New Off Grid Electrical System - StrEATery and Little Donut Stall
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New Off Grid Electrical System

Our Little Donut Stall in Cheltenham high street has to be completely self sufficient, as it has no access to an electrical connection.

This has meant we have always had to use a small generator for our electrical needs, with gas powering the burners on the donut & coffee machine, as well as the crepe plate.

We have always used Honda generators as they are the market leader, offering the best quality, lowest emissions and noise levels.
Our policy is to use and support local businesses when we can, so purchasing and servicing has been from/by Cheltenham Garden Machinery down the lower high street. Their service has always been first class, maintaining our generators in good running order, so keeping the emissions down.
We have always managed the load on the generator, so it runs in the eco setting, keeping noise and emissions to a minimum.
All lighting was changed to LED back in 2007 to enable this.

With the hustle and bustle of the high street and passing traffic, the noise from the generator was hardly noticeable. But we have always been conscious, that in the morning when the town was quiet, it was a lot more noticeable.

We have been focused on living and working towards a more sustainable lifestyle for some time, making many changes and improvements to our personal & business life over the last few years.

  • Cutting our use of plastics
  • Sorting & recycling all our waste
  • Serving Donuts in cardboard boxes with Nutella drizzled on, instead of in plastic dip trays
  • Wooden forks for the Fully Loaded Donuts
  • Cutting our travelling and focusing on working locally from home
  • Moving to Vegware compostable cups and lids.

However, of course it is not ideal to have to run a generator all the time, with no option in the near future of an electrical connection. We have been looking at replacing it with a battery and inverter system for some time. With a south facing roof, would it be possible to get enough power from solar panels to recharge the batteries for a proper off grid solution?

Honda EU20i generator in the corner providing electricity.

Our Electrical Requirements:

I already knew our basic electric loads, but went back through them, monitoring & logging figures with a few different meters and the Honda generator app to check they were correct.

Static all day (10H) electrical demand

  • 150w Fridge
  • 120w Exterior lighting (LED)
  • 50w Interior spot lights (LED)
  • 20w Christmas lights (LED)
  • 340 watt in total

On Demand Electrial Requirements

  • 400w Grinder
  • 300w Espresso Coffee machine pump
  • 100w Mixer (1000w motor, our use has never pushed it over 100w)
  • 30w Water pump
  • 50w Donut track

Our on demands vary with the work load, averaging around 700w, but can peak at 1200 watt

However, I had no idea of how much electricity we used through out the day, and a key requirement for speccing the battery.
None of my electrical meters/apps had a gauge/reading for this. Luckily my wife found a small electrical meter with this feature, which we were able to plug in to the generator and get a few all day readings.

Our average reading was around 2kWh a day in the summer.
We knew we would have to factor in for more heavy on demand loads during the busier Christmas trading, so we decided to plan for up to 3kWh day.
Side note, if we were connected to the national grid, at 35p per kWh, our daily use would only be 70p in the Summer, with a max forecast of under a £1 in the winter.
With record level fuel prices, running the generator was costing us £8 a day.

Which Inverter

The inverter changes 12v DC power to 230v AC power and there are two basic types, Pure Sine Wave & Modified Sine Wave.
With a bit of research, I found the advantages of Pure Sine Wave over Modified Sine Wave were:

  • Cleaner out put with less noise like we receive from the national grid
  • Inductive loads like water pumps, fridges and motors run faster, quieter and cooler
  • Reduced audible and electrical noise in fans & fluorescent lights
  • Prevents computers crashing, strange print outs, glitches & noise in monitors

Having experience of using modern electrical systems fitted with plc computer control systems, and inverter drives, I know the importance of a clean and stable electrical supply. So Pure Sine Wave was the obvious choice.

What Make & Model to choose

As with most things, there is a very wide range of products to choose from at very different price points.
Our electrical needs required a model with at least 1500w output.
The inverter would be used daily to provide electricity for our little business, so I quickly moved away from makes that we’re targeted at intermittent use.
Watching a number of off grid energy builds for houses, food trucks & camper vans on You Tube, Victron Energy were always highly recommended for quality, reliability & back up. With a vast range of products, they have everything we could need to to build a suitable system, expand if needed, and able to add solar at a later date.

What size battery

Getting a suitable inverter seemed easy enough as I had my static and max load figures.
Working out what size & type of battery/batteries however, was a lot more complex. A standard leisure battery may have enough output, but only for a very short time & not able to meet our all day demands. With charging cycles of only around 250 common, our need to recharge daily would mean we would constantly be replacing the battery, so bad for the environment.

More research showed that Lithium (LiFePO4) batteries were designed for our intended use and similar to those used in electric cars. With a BMS (battery management system) and bluetooth monitoring built in. They can deliver a high continuous charge/discharge rate. State of the art cells also ensure stable voltage throughout the charge and discharge curve and a long lifespan of up to 5000 cycles at 80% depth of discharge, so looking at a 10 year life span. Not discharging the battery to flat would increase the life cycle, so important to spec a battery that would cope easily with our demands.

I contacted a few companies and was disappointed in their poor knowledge, they just sold the kit, so I started looking for a specialist company with experience in speccing, building and delivering systems for a wide range of use.

I came across Rayne Automotive a small family run business specialising in off grid solutions, with great reviews, and over a decade of experience. I contacted them and arranged a phone consultation, James called at the arranged time and we discussed my current and future requirements. With my detailed break down of our electrical loads and operating hours, he was able to work out what size battery we would need over the phone, giving me two options of a 200Ah or 300Ah LiFePO4 battery. I received an email later that same day, with a list of system build options to suit our current, and future solar needs.
I was very pleased with James’ knowledge and service, even though it was a very big investment for us, I now felt confident to order a system.


As I was worried about range anxiety, I decided on the larger Roamer 300Ah battery option. The cost was nearly 50% more, but would give us spare capacity and save running the battery to nearly flat, which affects the life cycle.


We went for the Victron Energy Phoenix Smart 1600 inverter. With its industrial quality metal case and bluetooth connection to the VictronConnect app providing live status information from all connected devices, we thought it was the smart choice.


These expensive and specialist batteries need a professional quality charger, so James specced a Victron Blue Smart 25amp model to make sure the battery is charged, smartly… to perfect condition.

A seven-step charging algorithm gets the best out of the battery. The charger gives the battery the power it needs, maintains its health, ensures better performance… and a longer life.

Victron Energy

System Cost

A huge investment for our small business.

System delivery

With the invoice order paid, our system arrived with in 10 days and we were excited to get it set up, tested and running:)
Took the time to read all the manuals, then downloading the Victron Connect & Roamer battery apps. Pairing the battery and charger via bluetooth to my phone apps was simple and quick. Using the Victron app, I then set the charger to the correct settings for lithium, before connecting and fully charging the battery.

Charging battery.

Fitting the inverter

James at Rayne Automotive had supplied all the cables cut to size with terminal ends crimped on and the correct size inline fuse. Fitting the inverter was a simple enough job, taking in to account gas and electric regulations, air flow, battery placement and wiring an on/off switch for the inverter.

Inverter fitted

Testing and running the inverter

Once fitted and the battery connected, we tested the inverter output before connecting it to our electrical system. We were very impressed that the inverter was completely silent in normal use, with no buzzing like cheaper inverters. There is a fan that can come on to cool the inverter if it gets warm when working at max loads for extended times in warmer weather conditions.
The Victron Connect app is very good, showing load, AC out put, state and battery voltage in real time.

Victron Connect iPhone App showing our electric load.

Battery Run Times

We first used the system on a quiet weekday, turning on the inverter at 8:30am, for a 10h hour day. I was constantly checking the Roamer app to monitor the battery level, it was fine with a slow steady discharge and no sudden drops as the battery depleted. By the end of our day, we were pleased to still have over 40%
The big test came a few days later, as it was the town Christmas Lights switch on and the busiest day of the year for us. We put the generator in place as a back up power supply, but we were so pleased that after a 12 hour day, we still had 21% battery left.
Now confident with the battery power, we only check it once a day.

Roamer Battery BMS still showing 21%


After a lot of research and expense, we are so pleased with our Off Grid electrical system as it easily meets our needs. We highly recommend Victron Energy systems & Rayne Automotive for their knowledge and service👍

Turning on our electric with zero generator noise or emissions first thing in the mornings has been so rewarding, with noticeable reduced noise levels in the high street before the hustle and bustle of the later day.

Very proud to say we really have improved the high street visitor experience as well as our own working environment with this investment:)

Future Solar Plans

We will be looking into the possibilities of using solar panels to power the stall and keep the the battery charged for a complete off grid solution in 2023.

Benefits would be:

  • Less work with out having to take a large battery home every night
  • Zero recharge costs during the summer months
  • Lowering our carbon foot print even further
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