Rick Hurst Web Developer in Bristol, UK


Category: charging

Running a home office using solar power – part 1

Photonic Universe portable 100 watt solar panel kit

Although I like to use our campervan as a mobile office, I mainly work from a home “office” built in an existing shed. The breeze-block building was already there when we moved in, and luckily it is big enough to create an area where I can work.

It’s a typical “ongoing” project, started a few years ago by partitioning off an end section to remain as a proper shed, and then building out an insulated area with it’s own entrance. Nowhere near finished, it still looks very much like a shed on the inside, but I have plans for wood panelling (inside and out) and stylish lighting to make it instagram worthy!

We do actually have mains electric running out to the shed, so it doesn’t need to be off-grid, but as I already have most of the kit needed, why not?

The Solar panel

I recently bought a 100 watt portable solar panel kit made by Photonics Universe to use with the camper van, but also wanted to see if it would be possible to use it to keep my home office powered. The kit has a waterproof charge controller mounted on the back, so all you need to do is attach it to the battery, either with the crocodile clips as supplied, or via eyelets. I bought a second connector cable so there is one permanently wired into the van leisure battery and one on the portable battery, making it easy to swap from one to the other.

Photonic Universe portable 100 watt solar panel kit showing charge controller

The “Office” kit

It’s a pretty minimal set-up – like when i’m in the van, I work mainly from the laptop, but with the added luxury of an external monitor, which is pretty handy when i’m working on any visual layout stuff for a website or web app.

My laptop these days is a 2015 era 13 inch macbook pro, and from looking at the plug-in current meter that I use, it looks though this requires about 20-30 watts to maintain an already charged laptop and 40+ watts when charging. The monitor requires a further 25 watts. In addition to this, I plan to occasionally run a USB powered fan and 12 volt LED lighting, both of which don’t require much power – at least in comparison to the mains appliances.

Minimal home office freelance web developer set-up

The Battery and electrics

A while ago I took a spare 90Ah car battery and built it into an old toolbox, with voltmeter, 12volt socket and USB sockets to use as a portable leisure battery set-up, so I have the solar panel charging this. Unlike the leisure battery in the van, this isn’t as proper leisure battery, so I need to be careful not to let the charge get too low, or risk permanently damaging it. The battery box has a fuse box inside with each item running off a separate fuse.

Leisure battery built into an old toolbox with USB sockets and voltmeter

I then wired in another external panel with voltmeter, usb sockets and 12 volt socket, which will eventually be mounted on the wall. I’ve then got plugged into this, an old Belkin 150 Watt (300 Watt peak) inverter that is usually in the van. I’ll likely replace this with something better – a pure sinewave inverter that gives a smoother AC output very similar to mains electricity.

12 volt panel with cigar lighter and USB socket

The challenge

The garden, whilst reasonably private for a city and offering plenty of shade, isn’t ideal for a solar panel. The light only reaches the garden from about 10am, and disappears about 6pm, even in mid-summer. The panel needs to be moved frequently to remain in the sun. I’ve spent time imagining building some kind of automated track system to do this for me, and although I have some ideas, I doubt I will ever have the time to realise them!¬†We also live in the UK, not famed for it’s year-round sunshine…

Solar panel in a shady garden

From experience in the van keeping a powered coolbox going (~60 Watts), the panel will have real trouble providing 75+ watts constantly, unless it’s in decent all day direct sunlight, so the battery will likely discharge throughout the day, depending on when I finish, how much sun there is and how often I get up and move the panel to be in the optimum position.

I’ve already found that my external monitor isn’t happy running from the inverter – it keeps going into standby, then attempting to power up again then back to standby, as if switching it on causes a power spike that then causes it to go back to standby. Not sure if that’s the inverter struggling, or the battery not supplying sufficient current – if the battery is plugged into a mains charger, the monitor stays on, so the inverter is certainly capable, but maybe the battery isn’t. It will be interesting to see if a different inverter would make a difference here, or whether the battery isn’t up to the job.

I need to try this out long-term to get a realistic idea, but i’m sure that I would benefit from a higher capacity battery (or batteries), so I can rely more on falling back to battery power, which can then be topped up from solar charging over the weekend to keep me going during the week. Having said that, if we are away in the campervan, the solar panel comes with us, so that’s not going to work! If I had the budget to do this seriously, I think i’d at least double the solar capacity and the battery capacity.


Even though it’s well insulated, there’s no chance of heating the space using solar (photovoltaic) power – any electric heating appliance, such as the Daewoo 2500 Watt oil filled radiator which I use in the winter uses way more wattage than could be provided by my inverter, and even with a high power inverter, massive bank of batteries and thousands of watts of solar panels you would struggle. The only realistic off-grid heating option is a wood burner or something gas powered, both of which aren’t cheap and would need to be carefully installed for obvious safety reasons.

Experiments with the solar gorilla

Solar Gorilla on the roof

I read loads of reviews of the <a href="solar gorilla before taking the plunge and buying one. I payed particular attention to mentions of the macbook (being my weapon of choice). One thing I noted was that when using the solar gorilla with the apple airline magsafe adapter, the reviews all pointed out that this would only power, not charge, a macbook. I was wondering if this was a limitation of the adapter, or insufficient power. I read somewhere that it was the former, so decided against buying an airline adapter (I had plans to make my own 12v plug adapter to link up with my butchered magsafe adapter). However, after speaking to powertraveller, they said they could send me a “sample” magsafe adapter, which connects directly to the power gorilla.

My first attempt to use it (by sticking the solar gorilla out on the roof on a cloudless day, but setting sun), and the charging status read “charged” (starting from a charged battery), but after running for about half an hour, the sun went behind some houses and the status changed to show it running on battery, which was now pretty flat, so the macbook had indeed been running from battery the whole time.

The second experiment today in the back garden, starting from a 50% full battery, the macbook status read “not charging”. There are a few clouds around, but it is a rare fairly sunny june day. I think I can therefore conclude that the solar gorilla is not a viable charging or powering option for a macbook in a UK climate when used on it’s own.

One question still open is whether the sample magsafe cable has the same limitation as the airline adapter – i.e. is it supposed to charge? To work that out I will try it with the power gorilla (waiting for me at olivewood HQ). If that doesn’t work, I will cobble together the DIY solution mentioned before, to rule out wiring.

I have worked out that it is possible to have the solar gorilla charging my leisure battery, while I simultaneously power/ charge the macbook via my DC-DC converter. I’ve yet to work out what rate the battery is being charged vs drained! Another concern is that I seem to have one of the earlier generation of solar gorilla (it has a green, rather than red LED), which possibly suffers from reverse charging i.e. in theory if I leave connected to the leisure battery after dark it might drain it – still inconclusive though.

Another annoyance is that the solar gorilla will not even charge my iphone when connected to the usb port. This is probably due to the “fussiness” of the iphone, probably a fluctuating or insufficient voltage causes the iphone to declare “This accessory is not supported”.

Preparation – keeping a laptop charged on the move

I have been buying and experimenting with some equipment to help keep my laptop charged while i’m away from mains electricity. I have few tools at my disposal:-

Halfords Portable Powerpack 200

Halfords Portable Powerpack 200

It’s basically a 12 volt leisure battery with a lamp, 240 volt inverter and air compressor built in. I only got it because I inherited it with the car (the previous owner bought it to jump start the car when it had been in storage too long and the main battery had gone flat). It can charge from a 12 volt car socket or mains adapter, plus I am having some success charging it from a solar gorilla. The battery sais that it is 20ah, whatever that means in lamens terms.

Using the 240 volt inverter is incredibly inefficient, so only for “emergencies” really. More efficient is using the 12 volt output with the Trust DC-DC converter (below) that allows me to step up from 12 volts to the 16 volts required to run my macbook.

The obvious downside of this battery is that it is very heavy, only suitable for lugging around in the back of a car, so while it will be useful on a campsite with no mains hookup, i’m not exactly going to lug it into a cafe!

Trust 130W Multi Function Notebook Power Adapter

Trust 130W Multi Function Notebook Power Adapter

This is really useful – if I wasn’t a mac user, there would probably be a charger tip included with this, but due to licensing there isn’t. Therefore I had to take the DIY approach of snipping a section of cable from my spare apple power adapter (doesn’t feel good doing that, knowing they are about £60 to replace!). I also modified one of the tips to allow me to fit a section of wire with spade clips, to make it easier to plug in other adapters if necessary.

Amazingly this works – charging and powering the macbook. I need to do some proper experiments to see how many charges I would get out of the leisure battery.

It also has a USB port so I can charge my iphone from it at the same time.

More details on the dealer’s site.

Solar Gorilla

solar gorilla

This is a lightweight portable solar panel that will apparently charge a laptop. Covered in more detail here