sure it took a few cycles off, but that's okay. If they last a year, it's all I need.
Someone is giving me a more expensive, programmable controller which I'll receive next week, so it's me and the Magneto lamp until then.
Any opinions welcome.
Thanks
Johnny