Leisure Batteries & Inverters for Mobile Coffee Van

[Commer Food Van]

Hi All

We're new here and looking for some advice to make sense of the world of leisure batteries and inverters.

We're setting up a coffee van in an old Commer Highwayman. We've got an LPG coffee machine with its own battery and inverter for the electrical parts of it (pump, lights etc)
We need to get batteries and an inverter for the other electrical equipment in the van - 2 undercounter fridges (27 watts altogether), Coffee grinder (620 watts), air-vent fan (32 watts), Juicer (240 watts), some LED lighting, iPad charger. We want to operate about 8 hours a day and can charge overnight.

The grinder and Juicer will be "on demand" usage with everything else running the whole time. How can we make this work?

Any advice would be welcome!!

Many Thanks

 

[marcuswareham]

A small generator could work out cheaper, like you see on burger vans etc, or is this out of the question due to the noise or needing to move location often

The loads you mentioned are around 75A at 12v if you were to use 100Ah deep cycle battery at full load it should last just over an hour, although of course it would be longer due to the juicer and grinder not being on for very long, but this gives you an idea to work out what capacity you need, its also fair to assume a 100Ah battery is only going to give you around 60Ah. You can add as many batteries as you like in parallel without effecting the voltage, and it might be worth considering Gel instead of lead acid batteries to remove the risk of leaking acid around food stuff (although I am sure this could also be done with a suitable battery container/compartment)

You can get cheap square sine wave inverters from china on amazon and ebay etc, but as this will be used for long periods of time and for a business it is probably worth getting a decent pure sine wave inverter from victron or similar (Also some appliances will not like a modified/square sine wave from a cheap inverter)

It would be very easy to have the lighting running directly off the 12v (or 24v) DC from the battery and likewise the iPad charger, can you install 12v or 24v fridges or do they need to be 230v?, by doing this you are depending less on the inverter and will not need as much 230v distributed around the van meaning the juicer and grinder could probably plug stright into the inverter

You also want to avoid running the batteries flat, as this reduces there life so a good battery monitor (not just a voltage indicator) is probably a good idea also.
A friend of mine who lives on a canal boat off grid was going though his batteries about once a year and having to replace 4 deep cycle batteries at some cost, He asked me to see why he keeps killing the batteries it turned out he was only monitoring the battery voltage, each time he ran his washing machine the batteries were taking a pounding and being drained, he would then run his engine to recharge, once he saw the voltage go up he would stop the engine thinking he had charged the batteries after just 30min/an hour but because the washing machine is such a high load he needed to run the engine for alot longer to recharge, Now he has a victron smart shunt battery monitor which will tell him the atcually battery charge and condition etc, and now the batteries last alot longer.

 

[DPG]

At those currents you would need to use some pretty hefty cable as well to cope with the current and also to avoid excessive volt drop.

 

[Lucien Nunes]

You need to do a proper energy budget to get a handle on the total energy storage needed. For each appliance, multiply the power by the run-time to get the energy. e.g.

Gadget 1: 200 watts x 0.25 hours = 50 watt-hours (Wh)
Gadget 2: 40 watts x 8 hours = 320Wh.
etc.

When you have the total we can decide how much of what kind of battery is needed to store it. The choice of battery and charging system is so dependent on the total energy requirement that there is little point speculating yet on what is best.

You also need to know the maximum continuous power the inverter must handle and the maximum peak power. For example, you give the fridges as 27W, but a 230V compressor fridge takes a momentary surge of up to 500W at starting. This has little impact on the energy usage but the inverter has to be rated to deliver the peak power without cutting out. You have to consider what happens if you start the coffee grinder at the same moment that the compressor kicks in - you don't want all the lights going off.

On the subject of fridges, I am suspicious about that rating, it seems very low. It might be true as a long-term average in a domestic environment, with the kitchen cold overnight and the door opened 10 times a day, so that for half of the averaging time there is very little work for the compressor to do. In a commercial serving environment on a peak summer day the compressor will probably be running all the time and the consumption might be four times that figure. You must budget energy on the daily maximum usage per battery charge, which usually means ignoring manufacturers' energy scores.

As @marcuswareham points out, there can be significant advantages to 12V DC equipment in this environment including reduced inverter losses. Some 12V equipment is designed to be especially efficient, e.g. a 12V fridge will often use less than a mains one for the same cooling performance. There is often a serious cost penalty though. My 102 litre marine fridge cost £700.

Do energy budget with your existing specs first. If any appliance data is unclear post it here.

 

[marcuswareham]

My 102 litre marine fridge cost £700

wow that aint a cheap fridge

 

[marcuswareham]

Could a gas fridge be used?, I suspect it's not allowed due to the confined space and also movement when in transit, but i don't know

 

[Lucien Nunes]

LPG (absorption) fridges suitable for commercial use do exist but they are even more expensive - think £1200 mark for a regular under-counter fridge. Normal 'leisure' grade absorption fridges might not have the cooling capacity or adequate temperature stability as the gas rate is not necessarily thermostatically controlled.

Beware the '3-way' 12V / 230V / LPG models. Because gas fridges can't usually be left running on gas while on the move, some offer electrical operation too. However in the 12V mode they are power guzzlers, with current drain five times higher than a compressor fridge or more, so they cannot realistically be operated on battery. The element is usually interlocked with the vehicle alternator so that it only operates when the engine is running, as the function is only to maintain temperature while driving.

 

[Marvo]

Usually with the ammonia absorption fridges they are slower to reach temperature and they compensate somewhat by manufacturing them with better insulation so usually they don't need to run whilst the vehicle is mobile for a short period as long as the contents of the fridge are already cold.