Power for mobile catering - batteries versus generator?

[Flipflop]

Hi all,

I'm new here and have a pretty specific question. We've got a vintage ambulance we've converted to a coffee bar. There's a mains voltage hookup to a 3 way consumer unit which runs everything including a 12v charger which charges 2 x 110Ah batteries. Now, we're looking at a pitch where we wont have the luxury of hooking up and I was wondering if anyone had recommendations for a best approach?

We have some power-hungry-appliances (espresso machine @ 3kw, taps @ 2kw, filter machines (2 of) @ 1kw plus lights and speakers). They're not all drawing max load the time, like the espresso machine is a lot less after it's initial heat.

Anyway, what would be the pros/cons of getting a smallish generator (we can't be noisy at our pitch) to charge the batteries (I have 2 extra so a possible maximum of 4 @ 110Ah each) and an inverter?

Thought and suggestions welcome and appreciated!

 

[Wilko]

Hi FF and Welcome to the Forum!
With several kW rated appliances you are probably better off with a generator in my humble opinion. There are some nice quiet ones that are designed for marine use, perhaps .

 

[telectrix]

what he said ^^^^^^. a genny is a must. hire one. the cost of an inverter for the load you have would be prohibitive and your batteries would go flat before the coffee water had boiled up.

teccy bit..... 2300watts @ 12V is 190Amps. allowing for losses in the inverter, call it 200. 20 minutes to flatten a 110Ah battery and the cables would be as thick as your wrist.

 

[Lucien Nunes]

As above, inverter is a non-starter. Your total stored energy is 110 x 4 x 11.5 = 5kWh. When discharged at a high rate, lead-acid batteries become less efficient, so in practice you might only be able to use 70% of that, and if you want them to last, you cannot discharge to zero. Call it 0.8 x 0.7 x 5 = 2.8kWh. That's your load powered for 20 minutes as Tel says, then 12 hours to recharge.

Back in the day when large inverters were new and exciting and I had just installed one, the (technical) customer flipped the 'All Loads to Inverter' emergency switch and deliberately heated a domestic cylinder-full of water from cold using battery power just to prove to himself that it was possible. His battery was heavier than your ambulance though.

 

[Flipflop]

Thanks for the great advice. I was looking at the cheapy inverters (on ebay and the likes) but having checked reviews I think they exaggerate the wattage. I hadn't even thought of the 190Amp draw... crazy. I'll have a look for a bigger generator - if you have any recommendations in terms of reliability & noise levels feel free to share. Thanks again, really helpful stuff.

 

[Deleted member 105166]

You want to be looking at a generator of 12kVA to 20kVA. You mentioned speakers - whilst your catering equipment will be reasonably tolerant of voltage fluctuations, electronic equipment won't be so tolerant - for powered speakers & other sound equipment you want a generator that will out put a reasonably stable voltage. I.E. your speakers won't like the voltage dropping from 230V to ~180V and back again, as the thermostats on your catering equipment operate. Automatic Voltage Regulation (AVR) would be recommended, definitely get a diesel set - avoid used & abused construction site sets and also avoid small petrol sets that you can buy in DIY sheds. The larger the set, the lesser the impact on the output voltage under fluctuating loads.

 

[Marvo]

Use gas (9 kilo LPG) wherever possible. Commercial espresso machines usually have a retrofit gas conversion kit available and any hot water requirements can be met by gas. Look at whatever is left, if it's a small load then batteries and in inverter could be back on the table as an option otherwise a small generator.

 

[telectrix]

petrol gennys are expensive on fuel. diesel ones will wake the dead. if you wait a few years i'll have designed a silent nuclear powered genny that only costs a few pence an hour. but find your own ocean to dump the radioactive waste.

 

[buzzlightyear]

what a about using a lamp post for a hook up ,travellers use them.

 

[buzzlightyear]

seen loads of the inv /gennys used abroad .for catering units .

 

[HandySparks]

How about a petrol genny converted to LPG. Very quiet and, I believe, cheaper to run than petrol.
Here's a top quality one if your max load is less than 7kW:
Honda EU70is Bottle Mount LPG Dual Fuel 7kw Silent Generator | Honda Engines and Generators | Gear GB - http://www.geargb.co.uk/product/5000-HOND-GEU70A/Honda_EU70is_Bottle_Mount_LPG_Dual_Fuel_7kw_Silent_Generator

 

[DPG]

what a about using a lamp post for a hook up ,travellers use them.

Be a bugger installing a lamp post at each site you visit though. And he would have to ask about earthing the lamp post as well - we've been there before.

 

[grantr37]

Rent a small diesel generator to run that lot and keep a gas hob and batteries with a good inverter or 12 volt system to run lights when the genny is off.

 

[grantr37]

How about a petrol genny converted to LPG. Very quiet and, I believe, cheaper to run than petrol.
Here's a top quality one if your max load is less than 7kW:
Honda EU70is Bottle Mount LPG Dual Fuel 7kw Silent Generator | Honda Engines and Generators | Gear GB - http://www.geargb.co.uk/product/5000-HOND-GEU70A/Honda_EU70is_Bottle_Mount_LPG_Dual_Fuel_7kw_Silent_Generator

LPG won't work with a small petrol generator, can't convert safely and it will damage the engine, the big companies like agrekko worldwide are experimenting with LPG and landfill gas generators and even gassified wood chip and they are working with specialist scientific companies, my exes father owns one of those companies over in America so that's why I know this.

 

[HandySparks]

LPG won't work with a small petrol generator, can't convert safely and it will damage the engine, the big companies like agrekko worldwide are experimenting with LPG and landfill gas generators and even gassified wood chip and they are working with specialist scientific companies, my exes father owns one of those companies over in America so that's why I know this.

I've not heard this before. LPG is widely used in 'petrol' car engines, either as a conversion or as supplied by the original manufacturer. Conversion of small engines to LPG has been available for many years. What exactly is the mechanism for damage?

Aggreko seems to be offering gas fueled generators for general use. Is this really just 'an experiment'? (Maybe not so relevant as generally not 'small' engines.)

Gas Generator Hire | Aggreko - https://www.aggreko.com/en-gb/products/power-generation-rental/gas-generator-hire

Your Project News | Aggreko signs contract for LPG-powered NGG Generator in St. Croix - http://www.yourprojectnews.com/aggreko+signs+contract+for+lpg-powered+ngg+generator+in+st.+croix_149096.html