Should i switch off solar panels ?

Thread Starter

Rufus Chucklebutty

Joined Mar 23, 2019
13
I have 500 w of solar PV which is laid on a flat roof of my houseboat , naturally it produces nothing significant at this time of year in that position so I boost the battery charge with a generator and digital charger, should I install a switch to isolate the solar panels before I charge with the back up generator ?

Can you switch off solar PV without damaging the panels ?

I'm thinking the backup charger will be sensing the battery voltage that is being kept higher by the solar although the solar is not adding any charge.
 

KeithWalker

Joined Jul 10, 2017
648
Can you switch off solar PV without damaging the panels ?
The solar panels will not be damaged if you disconnect them from your charging system.
You may damage them by externally charging the batteries with them connected. It all depends on the configuration of the solar charger. It would definitely be safest to disconnect the panels and solar charging circuit when you are charging the battery with the generator.

Keith
 

dendad

Joined Feb 20, 2016
3,313
What is the charge controller?
Some have solar panel inputs and mains inputs, and if there are different inputs for each, it will be ok to leave them connected. But if you are worried, by all means, switch them off.
But if you do want to switch off the panels, make sure you use a DC rated switch as the AC switches can fail when breaking an energized DC circuit. There has been quite a few problems with home solar power systems when some less than competent installers have saved money by using the AC switches instead.
 

ArakelTheDragon

Joined Nov 18, 2016
1,327
I don't know this controller. If you want you can disconnect the solar panels and connect some light bulb or something in place of the solar panels to see will the light bulb light up, explode or anything else when you start charging the battery externally. Please measure the voltage on the light bulb when you are charging the battery, but be careful! You risk the controller as well, a new one is about "$15". Do this procedure more than once to be sure.
 

Rich2

Joined Mar 3, 2014
149
The answer always given on the motorhome forum (motorhome fun) is always leave them connected. The engines alternator is also always connected as well as mains hook up.

My solar controller always backs off when the engine has been running and it takes it a few minutes to start charging by solar again. My controller is the Votronic duo 250 mppt.

I've fitted a 60a isolater trip switch so the panels can be disconnected for working on or to reset the controller, but it would never trip by the panel current.
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/333018610095
 

ArakelTheDragon

Joined Nov 18, 2016
1,327
Another option is this diode:
RBO40-40G
You can check more about it here.

Or any bridge rectifier IC that supports the needed current and voltage. The bridge rectifier is for AC, but it will work with DC also and there are a lot of them for a cheap price. Like this one for "$1". Just don't forget to add the heatsink.
 

Thread Starter

Rufus Chucklebutty

Joined Mar 23, 2019
13
My main concern is the digital mains charger basing its charging cycle on not the true battery voltage but the higher voltage when the solar is producing voltage but no significant charging amps.
 

dendad

Joined Feb 20, 2016
3,313
As you are connecting the charger to the battery direct, that is all the charger will see. It will not matter what the solar voltage is, the battery is the thing.
 
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