Advice for Portable power station/distribution system for 400 phones (for aid relief)

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1

Hey Members,

I recently volunteered in Calais to support people who have mainly fled conflict from Sudan.

The Charity currently use three Hyundai HY9000LEk Electric Start Open Frame Petrol Generators, which they plug extension cords into. People then plug their own chargers into these.

These are very heavy, noisy, dirty, and of course petrol needs to be bought.

It struck me as inefficient in terms of energy use, long-term cost, and of course it isn’t ideal using petrol.

The Charity has a base, and they take vans to various sites to give support. There’s approx 3-400 phones wanting to be charged, for 3 hours, 5 times a week. They could charge a battery at base, and bring it to site to be used.

I’ve converted a camper and done the electrics, but am my no means an expert. I’m in the process of designing something but would love some input and advice.

Cheers,
Sid

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Hi Sid,
My partner used to cook over there, I would be glad to contribute a bit too!
Batteries are a good idea in principle, with a couple of caveats:

  • they can go walkies (you will hear if a generator stops working, but you may not always notice right away when a battery is being taken for a walk ;0)
  • they are flippin heavy, so a daily move needs people who had some training and can be relied upon to not do something unhealthy because ‘in a rush’ / 'I feel fine, I don’t need to worry about how to lift etc.
  • you would also need to move additional electronics, cables and such, and plug it all up. Plugging and unplugging every day wears most affordable connectors out quite quickly. And the stuff I used to use touring with bands is not cheap…

I almost think that a box trailer would be ideal, if vehicles out there have tow-bars? Then everything could be mounted inside the box, with only replaceable cables to the outside. I will ask around the weirdos I work with, someone may have a small old trailer.
This would then also allow to make some weather-proof shape in the box where phones can be during the charge.

Once you have a battery and a dry, clean space to put it, the rest is (almost) entirely electronics which can be very simple.

At the most basic, you could provide 5V to everyone. Per outlet you’d need one fuse, one 5V regulator on a heatsink and a few components worth 1/10 of pennies.
Pro: every outlet is the same, and the system is really simple
Con: some phones can charge much quicker with modern protocols that require some more electronics

So that would be a starting idea. Happy to make some sketches. Oh and if anyone else has a short box trailer, shout out. If space is tight at SLMS I could park it in our front yard for a few weeks while we install stuff.

Speak soon!
Hanry

P.S. May I ask the name of the charity?

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Hey Hanry,

Huge thanks for your reply, appreciate it!

Nice to hear about your partner, the Charity is Care4Calais.

Thanks for your contributions, very valuable.

Definitly get your point about the walkies, def something to think about.

I like the box trailer idea…currenlty the generators they use are 80kg, which are lifted by several people in and out of vans, i wince a bit and I think everyone could do without that. I remember definitely one van has a towbar. I could check with them though.

They currently use a load of extension cables mounted on long wooden boards, if it rains they use tarps, and plan to get gazebos. The waterproof box trailer idea is great solution.

Looking at how much power they need, I think 5v is a good idea, and means everyone gets a fair share. Would you say 5v at 2A is good to go off?

Very kind about storing the box trailer, appreciate that.

Cost is also something to bear in mind, as they’d have to fundraise for it. They’d also want to run a pilot, I think how this would work out is to make a replacement for one of their generators (1/3 of total power needed) and take it from there. I’ve been looking online for where deals on good batteries, and wondering if a 12, 24 or 48v system makes sense.

Here’s my calculations: (happy to be corrected)

Working off 400 phones for 3 hours.
Assuming 2A charging from usb sockets:

5v x 2A (10W per phone)

each phone - 10W x 3 hrs = 30Wh per phone

30wh x 400 = 12kWh

Convert to 12v Ah: 12,000Wh ÷ 12V = 1000Ah
Convert to 24v Ah: 12,000Wh ÷ 24V = 500Ah
Convert to 48v Ah: 12,000Wh ÷ 48V = 250Ah
+10-15% for conversion and losses.

Continuous output:
Must support 400 x 10w = 4kw

So this would mean three roughly 4kwh modules, with 1.33kw continuous output.

Let me know what you think, and thanks again!
Sid

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It all depends on what you want to eliminate and your budget, you could have 6 or 8 KW of solar panels and a buffer battery, but you need space, it’s all depends on the local conditions, investment and space

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Hi Sid,
As an engineer I like overhead, but I think we have too much in your figures :0)
The iPhone 17 Pro Max has a 20Wh battery, and Androids are also between 15 and 20 Wh.
Of course you’ll have losses all through, but 10kWh should do to start with (of course I’d want to install some data logging to learn how the system actually performs in real life :0)

The smallest car battery I can see online right now was 40kWh and can supply high currents with ease - but a nightly charge at 20A may make it tired quickly. This is not my area of expertise, hopefully some of our makers have more experience here.

But … with three or four car batteries - even used ones, which can be had very cheap - you should be absolutely flying, I think.

Another question: are these phones handed over to a Charity staff/volunteer or are all the users plugging them in / disconnecting those themselves?

Power to the people!
Hanry

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Bother! Just spotted this seconds before the auction ended - they were asking for less than £50 and had no bid on it:

image
image1600×1200 546 KB

…probably a good thing since you had not confirmed yet whether a trailer was even an option for the charity :0)

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If you’re going the lead acid route (which makes sense from a cost POV) make sure to get the deep-cycle type intended for UPS or “leisure” batteries for campers. They’re more resilient to repeated drain and charge.

2 Likes
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Hey yea ideally solar would be great but there’s not space unfortunatley. There isn’t also a definite budget, I’ll put together a proposal for them to think about. But definitely trying to be easy on the pounds.

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Hey Hanry, very happy to hear i’ve overcalculated, makes things much cheaper and lighter!

Love to hear what your saying about batteries, as could be relatively affordable. I was previously looking at lifep04 which is what I use in my van and lighter but ofc more expensive.

The users plug them in and remove themselves. I was also going to mention in relation to the box trailer idea (and thanks for having a look on ebay) that we may need to think about access.

The way it works now, is they use extension cables mounted on long planks. They were previously mounted on square planks, but there wasnt enough room for people to situate themselves near their phone.

People will typically stay with their phone while charging, or get a friend to watch it while they do something else. I think having something lockable would be complicated, so I think we should still aim for people to be able to stay with their phone.

A box trailer would still be great to provide protection for the main components, and means there’s no loading/unloading of vans needed. I’d have to check if they have space in the yard.

Never a better time to say power to the people!
Sid