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oh definitely, an unshared 16A feed is yours for the day, in return for regular black coffeesWell you're a handy person to know - can I just follow you to all the events that you are at?
Discuss Mobile Barista at wits end! in the UK Electrical Forum area at ElectriciansForums.net
oh definitely, an unshared 16A feed is yours for the day, in return for regular black coffeesWell you're a handy person to know - can I just follow you to all the events that you are at?
Thank you. I think that my friend calculated 0.8kW and then said that I should have the 4 x 224Ah, 6V Powerline batteries. Would you advise against 6V ones?
There's a big 'Organic (green)' type place near me. It always amuses me looking at the long queue of cars waiting to get into the car park, most of them with their engines idling away, belching crap into the air ...It's a farce really all the weight you take there uses energy that has to be generated by some means . I bet there is a massive car park too.
Couldn't you just sell iced coffee?My exact requirements are:
APPLIANCE kW USAGECoffee machine pump 0.350 ConstantCoffee grinder 0.350 15min/hourFlo-Jet (water pump) 0.046 10min/hourFridge 0.300 Constant but fluctuatingTill 0.002 Constant'ishMain strip light 0.072 ConstantLED blue lights 0.075 ConstantTOTAL 1.195
I would run far far away from a 6v system. A 24 volt would be much better
watts = volts x amps
therefore amps = watts / volts
1200 watts / 12 volts = 100A
1 single 100Ah 12v battery in peak performance will provide you with 1200 watts for 1 hour.
this is the calculation, it is not negotiable!
the only thing to add is that that is the pure mathematical calculation and is not including any losses that you will get in the distribution and conversion of electrical energy.
I would estimate this to be 15% to 20%
I'd just take a giant bottle of gas with a camping stove...
You can get LPG conversion kits for Honda Eu20i etc, might be a good solution?
I agree with James the Spark that from your table of requirements, the average running load is around 700W. This assumes the fridge compressor runs about 50% of the time. It might be more on a hot day if you keep opening it.
What has been overlooked in all the above calculations is that the batteries have a rated capacity that represents their absolute maximum capability when new. Using that capacity cyclically, i.e. fully discharging and then fully recharging, is like working a horse until it collapses, reviving it and doing the same day after day and expecting it never to lose stamina. Ordinary leisure 'deep cycle' batteries will not last like this, their capacity will soon drop off. After a few hundred cycles use it might be down 25% or more, i.e. you needed to start off with 25% more battery to account for their decline, or your working day will end 25% early. The more deeply you discharge, the more rapidly the battery wears out. I.e. to give good working life, you need extra capacity discharged less deeply, but this means extra weight and volume to carry about.
Next you have to consider the discharge rate. The rated capacity of most lead acid batteries is given at the 20 hour discharge rate. If you discharge them faster, e.g. use all of their capacity in 10 hours, their usable capacity will be lower. Equivalent to the horse being able to make 10 round trips in a day if it trots, but only 8 if you make it gallop. Then, as Shaun points out, you have the minor detail of recharging. To fully recharge a lead acid in less than 12 hours is stressful for it, as the last part of the charge is absorbed only slowly. But if it does not get fully charged, it starts to lose capacity through sulphation. You can solve these problems using full spec traction batteries as used on electric vehicles. These are rated for discharge over 5 hours and for rapid recharging, so although they are more expensive, larger and heavier per Ah than leisure batteries, you need add less margin of capacity and will last longer.
What size battery do you need?
700 watts for 10 hours with an inverter efficiency of 85%
700 x 10 / 0.85 = 8.2kWh energy taken from the battery
I'd use 24V, not 12V, to reduce the currents involved and hence cable size and losses. 24V inverters may be a teeny bit more efficient for the same reason.
Taking the average usable voltage at the inverter terminals as 23.5V:
8200/23.5 = 349Ah at 24V actual capacity utilised.
With a full traction battery rated at the 5 hour rate, you will get 110% of rated capacity over 10 hours. If you want a 25% margin, then you need:
349 / 1.1 x 1.25 = 396Ah rated capacity.
Yuasa reckon on 1200 cycles / 4 years use at 70% depth of discharge to about 70% of rated capacity. If you want this kind of lifespan, you will need 396/0.7 = 565Ah rated capacity or more. At that capacity you would best have a battery made up from 2V cells. If you wanted to use series-parallel 6V blocks, we could use their GC200 as an example, wired as 3P2S (three parallel strings of two in series). These would need a battery box about 550mm square and 300mm high, total weight about 200kg. Hydrogen will need to be vented and not allowed into the vehicle.
I'll let you do the sums for the equivalent in leisure batteries, personally I'd stick with traction. But first, see what you can do to get that consumption figure down, and more accurately known, e.g. a more efficient fridge will save ££ in batteries. Or, switch to Li-ion, but make sure you're sitting down when you check the pricing!
NB. this is why small generators are popular!
But that's not going to power my coffee machine and instant coffee is NOT an option - the stuff should be banned!
grind the coffee at home prior to setting out. thats 0.35kW saved.
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