Portable high voltage DC power supply

[polgyver]

I was just curious if this would work. Probably more practical would be using portable AC supply with one battery and inverter.
170 V DC is dangerous, so it is NOT recommended to build such a unit without proper skills and care.
The batteries used boast 6.000 mAh - hopefully, they can deliver just 1.500 mAh...
Depending on device connected, they could last a few hours or more.
This pack can power receiver and small TV at satellite dish, without extension cord.
Of course, TV should be for 100 - 240 V - not the old one, with transformer.

 

[primestar31]

Nice setup, but WAY over-kill for double-conversion.

The MicroHD receiver works fine directly powered from a 12 volt battery. A battery operated mini tv set, OR a portable car dvd monitor screen could also run from the same 12volt dc battery. I've actually done this, and had no problems.

Why produce 120v AC and then just convert back to DC 12 volt of whatever?

 

[FaT Air]

LETHAL !
- - clock in camera must be off-time. (last picture) It's not that light at 16:59, here amyway - -
BTW, think it's only single conversion, 170VDC to 12VDC. (no inverter, just the PWM PS of the uHD PS. - although, think that if using one it wouldn't be quite as lethal - although not as efficient )

 

[USDownlink]

Why produce 120v AC and then

If I am understanding this correctly, he isn't producing 120AC.

So, something said earlier is worth repeating. For those that don't have the proper skills, this really isn't a good idea. Not just because of the high voltage involved, but familiarity with and ability to identify power supply topologies is a prerequisite. That, or blind luck. But it just doesn't seem like the sort of thing you want to stumble into.

 

[polgyver]

Oops... sorry, primestar, somehow I forgot to add in the thread title the letters "DC" ...
So, there are 42 lithium-ion batteries connected in series, which makes voltage of over 160 Volt DC.
Therefore it is single conversion, accomplished in devices' original power supplies.
In a typical Graetz bridge of 4 rectifying diodes, only 2 work all the time.
When connection is reversed, other 2 diodes work, feeding main electrolytic capacitor.
There is a home-made resistor, 5 Ohm, for limiting inrush current to this capacitor, saving these diodes.
I was also thinking to try this battery pack with 120 Volt AC/DC hammer drill, but the tiny wires between battery holders probably would melt...

 

[KE4EST]

I forgot to add in the thread title the letters "DC"

added

 

[Cham]

Did you fabricate a 230Vac -> 170Vdc supply to charge the whole battery at once?

That is a lot of battery; lots of series connections between the cells and all it takes is one bad cell... Might be more utilitarian to connect them all in such a way to obtain 15-18Vdc and regulate the output to 13.5Vdc, and add a small inverter for 120Vac loads... Would still have all the load capacity to do what you are doing now. Would have to beef up the wiring harness to handle the amperage.

I have to admit though most low->high voltage inverters are very inefficient. I expect most monitors/TVs these days likely have a built-in power supply that might convert the 120Vac to a much lower DC value to distribute to the internal components. This would make it easy convert. Ultimately a monitor/TV with an external 12Vdc power supply is preferred so there is no internal modifications required. (warrenty etc)

Always fun to play though!

 

[polgyver]

No charger made yet : probably voltage of 180 DC will be needed. Agreed : such a pack is not reliable, as there are so many shabby connections and just one cell can spoil the supply.
However, DC popularity is on the rise ... with even higher voltages ...
The clock on camera has been corrected (I forgot to adjust it after time changed from Summer Saving Time to normal).
But there are more bad news regarding the quality of batteries sold.
Annotated photos will say it better :

 

[Cham]

Agreed.. DC power is becoming more advantageous when dealing with solar and wind generators, and low voltage requirements of LED lighting, low voltage DC appliances, etc. Power is being transmitted these days for longer distances more efficiently using DC power lines, however a lot of that efficiency is lost in the DC->AC conversion at the terminations.
Problem is with transformers that easily change AC line voltage to house voltage, they are relatively efficient, and transforming high voltage DC from distribution lines to users would be the challenge.

 

[polgyver]

I was not 100% sure if my 24" Toshiba TV could be plugged in to this DC battery pack, as on the back of TV it was marked as 120 V AC (No mention of 100 - 240 V ).
Spent a lot of time on internet searching for a schematic (diagram) of this TV - without any luck - maybe my search skills are low?
Any input on better search would be appreciated...
Finally, I unscrewed 23 screws and had a look inside TV : sure enough, it had typical power supply with 4 diodes and a cap.
With its current draw around 200 mA, it could work close to 3 hours. If a sat receiver would be used also, the time of use would be shorter, less than 2 hours (it is still plenty
when working at the dish).
Another thing which frustrates me, is this shameless bragging by Li-ion battery manufacturers, claiming 5.000 mAh, when in reality it is only 600 mAh.
Any idea, why they do this? Should not be there any legal restraints for such cheating ?
Four annotated pictures follow :

 

[polgyver]

Did you fabricate a 230Vac -> 170Vdc supply to charge the whole battery at once?

I decided to build a charger which can charge the 50 batteries in parallel. There are 5 rows supplied by independent regulators (4.2 Volt, 4.5 Amp each).
Batteries are easy to insert and remove, as they have plenty of room. Each row can take 10 batteries. Each "nest" is connected to 4.2 Volt through 2 miniature
bulbs with tungsten filament (salvaged from old set of Christmas outdoor lights) - if any battery is shorted, then the lamps will light, and limit the current to 0.5 A.
Cold filament has very low resistance - around 1 Ohm, so it does not limit charging. The regulators were $ 7.50 on e-bay. Trafo was salvaged from old UPS.
I wish the batteries had better capacity ... Well, who knows, perhaps the better quality batteries will become more affordable in future?