Mobile Barista at wits end!

[Seb217]

All I want to do is sell coffee!!! ... yet I have found myself stressing about power supply!

I have a mobile coffee van. I'm done with using generators and so are many event/festival organisers who are now banning petrol/diesel from their sites. In an ideal world I would like a battery fed inverter to power all the equipment that I can't run on LPG.

I would like to achieve 1.5kW of power - I actually currently need 1.2kW of power (not all continuous) but want the extra to future proof against any further equipment that I may want to put on the van in the future.

I need to be able to have power for approx. 10hrs per day. I have sufficient space (but not endless amounts of) to house the batteries and inverter.

As all the equipment that requires power is plugged in to sockets on the walls of the van, can I plug the ‘hook up’ plug into the inverter?

I understand everything there is to know about coffee (and it's more of a science than many people may think) but I know nothing about power. Is there anyone that can please please help.

 

[James]

All I want to do is sell coffee!!! ... yet I have found myself stressing about power supply!

I have a mobile coffee van. I'm done with using generators and so are many event/festival organisers who are now banning petrol/diesel from their sites. In an ideal world I would like a battery fed inverter to power all the equipment that I can't run on LPG.

I would like to achieve 1.5kW of power - I actually currently need 1.2kW of power (not all continuous) but want the extra to future proof against any further equipment that I may want to put on the van in the future.

I need to be able to have power for approx. 10hrs per day. I have sufficient space (but not endless amounts of) to house the batteries and inverter.

As all the equipment that requires power is plugged in to sockets on the walls of the van, can I plug the ‘hook up’ plug into the inverter?

I understand everything there is to know about coffee (and it's more of a science than many people may think) but I know nothing about power. Is there anyone that can please please help.

 

[James]

I will do some calculations for you.
hang fire.

 

[Seb217]

I will do some calculations for you.
hang fire.

THANK YOU!!!!!

 

[James]

so 1.5kw for 10 hours is 15Kwh
at 12v that works out to be 1250Ah capacity required
add in 20% for losses and battery degradation over time gives around 1500Ah
or 15 leisure batteries at 100Ah each.

at 20Kg each, that is a total weight of 300Kg

 

[James]

I it will be drawing around 130A from the batteries at 1.5Kw load so you will need some big cables (starter motor size) from battery bank to the inverter.

 

[Seb217]

That's all reading as though it is not going to be feasible - where is the sad face emoji on this website.

I asked a friend of mine and they said that 4 x 224Ah 6V batteries (weighing 30kg each), would give me 2.7kW per hour for 10hrs. Could they have been so wrong?!!

 

[James]

so around £1200 for the batteries, £250 for the inverter, £150 for all the other bits like cable and battery connectors etc.
its not cheep at around £1600 parts.

 

[Seb217]

so around £1200 for the batteries, £250 for the inverter, £150 for all the other bits like cable and battery connectors etc.
its not cheep at around £1600 parts.

More expensive than a Honda EU22i!!

These are the batteries that the friend of mine reckons I only need 4 of - Powerline T105 AGM

 

[James]

at 12v 1.5kw draws 125A
so for 1 hour you will need 125Ah of battery
for 10 hours you will need 1250Ah of battery.

at 6v the current draw will be 250A, you can do the maths yourself on that one!
but you have also got to remember that these things are not 100% efficient so you will need a bit more to cover it.
however, you are probably not using anything like 1.5Kw continually, so that would reduce the storage requirement

 

[James]

anyone fancy checking my maths?
I don't think I have got it wrong but I have had a beer so its always possible!!

 

[Seb217]

at 12v 1.5kw draws 125A
so for 1 hour you will need 125Ah of battery
for 10 hours you will need 1250Ah of battery.

at 6v the current draw will be 250A, you can do the maths yourself on that one!
but you have also got to remember that these things are not 100% efficient so you will need a bit more to cover it.
however, you are probably not using anything like 1.5Kw continually, so that would reduce the storage requirement

My exact requirements are:

APPLIANCE​	kW​	USAGE​
Coffee machine pump	0.350​	Constant​
Coffee grinder	0.350​	15min/hour​
Flo-Jet (water pump)	0.046​	10min/hour​
Fridge	0.300​	Constant but fluctuating​
Till	0.002​	Constant'ish​
Main strip light	0.072​	Constant​
LED blue lights	0.075​	Constant​
TOTAL	1.195​

 

[The Ghost]

How about gas or coal or wood.

 

[Seb217]

anyone fancy checking my maths?
I don't think I have got it wrong but I have had a beer so its always possible!!

I'm mathematically brain dead and don't understand even the basics of electricity - so as far as I'm concerned you could be right and my friend could be wrong. All I know is that I am having some construction work done on my van and need to whether or not to allow space for batteries or not.

 

[Seb217]

How about gas or coal or wood.

I'm having gas installed on the van to power the coffee machine and water boiler. I'm not sure that the EHO would approve of me using coal or wood

 

[snowhead]

at 20Kg each, that is a total weight of 300Kg

Just turn up with that lot in a separate smokey Diesel van, the organisers will soon change thier mind.

Why not use an LPG generator?

These organisers are going to have to supply all power to stallholders in the future if they ban small portables.

 

[Seb217]

[QUOTE="James the Spark1976, post: 1547792, member: 118821"

at 20Kg each, that is a total weight of 300Kg

Just turn up with that lot in a separate smokey Diesel van, the organisers will soon change thier mind.

These organisers are going to have to supply all power to stallholders in the future if they ban small portables.
What are the organisers using for thier own power?
[/QUOTE]

That is a very good question!! They are making all mobile caterer's lives hell! As if all the other regulations that we have to abide by aren't enough!

 

[Lister1987]

Stupid addition; whack a solar panel on the roof of the van to trickle feed the batteries, or if you can get enough power from thrm, hookit up to your most power hungry machine as dedicated. might be helpful?

 

[James]

ok so although your peak demand is 1.2kw your average consumption is more in the region of 700w (0.7kw) that would halve the required battery's. so 7 rather than 15 should be sufficient. but I would be putting in 10 if it were my van.

 

[Seb217]

Stupid addition; whack a solar panel on the roof of the van to trickle feed the batteries, or if you can get enough power from thrm, hookit up to your most power hungry machine as dedicated. might be helpful?

Not a stupid addition at all - I was going to think about a solar panel once the basic battery set up had been sorted

 

[The Ghost]

EHO would approve of me using coal or wood

What has this world come to.../sigh!

 

[Seb217]

ok so although your peak demand is 1.2kw your average consumption is more in the region of 700w (0.7kw) that would halve the required battery's. so 7 rather than 15 should be sufficient. but I would be putting in 10 if it were my van.

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?

 

[Seb217]

What has this world come to.../sigh!

Like I said - All I want to do is sell coffee!! It's not like I've got masses of equipment or that I am selling a huge menu - I'm only selling coffee, no food being cooked at all!

 

[Lister1987]

I'm having gas installed on the van to power the coffee machine and water boiler. I'm not sure that the EHO would approve of me using coal or wood

"No EHO, this isn't coal, it's a bag of VERY LARGE AND CHARRED coffee beans/pods"

 

[ruston]

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.

 

[Seb217]

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.

The banning of generators is to supposedly prevent even a drop of fuel getting onto the grass! ... and before anyone suggests it, I've had an LPG generator - it was so bad that I sold it after only 3 days trading!

 

[James]

I suspect he was going to configure them as 2 banks of 6v in parallel, giving the equivalet of 2 x 110Ah 12v batteries in parallel. its not going to make a big difference to the cost or size requirements however you must remember that every week you will have to top these batteries up with distilled water, so make sure they are easy to access.

 

[ruston]

And storing batteries is safe from accident . It makes you wonder.

 

[Seb217]

I suspect he was going to configure them as 2 banks of 6v in parallel, giving the equivalet of 2 x 110Ah 12v batteries in parallel. its not going to make a big difference to the cost or size requirements however you must remember that every week you will have to top these batteries up with distilled water, so make sure they are easy to access.

What? They need watering?? I can barely keep a house plant alive!! There is nothing on the website nor datasheet that says anything about watering - not that I was really able to understand anything on the datasheet

Would 4 of the aforementioned batteries be enough then?

 

[James]

my best guess is they would be dead in around 4 hours

 

[Seb217]

my best guess is they would be dead in around 4 hours

The house plants or the batteries
Not what I wanted to hear but glad for the second opinion. Can you suggest any alternative power solutions/ideas?

 

[James]

offer a 30% discount to people who pedal enough charge into your eco friendly bicycle generator?
sorry to be the bearer of bad news but maths is maths and the sums add up to a lot of batteries!!

 

[Seb217]

offer a 30% discount to people who pedal enough charge into your eco friendly bicycle generator?
sorry to be the bearer of bad news but maths is maths and the sums add up to a lot of batteries!!

I just don't understand how the maths could be so wildly different. I'm not saying you are wrong (as much as I would like you to be if you get my drift) but I stressed to the friend of mine how nervous I am about having enough power - the last event that I was at, my generator broke down and I was unable to trade for 40mins until it was fixed, I told my friend this.

 

[Deleted member 105166]

I’ve had a few instances recently at events where traders who initially said they don’t need power as they have their own inverters, come asking for a feed as their batteries are drained or cut out when refrigeration compressors kick in. On the upside, this typically results in free food and beverages.

 

[Seb217]

Feeling the need to rant now .... All other caterers must be having the same problem. It's not as though I need a lot of power! I only need 1.5kW, that's less than a domestic kettle! I see other traders flouting the new rules with their petrol/diesel generators, maybe I should just follow suit .... but my downfall is my conscience. I always want to make sure that I do the right thing and the one time that I don't, it'll be me that gets caught, thrown off site and there goes my reputation, pitch fee and income for the day!

 

[Seb217]

I’ve had a few instances recently at events where traders who initially said they don’t need power as they have their own inverters, come asking for a feed as their batteries are drained or cut out when refrigeration compressors kick in. On the upside, this typically results in free food and beverages.

Are you a fellow trader or event organiser? If you are a trader, how have you got spare power to share?

 

[Deleted member 105166]

Are you a fellow trader or event organiser? If you are a trader, how have you got spare power to share?

Temporary power provider

 

[Seb217]

I'd happily pay for hook up buy very few places even offer it. FYI, I always give my event organiser free coffee for the day ;-)

 

[Seb217]

Temporary power provider

Well you're a handy person to know - can I just follow you to all the events that you are at?

 

[Seb217]

I've not had dinner yet and the mood I'm now in, I'm going to end up binge eating loads of unhealthy stuff and then I'll feel fat and then I'll be in an even worse mood. In the meantime, while I'm away, if anyone comes up with a fantastic solution to my dilemma, please just let me know.

 

[Deleted member 105166]

Well you're a handy person to know - can I just follow you to all the events that you are at?

oh definitely, an unshared 16A feed is yours for the day, in return for regular black coffees

 

[James]

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%

 

[StephenRowley]

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?

I would run far far away from a 6v system. A 24 volt would be much better

 

[Strima]

Event organisers tend to knee jerk at the slightest thing, a bit of spilt fuel is the end of the world in their eyes and a lot of money and paperwork. All they need to do is ensure that any spills are captured before they have chance to make contact with the ground such as using drip trays and absorbent matts etc. Good housekeeping and working practices make a lot of problems disappear.

I have worked in Germany where their environmental regulations have always been much stricter and they still allow generators. Spilt fuel meant the soil being bagged up and sent for cleaning to then be returned and replaced to the same spot at the offenders cost and also a hefty fine.

Another thing that worries organisers is the risk of fire when filling up as some traders don't like to switch off when doing so.

Battery technology is moving along rapidly however at the moment it's still impractical for a lot of traders to rely solely on this technology as were not quite there yet, as pointed out the carbon footprint only shifts somewhere else as you need to move a much heavier vehicle around for a greener solution.

 

[Edtwozeronine]

I'd just take a giant bottle of gas with a camping stove...

 

[shaun1]

Remember as well that you will need a charging system capable of charging all of the batteries, and you will probably need to have the van plugged in all night to get a full charge.

You could buy a chesp home plug in energy monitor and use that next time you are running from generators/event power. You might find you are using lesd than you think.

 

[Lucien Nunes]

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!

 

[Silly Sausage]

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.

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 ...

 

[telectrix]

grind the coffee at home prior to setting out. thats 0.35kW saved.

 

[Silly Sausage]

My exact requirements are:

APPLIANCE​	kW​	USAGE​
Coffee machine pump	0.350​	Constant​
Coffee grinder	0.350​	15min/hour​
Flo-Jet (water pump)	0.046​	10min/hour​
Fridge	0.300​	Constant but fluctuating​
Till	0.002​	Constant'ish​
Main strip light	0.072​	Constant​
LED blue lights	0.075​	Constant​
TOTAL	1.195​

Couldn't you just sell iced coffee?
Brew up a big vat of juice at home, a great big ice box and a load of candles for lighting ... well cool, dude!