40 x Tablets in a cabinet @ ~0.7A each

AntiThesis

AntiThesis

Executive Member
Joined
Jul 30, 2005
Messages
5,595
Reaction score
218
Location
East London
OK so this is the deal.

I have 40 x tablets that draw a max of around 0.7A each when charging so for safety sake, let's work on 1A each.

I have a cabinet that I am retrofitting to store them in. I've fitted 220v fans to pull in cool air and push out warm.

Now I have to think about the best way to supply power in a way that will a) not burn down the building and b) be safe/OK with insurance and c) be legal.

The suggestion I'm NOT going to use is a piece of electrical trunking with 30 x female two prongs connected in parallel to a regular plug socket. From what I understand, that's silly since it's then 30A going to a max 16A plug.

Is the easiest/safest solution going to be regular multiplugs with say, 10 devices on each and then going to their own plug?
 
I'm more interested in WTF you're busy with - and is it 30 or 40 tablets?
 
YingYang said:
I'm more interested in WTF you're busy with - and is it 30 or 40 tablets?
Click to expand...

Sorry, 40 :) The strip that I was given will take 30 but will probably burn the building down. Just what it says on the box - constructing a cabinet to hold and charge 40 tablets.

dabean said:
View attachment 350365

http://www.dhgate.com/store/product/48-ports-300w-60a-usb-charger-ac-phone-charging/371367535.html

Remember that the 0.7A draw you're talking about is at 5V.
Click to expand...

*heavy breathing*

Know if those are available in SA somewhere?
 
30 2 prongs with tablet chargers in them are not going to overload a 16A socket... It's a 1A charger at 5V which is 0.02A at 240V each for a grand draw of 0.8A total, double that for inefficiencies and you're under 2A, no need to worry.

Also your multiplug suggestion does exactly the same thing as your "definitely not going to do this" suggestion.

The single transformer above will be more efficient though.
 
Last edited:
AntiThesis said:
From what I understand, that's silly since it's then 30A going to a max 16A plug.
Click to expand...

You understand wrong. Your plug/multiplug/lead/extension can take 16A at 220V.

220 * 16 = 3520 watt.

Typical tablets/phones run at 5V say at 1A. 5 * 1 = 5 watt.

So because the charger down steps 220V to 5V it one tablet would be pulling like 0.02A at 220V.

So in theory you could charge 704 tablets from one 16A plug.
 
$m@Rt@$$ said:
You understand wrong. Your plug/multiplug/lead/extension can take 16A at 220V.

220 * 16 = 3520 watt.

Typical tablets/phones run at 5V say at 1A. 5 * 1 = 5 watt.

So because the charger down steps 220V to 5V it one tablet would be pulling like 0.02A at 220V.

So in theory you could charge 704 tablets from one 16A plug.
Click to expand...

Thanks! That makes sense. So it's effectively:

1 [for one tablet] * (5/220 [for the stepdown]) = 0.023A per tablet so what, 0.91A for 40 [40 * (5/220)]?
 
AntiThesis said:
Thanks! That makes sense. So it's effectively:

1 [for one tablet] * (5/220 [for the stepdown]) = 0.023A per tablet so what, 0.91A for 40 [40 * (5/220)]?
Click to expand...
Yip. Plus add some inefficiency buffer because step-down transformers aren't 100% efficient.
 
gregmcc said:
Get yourself a few PC PSU's - far cheaper than these other fancy devices.
Click to expand...

That's actually the first thing I thought of when I saw the question: a 300W power supply should handle that easily. Then I thought that someone's probably already made one, so I googled "300W usb charger".

DIY would require some knowledge of electronics though and there are lots of other factors to take into account.
 
You didnt tell us what you are doing with them. Please, for the sake of the children, spill them beans.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X