[Swansea Hackspace] New Project - Powerpack for a laptop

Fri Sep 12 10:28:22 BST 2014

Would anyone be willing to throw up a reference page on the hackspace wiki for batteries? 

I for one would love to know what battery and charger I should be using for the syringe pump I’m building (somewhere between 5V and 10V, let’s say 1A @ 5V).

On 12 Sep 2014, at 09:53, Emyr Morris <em at preseli.com> wrote:

> Long post warning - Batteries are a  bit of a passion of mine...
> 
> these little battery packs you linked to are wonderful - I have a 'waterproof' one from Maplin for my iPhone etc - I used parenthesis because it isn't waterproof by any stretch of the imagination!
> 
> http://www.maplin.co.uk/p/maplin-waterproof-power-bank-7800mah-n03qn
> 
> I bought mine when it was on offer - I paid 19 quid for it - well worth keeping an eye on their special offers - a couple times a year they have something really good in their 'powerbank' section.
> 
> Apple iPhone/iPad chargers deliver 2.1A for a fast charge - the good car chargers from the likes of Belkin will also offer 2.1A
> 
> The 'easiest' way to charge a laptop is from 240VAC using the supplied mains charger - and the safest batteries to use in a 'project' are SLA (Sealed Lead Acid) - Lithium battery packs used incorrectly _can_ explode.
> 
> This is a dire warning - misuse of LiIon or LiPo can and will result in fire and possibly an explosion!
> 
> In my line of work we tend to put SLA batteries into small Peli Cases - we often build the charging circuitry into the same Peli 
> 
> Mike Harries (top bloke) has this page of examples - http://www.mikesfilmsound.com/new_batterys%20&%20ChargersQ.htm
> 
> We use 4pin XLRs for 12V in Film & TV - Pin 1 (negative) and can you guess yet? Yes, pin 4 for positive (because they look like a '-' and '+') source always on Female connectors - and equipment always on Male.
> 
> A tidy sized SLA could power a 200W - 300W inverter for a while, enough to power your laptop.
> 
> These are also very handy (search for LM2596 on eBay or Ali Express), they take any DC volts from 4V to 40V and you can set it to output any DC voltage from 1.25V to 37V.
> They are a bit noisy as DC-DC regulators are prone to be, but you could filter that if it became a problem (if you were to use one to power a small audio amp for example or a ham radio TX)
> 
> http://www.ebay.co.uk/itm/LM2596-LED-Voltage-Regulator-DC-DC-Buck-Adjustable-Step-Down-Converter-Module-/161206839226
> 
> This one is interesting, it has a current limiting option on it, useful for charging a small battery
> 
> http://www.ebay.co.uk/itm/Power-LM2577S-LM2596S-DC-DC-Step-Up-Down-Boost-Buck-Voltage-Converter-Module-/371050459165
> 
> Their perfect use is for making 5V to provide volts for USB sockets!
> 
> Talking about USB sockets, I like these... ready built... and cheep and a total of 3A for both sockets
> 
> http://www.ebay.co.uk/itm/DC-DC-Converter-Module-12V-To-5V-3A-15W-Dual-USB-Output-Power-Adapter-OZ-/321460838700
> 
> A Peli case with a nice big battery inside peppered with these would provide an excellent power source for a long camping weekend for the whole family... you could even fill the lid of the Peli with some strips of LEDs to provide in-tent lighting!
> 
> This should be chunky enough to power a laptop
> 
> http://www.ebay.co.uk/itm/300W-Watt-Car-Battery-Power-Inverter-Auto-DC-12V-To-AC-230V-USB-Adapter-Voltage-/151262613703
> 
> Remember that at 300W - with a 12V source, you will draw 25A from your batter!!!! (can you see why LiPo is now a very bad idea?) So for two hours use you will need at least a 50Ah battery that is capable of delivering 25A constantly... (a tall ask)
> 
> We are almost in the realm of a caravan Leisure Battery already - 100Ah and deep cycle - and certainly not something that you will want in your rucksack for your train commute to London
> 
> If you power your laptop while it is fully charged then the inverter wouldn't have to work so hard... simply powering your laptop. On the other hand if you run your laptop until it is flat, then plug in to your inverter - your inverter would have to power the laptop AND charge it at the same time... At 240V, each amp drawn is 240W - starting to get critical here...
> 
> Some laptops manage this better - my old dell would draw 3.5A (Almost a kilowatt) from mains regardless if the battery was full or not - but if I took the battery out and just powered it from the mains, the current draw would be down to as little as 0.5A (120W) from the mains... My Apple Macbook Pro seems to be very power efficient, only drawing what is absolutely necessary - I will plug it into an ammeter one day and do some better checks.
> 
> Going back to the SLA batteries - most of these are designed to stay at full charge - for example in your home burglar alarm where they are trickle charged all the time - these can not withstand being discharged until flat and recharged to full time after time... for this application you would need a deep cycle battery (leisure battery) - these are more expensive!
> 
> It is worth watching out for the chaps who come to service the UPS power supplied in your office - they should change the batteries in UPS at least every two years - as long there hasn't been a prolonged power outage in that time those batteries should have some life in them.
> 
> They can be 12V 30Ah or 12V 100Ah batteries... and they will be glad to give them to you FOC as they are a pain to get rid of in big quantities. Nine times out of ten they are worth having, but don't expect them to last years... 12 months will be good. And you will be able to dispose of a couple at a time at your local dump
> 
> I did warn you it would be a long one! LOL
> 
> see you later
> 
> Emyr
> 
> 
> 
> 
> On 12 September 2014 09:12, Justin Mitchell <justin at discordia.org.uk> wrote:
> On Fri, 2014-09-12 at 07:50 +0100, Richard Morgan wrote:
> > Hi All,
> > I'm looking to 'make' a battery pack that I can use for travelling and
> > charging up my kit (iPhone, iPad, Mi-Fi and laptop) - laptop is a
> > priority.
> 
> Laptops have some pretty crazy and varied voltage inputs, so purely off
> the shelf parts is unlikely.
> 
> You'd need a fairly large LiPo battery, but these are cheap and easy to
> get from the likes of HobbyKing
> 
> Charging, your going to need a fairly sophisticated multi-cell lithium
> charging circuit, preferably one with a thermistor and auto-shutoff if
> it starts to over-heat.  as charging is the most dangerous point.
> 
> for discharge, either you have enough cells to get close to the right
> voltage, or you use a custom switch mode psu circuit, or a buck
> convertor, linear regulators suck for efficiency.
> 
> but i'm no expert, and this is a project i would be wary of working on.
> 
> if you were to bodge something simple, use a stand alone dedicated
> charger for the battery, and then just build, possibly from off the
> shelf parts, the dc output stage, it would be a lot simpler.
> 
> 
> 
> 
> 
> 
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