Mobile coffee power problem.

[curbside coffee]

Hi. I want to open a mobile coffee shop. I'm finding it difficult to power it without going duel fuel. I'm thinking 4x110ah 12v agm leisure battery's with a b2b charger to the alternator, 200w solar system. And a generator for back up. With a mains hook-up too.
My math got it to 45 mins, (battery only) running flat out! No power top up.
I only need it to run for 2 hours.
The coffee machine gets up to temp in 10 mins.
Coffee machine 2.7k (For 10 mins then when required)
grinder 250w (when required)
water pump 35w (when required)
Also car is a Citroen c1.
Double also! could I run a 2.7k 1 group coffee machine on a 3k pure sine wave inverter?
I already own the car, coffee machine and grinder.
Is this possible before I go knee deep?! (already ankle deep..)

 

[marconi]

What is your budget for the provision of mains power in the van? To the nearest £500, ie £1000 or £3500 or £10000.

How many years do you expect to operate the mobile coffee business?

How many days per week and weeks per year do you reckon the business will trade?

I am wondering if the best investment is an ac power wall which is charged when the van is parked at your home.

Something like this:

Tesla Powerwall 2 Cost, Tesla Home Battery Storage - Joju Solar - https://www.jojusolar.co.uk/batteries-smart-grids/tesla-powerwall/

 

[davesparks]

A dual fuel coffee machine would be a much simpler solution, they use gas to provide the heat and just use electricity for the electronics,pumps etc.

 

[pc1966]

Heating/cooking is often the biggest power draw and really exposes how hard it is to get enough power stored in batteries.

Dual fuel is the obvious solution. You can get small generators but they are often quite nasty things to use. The quiet ones are often massive in size, weight, and cost.

 

[marconi]

Davesparks idea does keep things nice and simple which is always a good thing for reliability and low cost.

My brother in law’s catering vans use gas for all heating of water, fryers, grills and hob and solar leccy, batteries with genie back up for the freezers, chillers, refrigeration and lighting, till and mobile phone.

Actually not quite accurate. With peak summer sun it uses a 1kW 5litre electric water heater.

 

[Rockingit]

As Davesparks said, the vast majority of traders will use LPG for any heating requirements and just minimal electricity for the other paraphernalia.

 

[curbside coffee]

What is your budget for the provision of mains power in the van? To the nearest £500, ie £1000 or £3500 or £10000.

How many years do you expect to operate the mobile coffee business?

How many days per week and weeks per year do you reckon the business will trade?

I am wondering if the best investment is an ac power wall which is charged when the van is parked at your home.

Something like this:

Tesla Powerwall 2 Cost, Tesla Home Battery Storage - Joju Solar - https://www.jojusolar.co.uk/batteries-smart-grids/tesla-powerwall/

Hi thanks for the reply. I'm looking at £500-£1000 for all the power provisions. It will be weekends only with the intention to do it full time, if thinks work out. But only in the mornings. 6am to 11am.
I've not come across the tesla powerwall. ,I think its out of my budget!
Would building my own power station work? If i built 2 4x110ha battery boxes?

 

[brianmoooore]

I've not come across the tesla powerwall. ,I think its out of my budget!
Would building my own power station work? If i built 2 4x110ha battery boxes?

Give it a few years, when the breakers/scrap yards begin to fill up with end of life electric vehicles.

 

[pc1966]

Would building my own power station work? If i built 2 4x110ha battery boxes?

If you can cope with the weight and have a reasonable means to charge it at home its not such a bad approach. However, you must remember that each battery is capable of delivering a lot of power in a short time and if faulted that can lead to them exploding which is going to ruin your day at the very least.

Determining the load you expect and putting in separate fuses for each battery in parallel is one way to do it. Alternatively you can get inverters that take 48V and then series-connecting 4 of them is an option (a suitable fuse and lots of care with insulation around the terminals is still a VERY GOOD idea). The difficulty then is charging it unless the inverter you have is one that also charges off the mains as part of an off-grid sort of solution.

I have no experience of this product, but from a short overview this looks like the sort of thing:

EPEVER UP3000-M6142 48v 2400w inverter charger - Sunstore Solar

EPEVER UP3000-M6142 48v 2400w inverter charger The UPower series is a new type of the inverter/charger combining with solar & utility charging and AC output.

www.sunstore.co.uk

 

[marconi]

Here's a suggestion. Don't bother with a battery at all. Just buy a suitably powerful inverter with a 12V input. Connect it to your van's battery via a suitable ampacity switch/contactor. When you want electricity start the van engine so the engine's alternator is connected and charges the van battery. Close the switch/contactor to supply 12V to the inverter and thence provide mains current. Operate the for as long as you require electricity and then switch everything off and stop engine to conserve fuel. You may need a higher quality van battery to handle the increased number of start stops but plenty of delivery vans start/stop their engines all day long with the one they were bought with.

A chap in our town with a mobile knife cleaning business has this set up to power his grinders, polishers and tools.

Our new Ford Galaxy has a manufacturer fitted a 12V inverter powered 230V 50Hz ac socket (schuko and 13A) as standard. I think the power available is 150-200W.

 

[curbside coffee]

Thanks for the info. Could anyone tell me the benefit of going 48v instead of 12v?
Thanks.

 

[brianmoooore]

Size of cables, currents flowing through them and voltage drop as a percentage, are all reduced to a quarter.
It's the same reason that electricity is distributed around the country at such high voltages. (400,000 volts for the big pylons)

 

[pc1966]

What @brianmoooore said.

To get 3kW at 12V you need 250A (plus a bit more for conversion losses) and that is seriously thick cables and all of the issues that go with it. At 48V you are looking at 62.5A which is big, but within the cable size seen domestically (probably 16mm would do, depending on length and so voltage drop).

 

[curbside coffee]

I've been looking at hybrid All-in-one inverters, specifically the eco-worthy 3000w 24v pure sine wave inverter. QQ.
Could I wire my car alternator to this device without a b2b charger? (would it also be possible to add a small generator to boost the battery's?)
Would my 200w solar panels even register as input?
Could I run 4x12v battery's in parallel and series?

 

[marconi]

Pc1996 #13 has told you that the provision of 3kW at 240V from a 12V battery is not impossible but to be avoided because of the very high current drawn from the battery which will rapidly discharge it and the need for very short very thick cables to carry this large current at 12V. You would need a special battery to cope regularly with such prolonged high current otherwise its life will be rapidly consumed . My suggestion should have been clearer but I did give my car’s inverter and the knife grinder as an examples. Using you car battery perhaps supplemented by the engine generator is workable for up to about 500W for very short periods - the knife grinder example I gave or as in my car up to 150W for phones, lap top power supplies, tv, small fridge cool box maybe for a few hours but longer with engine running.

If one discharged the battery at a higher rate than the charging rate by the engine then over time it will become flatter and maybe then unable to start the engine nor run the car electrics satisfactorily.

As davesparks said gas is the answer for high power heating. Time to bite the bullet methinks.

Storing electricity at low voltages in batteries is demanding chemistry. And expensive per kWh stored. I did a solar off grid with gennie back up which had a 24V battery ( 4 x 12 V) each of 200Ah. Total Ah is 2 x 200 = 400Ah which is theoretically 400 x 24 = 4.8kWh.

They were agm batteries. To maximise their life they are never completely discharged over a 24 hour period. On demanding days they are 50% discharged. Thus they only reslly are used to store and then deliver 2.4kWh

We get this performance by supplying an equivalent low average power over a 24 hour period of 2.4/24 = 0.1kWh every hour or 100 Watts. This is a discharge current of 100/25/2 = 2 A through each of the 4 batteries - trivial for a 200Ah battery.

We this set up the batteries are never flat , quickly recharged by solar or gennie and their life is maximised ( 1800 cycles of charge discharge). Total cost of 4 batteries £1800 if I remember correctly with about £300 of cabling and sundries including a locked safe enclosure for them.

 

[marconi]

Pc1996 #13 has told you that the provision of 3kW at 240V from a 12V battery is not impossible but to be avoided because of the very high current drawn from the battery which will rapidly discharge it and the need for very short very thick cables to carry this large current at 12V. You would need a special battery to cope regularly with such prolonged high current otherwise its life will be rapidly consumed . My suggestion should have been clearer but I did give my car’s inverter and the knife grinder as an examples. Using you car battery perhaps supplemented by the engine generator is workable for up to about 500W for very short periods - the knife grinder example I gave or as in my car up to 150W for phones, lap top power supplies, tv, small fridge cool box maybe for a few hours but longer with engine running.

If one discharged the battery at a higher rate than the charging rate by the engine then over time it will become flatter and maybe then unable to start the engine nor run the car electrics satisfactorily.

As davesparks said gas is the answer for high power heating. Time to bite the bullet methinks.

Storing electricity at low voltages in batteries is demanding chemistry. And expensive per kWh stored. I did a solar off grid with gennie back up which had a 24V battery ( 4 x 12 V) each of 200Ah. Total Ah is 2 x 200 = 400Ah which is theoretically 400 x 24 = 4.8kWh.

They were agm batteries. To maximise their life they are never completely discharged over a 24 hour period. On demanding days they are 50% discharged. Thus they only reslly are used to store and then deliver 2.4kWh

We get this performance by supplying an equivalent low average power over a 24 hour period of 2.4/24 = 0.1kWh every hour or 100 Watts. This is a discharge current of 100/25/2 = 2 A through each of the 4 batteries - trivial for a 200Ah battery.

We this set up the batteries are never flat , quickly recharged by solar or gennie and their life is maximised ( 1800 cycles of charge discharge). Total cost of 4 batteries £1800 if I remember correctly with about £300 of cabling and sundries including a locked safe enclosure for them.

Correction of my sums in bold below-

Storing electricity at low voltages in batteries is demanding chemistry. And expensive per kWh stored. I did a solar off grid with gennie back up which had a 24V battery ( 4 x 12 V) each of 200Ah. Total Ah is 2 x 200 = 400Ah which is theoretically 400 x 24 = 9.6kWh of stored electricity.

They were agm batteries. To maximise their life they are never completely discharged over a 24 hour period. On demanding days they are 50% discharged. Thus they only really are used to store and then deliver 4.8kWh.

We get this performance by supplying an equivalent low average power over a 24 hour period of 4.8/24 = 0.2kWh every hour or 200 Watts. This is a discharge current of 200/25/2 = 4 A through each of the 4 batteries - trivial for a 200Ah battery.

 

[curbside coffee]

Thanks again for the info. it looks like I'll have to bite the bullet n invest in a lpg system.
Unless.. I can adapt my current coffee machine? to run on lpg? like.. could i "install" a lpg heating element on my machines 8l boiler? cutting down the initial 10 min heating time!
Or at least insulate the boiler so it gets up to temp quicker?!

 

[davesparks]

Unless.. I can adapt my current coffee machine? to run on lpg? like.. could i "install" a lpg heating element on my machines 8l boiler? cutting down the initial 10 min heating time!

If this is possible then it will probably cost more to do safely than it would to buy an LPG machine.

Or at least insulate the boiler so it gets up to temp quicker?!

Insulation won't noticeably decrease the time it takes to heat up the water, you still need to input the same amount of energy to raise the temperature. You can't cheat the laws of of physics!