Solar/ Battery cable (to sockets) specification please.

[Ian Wallis]

Hello, I'm about to buy 14 meters (from battery house to lounge tv) of 25mm or 35mm cable, and I need to know what specs they should be to comply with household regs.
There are a lot of cables out there with junk written down the sides and some with out. I just want to get it correct while I have the floor up.

I'm only planning to use about 15amps for about 8 hours, from my four 225ah batteries. It may look like overkill but things have a habit of changing.

 

[WHONOES]

Before anything else is discussed, you absolutely must without fail put a fuse or fast circuit breaker at the battery end of your wiring. The reason being the batteries you are proposing to use will quite literally deliver thousands of amps into your wiring. If your wiring should encounter a short circuit, would have a fire on you hands presumably under your floor boards in seconds. To do otherwise is courting disaster.

I would advise that you buy yourself a copy of the current Reg's.

See link below

Amazon.co.uk : electrical installation regulations

 

[Ian Wallis]

Yes, thank you for your recommendation.
I will of course be fitting an isolation switch (which I have) and a master fuse (I think it was 30, or 40amp, can't remember), and then a baby fuse box for secondary fuses. One fuse for each spur, which I shall rate just a bit above the estimated amperage that the spur will using. Start at 15 and if it keeps popping go up to 20amp. Each item that I will be using (laptop, satellite receiver etc) will have it's own fuse.

Your reaction to the battery bank power is puzzling though; I thought that 225ah batteries was a small to mediocre size in the deep cycle battery world of the off gridders.

Thank you for the link.

 

[Harald Kapp]

225 Ah may be small, but this type of battery can nevertheless deliver loads of amperes into a short circuit. Have a look at this video (just an example).

 

[WHONOES]

An ordinary 12V car battery is capable of delivering close to a 1000A into a load. They need to as starter motors typically run at several hundred amps. Your 225AH battery is probably 3 times what you would encounter in a car an will deliver a proportionately larger current. If you are using multiple batteries the problem is compounded.

 

[Ian Wallis]

Love that video, it reminds me of a guy fixing his motorbike by pouring nuts and bolts in to its engine like it was oil. Yep, it happened.
TechTips, lol, I'll have to subscribe ha ha.

 

[Ian Wallis]

I really don't know what the answer is, other than keeping it under control. Like a gas cooker, we control the gas from exploding.
It's just the nature of the beast. Just don't let the beast out of it's cage
I wont be going to Youtube for advice anytime soon

Thank you for your advice, I appreciate it.

 

[Ian Wallis]

This link (about inadequate fuses) is very interesting, and will no doubt be useful to others building their own off grid system.
An eye opener.
https://www.solar-wind.co.uk/off-grid-power-blog/post/when-is-a-fuse-not-a-fuse.html

While I'm here; if anyone knows of a good off grid website / forum could you let me know. Thanks.