techrtr

How do people recharge their batteries when they are away from an a/c powersource? I was wondering if you could use one of those portable power supplies that you can buy at hardware stores that are basically a car battery with a power converter and plug ins. Can you run a stardard DF charger off one of those things? Are there minimum amp or watt ratings required?

Sky High

I use an inverter that I got from Circuit City for $50 and it works just fine. You can get them just about anywhere.

techrtr

Cool, that's what I'll get.

TheHindmost

Inverter's a great idea...Those things are handy for lots of power needs!

There are also chargers for LiPos that run directly off a 12-volt battery. I've got a "Charge-All Sport" from WATTAge which runs off either AC or a 12-volt source. It'll charge LiPo, NiCAD or NiMH batteries. I don't use it for LiPos at the moment (I use it to fast-charge my TX pack, which I upgraded a NiMH), since I'm just flying at home right now, but for field stuff, especially if it's a long way back to the parking lot, having a 12-volt deep-cycle (marine-style) battery and portable 12-volt charger would be handy.

Will

Sky High

techrtr, I don't know what the minimum power requirement would be for these chargers but I would at least get a 300 watt inverter and then you could run alot of other devices when not charging batteries. They have some that are 600+ watts. That is an amazing technology how you can get more power from something that produces less power as the source. [sm=confused.gif]

TheHindmost

Sky, to quote Robert Heinlein, "There ain't no such thing as a free lunch."

You're not getting more "power" than the source, you're just getting the power (and less of it, actually) in a different form.

Using an inverter to power a battery charger is actually pretty inefficient, but it's sure convenient for chargers not designed to run directly off car batteries. The reason it's inefficient is because the inverter is taking the 12 volts DC from the vehicle's electrical system and converting it to 120 volts AC which you then provide the battery charger and which then promptly converts it BACK to 12 volts DC to charge the battery! Power is lost at each conversion step (generally in the form of heat), so it's more efficient to just run the battery charger directly off the 12 volts DC it wants in the first place.

Will

scottslc

Also keep in mind the capabilities of your car electrical system. If your going to get the full benefit of your inverter, and run more than one battery charger, clip the inverter directly to the battery rather than run it through the cigarette lighter. The power system in your car just doesn't have heavy enough wire, fuses, etc. to sustain that much of a power draw. When I'm out on location somewhere, I tend to have 2 batterys charging as well as a camcorder and some AA batteries. A direct feed from the battery is the only way this setup works. I even hooked up a coffe pot, which worked but ran my battery down. Was stranded for an hour or so till I got a jump...

Scott

Sky High

Yep, I agree about the unnecessary extra link in the chain. I usually plug a power strip into the inverter because those charger packs don't fit side by side on the inverter's outlets. I haven't charged more than two packs at a time with the inverter but I can run my laptop with it for a while without the engine running. As as far as running a device that requires more than 12v from a 12v source, that is where the magic happens.

That is a great lead-in to the following issue. I have had to use an A/V converter to convert analog video to firewire video to be able to record my flights from the helo because my camera doesn't allow analog IN recording, only firewire IN. Well, that converter only requires 5v and has a wall adapter to power it which means I can't go portable and must be tethered to my truck when on location somewhere. [:@] I attached a 1320 mAh and then a 2070 mAh pack to the A/V unit's wall converter to power it and it wouldn't work. Why not? That is a 12v pack so why won't it power the A/V converter that only rquires 5v to operate? Does the A/V unit's wall adapter require 100v - 120v IN (as rated) to operate properly? [sm=confused.gif]

12v 1320 mAh pack > 100v - 120v IN (as rated) to 5v OUT Wall Adapter > 5v IN A/V unit = NO POWER?

Fesfly

Your inverter probably needs a few amps to run - the lipo would need to put out about 3amps. The inverter I use cuts out when the truck battery gets low. You could always get rid of the inverter and us a simple voltage regulator plus resistance to convert 12v directly from your car battery to 5v at whatever current your AV needs.

Sky High

festusflyer, the issue I was describing doesn't use the power inverter we were talking about. I am talking about the power adapter that comes with the A/V converter, the thing you plug into the wall. It steps 110v-120v down to 5v to power the A/V converter. The whole reason for using the Lipo pack was to be able to go totally portable. The maker said the max the unit could handle is 2 amps so I guess I'll have to see what the minimum is. How many amps does a 1320 pack have?

techrtr

I picked up a 300 watt inverter today. I haven't tried it out but I would assume it should be plenty to recharge a 1320ma lipo. May pick up a deep cycle battery that I will keep charged all the time rather than using my vehicle battery. Not being very electicity savvy, I was a bit paranoid about frying my DF battery charger.

Sky High

techrtr, that should work just fine. As I mentioned earlier, I have charged two at once many times. The inverter will give you a tone if you exceed its capacity and if it's way too much of a power draw the fuse will pop.

TheHindmost

That won't work because the wall converter is expecting AC, not DC. The first step in the chain (inside the wall converter) is a transformer...which won't do much with the DC from your DF batteries except generate some heat. :-) If you could bypass the wall converter, you just might get away with running 12 volts DC direct into the A/V converter...That assumes the voltage regulator is within the A/V unit, not the wall converter, and that it'll be happy with that much overvoltage (it probably will, but it could run hot). But you can't run DC into an AC adapter, regardless of how much DC (volts and amps) you have. If you do, all that'll happen is you'll run down your battery and contribute to global warming.

Will

TheHindmost

Theoretically, a 1320 mAh (milliamp-hour) battery can deliver 1.3 amps for an hour. It can also deliver more amps for less time, as in the case of powering a DF, which draws 4+ amps in flight. Or, it can deliver fewer amps for more time, like .65 amps for two hours, etc. So it's a question of how many amps for how long, not just how many amps.

The other important thing to remember is that batteries have a maximum discharge rate. If you try to discharge them too fast, they get damaged (in some cases, violently). I'm not quite sure how far LiPos can go...I think it's in the range of 7 to 10 times rated capacity, so maybe up to 13 amps for 6 minutes. But I bet the pack would be HOT afterward!

Will

Sky High

Aha! Thanks for the info Will. That's just what I needed to know. I also noticed that the A/V unit's wall converter doesn't have polarity priority with the blades. I guess that's done internally in it's transformer too. The wall converter definitely does the conversion because it says on it that its input is 100v - 120v and it outputs 5v. So I would burn that A/V converter up without an external regulator. I guess I'm just going to have to wait until I can get a portable device that can record analog IN so I can be totally portable. [>:]

Fesfly

Sorry, I miss read - I thought you were trying to power the inverter with the lipos then plugging the ac adapter into the the inverter....
What I was suggesting was to get rid of the ac adapter - you can read the voltage on the back (5V) and the current ??? and make your own voltage regulator circuit so that the 12v DC from your car is brought down to 5v DC and proper current without cooking your A/V device.

TheHindmost

Festus beat me to the suggestion, Sky... I doubt that A/V converter draws more than an amp, and a 5V regulator that can handle an amp is a common "item of commerce" as my Dad used to say. You've already got clean DC coming out of the battery, so all you need is the regulator to bring the voltage down to 5 and also regulate it (electronics like A/V converters can't deal with unregulated supplies very well, usually).

You could get one of those little project boxes and a regulator at Radio Shack (and maybe a heat sink just to be safe) and make yourself a converter for your LiPos to power your A/V unit pretty easily. It'd probably cost about 10 bucks...

Will

TheHindmost

Sky, here's a link to the [link=http://www.radioshack.com/product/index.jsp?productId=2062599]Radio Shack page[/link] listing a type 7805 regulator. This is a 5V, 1 amp regulator which can take up to 35 V on the input side, so a DF battery powering it is no problem. The current draw in your A/V converter is probably low enough that you could get away with building an in-line cable using this component (as opposed to using an enclosure with a heat sink) to make an adapter to use DF batteries (1320s or 2100s or whatever) or any other 12V source to power your A/V converter.

It's been a while since I did this type of electronics hobbying, but I remember the type 7805 well. It is a venerable, durable and very reliable voltage regulator. I used it in many projects when I was a kid. They're bullet-proof as long as you don't wire them backwards or try to draw too much current through them. [X(]

The wiring is straight forward. It's a 3-pin IC. There's a common ground and then a Vin and Vout. You put the battery's positive side on Vin, the battery's ground on the common ground, and the A/V converter's positive input on Vout and its ground on the common ground. Voila, you have portable power for your A/V converter.

What's the output amp rating on the A/V converter's wall adapter? That'll give us an idea of whether the 1 amp limit on the 7805 is a problem and also how long you might expect a battery to last...One other word of caution: Be sure you don't leave the converter on and take the LiPo below its minimum voltage!

Will

Sky High

festusflyer, you've almost got the idea. Look at the flow chart in post #8. The whole idea is to take being tethered to the truck or anything not portable out of the mix.

festusflyer and Hindmost, thanks for the ideas about the DIY regulator but I'm not confident enough with electronics to do something like that. I've eventually got to get a portable recording device anyway and most of the newer ones allow analog video IN. I'm sure the main reason that DFI won't make a digital 1394 output an option is because of the licensing they would have to pay to Apple for using that interface.

TheHindmost

First of all, you're quite welcome...It's nice to be able to help out someone who's helped so many others here!

Anyway, I can sure understand the reluctance if you're not confident with electronics, but this particular project really is dirt simple and no more difficult than all the lighting stuff you've tried, or rewiring the camera, etc....It's basically making a cable with a small component in the middle of it. Did you check out the [link=http://www.radioshack.com/product/index.jsp?productId=2062599]Radio Shack page[/link]? That little regulator doesn't look that ominous, does it? (I just realized everyone must think I work for Radio Shack now! But nope, I don't...)

I only say this because I didn't want to give the impression that using a 7805 was a "big deal" from an electronics point of view...There's no "circuitry," just a single IC that looks an awful lot like a transistor. I'm sure NOT faulting you for not wanting to risk breaking your expensive equipment! But once you've made the cable (an investment of probably $5 and a half hour), you can verify its output with a volt meter to give yourself confidence to plug it into the A/V converter. That would be a short-term fix to your tethering problem.

DFI doesn't make that camera or the receiver themselves, do they? I always assumed it was third-party equipment, black-boxed to prevent us from ordering direct. Just curious...

Will

Sky High

Yes, protecting the more expensive video camera in this chain is a major concern. I can do basic electronic connections and other related non-invasive work but when it comes to specific components, I may know what they do functionally but not necessarily how or where to install them. That regulator does look simple to use though.

I would think they do have a supplier for their video components. My antennas do have DFI decals on them but the receiver doesn't have any decals or stickers on it. It does say Made in the USA though, which is unusual.