12V DC routing

[Kim Christensen]

It could get way off if there is electrical storm activity.  No?

It's possible to have voltage induced by an indirect strike. Another possibility is an electrical leakage/fault in the area or wet/faulty Christmas lights strung up on the garage if you do that sort of thing.

ie: I mention the Christmas lights because I strung some LED ones along my aluminum railing one year. It rains a lot here, and while I never got a shock off the railing, I did notice odd spot corrosion on the railing afterwards. The lights also failed because the legs of some LEDS had corroded away. They just bend the legs over a plastic "bulb base" and jam them in the socket. Not waterproof at all, but were rated for "outdoor use". Whatever faith I had remaining for CSA (UL in the USA. CE in Europe) evaporated that day.

[Zero999]

It could get way off if there is electrical storm activity.  No?

It's possible to have voltage induced by an indirect strike. Another possibility is an electrical leakage/fault in the area or wet/faulty Christmas lights strung up on the garage if you do that sort of thing.

ie: I mention the Christmas lights because I strung some LED ones along my aluminum railing one year. It rains a lot here, and while I never got a shock off the railing, I did notice odd spot corrosion on the railing afterwards. The lights also failed because the legs of some LEDS had corroded away. They just bend the legs over a plastic "bulb base" and jam them in the socket. Not waterproof at all, but were rated for "outdoor use". Whatever faith I had remaining for CSA (UL in the USA. CE in Europe) evaporated that day.

Yes connecting to earth will help to protect against induced transients. A transient voltage suppressor diode is also a good idea. I've had a problem with an LM317 based float charger, a couple of solar panels and lead acid batteries: a 24V system. The regulator kept failing randomly, which was fixed by adding a zener diode between the input and output of the LM317.

[paulca]

So maybe, I should at least ground the solar panel system to a plug socket earth.  Not to protect it from lightening, but to stop it floating to some silly ass voltage in electrical storms etc.  I mean just because the once or twice I have measured it, it was within a volt of GND, doesn't mean it's always like that.  It could get way off if there is electrical storm activity.  No?

That's a good idea. It's better to earth the negative, to reduce corrosion problems. The only down side to it being earthed is increased risk of short circuits, if the positive were to touch a grounded object. Obviously a fuse is a must, both to protect the cable and the battery from fire.

I'm all fused up

Battery is fused at 10 Amps with 16AWG wire to the solar system which has a 10Amp load fuse.  16AWG to the caravan/boat distribution panel.  5 Amp inline fuses on all those switched outlets.  This use case will require a 20Amp fuse on the 6mm (technically 6mm should be good for over 30Amps, which should never be blown as the 10Amp to/in or from the controller will go first.

The spark is going to leave the tail in a surface box for me.  What I need to decide is how I terminate it.  For some reason I have a vision of a set of 4, 2xpairs of Black Red 4mm banana ports on the surface mount box.  It's that or DC barrel sockets or something.  Maybe I should hardwire it to another 12V RV distribution panel at the other end.  Thoughts?

[paulca]

Tamed spark is just away and I have a lovely tail of 6mm solid core, tuff-someit outdoor cable clipped up neatly between the garage solar panel and the upstairs office.

I have it jury rigged with Wago's on a 5Amp fuse and am reading pretty good voltage the far end.  Still to load test it but I might junction it better first.

[paulca]

Initial tests it works fine.  On light loads under an amp it barely drops any voltage. 

Running it at 3 Amps currently, through a boost/buck PSU to run a LiPo charger.  0.5V drop on the whole 12V 6mm setup.  The efficiencies of the PSU+Lipo charger is another story.

The battery is getting 12V @ ~2.6A.  The charger is consuming 12V @ 3.0A and the PSU is drawing slightly more at 11.00V from the panel.  It's like 50W for a 40W charge.  Gotta love boost/buck and resistive balancing.

[calzap]

Don’t think I would want a lead-acid battery in my office unless it was quite small with a secondary container and a gel or glass-mat type.   I’ve experienced a lead-acid hydrogen explosion.  Fortunately, it was in an out-building, and there was a wall between me and the battery.  It was in a secondary container which was damaged but contained most of the mess.   Still, there were acid-coated chunks of plastic scattered around the room.  Wouldn’t want it to occur in an office.

Mike in California

[wizard69]

there is not a lot of info here to provide a good answer but so far I'd have to say "none of the above".    Now realize I don't know what your goals are but your best return would be to put a micro inverter on the solar panel and use it to reduce the electrical bill continuously.    This way you are not wasting a lot of energy to charge a battery and your limited solar panel will always be doing something useful in cutting your electrical bill.   You will have to make this legal for the local authority though.

Now if this is a backup supply, if that is the goal, then you will need an externally housed battery, charge controller and an inverter and associated electronics/electrics to make the system legal in your area.

[paulca]

there is not a lot of info here to provide a good answer but so far I'd have to say "none of the above".    Now realize I don't know what your goals are but your best return would be to put a micro inverter on the solar panel and use it to reduce the electrical bill continuously.    This way you are not wasting a lot of energy to charge a battery and your limited solar panel will always be doing something useful in cutting your electrical bill.   You will have to make this legal for the local authority though.

Now if this is a backup supply, if that is the goal, then you will need an externally housed battery, charge controller and an inverter and associated electronics/electrics to make the system legal in your area.

It's currently a 50W panel.  By the time you put that throw and inverter and try to put it on the grid, it wouldn't get noticed.  I mean in the last 2.5 years it has produced 60kwh.  A whole whopping £11 UK.  When the system cost about £100 all in.  It will be a while paying for itself LOL

No, no.  If I wanted a AC 240V setup, I'd just pay a certified installer to put 3kW on the roof with approved producer meter etal.

This is just an off grid, personal, hobby project.  It can and has in the past provided me with a way to run lights, a laptop and my mobile phone for internet while in a power cut.

My options were to mothball it or upgrade it.  For the later I first needed easier access to the power than trapsing to the garage to run stuff or charge batterys to run stuff. Now I have it on tap in the room 90% of my tech is in. 

Plan is to keep it off grid, keep it 12V, but put another 200W of panel on the garage roof and find even more bizarre things to do with it.