Home Backup Systems, Part Two

What You’ll Need

• A Home Backup System, in my case (AC300 + B300K)
• Solar panels 405w £50 each
• Solar cable, from Bluetti with connectors and 50m cable only from Electrical World
• Solar cable crimper
• Staubli MC4 connectors
• PV Solar Cable MC Window Feed-Through
• ECO-WORTHY 45″ inch Adjustable Solar Panel Mount Brackets Kit
• Wakects Mini Circuit Breaker, MCB 2P DC 500V 32A PV System DC Disconnect Switch
• Other bits and pieces included carriage bolts RV Roof/wall Feed-Through Solar Cable Entry Junction Box (not used so far) rebar ground anchors, basically large tent pegs, wire strippers etc

Setup

I thought about making an unboxing video. Meh.  The AC300 inverter/controller comes in one box, the B300K battery in another. They are large and heavy but I managed on my own. Setup is fairly straight forward, plug one box into another with the big cable and the charging cable into another socket in the AC300 and wall outlet. First try it wouldn’t switch on. The big cable wasn’t locked in the sockets correctly, phew.

Charging Options

• Wall Socket
• Generator ( I have my eye on a £300 3200W  inverter/generator)
• Solar Panels
• Car via cigarette lighter (Not sure I would recommend this)
• Lead Acid Battery (I have a spare and the cable but no idea what sort of kWhs I would get out of it)

Discharging

• 6 x UK 3 pin plugs
• 2 x DC 12V & 24V outputs
• 5 x various USB ports

Originally I lashed together the solar panels with ready made Bluetti solar cables, just to test it. I was impressed how much power they made even in January and February so ordered more solar panels and cable. The cable from Electrical World is dual cored, the Bluetti ones do not appear to be. I will replace the Bluetti cables with dual cored at some point.

I realised once I started setting everything up permanently that you can’t turn the solar panels off. You have to wait until night time to safely disconnect them. Do NOT disconnect solar panels under load. I solved this problem with two of these Wakects Mini Circuit Breaker, MCB 2P DC 500V 32A PV System DC Disconnect Switch on each string of panels. Flick the switch and the panels are safe to disconnect, plus they will hopefully trip if there’s any problem. Currently I am feeding the cables through a window using these PV Solar Cable MC Window Feed-Through but there is already a hole in the wall where I could use these Solar Double Cable Entry Gland with Photovoltaic Connector Male and Female Plug Waterproof ABS Solar Plate Bracket, which are designed for RVs but equally two of them make a good wall pass-through.

One of the most irritating problems was finding supports for the panels at a reasonable price and then working out how to anchor the damn things to the ground. I don’t know how good my calculation is but a windspeed of 50mph could create more than 500 Newtons of force on a 2m square panel. That is a lot! In the end I found the supports listed above, two for £67, then £80 for two. Everything is going up, all the time. They are not the sturdiest of frames but then they aren’t £100 each. Fortunately I have a load of old railway sleepers lying around the garden, anchoring the frames to these with carriage bolts should do the trick, but the panels are only £50 each, so if there’s a big storm . . .

Regarding orientation and angle to the Sun I originally placed one string 20° East of South (160°)and the other string 20° West of South (200°) thinking this would give me more power in the morning and evening than with all panels facing due South. Wrong! I just made myself more work. They are all facing due South now. I am not changing the angle of the panels for Spring, Summer, and Autumn, they can stay at about 35°, come winter I will change them to about 70° for maximum efficiency.

Belt, braces and money permitting I would buy one of these Excel Power XL3000iE 3.2kW Inverter Generator at £300. For deepest winter and Ed Miliband insurance. It has an Eco function so only delivers load under demand ie it doesn’t sit there and run at full power when there’s nothing plugged into it.

More B300K batteries wanted. Two should do it. Maybe one towards the end of the year, earlier if I can get a discount from Bluetti – No luck so far but they gave me a small thank you voucher for £10/15 for last week’s piece.

In terms of maintenance there’s not much required. The only change to the settings necessary to get full value being how much you want to charge from the grid overnight. This will depend on the time of year and the weather forecast for the next day. Compared to maintaining the woodburner this is trivial.

The system can currently generate so much power that even from a low charge state and in less than ideal weather the one 2.7 kWh battery is easily charged by midday. If only I could store more of it! The 3 kwH I use per day running everything in my living room comes free. That leaves the hot water tank and the freezer and anything I use in the kitchen (Which I could run with an extension cable if I needed to).

My system is probably a little over powered for my needs but bear in mind I only paid £1,199 for the AC300 + B300K. You may have to wait until their Winter sale to see that again but there are plenty of smaller and therefore cheaper options. All in all, total cost in the region of £2,000. Will it pay for itself? It should, cheaper bills, less wood needed for the woodburner and security of supply which will be priceless if the grid starts playing up.
 

© Swiss Bob 2025
 

PS Bash 2025 end of next month. Weather is looking good (OK, I’m guessing). Plenty of places on the pub campsite, including the GP tent, bring a sleeping bag and you’ll be fine. Hotels in Chipping Norton and Banbury if camping isn’t your thing.