Battery or Generator

Apr 17, 2018
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Hi,

I am looking to run 10 x 240v (UK) 65 inch TV's out of home. Each TV is rated at 140w, so 10 of them equate to 1400w. All 10 of them will run for 7 hours a day 5 days a week, so roughly will run for 240 days a year.

I know that using a generator will cost more, as fuel prices in the UK are quite bad. So I am considering going down the battery route, the problem is I don't know what size / type of battery I would need for such a project like this, I know it would be allot cheaper and charging them everyday after use wont be an issue as I will have accesses to home power at the end of the day.

I've looked into UPS etc but I don't know how to calculate what I need and if a UPS, or any other time of battery would hold up to the constant charge and discharge each day. The question I then find my self lasting is how long would the batteries last, and if a generator would out last the batteries and working out the cost.

Open to any suggests / advice what so ever, Thanks.

-Anton
 

13thmonkey

Titan
Moderator
Whatever you do it will not cheap to not use a generator. 10KWh at 240V sounds like a massive battery with an inverter to turn the DC in AC. The fuel costs will be the smallest part of in in all probability, a 1.4-2.0kW petrol engine will not use much fuel. I'd say maybe a gallon a day.

In fact a little hunting: https://www.clarketooling.co.uk/tools/Inverter_Generators.html

In the specs for the 2.2Kw version 1lt/hr at 75% load, which is spot on for what you want, so that's 7 hours from the 7ltr tank. So £9/day in fuel, probably less as although they are rated at 140W, they won't be 140W.

So that's a £2,200 fuel bill, plus the generator, £400 = £2,600.

On the battery side, I'm seeing units that might power 2 screens for a couple of hours, for £300ish, but you'd need 20 of them, so that's £6k, excluding charging which although simple is not free. With scaling for bigger units you might get down to 50% of the price of smaller units for the same capacity, but that's still 3k+ charging.

And that'll weigh, a lot, enough that you might need lifting gear to move it around.

Petrol rules in this case, you might find similar engines running of gas though, that might be a bit cheaper.
 
Reactions: antonyjlawlor
Apr 17, 2018
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Thanks for your answer, it's gave me something to think about. As a side note I was also look at the tesla power wall? I know that aint cheap ether but just thinking of different ideas. The generators seems like the most straight forward approach for sure going with your £9 a day figure.
 

13thmonkey

Titan
Moderator
A power wall will be 200-300kg is that a problem? and I think you are right at the edge (from memory) of their capacity. So what happens if you run out of juice, with care you add more fuel (or buy a bigger one with a bigger tank), are you in a position to charge the battery whilst in use? If you are then why use a battery?
 
Apr 17, 2018
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Ok, picture this.

A vehicle that moves around (a diesel powered van to be specific) in the back section of the van will be 10 TV's, which I need to power.

Already looked into powering them off the alternator but again, not sure if that would work / would have any adverse impact on the engine (would also probably need a beefy new alternator £££).

In the back of the van I know I can run and vent a couple of generators, it does mean cutting holes, installing fans and carbon monoxide detectors and boxing the generators in so the exhaust fumes only go one way. That and the maintenance and fuel costs and my main concerns when it comes to using a generator / generators. There is the extra labour of filling up the fuel tanks each day but it not much of a issue.

With battery power I don't really need to worry about carbon monoxide & fuel, I can park the van up when I go home at night and plug it in to charge over night, and it's ready to go in the morning, that was my thinking at least. Again though I have concerns around constant draining and charging and the initial BIG cost of such a large battery, but running costs (i.e. charging the batteries from my house mains for example) would be cheaper? at least I think it will cause electricity is cheaper than fuel? then again, do i need a special charger in my house to charge such a big battery over night to full capacity (probably) is another question, and how much is that going to cost.

So yea, allot to consider hence why I'm looking for some advice.
 

13thmonkey

Titan
Moderator
OK that removes some constraints, and de-risks things a little.

A powerwall or similar could then easily work and the weight is more or less irrelevant. You could have an LPG generator, I think that there is no CO risk with these (please check), you could use this or smaller to top up the powerwall if it got low.

https://www.calor.co.uk/shop/all/commercial-gas-appliances/generators/greengear-3kw-portable-lpg-power-generator.html

A 10KWh battery charged from a 13amp socket would be charged at 3KW, so 4 hours, call it 5 to be sure, and that would cost at 15p/unit £1.50/day

So some kind of setup for home solar power storage could be made to work and plugged into the mains with the right combination of inverters.

https://www.businessinsider.com/rechargeable-battery-options-compete-tesla-2017-5?r=US&IR=T#tesla-has-offered-battery-and-solar-installations-as-one-process-ever-since-it-acquired-solarcity-last-november-tesla-is-now-selling-solar-roof-shingles-that-are-designed-to-look-like-an-actual-roof-to-compete-with-rival-solar-installers-like-sunrun-and-vivint-on-an-aesthetic-level-3

You'll need an installer who is more electrical engineer than installer as what you're doing may be beyond most.

You may even find that a hydrogen fuel cell is not a bad option, if you can find one.
 
Apr 17, 2018
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So running costs going down the electrical route will equate to £360 a year, over a few years that's quite a saving when stacked against £2000 - the battery would pay for it's self in the first 2 years, that's presuming it last that long.

I think the big battery rout might be the way to go, with a small backup generator just encase. The next questions is which battery, i threw in the tesla power wall there as an example, ideally though I was to do it as cost effectively as possible, any battery suggestions?

A hydrogen fuel cell you say Mr Stark! - that road sound expensive and more complex than I dare venture into haha!
 

13thmonkey

Titan
Moderator
Hydrogen FC = tank of hydrogen, plug lead into fuel cell, out comes electricity and water, v simple.

Big battery, oversize it by 50% and even after 1000's of cycles it'll be enough.

The 2nd link in my previous post will give you some options. Ikea even do a house battery now, most house batteries are around the 3kwh mark though.

Depending on how cheeky you feel you could ask them if they would help you be a technology demonstrator, put them on show in the lorry, bit of sponsorship, they might even help with the electrics of the installation.
 
Reactions: antonyjlawlor
APC has a battery capacity calculator if u google.

At some point u may have to go the generator route if u need long on-time. They tend to be noisy so I hope they don't disturb you/neighbors, and properly vented as mentioned.
 
Apr 17, 2018
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After thinking about it all over the last few days and readying a bit about the batteries, I think long term they are the way to go, both environmentally and cost wise (0 carbon monoxide is another +).

So far I have worked out that i'll have 10 TV's at 130W, and 2 computers at 160W.

The Math
10 x 130W = 1300W
2 x 160W = 320W
Combined = 1620W

1620W / 1000 = 1.62kW

1.62KW * 7 (Hours) = 11.34kWh

So ideally I want to be looking at a 12kWh battery (I'm also thinking a solar panel to trickle charge the battery would also be a good idea but i'm forgetting about that for now).

Looking at the Tesla power wall on this page https://www.tesla.com/en_GB/powerwall in you scroll down to where it says Technical Specs, notice the usable capacity is 13.5kWh, but underneath that there is a real power number that says "max continuous 3.68kW/5kW".

My presumption is when hunting for a battery I will need one that provides 12kWh of continues power? Meaning this particular power wall isn't going to cut it, as I would need 2 of them + a smaller one to get 12kWh continues?

Just trying to concrete my answer before I start trying to work out which battery is going to work best for my application.

Thanks again for all the help thus far!
 

13thmonkey

Titan
Moderator
No, you need greater than 1.62kw of continuous power (so 1/2 of a 13amp socket at home)
And greater than 11.35kwh of capacity.

Note the h in the units, this is kw times by hours. An analogy (poor but it'll suffice) is a car a 2litre engine might produce 200 hp (kw), how long it can do that for is related to the size of the fuel tank (kwh). OK so it is stretching the analogy a bit, but it works just about.

I'm sure that there are rules of thumb, but i'd add at least 25% to both the capacity and continuous power ratings, not for aging it'll be 2-3 years before you see that, but for temperature, for when you think that adding a kettle for a brew is a good idea, if you find you need a 3rd PC etc. etc.
 
Apr 17, 2018
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No, you need greater than 1.62kw of continuous power (so 1/2 of a 13amp socket at home)
And greater than 11.35kwh of capacity.

Note the h in the units, this is kw times by hours. An analogy (poor but it'll suffice) is a car a 2litre engine might produce 200 hp (kw), how long it can do that for is related to the size of the fuel tank (kwh). OK so it is stretching the analogy a bit, but it works just about.

I'm sure that there are rules of thumb, but i'd add at least 25% to both the capacity and continuous power ratings, not for aging it'll be 2-3 years before you see that, but for temperature, for when you think that adding a kettle for a brew is a good idea, if you find you need a 3rd PC etc. etc.
Thanks for that, I know more about cars than batteries and this as an amazing and really simple analogy, I total understand the difference between kW and kWh now!

I forgot about heat, being from Scotland the cold might be an issue (it can get down to -5c or worse in the winter.) I fly RC models and use li-po batteries, I've had 1 die because I left it in my car overnight, fully discharging it probably made matters worse mind you.

So with a 25%+ adjustment i'm looking at (roughly) 2kw of continuous power and 14kWh of capacity, to be on the safe side?
 

13thmonkey

Titan
Moderator
Yep, and you'll be lucky to find anything at your nodes, so you'll have to upsize it anyway. The KW is why you could get away with really small generators, you're pulling naff all power, but you want to do it for quite a long time.
 

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