Charging in the field...

[jason]

Might check the DJI battery charging specs carefully. Some power inverter produce a square wave output vs a sine wave. If you just use an inverter from a 12 volt (13.7v) source to power the DJI charger, the DJI unit might not like the square wave. I have no idea if it would or not, I'd just find out more about using an inverter inline before charging those expensive batteries. Has anyone used a simple 12 volt, like Amazon sells, to recharge a DJI battery? I bought one but am kinda concerned about using it after reading on how finiky the batteries are with their charging requirements and long life.
Jim
WA5TEF

Your house hold current only uses 70% of a sinewave so what's your point.

 

[jason]

if you have a harbor freight near you they have a 12v 35ah deep discharge solar universal battery at 70 bucks.
I just used the %20 off on 2 of them for a small 50 watt PV solar setup I am building for portable/temp backup power.
$54 dollars each after discount.

just bought 2 -50w solar kits at Home depot for 83 each kit--special buy this month!
add this battery and you have decent off grid setup that can grow.

sorry for detour on thread...

There's a lot more to solar power you haven't mentioned.

 

[skiptv]

I'm looking for a way to charge my batteries while out flying. I'm not talking about a car charger, but a portable power bank. I saw one by Energen, called the Dronemax P40, but I can't find it for sale or even a price for it.

Does anyone have something they use to charge while out of the car?

Thanks.

The Energen is coming out next month, I have been field testing it. It is hands down the absolute best way to stay out in the field, charge batteries and get your work done if you are a professional. DONT EVER use a 12 volt charger plugged into car. I had a brand new rental car, that the 12 volt adaptor worked without starting car. I charged two Phantom 4 batteries with the 12 volt adaptor and killed the car battery dead, completely dead. The Energen charges fully over night. It will charge 4 batteries ALL AT ONCE one time or one battery 4 times, and its fast very fast. I flew with two batteries put them on the Energen Charger, flew two more batteries and the batteries on the charger were fully charged when I came back. I'm an instructor for the UVX University and I am out in the field teaching drone pilots for hours. This is absolutely the best system I have used. Oh and its very light and comes in a great case. Pic shows me, student and charger in trunk of my Mazda Mita.

 

[FunN4lo]

There needs to be some clarification here. Inverters are not the way to go.

Because the DJI LiPo batteries have such a high energy density, it would take a big, heavy lead acid battery to charge them even once. (A car battery sized deep cycle battery is usually less than 100 amp hours and should never be discharged more than 50 percent, netting less than 50 amp hours.)

I think you are confusing milliamp hours (mAh) of the DJI batts and amp hours (Ah) of the deep cycle batteries.

A high capacity P4P bat is 5870mAh. That is 5.870Ah. If 50Ah is the most you can pull from your automotive style deep cycle batt... then 50Ah divided by 5.870Ah = 8.5
So that automotive deep cycle batt will give you about 8 1/2 charges of a DJI high cap batt. Of course millage will vary do to energy loss in the charging/transfer process but you should be able to bet on 6 or 7, and you might even make 8 or 9 as you are never even coming close to draining your Phantom batt to zero

 

[jason]

There needs to be some clarification here. Inverters are not the way to go.

Using a typical inexpensive inverter to charge from a 12 volt source is very inefficient. The inverter first converts the 12 volts DC to 110 volts AC. Inexpensive inverters lose about 30 percent of the power in the conversion, and they don't produce the perfect sine-wave power like the power company delivers, but a modified square-wave. (Sine-wave inverters are available, but they're much more expensive,) That's important, because the DJI battery charger, like most battery chargers, don't behave well with square wave power and will lose another 15-30 percent converting the power back to DC. Overall power lose could be as high as 50 percent.

If you must charge in the field, use a DC car charger instead. They aren't perfectly efficient, but lose only about 5-10 percent of the power.

Because the DJI LiPo batteries have such a high energy density, it would take a big, heavy lead acid battery to charge them even once. (A car battery sized deep cycle battery is usually less than 100 amp hours and should never be discharged more than 50 percent, netting less than 50 amp hours.)

And even if you had an DC/AC inverter that produced a perfect sinewave only 70% is useable the same as the current in your home electrical system.

 

[FunN4lo]

Pure sine wave?!?!?
I get it for sensitive electronics. But here is my theory from charging dumb lipos for years from my truck. I have been charging DJI smart batts from my truck for my P3 for 18 months. And I fly ALOT. And now I am charging P4 batts from my truck.

I have NEVER had a battery failure, or swelling, or any issues other than no batts last for ever and you will eventually need to replace them from old age. Although my original P3 batts are still flying. . The lowest one shows 91% life after all those charges in my truck

But wait... when does the sine wave don't matter theory part start?

My (everyones car) truck batt is 12.6 DC. (direct current) The system will be around 14.8v DC when the truck is running

I connect my inverter to my truck batt. It converts the DC current into the "non-pure" sine wave 120v AC (alternating current) like at your house.

Next, I use a triple charger that will charge 3 batts and my controller. I plug that charger into my inverter. That charger immediately converts that 120v "non-pure" sine wave right back to 17.4v DC (no sine wave in DC voltage) to charge my DJI batt.

So in my case nothing from DJI ever sees "non-pure" sine wave. The only thing that does see the "non-pure" is my my triple charger. It only cost $50, and has never failed me. If you use the single DJI charger, same thing. The only thing that sees the "non-pure" sine wave is the charging brick, and those things are cheap too.

Here is a mini build log on my charging set up
In Truck Charging Station

 

[With The Birds]

And even if you had an DC/AC inverter that produced a perfect sinewave only 70% is useable the same as the current in your home electrical system.

I'm curious, what do you mean when you say only 70% of a sine wave is usable?

 

[robca]

Pure sine wave?!?!?
I get it for sensitive electronics. But here is my theory from charging dumb lipos for years from my truck. I have been charging DJI smart batts from my truck for my P3 for 18 months. And I fly ALOT. And now I am charging P4 batts from my truck.

I have NEVER had a battery failure, or swelling, or any issues other than no batts last for ever and you will eventually need to replace them from old age. Although my original P3 batts are still flying. . The lowest one shows 91% life after all those charges in my truck

But wait... when does the sine wave don't matter theory part start?

My (everyones car) truck batt is 12.6 DC. (direct current) The system will be around 14.8v DC when the truck is running

I connect my inverter to my truck batt. It converts the DC current into the "non-pure" sine wave 120v AC (alternating current) like at your house.

Next, I use a triple charger that will charge 3 batts and my controller. I plug that charger into my inverter. That charger immediately converts that 120v "non-pure" sine wave right back to 17.4v DC (no sine wave in DC voltage) to charge my DJI batt.

So in my case nothing from DJI ever sees "non-pure" sine wave. The only thing that does see the "non-pure" is my my triple charger. It only cost $50, and has never failed me. If you use the single DJI charger, same thing. The only thing that sees the "non-pure" sine wave is the charging brick, and those things are cheap too.

Here is a mini build log on my charging set up
In Truck Charging Station

Please look at this: Could a modified sine wave inverter destroy/damage the AC adapter for a laptop?

The battery is not at risk with an inverter, nobody said it is. The DJI charger is (or whatever charger you use). That switching power supply is designed to work with a pure sine wave from your home AC. It's been designed and optimized for that case.When you feed a modified square wave or even worse a square wave, you have significantly different input signal that not only has significant overshoot and undershoot (increasing peak to peak voltage), it also makes the rest of the circuit work differently that it was designed for. Sooner or later you risk damaging your $40-50 DJI charger. Since a car charger compatible with the Phantom battery cost $15, and can charge multiple batteries in parallel as well as your setup, it's a poor choice to use an inverter

Will it get damaged if you use an inverter once? very unlikely...but over time damage is more and more likely

 

[robca]

And even if you had an DC/AC inverter that produced a perfect sinewave only 70% is useable the same as the current in your home electrical system.

Not sure what you mean by 70%... unless you are using RMS power, which is not really the case here Power). But in this case you have a switching power supply, that has been designed explicitly to use a sine wave as input, and its efficiency is based on a pure sine wave. Since a switching power supply is converting from AC to DC, the average max power of a sine wave is irrelevant, and all that matters is how efficient the power supply design is.

A good switching power supply is usually around 80% efficient with a sine wave input (i.e. for every 100W that it "gets" from the AC, it provides 80W (at a lower DC voltage, in our case). With a modified sine wave it's much less efficient, not to mention can be damaged. See here Could a modified sine wave inverter destroy/damage the AC adapter for a laptop?

If you have a DC battery as the power source, using an inverter and going DC-AC-DC again is a huge waste. The inverter is probably only 70% efficient (very good ones can be as high as 80%), the DJI power supply probably less than 60% efficient when used with a square wave, so you have only 40% of the original battery capacity used to charge the P3 batteries. With a DC-DC setup (i.e.using one of the $15 car adapters like Amazon.com: Travelocity Car Charger, Car Battery Charger for DJI Phantom 3,One USB for Other Devices(87W,Black): Cell Phones & Accessories), you should be ~85% efficient..If you are using a huge car battery, might not be an issue, but with smaller batteries it is... not to mention there's no risk to damage the AC battery charger

 

[jason]

Not sure what you mean by 70%... unless you are using RMS power, which is not really the case here Power). But in this case you have a switching power supply, that has been designed explicitly to use a sine wave as input, and its efficiency is based on a pure sine wave. Since a switching power supply is converting from AC to DC, the average max power of a sine wave is irrelevant, and all that matters is how efficient the power supply design is.

A good switching power supply is usually around 80% efficient with a sine wave input (i.e. for every 100W that it "gets" from the AC, it provides 80W (at a lower DC voltage, in our case). With a modified sine wave it's much less efficient, not to mention can be damaged. See here Could a modified sine wave inverter destroy/damage the AC adapter for a laptop?

If you have a DC battery as the power source, using an inverter and going DC-AC-DC again is a huge waste. The inverter is probably only 70% efficient (very good ones can be as high as 80%), the DJI power supply probably less than 60% efficient when used with a square wave, so you have only 40% of the original battery capacity used to charge the P3 batteries. With a DC-DC setup (i.e.using one of the $15 car adapters like Amazon.com: Travelocity Car Charger, Car Battery Charger for DJI Phantom 3,One USB for Other Devices(87W,Black): Cell Phones & Accessories), you should be ~85% efficient..If you are using a huge car battery, might not be an issue, but with smaller batteries it is... not to mention there's no risk to damage the AC battery charger

RMS is exactly what i meant. There are many members here who use DC/AC/DC inverters that are not producing a pure sinewave to charge their batteries without any problems or damage.

 

[robca]

RMS is exactly what i meant. There are many members here who use DC/AC/DC inverters that are not producing a pure sinewave to charge their batteries without any problems or damage.

RMS of the AC input doesn't come into play with switching power supplies...

Using electronics outside of their design parameters is never a good idea, even if it works for some. Square wave in particular play all sorts of havoc (most people don'trealize how much a square wave causes overvoltages and noise) Since cheap inverters are all different, results can be different, too. Moreover, switching power supplies are designed to provide a certain voltage with a certain input signal: changing the input signal might change the output voltage. So would be a good idea to check the output with a multimeter or even better an oscilloscope to ensure that the battery is really getting 17.5V DC

I don't doubt that people use them... I also know that a lot of people complain of mysterious failures. I personally prefer to know the risks and play it safe. It is a known fact that modified square waves can damage switching power supplies, and I think that people reading this thread should have all the facts. A DC/DC battery charger is cheap, much more efficient and safe. Using an inverter is neither(even if it works for some)

 

[FunN4lo]

Please look at this: Could a modified sine wave inverter destroy/damage the AC adapter for a laptop?

The battery is not at risk with an inverter, nobody said it is. The DJI charger is (or whatever charger you use). That switching power supply is designed to work with a pure sine wave from your home AC. It's been designed and optimized for that case.When you feed a modified square wave or even worse a square wave, you have significantly different input signal that not only has significant overshoot and undershoot (increasing peak to peak voltage), it also makes the rest of the circuit work differently that it was designed for. Sooner or later you risk damaging your $40-50 DJI charger. Since a car charger compatible with the Phantom battery cost $15, and can charge multiple batteries in parallel as well as your setup, it's a poor choice to use an inverter

Will it get damaged if you use an inverter once? very unlikely...but over time damage is more and more likely

Use an inverter once?!? I have 18 months of charging multiple times a week my P3P batts and no damage to any part of my equipment. I have 6 weeks charging on my P4P and no damage to any of that equipment.

Parallel charging is 3 batts is 3 times as long as one batt. Not to mention feeding your $170 batt with a $15 charger is probably light years dumber than using an inverter, and a quality charger as a go between

Series charging 3 batts is no longer than charging one batt. I have 5 batts for my P3P and 4 for my P4P. I have 7 batt recurring commercial flights. I don't have time to wait all day on site to charge batts.

My system is proven over time, and does exactly what I need. YMMV

 

[jason]

RMS of the AC input doesn't come into play with switching power supplies...

Using electronics outside of their design parameters is never a good idea, even if it works for some. Square wave in particular play all sorts of havoc (most people don'trealize how much a square wave causes overvoltages and noise) Since cheap inverters are all different, results can be different, too. Moreover, switching power supplies are designed to provide a certain voltage with a certain input signal: changing the input signal might change the output voltage. So would be a good idea to check the output with a multimeter or even better an oscilloscope to ensure that the battery is really getting 17.5V DC

I don't doubt that people use them... I also know that a lot of people complain of mysterious failures. I personally prefer to know the risks and play it safe. It is a known fact that modified square waves can damage switching power supplies, and I think that people reading this thread should have all the facts. A DC/DC battery charger is cheap, much more efficient and safe. Using an inverter is neither(even if it works for some)

Look i spent 20 years repairing electronic equipment and have forgotten more than some of you fellows think you know.

 

[robca]

Parallel charging is 3 batts is 3 times as long as one batt. Not to mention feeding your $170 batt with a $15 charger is probably light years dumber than using an inverter, and a quality charger as a go between

I checked the output of the $15 charger with an oscilloscope and multimeter. It's a a perfect 17.5V DC.So I know for a fact it's safe. I don't know of anyone who checked the output of their charger using a modified sine wave inverter, so the facts are far from being clear... but thanks for implying "light years of dumbness" on my part

People here were talking about a $15 inverter... those are surely going to produce a much worse result that a known-good $15 DC-DC charger (a DC/DC circuit is btw a very simple,commodity circuit)

Your inverter might not cause problems...Once again, if we are providing advice to people, it should be comprehensive. Electronics theory says that DC/DC is a better way to go. If you need to truly parallel charge at max current, use a 3-in-1 plug on the 12V supply and use 3 of those $15 chargers in parallel: it would be much safer and much, much more efficient (i.e.would draw less current from your 12V battery and overload the 12V circuits much less). If being safer and more efficient is more or less dumb, I'll leave it as an exercise to the reader

 

[TheLightSpeedz]

Everything Ravpower is great! I love my 24,000mah bank.

 

[With The Birds]

Not sure what you mean by 70%... unless you are using RMS power, which is not really the case here Power). But in this case you have a switching power supply, that has been designed explicitly to use a sine wave as input, and its efficiency is based on a pure sine wave. Since a switching power supply is converting from AC to DC, the average max power of a sine wave is irrelevant, and all that matters is how efficient the power supply design is.

A good switching power supply is usually around 80% efficient with a sine wave input (i.e. for every 100W that it "gets" from the AC, it provides 80W (at a lower DC voltage, in our case). With a modified sine wave it's much less efficient, not to mention can be damaged. See here Could a modified sine wave inverter destroy/damage the AC adapter for a laptop?

If you have a DC battery as the power source, using an inverter and going DC-AC-DC again is a huge waste. The inverter is probably only 70% efficient (very good ones can be as high as 80%), the DJI power supply probably less than 60% efficient when used with a square wave, so you have only 40% of the original battery capacity used to charge the P3 batteries. With a DC-DC setup (i.e.using one of the $15 car adapters like Amazon.com: Travelocity Car Charger, Car Battery Charger for DJI Phantom 3,One USB for Other Devices(87W,Black): Cell Phones & Accessories), you should be ~85% efficient..If you are using a huge car battery, might not be an issue, but with smaller batteries it is... not to mention there's no risk to damage the AC battery charger

A good switching supply is significantly more efficient that 80%, 97%+ at 30% load and mid 90's at 100% load are not uncommon numbers.

What go you think is inside the DC to DC converter? It is outputting a higher voltage than input So there must be some form of switching. It almost certainly wont be a pure sine wave, it will be modified sine (stepped square wave), The example you posted was someone who used a cheap inverter with an inadequate DC source, it was switching on and off constantly (almost certainly Low input voltage/over current protection circuit).

 

[robca]

A good switching supply is significantly more efficient that 80%, 97%+ at 30% load and mid 90's at 100% load are not uncommon numbers.

What go you think is inside the DC to DC converter? It is outputting a higher voltage than input So there must be some form of switching. It almost certainly wont be a pure sine wave, it will be modified sine (stepped square wave), The example you posted was someone who used a cheap inverter with an inadequate DC source, it was switching on and off constantly (almost certainly Low input voltage/over current protection circuit).

I don't have a power meter handy right now, but the 57W DJI power supply doesn't seem to be very efficient (the sticker says it draws 1.8A, even if it's really hard to believe it's that much... that would be almost 200W at 120V), and it's surely used above 30% load. Most laptop power supplies are usually ~85% efficient based on most available tests, since cost/space is a design consideration. All those tend to work at the max of their rating, so efficiency drops, inevitably.

And, yes, I know how a boost converter works. I hope we can all agree that driving a switching power supply with a modified square wave is less efficient that using the AC sine it's designed for, and that going DC-AC-DC is much less efficient that DC-DC

Anyways, I wanted to provide a piece of info that was missing: cheap inverters (and a few were discussed here) can damage your power supply. Using an inverter is less efficient that using a DC-DC converter, and uses more of the source battery capacity. If you parallel charge lots of batteries using an inverter, the reduced efficiency implies drawing a much higher current than using multiple DC-DC converters in parallel. Looks like I touched a nerve with people who seem to think I'm insulting their use of an inverter: if you know what you are doing, using an inverter can be safe. Otherwise a DC-DC converter is a safer/more efficient choice

 

[With The Birds]

I don't have a power meter handy right now, but the 57W DJI power supply doesn't seem to be very efficient (the sticker says it draws 1.8A, even if it's really hard to believe it's that much... that would be almost 200W at 120V), and it's surely used above 30% load. Most laptop power supplies are usually ~85% efficient based on most available tests, since cost/space is a design consideration. All those tend to work at the max of their rating, so efficiency drops, inevitably.

And, yes, I know how a boost converter works. I hope we can all agree that driving a switching power supply with a modified square wave is less efficient that using the AC sine it's designed for, and that going DC-AC-DC is much less efficient that DC-DC

Anyways, I wanted to provide a piece of info that was missing: cheap inverters (and a few were discussed here) can damage your power supply. Using an inverter is less efficient that using a DC-DC converter, and uses more of the source battery capacity. If you parallel charge lots of batteries using an inverter, the reduced efficiency implies drawing a much higher current than using multiple DC-DC converters in parallel. Looks like I touched a nerve with people who seem to think I'm insulting their use of an inverter: if you know what you are doing, using an inverter can be safe. Otherwise a DC-DC converter is a safer/more efficient choice

DC to DC for an increased output voltage is, and can't be anything other than, DC-Moified waveform (sine, square, triangle etc)-DC. Depending on design and quality it may be less efficient than using an inverter to drive a switching PSU. A modified sine wave (stepped square wave) can, through a PWM generator feeding the switching devices and a feedback winding in the transformer have a waveform approximating the same RMS voltage as a pure sine wave. The efficiency of any switching supply driven by it will be the same. The weak link might be any decoupling/filter caps close to the input where voltage ratings might be exceeded but this would only be an issue for the nastiest of the cheap equipment.

 

[FunN4lo]

I checked the output of the $15 charger with an oscilloscope and multimeter. It's a a perfect 17.5V DC.So I know for a fact it's safe. I don't know of anyone who checked the output of their charger using a modified sine wave inverter, so the facts are far from being clear... but thanks for implying "light years of dumbness" on my part

People here were talking about a $15 inverter... those are surely going to produce a much worse result that a known-good $15 DC-DC charger (a DC/DC circuit is btw a very simple,commodity circuit)

Your inverter might not cause problems...Once again, if we are providing advice to people, it should be comprehensive. Electronics theory says that DC/DC is a better way to go. If you need to truly parallel charge at max current, use a 3-in-1 plug on the 12V supply and use 3 of those $15 chargers in parallel: it would be much safer and much, much more efficient (i.e.would draw less current from your 12V battery and overload the 12V circuits much less). If being safer and more efficient is more or less dumb, I'll leave it as an exercise to the reader

Link me to your $15 charger. Ill check it out. If it is not using hair sized wiring, I might hack three or 4 of them into a mobile multicharger

 

[RocketBrew]

Despite having 5 batteries for my P3P's, I couldn't charge them fast enough while filming on a movie set in the middle of the desert.
I was using a $15 Anbee car charge from Amazon, and had also rigged up a marine battery from Costco with a Samlex pure sine wave inverter that ran two regular DJI 100w chargers non-stop. The plastic tip of the Anabe literally melted!

I have now packaged up the battery and inverter into a battery box that makes it simple to move in and out of the car. With two DJI chargers plugged into the inverter and a car charger plugged into the 12v outlet I can charge three batteries simultaneously without using the vehicle battery (and risk getting stranded in the desert!) This has lasted for charging at least ten batteries so far, and is much simpler than having to run and maintain a generator.


For the Phantom 4/Pro DJI has a nice car adapter, but costs a bit more than $15...