Using a charger as a laptop power supply

[Shabill]

So I find myself on a farm in Denmark (my home is outside of Boston), and first of all, I'm really glad I brought a heli ... I've never flown truly big sky before and it's awesome.

But my laptop power supply died, and being on a farm in rural Denmark, it isn't easy finding a replacement. It requires 20V @ 4.5 amps. It occurs to me that I might be able to use 2 3S lipos in series, or better yet, maybe there is some way to get my charger (a Hyperion Duo 610) to output 20V @ 4.5 amps and act as its power supply. If I set it to charge 14S NiMH, that would be 21V I think, but I don't think it's a steady 4.5amps ... I don't know enough about what the algorithm is to charge a NiMH (of NiCD) battery. Is this just a crazy thought, or is it possible it would work?

[Bladecpnitro]

I vonder if the NiMh charger would work more steady?

[shreddedpaper]

Wouldn't it be more feasible to attempt to charge the laptop battery when needed through the charger, outside of the laptop?

[dcope17]

I don't know the specifics of your charger but most are constant current.
Meaning it puts out 3A no matter what voltage is needed to have that current draw.
Your laptop power supply is constant voltage. Meaning always 20v no matter how much current draw.
Both different animals.

[Mr-Mike]

Probably easier to splice on a connector tip for the laptop than the laptop battery. I would set the chemistry and just plug it up at a setting no higher than spec. A little lower will be fine and just take longer to charge the battery but would probably still run the laptop. Consider your laptop running on battery after an hour or so...

Disclaimer: I haven't tried this and take no responsibility

[dyuen888]

It occurs to me that I might be able to use 2 3S lipos in series

This will be the better of the two solutions... Make sure you get the polarity correct.

As mention above your charger will not supply a constant voltage.

I guess there is not a "Staples" "Office Depot" "Radio Shack" store to buy a generic charger for the laptop?

[lucidchaos]

I would like for this to be vetted by the community before you try it...

Amps should be the capability to supply current. If your charger is supplying twice as many amps as required by the laptop, this should not yield a problem...

[willr001]

I feel like setting it for a 5s lipo and 4.5 amps would be close enough.

5% over voltage shouldn't hurt. Our chargers regulate voltage better than a laptop supply anyways.

It should make it drive to 21 volts, then sit at that constant voltage and supply whatever current is needed. If current drops to less than half an amp, the cycle will finish, but unless your laptop goes to sleep with a full battery, you should be fine.

[willr001]

Originally Posted by dcope17

I don't know the specifics of your charger but most are constant current meaning it puts out 3A no matter what voltage is needed

Originally Posted by dyuen888

As mention above your charger will not supply a constant voltage.

These statements are only correct for the first charge phase, which completes as soon as it hits the max voltage, at which point it switches to constant voltage to maintain that max.

If you set it to 5s and it makes it to 21 volts, you're home free, unless your laptop requires a signal line to identify "authorized" chargers. (Never buy a Sony laptop)

[Fuzzy Toaster]

I wouldn't do it. The charger is constantly trying to read battery voltage and change its output if needed, but your laptop is doing that too. I think there's a high chance you'll damage your laptop. If you were lucky enough for your charger's PSU to match the laptop's needs that would work.

[Dr. M]

Yes you can. Use the charger in Lead battery charging mode. Set it up with an appropriate number of cells to get close to 20V nominal. The Pb charging cycle is very amenable to being used as a power supply at constant voltage/Variable current.

[Shabill]

Originally Posted by shreddedpaper

Wouldn't it be more feasible to attempt to charge the laptop battery when needed through the charger, outside of the laptop?

6 pins on the laptop battery; I have no idea which is for what ... no multimeter here on the farm ... and even if I had one, rigging up a connector would be tough based on the fact that they're all recessed and not standard to anything else I have. However, I stripped the laptop cord on the laptop side of the brick, and thankfully underneath the insulation is a black and a red cable going to the laptop. It should be as easy as attaching red to red and black to black, assuming (the big assumption) I can get 20V and at least 4.5 amps.

[Shabill]

Originally Posted by Dr. M

Yes you can. Use the charger in Lead battery charging mode. Set it up with an appropriate number of cells to get close to 20V nominal. The Pb charging cycle is very amenable to being used as a power supply at constant voltage/Variable current.

That was my first thought. Unfortunately, the charger won't let me choose the right number of cells. When I tried it earlier tonight I had the option of 1,2,3,4,5,6 or 12 cells. I guess nobody makes a 10 cell Pb battery...

[dcope17]

Originally Posted by willr001

If you set it to 5s and it makes it to 21 volts, you're home free, unless your laptop requires a signal line to identify "authorized" chargers. (Never buy a Sony laptop)

I see how that could work... As long as the laptop never goes too low on the current draw or else the charger will shut off as the battery seems fully charged.

I have a Sony laptop...

[Mr-Mike]

Originally Posted by willr001

(Never buy a Sony laptop)

Truth! Had to replace a VIAO Z series hard drive (SSD). $1100 !!! Couldn't sit down for a week after that one

[dyuen888]

Most charger will NOT charge if it see a low voltage or no voltage on the other end. In your case the other end is your laptop. (zero voltage). This is to prevent charging a dead cell.

Wiring up your two 3S pack in series maybe the only way to go.

[dcope17]

Originally Posted by dyuen888

Most charger will NOT charge if it see a low voltage or no voltage on the other end. In your case the other end is your laptop. (zero voltage). This is to prevent charging a dead cell.

Another good point... if the pack voltage is too low... My charger will charge for a minute or two and then shuts off if the pack isn't at least 3V per cell.

2nd. without a battery hooked up... it won't even start charging...

[Shabill]

So I'm running off my 2 3S lipos in series and seems to be doing great. It's a little less convenient in that I'm using relatively small batteries (2100 mah ... I brought the 450), but hey, it's working, and with this method I'll be able to charge up the laptop battery for the trip home. I was ultimately concerned with dyuen888 and dcope17's points ... I'm plugging into the laptop, not the laptop's battery, so I don't think there would be any voltage there for the charger to see (again, no multimeter to check). Also, I've watched the voltage display on my charger when charging lipos and it's constantly switching off (on for a 5 seconds, off for 1, or something like that), presumably as its checking pack voltage. I figured that the laptop wasn't designed to see its power constantly being switched on and off.

Thanks all!