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Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 1:47 am
by peterlite
Delta ADP-40th A power supply for an Acer. Sitting there in perfect condition after the Acer died. Well, the Acer was murdered during a hardware experiment. I know have a collection of odd power supplies. Could I cost effectively recycle them in a UPS power supply for my Pi or my disks?

Some devices require 12 volts. My 3.5" disks for example. A 12 volt battery needs more than 12 volts to charge. A 19 volt power supply could be limited to 13 or 15 volts, whatever is needed to charge. Then again I can get a $50 12 volt battery charger for $25 every time the local shop has a sale. The 19 volt conversion would have to be reliable because the batteries cost more than the power supply. The conversion would have to be cheap to warrant building it instead of buying the finished unit.

19 volts is probably way over the top for conversion to a 5 volt USB supply. Simply limiting the voltage would be inefficient. For 5 volts with a limiter, I would start with one of the 6, 9, or 12 volt power supplies I have spare.

Hundreds of years ago I tried to build a voltage divider for a similar project but the result was messy, the output voltage unstable at high and low loads. Would a modern equivalent be easy, effective, and efficient? 19 volts divided would be 9.9 volts. If you could divide by three, you would get 6.3 volts then limit to 5 volts.

Should I build something or toss the 19 volts 2.15 amp brick and look at one of the lower voltage power bricks?

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 2:04 am
by klricks
Look for switching or 'buck' type DC to DC converters.
This type is used in almost all modern power supplies and will have no trouble converting 19V to 12V or 5V etc.
The efficiency approaches ~90%

Avoid linear converters such as 7805.

A voltage divider is totally out of the question.

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 2:30 am
by Gavinmc42
Some of those cigarette USB power supplies are rated 24V.
If you pull them apart you can look up the datasheet of the chip and ratings of the caps.

A Simple Switcher circuit does not use many parts.
You can even get them as modules.
http://www.ti.com/ww/en/simple_switcher ... pr-lpss-en

You could use the 19V to charge a 12 gell cell (lead acid) and make a UPS.

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 6:10 pm
by stderr
peterlite wrote: Sitting there in perfect condition after the Acer died. Well, the Acer was murdered during a hardware experiment.
Do tell.
I know have a collection of odd power supplies. Could I cost effectively recycle them in a UPS power supply for my Pi or my disks?
Given that you just destroyed the laptop by "experimenting", I would suggest careful consideration before doing anything with batteries, especially if they are lithiums which can explode, actually any battery can explode. Have you considered how you are going to recharge the battery now that the laptop is destroyed? The charge circuit should be inside the laptop.

Of course if it turns out that the battery is made from standard cells of some sort, it might be possible to remove them and reuse them. But you should be careful about all this, I know this sounds paranoid, but I don't want to hear about some sort of fire, good grief.

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 6:26 pm
by ewaller
You absolutely want to use a switcher (as suggested above) instead of a linear regulator. Linear regulators are great as long as you are only dropping a low voltage across them. 19 Volts down to 5 Volts is a 14V drop. 14V at 2 A is 28W. There is no way you could easily cool that and you efficiency would be less than 10%.

Over discharging them will kill them. Even once.

As to the charging. Be extremely careful. Li-Ion and Li-Polymer batteries have staggering energy densities and are extremely unforgiving when it comes to charging them. They are not like other chemistries (lead-acid, Ni Metal Hydride). Overcharging them, or charging at too high a rate, or when the temperature in the cells are too high or too low and you are likely to have a fire on your hands. A nasty fire with bad things being out-gassed. Most of these batteries are "Smart" and have an internal controller that communicates via SM Bus. You really should have a charger that is designed for the putpose.

http://sbs-forum.org/specs/sbdat110.pdf

Edit: I just realized, you might be talking about the power supply/charger for that laptop -- not it's batteries. Never mind the previous paragraph. But I will still leave it there as a general warning

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 8:47 pm
by peterlite
"but I don't want to hear about some sort of fire, good grief"
Thank you for your concern. I am not trying to reuse batteries from the dead computer. After Apple set fire to a few people and homes using lithium batteries, I am careful.

I noticed that Samsung successfully copied the "hand warmer" feature from Apple.

I dismantled the very old notebook to upgrade the disk but the device was not worth upgrading due to a non standard construction. I experimented with alternate upgrades then stopped because the new disks were worth more than the old computer.

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 9:00 pm
by peterlite
"switching or 'buck' type DC to DC converters"
Reading https://en.wikipedia.org/wiki/Buck_converter and https://en.wikipedia.org/wiki/DC-to-DC_converter to learn the terminology.

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 9:45 pm
by ewaller
This (a little pricey) evaluation kit would do this out-of-the-box

http://www.digikey.com/product-detail/e ... ND/4288725

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 10:34 pm
by peterlite
From a suggestion above, I looked at ripping apart https://www.pccasegear.com/products/280 ... 2-1a-black. Their shipping is $13, making the total price $22. An alternative is http://www.supercheapauto.com.au/Produc ... om=1021628. $19.95 in a local shop.

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 11:09 pm
by klricks
Google [UBEC] UBEC's are popular with the RC people. Available in 12V and 5V output and have leads so you don't have to crack them open like a auto plug type adapter.

Re: Power supply to reuse 19 volt power pack

Posted: Mon Oct 10, 2016 11:54 pm
by Gavinmc42
Keep your eyes open for sales of the cigarette USB chargers.
The last lot I got were $2 each.
Had Chinese chips but they work ok.
I usually rip them apart, solder wires and put heatshrink around them.

DIY with Ti/Onsemi etc chips is not that hard.
Element14/RS also sell switchmode regulator packages that fit the three pin LM7805 TO-220 footprint.

Re: Power supply to reuse 19 volt power pack

Posted: Tue Oct 11, 2016 12:16 am
by peterlite
I googled UBEC and found one for the required voltage/power. It is $5 more than the car USB device. I also looked at the cost of 5 volt power supplies. The Zero power supply is $8. The Pi 3 power supply is $13. Buying a new 5 volt power supply is half the price of adding a converter to the 19 volt power supply, making the 19 volt power pack option too expensive.

The 19 volt power pack still looks like a good option for a 12 volt battery UPS by using the power pack as if it is a solar panel. Use a solar controller/charger to charge the 12 volt battery then use a 12 volt to 5 volt converter. I would then have a UPS.
Controller: https://www.jaycar.com.au/12v-5a-batter ... s/p/AA0348
Battery: https://www.jaycar.com.au/12v-9ah-sla-battery/p/SB2487

12 volt to USB is generally cheaper than the 24/19 volt to USB for the level of power needed for a Zero. There are limited choices for the 2.5 amps needed for my Pi 3 projects.

A whole mains power UPS ready made costs just $80. Add a Pi 3 power pack for $13. The 19 volt power pack reuse project would have to cost less.
:?

Re: Power supply to reuse 19 volt power pack

Posted: Tue Oct 11, 2016 12:23 am
by peterlite
As Gavin mentioned, sales do change the cost. The battery I looked at is $5 off today. One of the shops has random 50% discounts. Would be good if I could get all the components on 50% off deals. I scored a $50 car battery trickle charger for $25 last year. If they have the same sale this year, I will get the cheap trickle charger and use that instead of the solar charger/controller. The 19 volt pack would then go in the bin.