I am thinking about purchasing and/or assembling a cheap external dc power supply for my DSLR camera. I have been reading a number of articles on this topic including this one: http://www.diyphotography.net/how-to-make-a-dslr-battery-run-4-times-longer I have found that the technical level is somewhat high for me. I am very poor at soldering and taking things apart and putting them back together. I am considering purchasing this ready made item from Ebay http://www.ebay.ca/itm/180659453326?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 which I hope will provide a safe external AC power supply. I am hoping to modify this device such that I can also use the dummy battery as a connector for a portable DC power supply. I intend to simply cut off the adapter and use the dummy battery as a ready-made connector and simply connect a cigarette lighter adapter to the wires to plug my camera into my 12vdc to 120vac inverter via the 12-volt receptacle in the inverter. It is sold by Canadian Tire similar to this http://www.canadiantire.ca/AST/brow.../Eliminator+600A+400W+Power+Box.jsp?locale=en
except that it is 300amp/300watt instead of 600/400. It produces square ac waves but I presume this is irrelevant. I will simply be drawing on the small 12-volt battery inside it. I propose using a simple buck step down inverter such as this one: http://www.ebay.ca/itm/331021547239?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
The output is rated at 7.5 volts and the camera batteries are rated 7.4 volts so I'm assuming that will be close enough. Any comments on any problems I may encounter would be appreciated. Mainly, I want to be sure I do not fry my Canon T2i camera. Thanks in advance for any comments.

 

This is where you find out about 12V to 7.4V adapters.
Sine wave inverters (that are really square waves) can cause problems. Some of them are incredibly poor quality.
I don't even know why you are looking at a 600 amp backup battery. Are you going to time-lapse Alaska for 6 months?

Get real about what you need and we can get you into a real voltage adapter.
We even use real math.

 

Thanks for the reply. I already own the inverter. It was given to me as a gift 6 or 7 ago. It gets used mainly for powering 12-volt car accessories or to light lamps during power outages. We have used it camping a few times as well. It would be inconveniently bulky with photography but it could be managed. It could theoretically be used to simultaneously power a laptop or external monitor, cooling fan for camera, LED camera lights, etc. Would it be likely to fry my T2i camera using the dc voltage step down gadget? The problem with the camera is that I only get around 60 minutes of video with the dual-battery grip attached. I sometimes record 3-hour concerts which are a challenge even with one change of the two batteries half way through. My main concern would be avoiding damage to equipment.

 

We need to start with vocabulary.

An inverter makes AC.

Something that plugs into the wall and makes DC is commonly called a DC wall wart.
I see you found one advertised as an AC converter. That's just confusing because it doesn't convert AC, it makes DC. It will not "make a safe AC supply". It will make a safe DC supply.

I take it that "DC coupler" means, "dummy battery".

Apparently a Digital SLR camera is a video camera. I thought it was a one shot at a time camera.

Then there is this great run-on sentence:
"I intend to simply cut off the adapter and use the dummy battery as a ready-made connector and simply connect a cigarette lighter adapter to the wires to plug my camera into my 12vdc to 120vac inverter via the 12-volt receptacle in the inverter."

I simply think that says you simply want to simply plug your camera into a 120 volt AC inverter with a 12Volt DC socket in it. Why would you want to plug an inverter into a 12 volt battery in order to get 12 volts out of its 12 volt receptacle?

So, you want to buy a 600 amp, 12 volt DC battery, to run an inverter, in order to get 12 volts DC to run a 7.5 volt DC voltage reducer. Right?

That's the end of your first post. Now for your second post.

You have a free inverter that "gets mainly used for powering 12 volt car accessories".
I don't think so. An inverter would apply 120 volts of fake sine wave AC power to a lot of stuff that is plugged into it, like a cooling fan, laptop computer, external monitor, and a bunch of other stuff that has nothing to do with a camera.

Would it be likely to fry your camera if you plugged a DC to DC step down converter into a 120 volt AC inverter? Yes.

Why do you want to connect an inverter to a 12 volt battery in order to get 12 volts???

I think you should do as the first link says and get a bigger 7.4 volt battery, then use a dummy adapter to connect it to the camera.
Failing that, use a 12 volt battery to power a DC to DC step-down converter to get 7.5 volts, and use the dummy adapter to plug that into your camera.
Then, connect the 120 volt inverter into some other battery and use it to power a bunch of stuff that isn't a camera.

Please forgive me if I sound frustrated. It's only because I am.
Trying to sort all this out is not making sense to me.

 

Buying extra batteries for the camera and charging them at home, is safer. Is it worth blowing up your camera doing a "home made/diy" approach? I guarantee that you cameras guarantee won't cover any diy stuff you add to it.

 

Actually, my warranty will have been expired for two years come December, so repairs or replacement costs are on me from here on in. Nevertheless, I agree with the principle of what you're saying. Still, I welcome opinions of other members on what I have in mind and if there is any way to do what I'm thinking in a safer way. I suppose it is not impossible that the Chinese may come up with something cheap and ready made in the next year or two. I hope that they stumble upon this thread All they would need to do would be to manufacture a case capable of holding multiple (e.g. four) LP-E8 batteries connected in parallel (in place of the plug in AC to DC power supply on the existing AC gadget). I wonder how safe it would be for me to tape four LP-E8 batteries together in parallel myself by simply using wire and hot glue. Perhaps short wide rubber bands would work instead of tape. Those 3-hour recording events wouldn't occur regularly. In the meantime, I am likely to end up with a extra batteries over time regardless. They don't hold their charge as long after a year or two of use though.

 

My suggestions are as follows:

1. To buy - Waterproof DC Power Converter 12V Step Down to 7.5V 3A 15W Power Supply Module.

2. To buy - 8x 18650 GTL Li-ion 5300mAh 3.7V Rechargeable Battery for LED Torch
or buy some 4000mAh.
http://www.ebay.com/itm/8x-18650-GT...hargeable-Battery-for-LED-Torch-/190885409719

3. To buy a 18650 battery charger.

4. To DIY a portable power source using 18650 batteries, and set it close to 12V, about in series with three 18650 batteries.

5. 18650 power source → Power converter → Camera

Is this manual for your camera? (Canon LP-E8 Battery Rebel T2i)
http://www.erc.ndhu.edu.tw/ezfiles/48/1048/img/1692/eosrt2i-eos550d-im-en.pdf

Genuine Canon LC-E8C LC-E8E battery Charger for Canon LP-E8 Battery Rebel T2i
http://www.ebay.com/bhp/canon-lc-e8e-battery-charger

 

Thanks for your suggestions. Yes, that is my camera and, of course, I already have one of those battery chargers. I don't understand why you need to create a 12-volt source and then step it back down to 7.5. Why use the 18650 batteries in preference to the LP-E8?

 

If you using 18650 to make a 12V power source, and use it to charge your LP-E8 battery, when LP-E8 bettery is low, and you can treat 12V power source likes as a portable power source.

 

I am looking back at what #12 said about buying a bigger 7.4 volt battery. If I buy this one: http://www.ebay.ca/itm/140949360324?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 how would I go about attaching the wires to the battery terminals without damaging the battery? I haven't been able to find a battery plate like the first DIY project link described.

 

If you want to buy the 7.4V/6300mAh battery, then you can find the copper screw and copper nut, and it's more easy to solve the contacts problem, some multimeter used that way to fixed the 1.5V batteries.

Put the Battery into a case, and using the copper screw and copper nut to contact and fixed the battery polarity pins.

 

Thanks for the reply. I assume that the screws are attachable to the case that I would need to buy for the battery. Can you please point a case for this particular size battery?

 

Could I use this to connect to the Canon 950G compatible battery?
http://www.ebay.ca/itm/Ikan-BP2T-C-...102?pt=LH_DefaultDomain_0&hash=item258309560e
It's meant for a monitor (12 volts?) but if it keeps the voltage constant at the battery voltage I figure it should be good.

 

I can't find the size of battery, So I don't know what kind of the case you should buy, buy I always went to the local EE shop to buy the plastic case.

I also offer two ideas for you to refer to, when you want to DIY.

The plug of power

I'm not sure the battery contacts will match the Ikan BP2T-C Canon DV Battery Plate or not, and does the size match?