High current car charger for P4P batteries...Part III...

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Hey doods!

So all my parts finally came in...

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...so I decided to build the DFHCCC (Donnie Frank High Current Car Charger) today. Version 1.0 is finished and tested.

I started the test charging each battery @ 5 Amps (87 watts).

With my Honda Civic engine idling, car battery voltage held fast @ 12.4 VDC. So I decided to up the game to 6 Amps/battery (105 watts). This caused car voltage to drop to 12.1 VDC. Because I changed the source current roughly 16 minutes into the charging regimen, I feel I could've knocked maybe 5 or more minutes off each charge had I started @ 6 Amps.

Battery 1 started @ 29% and took 49 minutes and 56 seconds to charge.
Battery 2 started @ 24% and took 56 minutes and 56 seconds to charge.
Battery 3 started @ 25% and took 56 minutes, 19 seconds to charge.

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You may noticed I used a banana plug interface. This is so I can use this to charge my Mavic Pro or Inspire 1 batteries.

This is version 1.0. If all works well, I will probably repackage this into some kind of case...perhaps with active cooling for summer time.

Worth noting: These chargers are rated @ 900 watts / each. Because I'm running them at a mere 105 watts, they stay very cool. There is an active fan on the heat sinks that DID run while charging, but the heat sinks stayed very cool to the touch.

Total cost of this is hard to say because I had so many parts already. By my estimate, I spent about $130 in parts (including $30 for the HDPE plastic substrate), but had probably $40 worth of parts laying around (terminal blocks, banana plugs, wire, shrink wrap, etc.). I would say anyone could build this version for under $200. Considering that this is the cost of one battery, it's a good investment IMHO.

Also worth noting: Notice the shunt in the upper-right corner. This is for a combination amp/voltage meter. I just didn't feel like installing it today. When installed, it will give me total current draw and car battery voltage.

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Right now I get readings off my voltmeter in my cigarette lighter plug.

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D
 
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What a Very nice breadboarded set UP.....very neat O wiring too.....you surely must be a electrician !
 
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What a Very nice breadboarded set UP.....very neat O wiring too.....you surely must be a electrician !
I was in a past life...<;^) Thanx. I didn't want to put too much time into packaging on the off-chance that this didn't work out. So far it is working well. Can't wait to try it in the field. If it works as well as I think it will, I'll come up with some nicer packaging. It might be time to get a 3D printer!

D
 
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Very cool set up. Is there anything in the series that will regulate the output to a constant voltage/amperage? The difficulty with car charging (that I've run across) is the variances can make the battery life shorter versus wall charging.
 
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I admire your inventiveness and ability.
As a humble “civilian”, I just plug an inverter into 12v/10A (lighter) and plug a DJI charger into it. Admittedly, this limits output to 120W but it sure is simpler and less expensive!

“A” for effort to you!
 
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I admire your inventiveness and ability.
As a humble “civilian”, I just plug an inverter into 12v/10A (lighter) and plug a DJI charger into it. Admittedly, this limits output to 120W but it sure is simpler and less expensive!

“A” for effort to you!
Thank you sir. This system was driven by the need to quick charge 3 batteries simultaneously on long days when we fly back-to-back all day long. It's also scaleable to any drone battery, which is important since I sometimes shoot all day with the Inspire 1 (film) or all day with the P4P (mapping).

D
 
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Very cool set up. Is there anything in the series that will regulate the output to a constant voltage/amperage? The difficulty with car charging (that I've run across) is the variances can make the battery life shorter versus wall charging.
Do you have any evidence of a DJI smart battery usable life being shortened or it might have suffered any other performance degradation that can be attributed to a car charger?

I suspect you don't. Simply because the charge controller that is built into the battery provides additional regulation and will discontinue the charge in response to numerous prescribed fault conditions including voltage being outside tolerance. Constant current is not a requirement. Current demand will vary during the charge cycle however should the supply be current limited all that might happen is the pack will take longer to charge.
 
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Do you have any evidence of a DJI smart battery usable life being shortened or it might have suffered any other performance degradation that can be attributed to a car charger?
I have not. All I can do is spec. out a robust boost converter well within the standards required for charging. According to my research, a good charger has < 3% voltage ripple. My system has < .03% voltage ripple. So, as you can see, I'm VERY well within tolerances.



I suspect you don't.
I just put the thing together yesterday. It's going to take time to see. I can tell you that I used the batteries today that I charged last night, and they worked flawlessly.



Simply because the charge controller that is built into the battery provides additional regulation and will discontinue the charge in response to numerous prescribed fault conditions including voltage being outside tolerance.
Sure. But the beauty of these boost controllers is they net CV (Constant Voltage) and CC (Constant Current) data during the charging process. Nominal voltage drop is normal for any charger. So when not charging, voltage is constant @ 17.5 VDC. But when charging, current remains constant (6 amps - 105 watts) and voltage drops to about 16.3 VDC. As the batteries charge, voltage increases. Right around 28 minutes all 3 converters reached CV or "Constant Voltage" (17.5 VDC). It all seems to chug along quite nicely.

Check this screen capture right @ 27 minutes. You can see that 2 of the batteries have reached 17.5 VDC (CV mode) while the third is still in CC mode. 1 minute later, the third battery joined the other 3.

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Within a minute the third battery went into CV mode.



Constant current is not a requirement. Current demand will vary during the charge cycle however should the supply be current limited all that might happen is the pack will take longer to charge.
Max current is user-defineable. For the test in the above photo, I set max current @ 6 Amps (105 watts). Around 27 minutes the demand for current trickled off, which allows the voltage to recover to a full 17.5 VDC. So basically throughout half the charge process, voltage was @ 17.5 VDC. I assume all this is based on the changing resistance of the battery. As far as I can tell, it's flawless. Time will tell.

D
 
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Very cool set up. Is there anything in the series that will regulate the output to a constant voltage/amperage? The difficulty with car charging (that I've run across) is the variances can make the battery life shorter versus wall charging.
During the first half of the charging cycle, when current demand is high, the boost converter is in CC mode or "Constant Current" mode. During this time, voltage drops to about 16.3 VDC, and slowly climbs to 17.5 VDC over a 28 minute period. For the second half of the charge cycle (CV mode), current continues to trickle down to .4 amps, at which point the charging process ends around 56 minutes.

D
 
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I have not. All I can do is spec. out a robust boost converter well within the standards required for charging. According to my research, a good charger has < 3% voltage ripple. My system has < .03% voltage ripple. So, as you can see, I'm VERY well within tolerances.





I just put the thing together yesterday. It's going to take time to see. I can tell you that I used the batteries today that I charged last night, and they worked flawlessly.





Sure. But the beauty of these boost controllers is they net CV (Constant Voltage) and CC (Constant Current) data during the charging process. Nominal voltage drop is normal for any charger. So when not charging, voltage is constant @ 17.5 VDC. But when charging, current remains constant (6 amps - 105 watts) and voltage drops to about 16.3 VDC. As the batteries charge, voltage increases. Right around 28 minutes all 3 converters reached CV or "Constant Voltage" (17.5 VDC). It all seems to chug along quite nicely.

Check this screen capture right @ 27 minutes. You can see that 2 of the batteries have reached 17.5 VDC (CV mode) while the third is still in CC mode. 1 minute later, the third battery joined the other 3.

View attachment 110402

Within a minute the third battery went into CV mode.





Max current is user-defineable. For the test in the above photo, I set max current @ 6 Amps (105 watts). Around 27 minutes the demand for current trickled off, which allows the voltage to recover to a full 17.5 VDC. So basically throughout half the charge process, voltage was @ 17.5 VDC. I assume all this is based on the changing resistance of the battery. As far as I can tell, it's flawless. Time will tell.

D
Might be crossed wires here HD. I was reponding directly to propsontop. I see no evidence for his claim so was curious if it was based on fact.

Your setup looks great to me and I suspect will work very well- better than the DJI dedicated solution. The only concern I had was with the limitation of a cranking battery to charge multiple packs and still crank the engine over but you confirmed that in the first 5 minutes.

We should expect very good ripple rejection given the active regulation in the converters.

The change in current draw is standard for any LiPO charging regime- it will go from Constant current to constant voltage later in the charge cycle. Once you get to a certain point in the current setting it will be irrelevant as the charge controller limits the Max rate if charge.
 
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No guys, I don't have any DJI smart battery data on the subject. My experience was with 5500mah 22.8V 6S batteries and a field charger, not with the DJI smart battery. That's why I asked the question. I had no referent to the DJI smart system's capability in regards to a variable output vs. a fixed output, so I wanted to understand if it would damage the battery. You have very thoroughly answered my question. My apologies for any confusion as to why I was asking.
 
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Hey doods!

I finally got around to taking some temperature readings today. It's pretty chilly outside, and therefore chilly in the garage. Before plugging in the charging system, I took temperature readings of all the components and the bread board. Temps were consistently 61° or 62°. So then I plugged everything in and initiated a fairly robust charge of my P4P @ 6.8 amps or 105 watts. I let the thing run for a minute and then took temperature readings. The hottest item was the heatsink, which never got above 84°. So...needless to say this charger runs very cool.

DSC03346.JPG


Less heat = more efficiency.

D
 
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Hey any update for this? Any interest in just making me a parallel charging board for my icharger 306b?
This charger won't work on any DJI offerings post Phantom 1, as it requires a Balance connection. I have several balance chargers and if you don't connect the balance wire, they net an error and won't charge.

D
 
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This charger won't work on any DJI offerings post Phantom 1, as it requires a Balance connection. I have several balance chargers and if you don't connect the balance wire, they net an error and won't charge.

D
Interesting. I have an older lipo without a balance connection somewhere that I’ll have to experiment with. Never tried to charge with this charger, always used a triton which doesn’t care about the balance port. ( I’m actually surprised it never blew up, always placed in a charger bag) It’s a 3s I just used to power a 12 volt bicycle light for night trail riding... it’s stored at 1/2 charge...

Anyway i digress lol, are you selling your system or plans yet? I purchased the DJI DC charger, which is pricey for a 1 battery charger... $80 but it does work when I have lots of jobs and I run through my 3 batteries.
 
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Interesting. I have an older lipo without a balance connection somewhere that I’ll have to experiment with. Never tried to charge with this charger, always used a triton which doesn’t care about the balance port.
I have a couple balance chargers and both demand a balance port connection. Neither are a Triton.



Anyway i digress lol, are you selling your system or plans yet?
No, not yet. I'm still beta testing this system. It's been used on only one job site, which hardly qualifies as full field testing. I'm really interested in its hot weather performance, as this system generates almost no heat, which leads me to believe it will do well in hot weather conditions. Once I'm convinced it works, I'll probably create a component list for those interested.


I purchased the DJI DC charger, which is pricey for a 1 battery charger... $80 but it does work when I have lots of jobs and I run through my 3 batteries.
If it's the cigarette lighter model, those aren't nearly fast enough for my needs. With my system I can charge 3 batteries simultaneously at full bore. And by "full bore," I mean the battery's capabilities, which far exceeds DJI offerings. For example, the Inspire 1 battery can sink 180 watts. The DJI OEM charger sources only 100 watts. One can purchase a 180 watt DJI quick charger, but that's an AC-only device and charges only one battery at a time. With my system, I can charge 3 Inspire 1 batteries simultaneously @ 180 watts each. BUT...if I have more time, I can back the charger down to a 100 watts, which is easier on the batteries I'm told. It's all about options and efficiency....<:^)

D
 
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Yeah I have the DJI car charger... charges 1 battery at a time. That plus my 3 batteries let me do 5 jobs in one day though. Luckily I had to drive some distance in between... I’m just starting in the real estate aerial business and hopefully eventually I’ll have more jobs and will need a better charger or lots more batteries.

I read somewhere the smart internal wiring on the DJI batteries limit the input charge to 1 C or something like that... so it’s based on an average charge of 1 hour (approximately) anyway right? If you try to up the input charge to say 2C will the battery wiring allow it?

Not an EE but I started down that path in college but that was back in early 90’s lol.

Anyway, interesting stuff...
 
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Yeah I have the DJI car charger... charges 1 battery at a time. That plus my 3 batteries let me do 5 jobs in one day though.
Most of my jobs are 5-8 batteries, with a decent percentage using more than a dozen. Between my partner and I we have 9 P4P batteries. We figured out that we only need 7 batteries to continuously fly and charge all day. But that's with a single drone. For larger jobs we deploy 2 drones, which will require more batteries or more chargers. Presently we can charge 6 batteries via his DC->AC converter and our 2 fast chargers (3 batteries each charger). And now we have my 3-bay charger for a total of 9 chargers spread out over 2 vehicles. Aside from the obvious advantages of deploying two drones simultaneously, the not-so-obvious advantage is our "wind window" is cut in half. Often times we only have a 2 or 3 hour window. If we have a 4 or 5 hour job, we can keep within that window with two drones. But I digress... My point is that my charging needs far exceed a single, cigarette lighter charger....<;^)



Luckily I had to drive some distance in between...
I don't often have 2 jobs in one day, but when I do, I've been lucky that I use different birds, so batteries aren't an issue. And the time I spend driving between jobs is pretty minimal...10 minutes or so.



I’m just starting in the real estate aerial business and hopefully eventually I’ll have more jobs and will need a better charger or lots more batteries.
Ahhh...good luck. I found real estate in this area to be a bust. There's SOME money in commercial real estate (just did a shoot last week), but the residential market was a bust for me.



I read somewhere the smart internal wiring on the DJI batteries limit the input charge to 1 C or something like that... so it’s based on an average charge of 1 hour (approximately) anyway right? If you try to up the input charge to say 2C will the battery wiring allow it?
I don't know. I haven't tried to push that much current, and I'll tell you why. Most DJI chargers charge @ .5C or .6C. DJI makes a 180watt charger for the Inspire 1, which I assume is 1C. The P4P batteries can sink the same wattage, but there are no chargers on the market that push that much current. I think 100 watts is the highest you can get. And I believe the OEM charger is a mere 60 watts. Cigarette lighter chargers are no more than 60 watts, I believe. All that said, I haven't tried for force feed a bunch of current down the gullet of these expensive batteries. 180 watts is as high as I'll go with the P4P and Inspire 1 batteries. I haven't tried charging my Mavic Batteries yet, but I'm sure my charger will work just fine on those, too.




Not an EE but I started down that path in college but that was back in early 90’s lol.

Anyway, interesting stuff...
I have zero EE classes under my belt. So you got me beat....<;^)

Good luck.

D
 
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Wow thanks for the in-depth response. I appreciate it, people like you are why I joined this forum!!

I started in real estate just to get my business up and running. I hope to diversify later so i can retire from my police job lol. However, for now I actually like getting to check out all the listings and houses. Most jobs are 1/2 hour, then I’m off to next one so it’s not boring (yet). I seldom deplete a battery fully on a job, which reduces its re-charge time.

Well if you decide to sell plans or complete kits hit me up.

Thanks
 

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