Expanding a 100W off grid 12V solar system

crey

I currently have a 100W panel on my shed with a charge controller and 100Ah battery supplying 12VDC to some LED lighting inside and outside the shed plus the pump and led's in a water feature.

I'm looking to add another 4 100W panels, upgrade the charge controller, add another battery and an Inverter to enable me to run a few power tools in the shed (one at a time).

My question is. How should I connect the new panels? In series or parallel?

I would assume parallel as I still want the 12V system to ruin alongside the 240V AC.

Am I right thinking this?

zeupater

Hi

Would it not be more convenient & cheaper to simply run an armoured mains cable from the house to the shed, thus guaranteeing you'll be able to power the power tools?

Z

QrizB

crey said:

My question is. How should I connect the new panels? In series or parallel?

I would assume parallel as I still want the 12V system to ruin alongside the 240V AC.

Am I right thinking this?

It's going to depend on your controller.

The simpler ones - shunt or PWM conrollers (example) - need the solar panels to run at battery voltage.

Smarter ones - MPPT controllers (example) - can convert the solar voltage to match the battery.

MPPT controllers are usually 25-25% more effective at extracting power from your panels (see this article). If you're looking add four more panels to you system, you should look at changing to MPPT - it's equivalent to adding a 6th panel plus part of a 7th.

zeupater

QrizB said:

crey said:

My question is. How should I connect the new panels? In series or parallel?

I would assume parallel as I still want the 12V system to ruin alongside the 240V AC.

Am I right thinking this?

It's going to depend on your controller.

The simpler ones - shunt or PWM conrollers (example) - need the solar panels to run at battery voltage.

Smarter ones - MPPT controllers (example) - can convert the solar voltage to match the battery.

MPPT controllers are usually 25-25% more effective at extracting power from your panels (see this article). If you're looking add four more panels to you system, you should look at changing to MPPT - it's equivalent to adding a 6th panel plus part of a 7th.

Hi

In not knowing what tools are going to be used (now & future) and what power would be drawn under startup or load conditions, I'd be looking at running a 240V supply from the house & if the shed was remote, such as on an allotment, well, it's simply a case of security & the value invested.

I'm guessing that the 'tools' wouldn't be run of the mill DIY type because the sensible solution would simply be to not worry about spending on PV+charge controller+deep cycle battery+inverter and simply buy the interchangeable rechargeable battery variant of what you'd need and save a £shedload (forgive the pun!), in which case we could be looking at shed based man-cave workshop with a small wood lathe or pillar drill etc which are notorious for high current & power draw on startup, often greater than double the rated continuous figures quoted in the specs ... with all of the implications of sizing the inverter ... so without more detailed information it's virtually impossible to recommend any solution.

Why do I not immediately recommend an 'off grid' solution in a garden shed? ... well, I've played with a 12v setup down the garden for years (light/radio etc - similar to the OP) and looked at upgrading to a similar DC12v/AC230v solution well before having a grid connected PV installation & couldn't make the sums add up to anything near the cost of running a link to the house ...

HTH - Z  

QrizB

zeupater said:

In not knowing what tools are going to be used (now & future) and what power would be drawn under startup or load conditions, I'd be looking at running a 240V supply from the house & if the shed was remote, such as on an allotment, well, it's simply a case of security & the value invested.

Agreed, but we could speculate all day. In the meantime I've answered the OP's question as best I can, based on the information provided.

I've been building and using recreational off-grid solar for a while, in boats / caravans / campervans / sheds and I'd agree that running a cable is a better idea if you can - but sometimes it's not a practical option.

crey

QrizB said:

crey said:

My question is. How should I connect the new panels? In series or parallel?

I would assume parallel as I still want the 12V system to ruin alongside the 240V AC.

Am I right thinking this?

It's going to depend on your controller.

The simpler ones - shunt or PWM conrollers (example) - need the solar panels to run at battery voltage.

Smarter ones - MPPT controllers (example) - can convert the solar voltage to match the battery.

MPPT controllers are usually 25-25% more effective at extracting power from your panels (see this article). If you're looking add four more panels to you system, you should look at changing to MPPT - it's equivalent to adding a 6th panel plus part of a 7th.

Thanks everyone, Running a mains input from tghe house isn't impossible, but certainly not convenient. Nor is it a green solution.

@QrizB I am looking at MPPT controllers for the increased efficiency, thanks for confirming my thoughts on that..

I have a rage of power tools some battery, some 240V. The biggest power draw would be the Mitre Saw I think but I doubt it will draw more than 500W at start up. So a 2kW inverter should see me with enough power to fire it up at worst case scenarios. I appreciate I would have to make sure I only use one power tool at a time. But then, I only have one pair of hands

My reasons for looking into this are, in no partyicular order: Be a bit greener, Save a bit on electricity bills (I know I could go solar in the house but that's not feasable just yet), have a play with solar technology (I'm a bit of a geek).

QrizB

My elderly dad has a shed in a corner of a field (so no option for mains). He's got an Epever MPPT controller with 750W of solar. His kit was something like this (but with used panels not new ones, and a slightly lower-rated controller, which brought the price down): https://www.bimblesolar.com/12v-610w-solar-kit-gland