Portable DC source

I am lloking something like: www.rsfinland.com Quick Search for: 157-3953
But something with preferrably bigger batteries
like 40Ah or 60Ah.
Commercial units only, so I am not intrested in how to make one myself(or I may be intrested, but wont help me with the search.)
220V mains units and reseller willing to ship to Finland.
The usage will be to power A laptop computer for 20h.
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You can make one very easily yourself... buy two 900 amp hour car batteries, and and a 12vdc to 120 or 220vac 10 amp dc to AC sine wave inverter, square wave might work, you have to check with the inverter mfgr etc for thier experience with that application, (50 cycles if that is what you have in finland, whatever matches the power supply to the lap top)_ ($300-$600 or so at Radio Shack or any electronics supply for the inverter in that size range...full sine wave converters are the most expensive)... connect it to the batteries in parallel.. and plug in yer computer.
Don't skim on the inverter size...go double your lap top wattage at least.
1800 amp hours at 12 volts is a net 21,600 watt hours... divide that number by the lap top wattage rating (or the VA rating on your computer, close enough) and you will get a run time using that much battery power... add or subtract batteries to change this run time.... a *theoretical figure.
In *actuality the run time might be close to half of that due to loss of performance in the batteries as they reach threshold charge levels and the quality and performance of the inverter you buy.
So buy a good one, rig up with the inverter.. and test while monitoring output amperage and frequency.
Say that figure is 20 hours of clean power.. then understand that as the batteries age the run time will shorten...each time the batteries are recharged they loose amp hour capacity.
It wouldnt take much in the way of a combination solar and wind generator though to keep the rig running at full charge most of the time (and greatly extend battery life).. .. but for your use thats probably extreme..... if you are limited on sun grossly oversize the solar panels.
for longer battery life go to the gel cell type battery..used in some high end automobiles..and safer than acid cell that can be a hazard when regenerated in a closed space, such as a closet, Hydrogen gas can develop..when it reaches higher concentrations its explosive in air. Ventilate your battery space in any even to outside air.
You could purchse those parts and put the rig together in less than 5 minutes...see the inverter people... its very easy...call em they will have figures on computer run times etc also (viability varies with computer power supplies, but most are compatible with this scheme)
http://www.dcacpowerinverters.com /
Phil Scott
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Phil Scott wrote:

1800 Ah to power a laptop for 20 hours??! What am I missing?
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<snipped>
Sounds like someone's calculator burped.
1800AH * 12V = 21KWHR
Most laptops are in the 100watt range so you might get more like 200 hours of power from such a setup.
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missing?
like 200 hours

I think there are bugs in how the battery is rated.. the entire 1800 amp hours is not available at the batterys rated 12 vdc.. maybe only the first 10% of charge is useful in the inverter. that would take the useable capacity to 20 hours...as an utterly wild guess.
Looking at these two batteries with an inverter attached its hard to fathom they could actually run a hundred watt bulb for 4 days... maybe even 20 hours is a stretch.
I used to make love to my girlfriend when were in high school in the back seat of my daddys' buick road master...we could drain that battery in two hours of just running the radio and fogging up the windows...(but those were tube radio's... maybe 100 watts). Those were probably 400 amp hour batteries in those days.
So it might take more batteries than it appears to get the 20 hours run time.
Phil Scott

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dc
to
for
VA
run
figure.
due
the
while
understand
capacity.
charge
on
battery..used
a
battery
less
but
divide the 1800 Ah at 12vde by say 10 amps of 12 vdc (120 watts for the computer, thats a high figure for most) and you get 150 hours...if you could run the battery dead flat and still get the 12 volts...which you can't.
( the 1800 Ah rating is theoretical, net electron storage capacity...but the voltage drops off fast as it discharges..so usable power to supply the inverter is much less).
So I am *guessing you loose sufficient voltage to power the inverter at 90% of full charge or so.. that would give 15 hours of run time...and that might be high.
thats why I think you need to run a test on the rig using a light bulb...and voltage meter on the ac outlet of the inverter.
Depending on the inverter etc you might get less run time than 15 or 20 hours.
a test is required...if its less though the fix is easy. just parallel in another battery.
Looking at the mass of a typical laptop battery vs a gel cell.. the 15 to 20 hour figure might be close.
Phil Scott
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Why can you not buy this supply in Finland? You asked for unitS so you may be planning to sell thies items.
Most countries have strict certification requirements and one purchased in USA may well not comply with the reqirements in Finland. USA is 60hertz and Finland is 50 hertz for a start.
--
John G

Wot's Your Real Problem?
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items.
one purchased

an astute sort of question...I should learn from that in other areas of business.
Phil Scott

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Go to your local computer store and ask for UPS units rated sufficiently to run your laptop for 20 hours...then buy one twice as large so you get better battery life.
take your lap top so the watts rating can be read off of it.
Or I will sell you one in a NEMA 2 metal encclosre..with UL listed 20 amp inverter, and digital volt and amp meters on the output... $4,471 (USD). shipping included. This will feature heavy duty deep cycle gel cell batteries...and UL listed dual speed charging unit, 4 hours on a fast charge and 16 hours on a slower charge that will provide longer batter life though many recharge cycles.
I will guarantee the unit to run your 100 watt lap top for at least 30 hours when new, at at least 20 hours after 50 recharge cycles.
The unit will weigh 130 lbs ( or roughly 60 kilo's).. be 36" tall, 36" wide and 12" deep, with a hinged lockable cover)... and hammered finish in metalic grey. Cabinet will be fit with 4 casters for easy moving.
Terms: 10% with order, balance less 20% on delivery... final balance due in 30 days if unit continues to perform exceeding stated capacity. your warranty is bonded.
email or post this thread if you are interested.
Phil Scott

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wrote:

There is a high premium price for the fancy case, this is a 12V 24 AH battery pack with charger and supply cords. Ignore the 1800AH suggestions, there are not any 900AH car batteries.
I suggest that you buy the RS 405-8643 charger for 73.50 and purchase a sealed 12V 40-50 AH battery locally. In the USA a Panasonic 12V/20AH sealed battery is about $45, 12V33AH is about $60.
In stead of a carrying case like the 157-3953, consider a large plastic tool box and buy batteries that will fit.
A complete kit is not common, but may be available for camping. and Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz
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"Bill Kaszeta / Photovoltaic Resources"
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I don't think so. Are you possibly talking about "cold cranking amps" or perhaps "minutes of reserve" ? 900 AH and 12 V in lead-acid batteries would weigh a good part of a ton. Could you point me at a Web page that lists 900 amperehours capacity for an automotive-style 12 V battery?

Automotive-style cranking, lighting and ignition batteries are not really designed for constant drain, deep discharge applications. But if you check the supplier's web pages for large stationary batteries (Exide, and Saft, to list just two), you'll find that you can get a lot more than 10% of the stated ampere-hour rating.
Bill
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Finland.
is
but
if
Ah
cranking amps"

batteries would

amperehours
Ahhh you are correct. I used the wrong term entirely. I was thinking of cold cranking amps.
Phil Scott

using
inverter
with
to
VA
(reactive)
AC
are not

But if you

batteries (Exide,

of the

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"Bill Kaszeta / Photovoltaic Resources"

Taking a look at the Exide catalog - an 1800 AH 12 V battery would be six of their model GROE 1800 cells, each weighing 240 kg. So, an 1800-ah 12 V battery would *weigh* more than many cars - that's 1440 kg, my car weighs a little over 1200 kg empty.
I've often thought that if we could store 10 kwh in something the size and cost of a common car battery, that internal combusion engines would become a curiosity!
Bill
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