Probably the same place as last time it's out of the way and shaded; there seem to be loads of cheap simple mechanical thermostats available.
Some even have the temperature sensor on a lead up to a metre long which might give more options and better results.
It's a really neat idea and with the right type effectively gives the on/off function too, but better.
Just need to get the right sort, typically described as "blue button" that closes at high temperature, usually for fans/aircon etc.
So my Buck Converter arrived this evening from China.
No instructions of course but I quickly found this handy video of almost that exact model (9A vs my 10A):
It's a few mm thicker than the Steca original so may not fit in the original locations, but it doesn't need to be there of course, though probably safest.
It has adjustments for both maximum voltage and current, so I'll start off setting it to 12V and something less than 10A (the max on my multimeter) and see what the blower fan does when I connect it up.
I don't know what the output of the panel is capable of doing, or what the blower motor needs to operate gently but I'll work it out.
Does anyone have any thoughts on what limits to set on Voltage and Current? Given the information I've had from Sean (old model panel) I suspect they were set around 9V and the later model at 12V or slightly less.
IIRC the main blower fuse is 40A, though obviously the solar panel isn't going to get anywhere near that - it's almost 500W!
The panel is actually about 400*800mm so 0.3 sqm, which given the suns maximum power of at most 1000W/sqm and likely panel efficiency under 20% is just 60W, i.e. 5A at 12V. Research suggests 14AWG wiring (around 2sqmm) would be more than adequate and probably thinner would be fine.
Normal UK ring main cable is actually thicker at 2.5sqmm, lighting cable at 1.5sqmm would probably be fine.
Last edited by HPsauce on Mon Aug 17, 2026 10:49 pm, edited 1 time in total.
HPsauce wrote: Mon Aug 17, 2026 9:14 pm
Does anyone have any thoughts on what limits to set on Voltage and Current?
Interestingly when I asked AI it came up with some fairly low numbers, I think for the original version, with efficiency only about 10% in peak sunlight.
These were only around 12W, regulated to a mere 3.5V and up to 4A.
Thanks MJ. I've done a little bench test using a multi-voltage PSU designed for laptops that can do 12v-24v in steps and over 6A at any setting.
Seems to do what it says set to 10V and 5A with only minor variations at lower input voltages.
Intriguingly it has green and red LEDs, the green one comes on when there's input voltage and when testing output voltage; the red one when drawing significant current. No explanation I've seen of what they signify, but I guess green means ready and red working with a load.
Next step is to connect it to the solar panel and see what output that generates. If it looks sensible I'll try the blower connections briefly.
Incidentally the multimeter I used has rather thin (replacement, not original) leads and they did noticeably warm up with 5A through them, the actual unit itself not really much at all. I've changed it down to 6V/5A for initial testing in the car. That's limiting it to 30W of the theoretical (unobtainable) 60W maximum.
Grey day, definitely no sun, output is 6V/0.66A = 4W.
No idea if that will turn the fan at all though, I need to make up some appropriate connections/leads.
I'll see what happens set back at 10V.
Interesting, happy to run at both 10V and 12V so the panel is putting out something higher without sun.
Getting almost 0.8A on both so 9W which isn't bad at all. Just need to make up some connecting leads now, maybe after lunch.
