Battery Discharge < 10 days

ff22 · Jan 5, 2019

Gregdd said:
Got this rig from Amazon. Pulls a solid 2 amps at 5 volts so sucks out 50% of a full battery much faster than using phones or tablets to discharge. The USB adapter that plugs into the battery gets pretty hot and the actual discharging units get very hot. The discharging units are switchable between 1 amp and 2 amp so if you don't like it getting so hot just run it at 1amp but obviously will take twice as long.

Just to clarify something somebody mentioned previously: I wouldn't discharge my batteries if I knew I was going to fly them within a week or so. Discharge/charge cycles also wear down the battery so I would only use this if you know they are going to be sitting around for a while.

I will ask: Does this "thing" do anything? Is it a battery bank or does it just drain off power from the batteries and "throw it away?"

WithTheBirds · Jan 5, 2019

Gregdd said:
Yes you are allowed to have your own opinion . I base my decisions on science and past history. Past history has shown that lipos shouldn't be left fully charged if not used (There is a lot of evidence for this if you care to research). Until someone shows me differently I will discharge if I don't plan on using the bird for a while. No use waiting 10 days in those cases. The rig i posted above is also very handy if you are about to board a plane and don't have time (or weather) to go fly all your batteries down. It would also be handy to perform the 3 month full discharge recharge as recommended by DJI.
I am not sure how much experience people have on this forum but the ability to discharge your batteries is important.

I don’t understand what problem you might have- the idea of these forums is to share facts and observations so people might make informed decisions.

Let’s look at some known numbers here. It is well understood that LiION chemistry suffers usable capacity loss over time and that SOC and temperature are known contributors. At 25degC and 100% SOC (rated max terminal voltage) usable capacity after 12 months can be reduced by up to 20% (compared to 4% at 40% SOC). Most current LiPO cells perform better than this and lower temps reduce the effect so you might take 16% as worst case scenario. My point was simple, if you allow for auto discharge taking two days to complete and initiating after 10 worst case the cell capacity might be degraded by 0.5%. Unless you find yourself constantly charging batteries before putting your gear in long term storage there isn’t a great benefit to be had here.

No airline requires LiION do be discharged in carry on. Air freight has requirements for maximum SOC.

The routine discharge is no longer recommended by DJI and with the current battery management is largely unnecessary. If you look at how gas gauging, impedance track and health algorithms are implemented (TI has many white papers available) this should be readily apparent. The days of straight coloumb counting to ascertain available capacity are long gone.

mnis · Jan 5, 2019

ff22 said:
I will ask: Does this "thing" do anything? Is it a battery bank or does it just drain off power from the batteries and "throw it away?"

Electrical energy is converted to thermal energy, nothing more. That means you can use it to simulate an electrical load with a fixed amp load. There are also devices for USB with adjustable load. Useful are such dongles or devices, for example, to check USB outputs. The maximum load that can be delivered and the temperature development of the components involved are tested.

ff22 · Jan 5, 2019

mnis said:
Electrical energy is converted to thermal energy, nothing more. That means you can use it to simulate an electrical load with a fixed amp load. There are also devices for USB with adjustable load. Useful are such dongles or devices, for example, to check USB outputs. The maximum load that can be delivered and the temperature development of the components involved are tested.

Ah, so an exotic hand warmer - that is what I thought.

mnis · Jan 5, 2019

WithTheBirds said:
I don’t understand what problem you might have- the idea of these forums is to share facts and observations so people might make informed decisions.

Let’s look at some known numbers here. It is well understood that LiION chemistry suffers usable capacity loss over time and that SOC and temperature are known contributors. At 25degC and 100% SOC (rated max terminal voltage) usable capacity after 12 months can be reduced by up to 20% (compared to 4% at 40% SOC). Most current LiPO cells perform better than this and lower temps reduce the effect so you might take 16% as worst case scenario. My point was simple, if you allow for auto discharge taking two days to complete and initiating after 10 worst case the cell capacity might be degraded by 0.5%. Unless you find yourself constantly charging batteries before putting your gear in long term storage there isn’t a great benefit to be had here.

No airline requires LiION do be discharged in carry on. Air freight has requirements for maximum SOC.

The routine discharge is no longer recommended by DJI and with the current battery management is largely unnecessary. If you look at how gas gauging, impedance track and health algorithms are implemented (TI has many white papers available) this should be readily apparent. The days of straight coloumb counting to ascertain available capacity are long gone.

Did you mean counting the cycles with "Coulomb counting"?

WithTheBirds · Jan 5, 2019

mnis said:
Did you mean counting the cycles with "Coulomb counting"?

In this instance simply the basic method of the battery monitoring circuity measuring power into and out if the cells (during charge and use).

mnis · Jan 5, 2019

ff22 said:
Ah, so an exotic hand warmer - that is what I thought.

Yes exactly. And if you do it skillfully, you can use your Mavic battery for just that purpose. Even more, the DJI batteries are largely self-protecting. With relatively little effort, you can use this energy source to cook your breakfast egg, or more useful, for example, to use a soldering iron, small computer (Arduino) and much more. This electronic load is available for many applications. And that there are those things, shows that there is also a market for it.

Gregdd · Jan 7, 2019

ff22 said:
Ah, so an exotic hand warmer - that is what I thought.

Actually you would be more like a hand burner. You definitely cannot touch them when they're discharging it at 2 amps. My trial was done on the top of my stove because I was warned they get very hot and that is likely the only place I would do it except for maybe on tile.

mnis · Jan 8, 2019

I use this to check USB power banks, USB cables, and small batteries:
https://www.amazon.com/Yeeco-Adjust...harging/dp/B01GFZ6LWE/ref=sr_1_9?ie=UTF8&qid= 1546998882 & sr = 8-9 & keywords = usb + load
It is much more expensive than using two resistors on a small electronic board with USB, but much safer because of active cooling. Measurements are inclusive and indeed very accurate, and the current can be set very finely. It uses the same gauge as the USB Safety Tester J7-t (Muker):
https://www.amazon.com/Yeeco-Adjust...1GFZ6LWE/ref=sr_1_9?ie=UTF8&qid=1546998882&sr = 8-9 & keywords = usb + load
It is also very well suited to be connected directly to a Mavic battery. For this to work, for example, the M1P requires such a cable:
https://www.amazon.com/Charging-Con...WHQGN/ref=sr_1_26?ie=UTF8&qid=1547000189&sr=8 -26 & keywords = Mavic + charging cable +
The banana plugs are replaced by matching wire end ferrules, which then come in the two-pin screw terminal of the YEECO. This is the only work to be done on the matter.

For safety:
Application of course in own responsibility!
And never leave the working device unattended!
Do not use such a device if you have no basic knowledge of electronics.
Maybe a friend will help you with the assembly and the first use.

WithTheBirds · Jan 8, 2019

mnis said:
I use this to check USB power banks, USB cables, and small batteries:
https://www.amazon.com/Yeeco-Adjust...harging/dp/B01GFZ6LWE/ref=sr_1_9?ie=UTF8&qid= 1546998882 & sr = 8-9 & keywords = usb + load
It is much more expensive than using two resistors on a small electronic board with USB, but much safer because of active cooling. Measurements are inclusive and indeed very accurate, and the current can be set very finely. It uses the same gauge as the USB Safety Tester J7-t (Muker):
https://www.amazon.com/Yeeco-Adjust...1GFZ6LWE/ref=sr_1_9?ie=UTF8&qid=1546998882&sr = 8-9 & keywords = usb + load
It is also very well suited to be connected directly to a Mavic battery. For this to work, for example, the M1P requires such a cable:
https://www.amazon.com/Charging-Con...WHQGN/ref=sr_1_26?ie=UTF8&qid=1547000189&sr=8 -26 & keywords = Mavic + charging cable +
The banana plugs are replaced by matching wire end ferrules, which then come in the two-pin screw terminal of the YEECO. This is the only work to be done on the matter.

For safety:
Application of course in own responsibility!
And never leave the working device unattended!
Do not use such a device if you have no basic knowledge of electronics.
Maybe a friend will help you with the assembly and the first use.

The DROK or whatever the two resistor unit is called is a joke for continuous operation.- might be ok for running a brief test to check the charge function of a USB port. It is totally unsuited for discharging. The insurance company probably wouldn't pay out if someone managed to burn their house down with it.

mnis · Jan 8, 2019

WithTheBirds said:
The DROK or whatever the two resistor unit is called is a joke for continuous operation.- might be ok for running a brief test to check the charge function of a USB port. It is totally unsuited for discharging. The insurance company probably wouldn't pay out if someone managed to burn their house down with it.

That's right ... That's why I prefer to use something with active cooling. Nevertheless, I would not leave the YEECO I have shown in this example unattended. Although I have been using the device for more than a year, there is always some suspicion.

Gregdd · Jan 12, 2019

mnis said:
I use this to check USB power banks, USB cables, and small batteries:
https://www.amazon.com/Yeeco-Adjust...harging/dp/B01GFZ6LWE/ref=sr_1_9?ie=UTF8&qid= 1546998882 & sr = 8-9 & keywords = usb + load
It is much more expensive than using two resistors on a small electronic board with USB, but much safer because of active cooling. Measurements are inclusive and indeed very accurate, and the current can be set very finely. It uses the same gauge as the USB Safety Tester J7-t (Muker):
https://www.amazon.com/Yeeco-Adjust...1GFZ6LWE/ref=sr_1_9?ie=UTF8&qid=1546998882&sr = 8-9 & keywords = usb + load
It is also very well suited to be connected directly to a Mavic battery. For this to work, for example, the M1P requires such a cable:
https://www.amazon.com/Charging-Con...WHQGN/ref=sr_1_26?ie=UTF8&qid=1547000189&sr=8 -26 & keywords = Mavic + charging cable +
The banana plugs are replaced by matching wire end ferrules, which then come in the two-pin screw terminal of the YEECO. This is the only work to be done on the matter.

For safety:
Application of course in own responsibility!
And never leave the working device unattended!
Do not use such a device if you have no basic knowledge of electronics.
Maybe a friend will help you with the assembly and the first use.

I would like this solution but I cant find a conversion cable for the Mavic 2. Has anyone seen this somewhere? I have no issue discharging using the two resisters that I have shown but bypassing USB would be nice to discharge a little faster.

mnis · Jan 12, 2019

Search for example on eBay, Amazon or anywhere else with these terms: Mavic Pro charging cable ;It may take a while to find suitable cables for the still young M2x available from the relevant online retailers. But you can also buy an additional charger and cut the cable at the desired location. Then you make XT60 connectors on both ends. Of course, then you need some soldering experience. If you can not make the cable yourself, then please someone with the appropriate experience to help you.

Gregdd · Jan 12, 2019

mnis said:
Search for example on eBay, Amazon or anywhere else with these terms: Mavic Pro charging cable ;It may take a while to find suitable cables for the still young M2x available from the relevant online retailers. But you can also buy an additional charger and cut the cable at the desired location. Then you make XT60 connectors on both ends. Of course, then you need some soldering experience. If you can not make the cable yourself, then please someone with the appropriate experience to help you.

Yes as I mentioned, I did search extensively. I was asking if anyone can give me a link. Is there anyone on this forum that does not know how to solder? Not many I would guess. In any event I am not going to spend that much money just to get a cable.

mnis · Jan 12, 2019

Gregdd said:
Yes as I mentioned, I did search extensively. I was asking if anyone can give me a link. Is there anyone on this forum that does not know how to solder? Not many I would guess. In any event I am not going to spend that much money just to get a cable.

Hm ... I would assume that only a few Mavic pilots are at the same time RC model makers, electronics technicians or electrical engineers.

Anyway ... I just did a quick search on eBay-DE, here is a nameless M2x Car-Charger for 10.44 Euro including shipping costs. Shipping is already from DE, so no long wait.

Finished cables will not be much cheaper later either. By attaching the XT60 plug further use of all parts is ensured, nothing needs to be thrown away.

Much more ... As the batteries have integrated charging electronics, car adapters or power supplies deliver only the maximum required voltage (M1x = 13.05 volts / M2x = 17.4 volts). The maximum current is usually limited to about 1C, but of course there are stronger and weaker adapters / power supplies.

Thus, these adapters or power supplies can be used to great advantage for RC chargers. For example, many ultra-compact RC chargers do not have their own power supply. Their input voltage range is usually between 7.5 and 27 volts. With the 50 to 60 watts of Mavic power supplies is something to start.

Another good example is RC chargers from ISDT, which also use XT60 connectors. With these chargers you can use almost all types of rechargeable batteries, including the DJI LiHv's without balancer connector.

You also have the opportunity to charge gently with less than 1C, and by the way you can see how much energy was supplied. However, only a few RC chargers are suitable for discharging, since hardly more than 6 to 8 watts can be drawn.

No matter what you choose, everything you need will cost less than a single DJI battery. And if you are safe in dealing with battery technologies, then the handling of the matter is by no means more dangerous than usual for you or your batteries.

Test pilot · Jan 12, 2019

huh ?

Test pilot · Jan 12, 2019

what ?

mnis · Jan 12, 2019

Test pilot said:
huh ?

Any thoughts / questions?

mnis · Jan 12, 2019

Test pilot said:
what ?

Maybe more than a word?
[emoji1787]

mnis · Jan 13, 2019

WithTheBirds said:
It’s a strange sort of nonesense this battery business eh....

Almost everything I learnt about LiPOs was the hard way and at significant cost. I destroyed plenty not having a clue how to treat them, mostly by leaving at full charge closely followed by over discharge (that’s the quickest way to puff them and permanently destroy them). That’s also where I learnt that a pack that might not even get a big rc heli off the ground for more than 20 seconds was still fine for other low current draw applications.

Given the 43.6wh rating of the flight pack for a 30min flight taking the battery to 0% in the GO app (optimistic) the average power consumption would be 87.2W (127mah/minute). Most importantly the C rate would be 2 (average). Higher obviously during increased load conditions.

It definitely seems you might have a higher than might be expected self discharge with your controller. I’m going to charge mine and watch it. I never have but haven’t been suspicious about it.

I had my MP remote fully charged until the LCD went off. Then I left the remote control for 7 days. Yesterday was day 7 and I hit the power button ... Bang, 98 percent was shown to me. Again another result than expected. No matter, surprised and unsettled, I connected the remote control with the smartphone. Then I played around with it, until 55 percent remained. Now the stuff stays up until better weather is expected.