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diy solar

UK based newbie looking to build portable solar battery for market stall appliances

LordPayso

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Mar 21, 2024
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Hi!

I am a chocolatier based in the UK who has spent the last two days trying to filter the wealth of information out there on various channels to help me build a portable DIY solar battery to help power appliances on my market stall in the summer months.

As a chocolatier my product is incredibly heat sensitive and my only point of trade at the moment is the markets that I attend in Kent and Greater London. I was at a market last weekend and watched some stock melt before my eyes which made me think that trading chocolate in the warmer months coming up is not the best idea. I made some calls and have secured a fresh fruit supplier to enable me to sell melted chocolate covered fruit; kind of like a fondue.

This is all well and good except that most of the markets I attend do not supply power and will not allow petrol generators. On this basis I have been racking my brains trying to figure out the "best" solar battery to buy off the shelf out of Bluetti, Jackery, Ecoflow etc.

I was just about to pull the trigger on a refurbished Ecoflow when I wondered about building one myself. Having watched multiple videos I kind of feel lost!!! The majority of the videos are for the States (I am UK based) which raises questions regarding the viability of builds done for the States that would translate to the UK in terms of comparable parts and most importantly safety testing. This build will have to pass PAT testing if I am to use it at markets.

The equipment I would want to power are two chocolate melters which are 200w and one ikea 700w microwave. The melters would be used continuously for a minimum of 4 hours and a maximum of 8. The microwave used to initially melt the chocolate quickly to get up and running.

I could use the melters on full power (60 degrees centigrade) to get the chocolate melted and then turn them down to 30 to keep the chocolate fluid. In this case I would happily not bring the microwave at all. I was also going to only use one melter but would like a battery that would accommodate two to future proof.

I would likely want to charge my phone during the day which is a Pixel 6 30w (I think).

I would like the system to be weather resistant and rugged as I will be dragging it around markets all summer. It does not need to be waterproof as I will be trading under gazebos.

Other features that are desirable are pass through charging, charging from car cigarette lighter, portable enough (I can put it in a trolley to take it to the stall), safe enough to pass PAT testing, at least two plug points for the melters.

If anyone could give me some starting points it would be much appreciated. Even if there is more you need to know from me as i am struggling to navigate UK based specific info on Youtube.
 
The melter at 200W for 8 hours is 1.6kW at most, likely less due to duty cycle.
2 would 3.2kWh microwaves pull a TON of startup VA but run for short times, so add in a kW for mw use.
You will need minimum 2400VA inverter to handle microwave startup...
A single 100Ah 48v battery would happily handle this.
 
The melter at 200W for 8 hours is 1.6kW at most, likely less due to duty cycle.
2 would 3.2kWh microwaves pull a TON of startup VA but run for short times, so add in a kW for mw use.
You will need minimum 2400VA inverter to handle microwave startup...
A single 100Ah 48v battery would happily handle this.
Thanks for the quick reply.

My budget for the whole build would be £1000 maximum for everything...

I think that would mean omitting the microwave and possibly one of the melters which would be totally ok to find my feet and validate that the product would work.
 
At that price point, you'd have to go with used equipment. Nothing wrong with that, just wanted to help guide you to a purchase point.

Some people have posted handcart builds.
 
Thanks for the quick reply.

My budget for the whole build would be £1000 maximum for everything...

I think that would mean omitting the microwave and possibly one of the melters which would be totally ok to find my feet and validate that the product would work.
Hmm...
A decent 1000W inverter, and a 150Ah 24v battery should have enough capacity.
Should be able to buy this under a grand...
It just might still be able to power the microwave too...
But you will be low by end of 8 hour shift with two heaters, and microwave use.

You also need a way to charge the battery, so look for one paired with a charger.
 
Hmm...
A decent 1000W inverter, and a 150Ah 24v battery should have enough capacity.
Should be able to buy this under a grand...
It just might still be able to power the microwave too...
But you will be low by end of 8 hour shift with two heaters, and microwave use.

You also need a way to charge the battery, so look for one paired with a charger.
I am sorry for the stupid question but why does it need 24v rather than 12v? Is that because of the higher power draw to fire all this up initially?
 
UK _ Essex here

We had a microwave for our motorhome 'adapted' by a company near Ashford in Kent - it took about an hour to reduce its power, especially the start up power, so its 'kinder' to your battery, that might be worth exploring?
The 'all in one' solutions are really just a battery, inverter and charger, you dont really need to be carrying the charger around, so you just need a battery and an inverter, which makes it simpler, so long as you can charge up at home
In our motorhome (RV for our friends across the pond) we use a Renogy 3kw inverter and a 304Ah lithium battery from Fogstar (UK) which allows us to use a microwave AND a kettle at the same time, so more than adequate for you to use your equipment at the same time.
We tried smaller inverters BUT the start up of the microwave kept overloading, so ended up with the 3kw Renogy, which for us works well, so i would suggest any inverter needs to be able to cover that initial power surge. The Renogy has two UK plug outlets, which again makes it simpler for you.

its then simply a case of working out which size/capacity battery you need. A ithium battery can be taken down to around 10% of its stated capacity but you will also need to look at the max discharge current - i would suggest nothing less than 200A .

you could easily put it all together for around £1000 and have much more power/capacity than an all in one 'named' unit.

https://offgridpower.solutions/ are in the UK and could probably build you a 'unit' fit for purpose, building the battery from scratch and housing it all in a purpose built unit, to the dimensions that suit you - i have no connections with them other than watching their videos on youtube, it might be worth watching some of their battery build videos ???
 
UK _ Essex here

We had a microwave for our motorhome 'adapted' by a company near Ashford in Kent - it took about an hour to reduce its power, especially the start up power, so its 'kinder' to your battery, that might be worth exploring?
The 'all in one' solutions are really just a battery, inverter and charger, you dont really need to be carrying the charger around, so you just need a battery and an inverter, which makes it simpler, so long as you can charge up at home
In our motorhome (RV for our friends across the pond) we use a Renogy 3kw inverter and a 304Ah lithium battery from Fogstar (UK) which allows us to use a microwave AND a kettle at the same time, so more than adequate for you to use your equipment at the same time.
We tried smaller inverters BUT the start up of the microwave kept overloading, so ended up with the 3kw Renogy, which for us works well, so i would suggest any inverter needs to be able to cover that initial power surge. The Renogy has two UK plug outlets, which again makes it simpler for you.

its then simply a case of working out which size/capacity battery you need. A ithium battery can be taken down to around 10% of its stated capacity but you will also need to look at the max discharge current - i would suggest nothing less than 200A .

you could easily put it all together for around £1000 and have much more power/capacity than an all in one 'named' unit.

https://offgridpower.solutions/ are in the UK and could probably build you a 'unit' fit for purpose, building the battery from scratch and housing it all in a purpose built unit, to the dimensions that suit you - i have no connections with them other than watching their videos on youtube, it might be worth watching some of their battery build videos ???
Thanks for pointing me in the right direction.

I was planning on solar charging at the stall but I'm wondering if that's worth it now. If there is no guarantee that you will get any decent sun then that part of the set up becomes more of a liability and hassle with brining solar panels along.
 
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UK _ Essex here

We had a microwave for our motorhome 'adapted' by a company near Ashford in Kent - it took about an hour to reduce its power, especially the start up power, so its 'kinder' to your battery, that might be worth exploring?
The 'all in one' solutions are really just a battery, inverter and charger, you dont really need to be carrying the charger around, so you just need a battery and an inverter, which makes it simpler, so long as you can charge up at home
In our motorhome (RV for our friends across the pond) we use a Renogy 3kw inverter and a 304Ah lithium battery from Fogstar (UK) which allows us to use a microwave AND a kettle at the same time, so more than adequate for you to use your equipment at the same time.
We tried smaller inverters BUT the start up of the microwave kept overloading, so ended up with the 3kw Renogy, which for us works well, so i would suggest any inverter needs to be able to cover that initial power surge. The Renogy has two UK plug outlets, which again makes it simpler for you.

its then simply a case of working out which size/capacity battery you need. A ithium battery can be taken down to around 10% of its stated capacity but you will also need to look at the max discharge current - i would suggest nothing less than 200A .

you could easily put it all together for around £1000 and have much more power/capacity than an all in one 'named' unit.

https://offgridpower.solutions/ are in the UK and could probably build you a 'unit' fit for purpose, building the battery from scratch and housing it all in a purpose built unit, to the dimensions that suit you - i have no connections with them other than watching their videos on youtube, it might be worth watching some of their battery build videos ???
So if I got a 3kw inverter and a 200A battery.

If I need it to be fully charged for the next day what sort of charger should I be looking at? I run stalls on Saturday and Sunday.

I really appreciate the reply. It's really helped me focus on what I really need rather than going way overboard with expenditure. It wolill also be a good learning experience to then be able to extend the setup later if need
 
The size of the inverter and battery don't tell you the size of the charger. How much energy in Kwh would you use on Sat and how many hours are available for charging Sat to Sun. So if you use 8Kwh on Sat and only have 2 hours for charging then you need a 4Kwh charger, 4 hrs give a 2Kwh charger and 8 hrs a 1kwh charger but you will need to charge more as there are losses so add 10% on to cover this.
 
The size of the inverter and battery don't tell you the size of the charger. How much energy in Kwh would you use on Sat and how many hours are available for charging Sat to Sun. So if you use 8Kwh on Sat and only have 2 hours for charging then you need a 4Kwh charger, 4 hrs give a 2Kwh charger and 8 hrs a 1kwh charger but you will need to charge more as there are losses so add 10% on to cover this.
Ah OK. That makes sense.
 
I was planning on solar charging at the stall but I'm wondering if that's worth it now. If there is no guarantee that you will get any decent sun then that part of the set up becomes more of a liability and hassle with brining solar panels along.
I was going to suggest the same ^^^. It could be cloudy or raining. Your stall may be shadowed by tall buildings or trees. You would have to physically mount the panels securely enough so they don't fly off in the wind and hit someone. And you'd have to transport delicate panels around every weekend.

IMO, better to just have battery and inverter for use at the stall. If energy cost is an issue, you could have a second battery at home and charge that by solar. Then a small solar system could charge up two batteries over the week and you use battery A on Saturday and battery B on Sunday.
 
I was going to suggest the same ^^^. It could be cloudy or raining. Your stall may be shadowed by tall buildings or trees. You would have to physically mount the panels securely enough so they don't fly off in the wind and hit someone. And you'd have to transport delicate panels around every weekend.

IMO, better to just have battery and inverter for use at the stall. If energy cost is an issue, you could have a second battery at home and charge that by solar. Then a small solar system could charge up two batteries over the week and you use battery A on Saturday and battery B on Sunday.
I am being offered the following on Gumtree:

Renogy 3000w inverter
2 x 200w solar panels
Victron mppt ip43 mppt 100 | 20
2 x 200ah Agm leisure batteries

Price seems very decent and well within budget... This seems like enough to get me started and would have lots left over for a decent charger, spare battery.

As this gear is second hand is there anyway I can validate it working before purchasing?
 
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This build will have to pass PAT testing if I am to use it at markets.
Its more than PAT testing. To comply with mobile regulations you will have to install equipment that allows safety equipment, RCD to prevent electrocution. Not all inverters allow easy implementation of the neutral to earth bond that is needed. Renogy Inverters are mostly not suitable, Victron are recomended.
2 x 200ah Agm leisure batteries
These are , if second hand, not worth investing In. As sugested go for Fogstar lithium.

With the recent price reduction Victron Smart Solar controllers are very competitive priced. For 400 watts at 12v you need a 100/30

The best option is charging a battery overnight and using an inverter to power your equipment, forget solar for the moment.

Later today I will give a more comprehensive reply.
 
Its more than PAT testing. To comply with mobile regulations you will have to install equipment that allows safety equipment, RCD to prevent electrocution. Not all inverters allow easy implementation of the neutral to earth bond that is needed. Renogy Inverters are mostly not suitable, Victron are recomended.

These are , if second hand, not worth investing In. As sugested go for Fogstar lithium.

With the recent price reduction Victron Smart Solar controllers are very competitive priced. For 400 watts at 12v you need a 100/30

The best option is charging a battery overnight and using an inverter to power your equipment, forget solar for the moment.

Later today I will give a more comprehensive reply.
Thanks for getting back to me so quickly and saving me money. Looking forward to your reply later.
 
I am sorry for the stupid question but why does it need 24v rather than 12v? Is that because of the higher power draw to fire all this up initially?
Price.

24V 150Ah battery is around $500 a pair of #8 leads for the inverter will be $20 and the 24V inverter should be around $400

If you go 12V, the same Wh battery will need to be 300Ah, and they run about $600, you will need twice the capacity leads around #4, so more money, but the 12V inverter could be cheaper,
Your call.
 
@LordPayso

I still suggest you speak to the guys at Offgrid Solutions, they will design and build to your needs/spec and to whatever regulations are needed. yes it may cost more than DiY (which is the intent of this forum !!) but you can be sure it will do as it says on the 'tin' ..
 
Price.

24V 150Ah battery is around $500 a pair of #8 leads for the inverter will be $20 and the 24V inverter should be around $400

If you go 12V, the same Wh battery will need to be 300Ah, and they run about $600, you will need twice the capacity leads around #4, so more money, but the 12V inverter could be cheaper,
Your call.
I don't think the prices in the UK are anywhere near that competitive.

A 12v 150ah is about £500 (~$600) and a 24v 150ah is a lot more dependent on brand but roughly double that.
 
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