Building an off-the-grid solar charger for my mavic 2 pro. Please correct me if I'm wrong, I'm fairly uncomfident with electricity.

[krikite]

You'll need 50W minimum to directly charge the M2 battery. I believe the DJI car charger is about 72W as it requires 6A@12v. It will work down to about 11.2v at the charger input before it cuts out, which is why it tends to not work when the car is not running. The car's internal wiring resistance creates at least a 1v drop when 6A is going through it.

So a 20W solar panel alone won't do it unless you have an auxiliary battery that you constantly charge, and charge the Mavic off of the aux battery less than half the time you're charging the aux battery.

Yes this is very much my plan !

But now I feel very dumb, I am learning about electricity but can't get a grasp on the units and things yet. I watched some videos on YT but I struggle applying what I learned to real life.

Let's say I want to charge my power bank with solar.

To recharge this power bank, there’s a DC input port that you have to use an AC adapter with and the recharge rate of the power bank is 19V/1.6A.

This is the data about the input charge of my powerbank.

How do I find the Voltage requirements for this powerbank ? I would like to buy a solar charger that I would be sure could charge this powerbank but I am not sure to understand.

Can the voltage output of the Solar charger be lower than the normal AC input of the battery ? If not, I do have to increase it using a little device, at the cost of some energy loss, am I right ?

 

[Flycaster]

May be easier to carry the car charger setup, and when you get into town/village, maybe you can trade some cash for using the car/gas charging system to charge the Mavic batteries....

 

[krikite]

May be easier to carry the car charger setup, and when you get into town/village, maybe you can trade some cash for using the car/gas charging system to charge the Mavic batteries....

I created a post about off the grid amigo and no I won't have that there.

 

[Flycaster]

OK then, so "no motorcar, not a single luxury." If you're going to be "in the bush" for extended time using solar to charge intermediate batteries (ie motorcycle batteries Gel type) Those can be heavy as above noted. I just don't think "you can get there from here", as your plan to charge while walking. the output of solar panels is just not there, and using a panel(s) to charge intermediate batteries That's a lot to schlepp.
It would be easier (over the "long run", as in multiple treks/hikes/walkabpouts) just buy the number of batteries you think you will need, plus one extra, and charge before you go out the door, is about the only way you'll acheive your off grid filming capabilities.

 

[krikite]

Arg. Please help complete my plan and answer to my question. I already told I can't pay 800 dollars for batteries. After all it's my back which is gonna suffer, not yours. I appreciate the concern though.

Quote from the same guy

Well I guess you are right! Well it takes about 6h of good sun for my Arc 20W to charge the Voltaic Battery of 20000mAh... so I guess it would be the same for the OmniCharger if it can accept variable input power

I just want to be able to solar charge my powerbank and don't understand how I should do it.

 

[Flycaster]

Well, the solar panels will charge the gel motorcycle batteries, but it will take a long time.
If you carried 2 (maybe more) panels one "charging" while you hiked, the second stacked underneath for portability, and when you set camp, and fully connect both panels to charge the Gel battery, you might get a half charge of the battery in a full day full, clear sun exposure.

You'll have to buy a panel, a Gel battery, and test it to get a baseline for what you'll really need.
One panel is not going to be enough tho, My guess, one panel at least 24/36 hrs of full sunlight just for the Gel battery, and I think that's only going to do 1 Mavic battery, if things go well....

Here's a thought, give National Geographic a ping/net search, and somewhere you might find what their photographers use.

Quick search popped this up:

https://www.google.com/search?client=firefox-b-1-d&q=how+to+charge+drone+batteries+with+no+AC+or+car

DIY Options for Charging Drone Batteries Off-Grid

DIY Options for Charging Drone Batteries Off-Grid

www.diyphotography.net

But again, you may not get the yield that you're looking for.
These option might get you 1 battery charge at best. Then your looking for a way to charge the bank back up, solar is sloooow...maybe more than a day......

"I just want to be able to solar charge my powerbank and don't understand how I should do it."
Well, the vid that you posted shows him doing just what you want. Just have to get the solar panel you want (go big in output), and then just the correct adapter cables to the charger to the battery.

 

[MAvic_South_Oz]

A step up transformer increases the voltage like the one you posted.

If a power bank output is only 12v or so, then a step up converter will be needed, if using the DJI 12v charger.
As mentioned in my post 2 link, I made this one up for the 4WD trips to take it to 13.8v, and it works great.

I'm not 100% sure how you charge from a decent powerbank to a mavic battery, as someone mentioned an adapter, maybe it can be done bypassing the DJI gear, be able to transfer power reasonably efficiently, and not damage a battery.

Just test anything on our warm up trips near home, and let us all know how you go, and what gear you find works.

My walks of 14 - 28 days would be nice with a simple charging system, and a Spark / 2 batteries tucked away

 

[MAvic_South_Oz]

You'll need 50W minimum to directly charge the M2 battery. I believe the DJI car charger is about 72W as it requires 6A@12v. It will work down to about 11.2v at the charger input before it cuts out, which is why it tends to not work when the car is not running. The car's internal wiring resistance creates at least a 1v drop when 6A is going through it.

Pretty sure the DJI M2 battery will be similar to my MP in charging specs, or close.

The DJI 12v car charger needs 13.1v to work reliably and constantly.
This is fine when you're driving, as soon as you stop and voltage settles to ~ 12.7v or so, the charger just doesn't work, it sort of flashes for 10 secs, stops, another 15 secs it might start again for 10 secs, repeat over and over.
Never did manage to charge one fully before solving this, maybe over a couple of days it might have charged one, but that's no good.

I made this for reliable charging on long 4WD trips . . . Step up converter
I charge it from my 2nd baterry (110ahr AGM).

 

[MAvic_South_Oz]

Maybe do some more reading on this forum @krikite.
I recall many posts in recent times about hiking and charging batteries.
This is a search >Search results for query: charge battery hiking

Check out some of these to find threads like this . . .

Hiking Mavic Pro - Battery Bank Charging System - Proven

Actually at least the Shorai one is only1.5lbs or so ... Military attractions, did you try it? I'd be curious to see if it works :)

mavicpilots.com

 

[AMann]

Im using the same type of step up transformer as above foe the battery I posted above, only mine has a 20amp 18v output for my refrigerator. They are stable and work very well.

 

[DanMan32]

Pretty sure the DJI M2 battery will be similar to my MP in charging specs, or close.

The DJI 12v car charger needs 13.1v to work reliably and constantly.
This is fine when you're driving, as soon as you stop and voltage settles to ~ 12.7v or so, the charger just doesn't work, it sort of flashes for 10 secs, stops, another 15 secs it might start again for 10 secs, repeat over and over.
Never did manage to charge one fully before solving this, maybe over a couple of days it might have charged one, but that's no good.

I made this for reliable charging on long 4WD trips . . . Step up converter
I charge it from my 2nd baterry (110ahr AGM).

As I mentioned, the cut off voltage of the DJI charger is about 11.2v measured at the charger input. The problem comes when the charger draws around 6A required to charge the M2 batteries. With that current, the resistance of the car wiring tends to generate a voltage drop of 1v, meaning the car battery would have to have a voltage of 12.2v.
V=IR where V is voltage, I is current, R is resistance. You can use simple algebra to move the variables around.
So to figure out what the car wiring resistance is, we fix the equation to solve for R. We do this by dividing both sides by I which makes the equation R=V/I.
I mentioned the wiring voltage drop is 1V when 6A is going through it.
R = 1/6 so wiring resistance from car battery to charger is 0.166 ohms.

Input to output watts in theory will be constant when stepping up or down voltage but in reality you'll have a loss in the conversion. It will take some more watts in than you get out. However you can treat it equal to give you an idea.
W=VI. So for the same wattage, if you raise the voltage, the current draw goes down. That's why in the USA, high wattage devices like servers are better run at 240V rather that 120V, though modern power supplies can handle either voltage. A 1000W server needs 8.3A at 120V or only 4.16A at 240V. With less current going through the power wires, there's less of a voltage drop and loss of energy in the wiring.

With the solar panels, if they can only deliver 20W, you can't get more wattage out of them no matter how you convert the voltage. If the charger draws 50W, you can see that won't directly work. However if you add an intermediate storage battery, then you can multiply the watt-hours.
That 20W solar, charging an intermediate battery for 2.5 hours will allow the battery to have enough energy to run the 50W charger for 1 hour.

 

[brett8883]

As I mentioned, the cut off voltage of the DJI charger is about 11.2v measured at the charger input. The problem comes when the charger draws around 6A required to charge the M2 batteries. With that current, the resistance of the car wiring tends to generate a voltage drop of 1v, meaning the car battery would have to have a voltage of 12.2v.
V=IR where V is voltage, I is current, R is resistance. You can use simple algebra to move the variables around.
So to figure out what the car wiring resistance is, we fix the equation to solve for R. We do this by dividing both sides by I which makes the equation R=V/I.
I mentioned the wiring voltage drop is 1V when 6A is going through it.
R = 1/6 so wiring resistance from car battery to charger is 0.166 ohms.

Input to output watts in theory will be constant when stepping up or down voltage but in reality you'll have a loss in the conversion. It will take some more watts in than you get out. However you can treat it equal to give you an idea.
W=VI. So for the same wattage, if you raise the voltage, the current draw goes down. That's why in the USA, high wattage devices like servers are better run at 240V rather that 120V, though modern power supplies can handle either voltage. A 1000W server needs 8.3A at 120V or only 4.16A at 240V. With less current going through the power wires, there's less of a voltage drop and loss of energy in the wiring.

With the solar panels, if they can only deliver 20W, you can't get more wattage out of them no matter how you convert the voltage. If the charger draws 50W, you can see that won't directly work. However if you add an intermediate storage battery, then you can multiply the watt-hours.
That 20W solar, charging an intermediate battery for 2.5 hours will allow the battery to have enough energy to run the 50W charger for 1 hour.

His problem is the intermediate storage battery he wants to use requires 19v/1.6amps (30.4 watts) to charge and the solar panel he wants to get is only 20 watts.

 

[MAvic_South_Oz]

As I mentioned, the cut off voltage of the DJI charger is about 11.2v measured at the charger input.

Dan is that the 12v or mains charger ? (Guessing it's your 12v charger.)
My MP 12v charger has 13.0v marked on it (and in specs), the mains has the usual 240v (or for US 110v).
Maybe the M2P chargers do have a lesser need.

I know mine simply doesn't charge after the vehicle alternator stops input, and the battery charge settles to 12.7v / 12.8v.

Solar charging from a panel hanging in a backpack is going to be very patchy.
Direction of travel and sun position will be a main factor, then angle of panel to the sun, cloud cover (indeed rainy days), partial shade on panel sections hanging, and general shade from overhead foilage canopy.
All will depreciate te solar panels output / effectiveness.

If you are base camping and can monitor the panel to face sun (when it's shining) then you will get closer to specs.
Also be aware, solar panel specs are often VERY greatly exaggerated.
Have seen this from many sources like similar threads on 4WD forums over the years, this is especially so for Chinese made / supplied panels.

 

[DanMan32]

I am referring to the car charger.
Ideal input voltage is 13.8v, the nominal voltage for a lead-acid based car electrical system. Batteries do drop in voltage as used so electronics powered by them have to tolerate less than nominal voltage. A few have tested M2 car charger behavior and found the cutoff was about where I said. The charger doesn't pull the full 6A right away, so voltage drop is near zero and charger seems OK. But then it actually starts charging, pulls 6A, significant voltage drop occurs, and charger shuts down. On shut down voltage appears higher, charger turns on, the cycle continues.

 

[MAvic_South_Oz]

But then it actually starts charging, pulls 6A, significant voltage drop occurs, and charger shuts down. On shut down voltage appears higher, charger turns on, the cycle continues.

Ah the step converter fixes this.
Might be the boosted amps thrown in there too.

I know the MP 12v charger is useless once a vehicle has been turned off for a short time, perhaps about 20 - 30 minutes to settle to about 12.7v.
Many others have posted on this forum about this issue in various threads, where voltage settles below required input.

 

[AMann]

Ah the step converter fixes this.
Might be the boosted amps thrown in there too.

I know the MP 12v charger is useless once a vehicle has been turned off for a short time, perhaps about 20 - 30 minutes to settle to about 12.7v.
Many others have posted on this forum about this issue in various threads, where voltage settles below required input.

That’s why I made this power bank for my refrigerator and Mavic charger:

Make your own 400Wh portable power battery for less than $100

I made this 12v 35Ah (420Wh) portable power battery with left over parts, but you can do it for $100 to $150 (or more) depending on options you want,...

www.tacomaworld.com

 

[MAvic_South_Oz]

That’s why I made this power bank for my refrigerator and Mavic charger:

Similar to what I did on a larger scale for my 4WD trips, but mine cost about a grand (AUD).
Use an Arkpak but without using the unreliable and slow 'smart charger' it could be just and $80 battery box with anderson plug input, a voltage gauge, and outlet plugs.
Set up with 6B&S dualcore wiring from the main battery via an isolator, it charges from the alternator to the 110ahr AGM battery it is more than enough to run 45lt fridge, led lighting, charging all sorts of gear via 12v system overnight.
I usually have 83% SOC next day when moving off, and that is topped off to 100% within 1/222 hr or so.
83% sounds a lot, but ideally lead acid be it wet cell, AGM, or calcium, should not be run down to less than 50% (often) or damage will occur shortening the life of the battery.

I usually just drive daily when touring, could easily camp a day / couple of nights without other input, but we do normally drive somewhere each day checking out the area, even when base camped.
On board I also carry a 100w or 150w folding solar panel (depoending on trip parameters) with inbuilt controllers, so can camp more or less indefinitely with that hooked up.

You can find smaller folding panels like those linked above, Projecta is one brand.

Useless for bushwalking / hiking of course, but if this sort of thing can be scaled.

If anyone wanted to lighten the load (be it 4WD but moreso for hiking), then lithium batters are less than half the weight, and you can run SOC down a LOT lower without battery damage, like 20% or even 10% is no problems.
It's just quite expensive battery technology still, but pricing is gradually coming down.

 

[AMann]

Wow, sounds like you’ve got quite the setup! The ArkPak looks nice, too! My 35Ah is actually charged up two ways as well- the 20A DC-DC charger bolted on the side of the box in the photo can draw power off my 2nd auxiliary truck battery to charge it when the engine isn't running, with a battery saver bypass if the voltage in the auxiliary battery goes too low, and I also have a 50w solar panel for it on the side as well. When we aren’t traveling offroad, my trailer has two 100w panels I can charge off of as well, but we use it much less than we used to since we got a rooftop tent and really have been enjoying being offroad nomads- touring during the day and pitching camp wherever we happen to be when nightfall hits us.

 

[lordofshadows]

I think you would want a battery to charge the drone, and a charge controller to charge the battery. Connecting directly to a solar panel is a bad idea because of varying voltage and relatively low current output. It’s like a slow drip

 

[DanMan32]

20W is a slow drip when it comes to charging the M2 batteries. You can regulate the voltage, but that won't increase the watt output. If the voltage is boosted, the deliverable current goes down for the same amount of watts.

20W@10v is 2A. 20W@13v is just over 1.5A.