Topic: powering inverter off 12v SLA

[replay]

Well i've looked all around (valence, powerpad, etc) & it looks like i can't find anything compatible with my laptop to power for over 2.5-3hrs in the field.  So what i was thinking of doing is to get an inverter & power it off of a 12 volt SLA.  I haven't seen anyone talk of this so my question is, will it work.  2ndly, if in theory it should work.  Should i just hack off the cigarette lighter & wire on a 4 pin xlr to hook it up to the SLA?  Or should i get a female conterpart for the cigarette lighter from RS & wire it to the SLA?  Thanks for any help.  

[dklein]

Ya might want to check out the power requirements of your laptop AC adapter.  These switching power supplies can deliver huge current and might require a heavy duty inverter, big ass SLA and reasonable gauge wiring (I think my Dell AC adapter can draw 4.5 Amps of current).

It's may be kind of inefficient to go DC>AC>DC, generating heat and noise along the way.  Do you know the input/output specs of your AC adapter?

[replay]

ya, i thought it would be rather inefficiant, but seems to be my only option for prolong power.  It's 1.5A 50-60hz input & 19v 2.64a output.  & it is a dell.  

[dklein]

Just confirm that the output is DC (I think they all are but never assume...)  
Then take a meter to it to see if it's actually higher than the 19v stamped on the box.  You could probably run 2 x 12v in without a problem.  Or 3 x 6v would get you there as well - there's usually some room to play with.  Now, to find one of the funky connectors...it really depends which model you've got.

david

[replay]

It is DC output.  The connector is one of those funky square plugs which i'm sure i can get through Dell's website.  Just so i'm reading your post right.  Your saying to run either 2x12v or 3x6v in parallel to get the voltage close to 19v.  If that's right, wouldn't i need some kind of voltage translator to get the signal down from 24v to 19v?  I don't have  a meter to test the actual voltage but will try & get it tested.  the actual plug looks like it has a voltage translator right before the rectangular plug to the laptop.  So i'm assuming it is actually higher than 19v.  thanks for the input.  

[dklein]

Actually, you want them in series, like a flashlight.  Then you add the voltage

 - battery +  - battery +

You supply the laptop from the far left and far right ends.  Suppose you use 2 x12 v 5 amp hr. batteries - this will yield 24 volts @ 5 amp hr

If you connect them in parallel, you'd get 12v @ 10 amp hr.

It wouldn't surprise me if the connector is tough to get - even from Dell.  You could always cut your existing wire and put your own connectors on either end of the cut and put a matching connector on your battery.  That would allow you to use the same part for either your AC or your battery supply.

I just measured the supply from my Dell 1100 and it was 20 v - exactly as marked.  So if it says 19, it probably is.  I'd recommend two 9.6 v packs and you won't have any worries.  Unless you really wanted to haul lead around    I'm really not sure if 24 is OK -  you might want to check that elsewhere before something blows up.  Safer to put a regulator between the battery and pc (easy but still more ambitious - the high current draw will probably generate a lot of heat).  Keep in mind that your built in battery back is probably 14.4v so you'd be safer with 3 x 6v or 2 x 9.6 v

Also, that thing near the end of the cord is a noise suppressor - you sometimes see them on modem cables as well.  I wouldn't worry about it.

[Lee]

couldn't you just buy a bunch of refurb batteries from dell and hot-swap them?  As long as you cut the display off and aren't running any devices off the USB bus power you'd be OK for about 3 hours with 3 batteries.  At least mine is...

[DaryanLenz]

I think, don't quote me on it, that the dell can run on 12v dc power.  You would need the specific car adapter, but I don't see any reason it wouldn't work.  Almost all laptops are capable of running on 12v dc, as that is what all car adapters run at.  I wouldn't dream of wiring three 6volts or 2 12volts in parralel, that is just downright way too heavy.  I would sell the laptop and get another one which suits your needs long before thinking of doing such a thing.  2 12volts would run like 15 punds I am guessing...forget it.  I still think it can run on 12v though!  If they make a car adapter for it, it can!  

[dklein]

3 hours with 3 batteries.

hmmm...if that's all you're getting with 3 batteries maybe the refurbs aren't such a good idea.  I don't know how cheap they are but I can get almost 4 hours of recording from the one battery that came with my new Dell Inspiron 1100 (the whole computer was <$700 shipped after rebates).

I believe that Lithium ion batteries are only supposed to be really good when they are freshly manufactured and used.  So even buying unused ones can be dicey if they are old stock.

Check this out - about half way down the page they talk about storing lithium ion
http://www.buchmann.ca/Chap15-page2.asp
 

[dklein]

I wouldn't dream of wiring three 6volts or 2 12volts in parralel, that is just downright way too heavy.  

yeah, for sure.  I was thinking NiMh, I wouldn't even want to haul one SLA.  I bought a little one and returned it a few days later when I realized I could address my needs with something much smaller and lighter.

But SLAs are good for giving your car a boost  

[replay]

Belive me, i already have to haul 2 6 volt SLA's to power the V2>MME & an M1.  So the last think i'd like to do is haul 10-15 lbs more of lead around.  It was just the only option i could think of.  I appriciate your guys input though & you've suggested much better options thus far.  Dariens idea seems it could be possible as my internal battery is actually 11.1 volts.  I have 2 of the stock batteries which are fairly new & i get 2hrs recording time with the screen shut.  I belive these are 4 cell batteries.  Dell sells replacement 6 cell batteries for my PC which if mine are actually 4 cells should yield approx. 3 hrs with the screen shut.  Reguardless i'd still like a bit longer runtime.  the 2hr ones just aren't cutting it.  I pretty much have to wait 'till the last minute to start up the PC sometimes missing a bit of the set which i then have to patch in from the DAT source.   I'll look into NiMH 9.6v's for the time being.  Thanks again for the help.