Solar controller question

Interesting thread because I have had the occasional blown fuse (cause now found) on the battery side of Solar Controller and never even thought, nor read in the van’s manual, to disconnect the PV panel before replacing the fuse. Likewise for Leisure Battery maintenance/replacement. Furthermore there is no user friendly method provided, such as a switch or fuse, for isolating the panel.

So the good info in the replies shook me a bit and will stick in my head. Thank you.

That said, as somebody who made some of the first “solid state” and computer controlled devices managing and protecting the national grid ( showing my age), I am disappointed that these solar controllers, with all the computing power I couldn’t even dream of, don’t have reliable fail-safe startup sequences built in. Moan over!!!
 
A MPPT controller basically turns the DC voltage from the panel into AC voltage so that it can be 'transformed' into a new voltage with maximum efficiency. This rapid switching creates noise and spikes every AC cycle which will be ocillating at several thousand times a second. These spikes get absorbed and flattened out by the battery when it's connected but could theoretically damage the controller if the output was left floating. Any decent manufacturer will add some sort of protection against these transient spikes and the long term ability to cope with not having the battery connected will depend on how well this protection circuitry is deployed.
So, there is an element of risk attached to having a panel connected to the controller when the battery is NOT connected but only if there is output from the panel.
Best to do any work which would leave a floating output when it's cloudy/evening, alternatively cover the panel or pull one of the cables going to the controller from the panel.
 
merl said:
Any decent manufacturer will add some sort of protection against these transient spikes and the long term ability to cope with not having the battery connected will depend on how well this protection circuitry is deployed.
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Is that what those rings inside with copper wire wrapped around them are for Merl? torroidal or something.
 
Loads of ways of skinning a cat, I suspect mostly a zenner diode across the output will be used. Here's a circuit that does just that below. D2 is the 24v 5 watt zenner and goes straight across the output and conducts/clamps/ shorts anything above 24v. It'll soon get hot though hence the 5 watt rating so wouldn't want to rely on it for long term protection when the battery isn't connected.
mppt .png

Those coils are to do with the actual voltage conversion, the ones about the size of your little finger end are typically used in the circuitry supplying 5V power to the usb port/ports which are often included on solar controllers these days.
The inductor/transformer used for the solar conversion on a MPPT controller is considerably larger, typically about the size of 1/2 a tennis ball depending on the capability of the controller, it's L1 in the circuit above.
Not thinking about starting up your own repair business are you Kev! 🤗
 
I have a vague recollection that the PCM-2012/2024 is not a genuine MPPT controller. Best way to be sure is check the current in and current out. PWM controllers will never have a higher current out than in. MPPTs will always have a higher current out than in.
 
It is genuine David, I bought it on the advice of two lads on facts both practising sparkies, very much into van electrics like yourself, one self employed, the other had a company doing work for british rail etc on charging equipment so knew his stuff.
 
trevskoda said:
The votronic has a fuse fitted which can be pulled if required.
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Are you sure that switch disconnects the solar panels? It would make much better sense to have a fuse in the battery lead at that point (to protect the controller, not the cable, in a fault condition). I do have one of those in a drawer. I'll try and remember to check what that fuse does.
 
Geek said:
Are you sure that switch disconnects the solar panels? It would make much better sense to have a fuse in the battery lead at that point (to protect the controller, not the cable, in a fault condition). I do have one of those in a drawer. I'll try and remember to check what that fuse does.
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Yes all in the instructions, and i have everything fused in my setup, im not a fan of the one bit does all in factory vans, most are junk.
electrics .jpg
 
Geek said:
Are you sure that switch disconnects the solar panels? It would make much better sense to have a fuse in the battery lead at that point (to protect the controller, not the cable, in a fault condition). I do have one of those in a drawer. I'll try and remember to check what that fuse does.
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I'd expect it to be on the solar side. As covered previously the controller needs a battery on it's output for protection so a fuse at that position would be potentially harmful rather than protective. BUT you do see some strange things sometimes!
 
merl said:
I'd expect it to be on the solar side. As covered previously the controller needs a battery on it's output for protection so a fuse at that position would be potentially harmful rather than protective. BUT you do see some strange things sometimes!
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I erred on the side of safety and had a fuse on the + above the roof and inside where it came in and also next to the LB +, I put fuse anywhere a + went through metal and grommets too on all circuits.
 
Pudsey Bear said:
I erred on the side of safety and had a fuse on the + above the roof and inside where it came in and also next to the LB +, I put fuse anywhere a + went through metal and grommets too on all circuits.
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I actually have fuses after the panel cable comes into the van as I didn’t realise the Votronic fuse did that when I first got it. I also have a Victron controller though (one panel to each) so it wasn’t wasted :)
 
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