Using a 12V UPS as a 240V inverter

[(unknown)]

I have a Data Guard 400VA UPS with shot batteries.  I also have a need for a 12VDC to 240V inverter to run a laptop for a few hours at a time from an auxilliary battery in my vehicle.  Is there anything stopping me connecing the aux 12V battery in place of the SLA batteries in the UPS and running the laptop from the 240V output of the UPS?

I've searched the forum and can't find anthing simple enough to answer this question.  The laptop draws about 70-90 watts or so.

I'd be grateful for help.

Dave

[oztules]

Well this is what I have and do.

The power on this island is quite patchy, and the good lady wife was becoming intolerant of power outages to her beloved telly.

So her satellite receiver and TV are permanently connected to the little cheap and nasty Opti 430e UPS. A largish (truck ) battery is hooked up where the 7ah sla was and provides about 8hrs run time if the power goes out for any reason. (utility poles on fire have been common over here for some reason lately).

Total draw is only about 170W for the TV. and sat reciever, and it does not overheat with these on for indefinat periods.

However, if we run her big 60" TV on it, the push pull power transformer in the UPS gets hot after about 20 mins. It draws 200w and the sat about 100w. So at 300w and more it overheats.

As you are asking a modest <100w, I see no problems for you here.

..........oztules

[DamonHD]

If you can, it will be much more efficient to use a 12V car laptop power adaptor (eg a Vanson) to do the DC-DC conversion in one step.

For example, the converter from 12V to 20V for my laptop consumes 1W itself.  The mains adaptor for the same laptop eats as much as 7W itself without the laptop connected, and the 12V to 240V in your case would clearly eat some more.

The Vanson I use only cost about £20...

Rgds

Damon

[(unknown)]

Problem is it is a Dell laptop and the connector is NOT available and in any case, it is three connections.  One of these senses that the computer is connected to the right power supply before it will allow the machine to charge/operate.  Pain in the NECK, but that seems to be Dell's way of doing things.  They do have their own car adapter, but I am waiting for the arm and a leg quote for it.  I do already have a 12 to 19V and 20V DC supply but can't use it!

Thanks for the reply.

Dave

downunder

[ghurd]

What is the laptop power supply marked for the VAC input?

Many show 100~250VAC input, meaning they are probably fairly efficient switchers.

A 300 or 400W inverter will handle it. Easy, small, cheap and reasonably efficient.

G-

[(unknown)]

100-240 V, 1.5A

[sPuDd]

Do a google search for your laptop model

and look for a hack for the PSU sensor thingie.

Then adjust your regular 12V-19V adaptor to do it.

sPuDd..

[(unknown)]

BLOW it.

I just opened it upo and find that there are two !@V batteries in series . . so 24 V all up.  Is ther any way I couldrun this inverter from the 12 V Aux battery in my vehicle?  

[nothing to lose]

I am guessing 240V your not USA. I am so what I do may not apply as well?

For 12Vdc to 120Vac power I use a cheap inverter, plug the laptop into that with the grid wall wort adapter. Fast easy simple, not most effecient though. For vehicle use you probably don't care about a small loss, I don't, so I do that.

Get a 12V adapter, I use those for some things, mostly the stuff that came with them. If too costly to buy the right one then I use the inverter.

Others can say better how to charge 2 12V batteries seperate than I can. I have done this for 24V inverters in a van or truck. I think I just put diodes on the wires, each battery was charged at 12V from the vehicle but wired to the UPS as 24V. Been along time and I have done other things with like battery isolaters etc.. so maybe I wired something else up, but it worked.

 If you have "OK" but low batteries that won't hold allot of charge this might work, run engine as needed.

 If you can get some cheap batteries and charge seperate like I did, figure out the runtime, you get sit awhile and use the UPS as the power source and just start engine as needed to charge back up, watch the run times.

 Mine was used while driving so I did not worry about it.

Be aware some UPS's may die if just ran on batteries with no load to long. I just fried a cheapo, real cheap, UPS running it on a 12V battery for hours and nothing was even plugged into it! What crap! My other UPS's, larger and better ones, run forever it seems with loads running and never a problem. Maybe that UPS was just bad to begin with??