Continuation of Mavic charging projects - portable charging - 4A vs 8A charge profiles

[Easty]

Not played with the chargers for a while, So I had a little play with a large 18650 pack I recently made and recorded the charge profile for 4amp(wall charger) and 8amp from the Battery pack. Really interesting to see how the Mavics battery BMS handles the different inputs.Also a question if we could have a 90% charge to save 20mins charge time how often we would use it.

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The charge comparison graph.

 

[MavicMasterPro]

So the 8amp portable did the job in 49 minutes and the 4amp wall was over an hour and seven minutes ( can't access rest of chart to right??). What's interesting is the plateau on the 4a wall charger as well. I was thinking how Tesla charge rates rapidly decline at about 80% charge to prevent cooking the batteries.

 

[thefrisbee995]

Find the battery pack interesting. How much would I be looking at if I made one? I have a family member who is an engineer and could probably make me one. Also how many mavic charges do you get out of the 18650 battery pack?

 

[Former Member]

I like and appreciate your experiment. It looks like you started out charging at approximately 2c (8000/3830 = 2.08c) and then it dropped rapidly and linearly after 5 minutes down to 0.5c between 30 and 45 minutes. What Im interested in is the temperature of the battery during the process and the voltage reading as well. Between 4.0v and 4.2v in a lipo is where the charging is the slowest but where it packs the most punch when discharging.

It looks like most of the time you saved was in between 0 and 20 minutes when your charger was charging at a higher rate than the wall charger. I wonder how many volts per cell per charger you would have at the time that the two chargers intersected at approximately 20 minutes?

I can see this of being great use for a person who has only 2 packs but wants to get another 10 minutes of flight time. Im thinking that using your charger, after around 20 minutes of charge time, the mavic battery would have around 4.0 volts per cell which would give the battery around 10 minutes of flight time before it discharges down to 15%.

What do you think? Once again, thank you for a great post and good analysis.

 

[Mugsyx74]

Nothing scientific here but, the ultimaxx car charger charges my batteries in 45min vs 1hr15min w/ supplied charger. Does the slower charge preserve the batteries life?

 

[Easty]

So the 8amp portable did the job in 49 minutes and the 4amp wall was over an hour and seven minutes ( can't access rest of chart to right??). What's interesting is the plateau on the 4a wall charger as well. I was thinking how Tesla charge rates rapidly decline at about 80% charge to prevent cooking the batteries.

That's the end mate, I just trimmed the data where it fell to zero amps. Another reason they take a along time at the end is the battery does a balance charge. Though you don't really need to do this every charge and you can see individual cells in the app.

Find the battery pack interesting. How much would I be looking at if I made one? I have a family member who is an engineer and could probably make me one. Also how many mavic charges do you get out of the 18650 battery pack?

You can customize it to suite, just buy good quality batteries as the ones with claims of high mah are generally junk. The Panasonic I used are $6.5 each and 3400 mah capacity. So you need 4 in series then you can put as many as you like in parallel to up the capacity.

I like and appreciate your experiment. It looks like you started out charging at approximately 2c (8000/3830 = 2.08c) and then it dropped rapidly and linearly after 5 minutes down to 0.5c between 30 and 45 minutes. What Im interested in is the temperature of the battery during the process and the voltage reading as well. Between 4.0v and 4.2v in a lipo is where the charging is the slowest but where it packs the most punch when discharging.

It looks like most of the time you saved was in between 0 and 20 minutes when your charger was charging at a higher rate than the wall charger. I wonder how many volts per cell per charger you would have at the time that the two chargers intersected at approximately 20 minutes?

I can see this of being great use for a person who has only 2 packs but wants to get another 10 minutes of flight time. Im thinking that using your charger, after around 20 minutes of charge time, the mavic battery would have around 4.0 volts per cell which would give the battery around 10 minutes of flight time before it discharges down to 15%.

What do you think? Once again, thank you for a great post and good analysis.

There was little temperature to raise in the mavic battery or battery back. I have a little thermal and checked on them. There was a lot on the Voltage regulator at first during it's 8amp stage, probably be best to have a fan on it for repeated use. It's hard to measure the mavic voltage as it has BMS inside so it always gives you the 13v. For me it would be great to have a 90% charge, would reduce it by over 20mins which ever charge method you use. Them just fully charge it once in a while to balance.

Nothing scientific here but, the ultimaxx car charger charges my batteries in 45min vs 1hr15min w/ supplied charger. Does the slower charge preserve the batteries life?

I don't have one to check it, I may pick one up, it's probably a very similar concept. I was messing with car charges in earlier videos and did an 8amp one. Car lighter sockets can provide 120W so they are good for the current. I could just run a 6amp charge form my bench and see if the
charge curve is optimal, maybe it retains the higher amp much longer. Does it work with ignition off? I'm guessing it's just a buck converter to step down from 14.8v to 13.1v.

 

[Mugsyx74]

Yes it charges without the vehicle running. Haven't really noticed yet if one battery last longer than the other. Will be part of the experiment!

 

[Easty]

Yes it charges without the vehicle running. Haven't really noticed yet if one battery last longer than the other. Will be part of the experiment!

Oh that's interesting maybe it has step-up step down voltage switching. I've ordered one to play with it.

Have you ever timed the charge? I just ran one from 18% and it took only a minute shorter than the 4amp. I'm going to do it again as I think maybe something was wrong or the battery just needed extended balance charging.

Here is the added graph for 6amp. I'll update it when I run the next one. Be interesting to understand

 

[TTFullTimer]

Best battery life is achieved balance charging every time. That also provides most capacity.

 

[Easty]

Best battery life is achieved balance charging every time. That also provides most capacity.

Everything with these batteries is a compromise. Actually charging a li-po to 100% is similar to leaving it discarding in respect to it's life. Charging them to 80%-90% they last longer. Also with my sports drone I rarely have to balance charge it. It's
a raw lipo with no built in bms which is the norm. So the idea here is to understand different options for what may be best in each situation.

 

[TallGear]

Thanks for your effort on this.

 

[Mugsyx74]

Oh that's interesting maybe it has step-up step down voltage switching. I've ordered one to play with it.

Have you ever timed the charge? I just ran one from 18% and it took only a minute shorter than the 4amp. I'm going to do it again as I think maybe something was wrong or the battery just needed extended balance charging.

Here is the added graph for 6amp. I'll update it when I run the next one. Be interesting to understand

Ok so head to head challenge @ 16%
Ultimaxx car charger - 48 min
Dji stock charger - 72 min
The truck was running only for about 8min of the charge before I got in my driveway and turn it off. 07 Toyota tundra. I have not flown them yet to see if one lasts longer in flight yet but will post results asap! Hatsoff to ultimaxx for that quick of a charge of it gives me remotely the same amount of flight time as the other option!

 

[Easty]

Ok so head to head challenge @ 16%
Ultimaxx car charger - 48 min
Dji stock charger - 72 min
The truck was running only for about 8min of the charge before I got in my driveway and turn it off. 07 Toyota tundra. I have not flown them yet to see if one lasts longer in flight yet but will post results asap! Hatsoff to ultimaxx for that quick of a charge of it gives me remotely the same amount of flight time as the other option!

That's really good bit of kit then. I wonder if it's current limited up to 8amp, I need to play with it and check. The reason I asked about the car being on off is cars normally fluctuate from 12v-14.8v depending when they are on or off. The Ultimaxx must have a step-up and step down converter to keep the voltage just right or the battery would shut off charging. thanks for the feedback.

 

[Mugsyx74]

That's really good bit of kit then. I wonder if it's current limited up to 8amp, I need to play with it and check. The reason I asked about the car being on off is cars normally fluctuate from 12v-14.8v depending when they are on or off. The Ultimaxx must have a step-up and step down converter to keep the voltage just right or the battery would shut off charging. thanks for the feedback.

So went to test my flight times and hit a bird! I didn't even get it on video 8( plus my MP went plummeting to the ground from 45'. I was in sport mode and saw on YouTube that you could do aerials, so I was eager to try them! 10 min in I'm learning to roll and kind of treat it like a stunt drone. (Pretty expensive stunt drone) anyway I look down to my screen and hear a pop and look up and see a poof of feathers and my drone crashing down. Fortunately, there was sage brush below and it saved the impact. Broke all 4 props, one from hitting the bird because I couldn't find 1/2 of the prop and I'm guessing the others from hitting the sage brush. It also knocked the gimbal out of place. However, a quick prop change, a good clean up and inspection along with gimbal recalibration looks like I just took it out of the box! So needless to say I didn't get any results for the amount of time flown but did bring the battery down to 15% and it took 50min with the ultimaxx car charger. Same as before about 8min with the truck running. Anxious to get back out and fly maybe no more aerials in that area though!