[Swansea Hackspace] New Project - Powerpack for a laptop

Fri Sep 12 13:23:04 BST 2014

It dependents on what type of battery you use,
If you use Ni-Cad, Ni M Hiidirit then its relay desired voltage (plus a
little for regulation) divide by 1.2 Volts/Cell.

charging is easy, constant current/voltage,

Negative delta V - for Ni Cad
Zero delta V for NiMH

both at up to 0.1 C for normal cool charging .. but 1.0 C in HOT charge

Ceri

On Fri, Sep 12, 2014 at 10:28 AM, Gerrit Niezen <gerrit.niezen at gmail.com>
wrote:

> 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.
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> Hackspace mailing list
>> Hackspace at swansea.hackspace.org.uk
>> http://swansea.hackspace.org.uk/mailman/listinfo/hackspace
>>
>
>
>
> --
> Mob: 07836 267426
>
> This e-mail and any files transmitted with it are confidential and
> intended solely for the use of the individual or entity to whom they are
> addressed.
>
> Mae'r e-bost hwn ac unrhyw ffeiliau a drosglwyddir gydag ef yn gyfrinachol
> ac at ddefnydd yr unigolyn neu'r corff y cyfeiriwyd hwy atynt yn unig.
> _______________________________________________
> Hackspace mailing list
> Hackspace at swansea.hackspace.org.uk
> http://swansea.hackspace.org.uk/mailman/listinfo/hackspace
>
>
>
> _______________________________________________
> Hackspace mailing list
> Hackspace at swansea.hackspace.org.uk
> http://swansea.hackspace.org.uk/mailman/listinfo/hackspace
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://swansea.hackspace.org.uk/pipermail/hackspace/attachments/20140912/1b62fdd7/attachment.html>