Power source suggestions

Hi all,

So I am in the planning stages of one of my first arduino projects. Basically it will be the heart of a outdoor BBQ / pizza oven area. I need a little help trying to decide what to power this with.

The area will not be used that often, perhaps once a week. When it is used it will need to run for 2-5 hrs max.

I can't really run mains power to the area, so need to rely on battery. Ideally I would also like to set up either solar or wind power to recharge the batteries.

At the moment this is what I need to power (and what I estimate I need to power them, correct me if I am wrong though)

Arduino 30Mah (so F all) 2x thermocouple ????? (but very little I assume) LED strip 6m 8ah led lighting 20ah touch screen 1-2 ah

So all up around about 30ah with everything on max. Obviously everything will not always be running.

I guess the "proper" way to do this would be with a bank of deep cycle batteries? But dear god they are expensive here in NZ.

I had thought of using 18V tool batteries (with converter), I have a bunch. I could charge them as normal, move them outside and cycle back and forth. With the added bonus that if I buy more they are useful as tool batteries when not in use. Is renewable energy going to be possible with 18V though?

Thoughts? Alternatives?

Thanks all :)

revisit running power from the house.

with all that lighting, you will need much more power than the batteries will give. also, the cost of batteries and life cycle are both of concern.

even if you just ran an extension cord for the day.

forgot to ask if you have a waterfall nearby ? ocean , with waves? if you could generate power as and when you need it, you would be better off.

Yeah, I had actually thought the same as I was typing that up and saw the ah adding up.

No, no running water. Actually no water in general. Just plenty of wind, but that isn't going to be enough to power as needed.

What's your "Ah" unit? Batteries have a capacity (Ah) and current limits (A) for continuous and maximum current. The maximum current never should be exceeded, and exceeding the continuous current reduces the capacity of the battery. Multiply the average current by the up time to get the required capacity (Ah).

When you use switching power supplies, the currents differ on the primary and secondary side. In this case you should compute the power consumption for each connected device (VA), sum up the total power, add 10-20% reserve for converter efficiency, and divide by the battery voltage to get the current drawn from it.

If you have multiple 18V tool batteries, you can use one for the LED strip, one for the LED lighting, and another one for the rest. This will allow to switch/exchange the LED batteries when empty, without interrupting everything else. Relays can be added to switch the batteries automatically, under control of the Arduino.

Also consider to use an old (12V) car battery, heavy but cheap and robust.

DrDiettrich: If you have multiple 18V tool batteries, you can use one for the LED strip, one for the LED lighting, and another one for the rest. This will allow to switch/exchange the LED batteries when empty, without interrupting everything else. Relays can be added to switch the batteries automatically, under control of the Arduino.

I hadn't even thought of that! That is a rather smart idea. So I could for example have 3 batteries, one for lighting, one for strip/mood lighting, and one for the Arduino itself. Can switch them out inpidpenintly of each other. Or just decide to forgo mood lighting for the night etc.

DrDiettrich: What's your "Ah" unit? Batteries have a capacity (Ah) and current limits (A) for continuous and maximum current. The maximum current never should be exceeded, and exceeding the continuous current reduces the capacity of the battery. Multiply the average current by the up time to get the required capacity (Ah).

The largest individual 18V I have is 40ah (+ 3 15ah) right now. I had thought of banking them. But running individual power sources would be smart.

DrDiettrich: Also consider to use an old (12V) car battery, heavy but cheap and robust.

I thought that auto batteries were considered no good for this type of thing as they do not like being drained over a period of time, or being drained low. Or is that all just smooth talk to get me to buy deep cycle batteries? It would also some what solve having to step down from 18V right?

As you can see this is not exactly my area of expertise! haha

Just a few things to consider: The loads seem excessive, how did you calculate the ah (Amp/Hour) requirement? 30ah would suggest 6 amps per hour for 5 hours? If so a 30ah battery will typically not support the load as most batteries sold here in NZ are rated at the C20 (20 hour) rate not the C5 rate.

What voltage will the system run on? 5VDC for the Arduino and 12VDC for the rest? if so 18VDC to 12VDC 6amp Converters will be difficult to find, (all though I am about to start learning Arduino and will look at PWM controlled power supplies, so this could be an option to reduce voltage to your equipment).

Solar regulators typically come in either Nominal 12VDC or 24VDC Outputs so charging the 18V power tool batteries may also be difficult, especially if they are Lithium.

Recharge current for a 30ah SLA( Sealed Lead Acid) battery needs 10% of the C20 AH capacity rating of the battery to recharge the battery to 95% within 14 hours (according to IEEE guidelines) or at least 10% more current than was discharged from the battery over a similar period.

If you are interested and can let me know where in NZ you are, I can probably help with sizing the Solar panel etc.

Sources: 15 years selling A.C. - D.C. battery backup systems and batteries for Industrial, Commercial and Marine sites.

jes2xu: I thought that auto batteries were considered no good for this type of thing as they do not like being drained over a period of time, or being drained low. Or is that all just smooth talk to get me to buy deep cycle batteries? It would also some what solve having to step down from 18V right?

As you can see this is not exactly my area of expertise! haha

For your application a decent car battery will be fine, I wouldn't run my house on one but for BBQ lights etc its certainly an option, particularly if you can pick up "Sealed" or "Gel" one at a reasonable price.

Kiwi_Bloke: For your application a decent car battery will be fine, I wouldn't run my house on one but for BBQ lights etc its certainly an option, particularly if you can pick up "Sealed" or "Gel" one at a reasonable price.

Well that makes things a whole lot more doable then! working in 12V would be much better. And I can get my hands on auto batteries easier.

You are very right though . . . . that load is huge! I hadn't actually considered the number when I calculated it I just copied the answer over blindly. Thanks for pointing that out! I will go back and work out what I did wrong! . . . . when I'm not at work ;)

So Kiwi blokes assumption was right! I had totally messed up my current calculations.

Depending on exactly what I use for the LED lighting (and how much of it) I am looking at the 4-6 amp range. So for one evening of use I am looking at around 10-20 amp hours (depending on usage and length of use).

Assuming that at the heigh of summer holidays I use it once a week (often more like once a month I would guess) I think this becomes a lot more doable with a wind turbine/solar panel and a 12v battery.

So basically giving a 12v battery 20ah over a week?

Yes? No?

jes2xu: Yes? No?

Maybe :)

If you like I will have a play with the calculators and give an opinion on solar panel choices, are you looking at using a PWM regulator or maybe building your own with the Arduino?

Also what are the thermocouples doing?

Kiwi_Bloke: Maybe :)

If you like I will have a play with the calculators and give an opinion on solar panel choices, are you looking at using a PWM regulator or maybe building your own with the Arduino?

Also what are the thermocouples doing?

The thermocouples are measuring temp at a few different positions in a wood fired pizza oven :)

Yeah I was thinkg of PMW to start with, probally building my own PWM5 based on a arduino, and then perhaps upgrade to a Arduino MPPT at some stage down the line.