Here is a link to MORE DETAILS associated to this thread, but since there was no more questions made to something I mentioned I believe is of sum Importance I made a separate thread to highlight the importance of it!
To all of you that have followed the thread above PLEASE take into consideration the Following:
Guys...after lots of testing I want to share a finding that it is of HUGE importance to those of you considering a DIY Battery Power supply. I have mentioned this before on this thread.. but I am surprised however no more questions were made about it... and I feel there has to be further explanation, and to bring it to this first post for people to notice it and pay as much attention to it as it is deserved, as many people do not take the time to read whole threads or just want to get the "idea" as to what is being exposed. All this before you go and try decide to spend the money on anything over 240W per battery..
The I1 batteries have an overamperage built in protection that limits the intake of power to 10A. What does this mean? it means that if you try to load MORE than 10 AMPS to a single charging terminal leading to a single battery (I.e putting 300watts (12.5amps) at 24V hoping the battery will only "take" what it wants/needs regardless of what is available (which for this battery is NOT the case after 10a) it will trigger an overamperage protection and it puts the battery into a "protection mode" that does NOT allow this higher amperages to reach/charge the battery. I do not know if this is a software driven harware operation, or simply via a "relay" of sorts that activates it. You can verify this state by looking at the LEDS. It would be the second LED from the bottom going up ...and this one would be blinking twice every second followed by a space and repeating the indication over and over until you press the power button to "turn off"/acknowledge the state.
There is a way to "disable" this "safety feature"I found out by turning the battery ON before starting the charge. I believe this is a defficiency on the "brains" of the battery and that it should NOT allow me to do this. I believe what happens is that by turning the battery ON, it's circutry is now ready to allow higher amperage rates to be delivered/discharged to/by BIRD while on flight and as so it disables the overamperage protection to accomplish this.. and since it is not expecting to be charged... at this time. If you do this..... (PLEASE DONT DO IT) the battery will start charging and take in excess of 450Watts (as verified via Watts meter) when connected singularly to a 500watts PS. It does charge it faster.... but at what cost? and how safe? I would not even want to find out what would happen if you do this while connected to a 1200W power supply for a while and you turn on the battery to "try it out".... my suggestion is DONT>>> not even with 500Watts.. as it might definitely burn the battery or even WORSE (this is a big unknown)and not something I will test as I have some ideas as to what the outcome might be...
Anyways... when confronted with this method, The battery then attempts to bring the amperage down to a manageable amperage over several minutes and seems to regulate it down to the 10A threshold... the cells are limited to the charging rate of (240watts at 24v).
I am not comfortable with this approach, as the Internal circuitry IS working overtime to try and regulate the over Amperage.
I made this video that shows this. Notice the beginning voltage. This is coming from the Power supply, as the battery is not yet connected. Once the battery is connected it starts to attempt charging and you see the spike of amperage from zero amps to about 25amps. The battery's voltage is now being displayed. Also notice how the battery takes in excess of 588watts at one point. (over 20amps) before establishing: " WHOAAAHH!!! wait a second... this is WAYY more than I can manage... I DONT WANT IT..." (lol) and shutting the charging off....
Somehow.. (at around 80% of battery capacity) the battery IS able to take in HIGHER AMPERAGES THAN 10AMPS (I tested 20amps only so cannot confirm if this is the case with higher wattage PSU's) and not struggle to regulate it's amperage. It brings the Amperage down to about 260watts and it is happy and all is OK. Near 90% and up, the Battery regulates the amperage to about 25 to 50watts consumption for the rest of the charge until it reaches 100%, hence the reason the Temperatures of the provided DJI power supply goes down (see diagram below) progressively towards the end of charge cycle, as it is only using about 50% of it's rated 100watts that it can provide.
The solution?
Get a power supply that has MULTIPLE charging terminals, preferably of 10Amps or less PER TERMINAL or that you can regulate them down to it... It is ok if you have 1200 WATTS JUST NOT ON A SINGLE TERMINAL unless you connect 5 batteries in parallel everytime you are charging to diminish the amperage Load to the manageable 10Amps. If you have 4 Batteries hooked on parallel onto a single 1200watt PSU there is still about 200 to 240watts of available power and this will be distributed among the batteries.. it is still about 2 amps or so OVER the 10amp each battery can take and this will result on the "relay being triggered". I tested this with my 500watt and 2 batteries.
Have an amperage regulator INLINE for each of the charging terminal leads and bring the wattage down to the 10amp/240watts the battery can handle. You might want to have something else drawing excess Amperage hooked on while charging.. .this might allow you to not have to charge batteries at once on a 1200W PSU if you are using 200watts on something else.
In my suggested Battery charger I have 3 Batteries charging to a 500watts multiple terminal PSU, however EACH terminal IS 20amps and not 10, but putting 3 batteries to it leaves the Power supply short of wattage. However, and because the batteries do not demand full 240watts to 260watts the entire time, the Power supply does not suffer.. A more suitable power supply though would be a 750W to 800w for 3 batteries...
The remote controllers draw less than 50 watts and they do not seem to have brains like the battery does... so they do take 20amps and charge... but I do not like to put soo much into them so I just use the provided DJI power supply to charge these.
As good measure and just to make sure...(not that the temperatures have raised to the alarming rates of the DJI power supply) I am using one of the Power supply leads and added yet a second fan (the Meind has a built in one) and have it blowing air right at the side of it.
I feel like this might be one reason that DJI's power Supply is only 100watts... (though it is still underpowered), If they do not change the way that the battery currently charges and can only take up to 10amps (as it is now)... and if they come out with a new Power supply... I see the cheapest avenue they have would be to just make a power supply in the range of 250W to 300watts... (this would allow to charge the remote controller and battery at once) and still not exceed the 10amp ceiling. If they come out with a larger wattage Power supply, then it would mean to me that a firmware update to the battery would be due or that the PSU has multiple leads to more batteries or in the case of a single terminal that they have added "brains" on the power supply that progressively "ramp up" the amperage over the charge cycle.
Nice warning there Genettico. I am not sure how many people are familiar with the 'C' rating system, when it comes to charging and discharging Lipo packs. Most lipo packs are designed to be safely charged at 1C. To work out 1C, you divide the mAh capacity of the battery by 1000. in the case of a TB47 that is 4500/1000 = 4.5A. in the case of a TB48, that is 5700/1000 = 5.7A
The stock DJI psu outputs 26.3V at 3.83A. Using the formula P=VI we see that 26.3 x 3.83 =100.7W output.
As we see, the DJI psu is only rated for 3.83A , so we can calculate the C rating for a TB47: ( 3.83/4.5 ) X 100 = C 0.85
For a TB48 we have even more headroom C rating for a TB48: ( 3.83/5.7 ) X 100 = C 0.67
Now DJI are going to release a 180W psu. Now assuming the voltage output is the same we can work out the max current using the formula I=P/V I=180/26.3 =6.84A
Now we can re calculate the C ratings C rating for a TB47: ( 6.84/4.5 ) X 100 = C 1.52
C rating for a TB48: ( 6.84/5.7 ) X 100 = C 1.2
So you see from these figures that C1.52 is the maximum charge rating that DJI are advocating for the TB47. C2 charging rates and beyond (C4, C5) are used frequently in some RC circles, but I really would not recommend that. The amount of charge cycles will be seriously impacted as you increase the C rating and if you push it too far, you will puff up and destroy the pack. One last thing to consider is that our Inspire batteries are not standard 6S cells (they wouldn't be would they? ) They are actually a type of hybrid consisting of 12 individual cells in a serial, parallel arrangement, so there is really no way to know how they will behave with higher charging rates.
If you are going to experiment with charge rates above 1.52C, I would do so with caution and care.
Thanks again Genettico for the great work and the timely warning.
im sure they will re-stock..l but if not im sure a search would lead to some more.. They were 11 available when I checked last..I guess people must have watched my post about them.. Lol! .if someone is interested ....I bought a third one that dont use.. Brand new... and would be willing to part with it.
JUST CHECKED again..l seems they will be back in stock on april 24th.
pops52 Posted at 2015-4-22 00:18
Well written, understandable, and not condescending or belittling. Nicely done GENETTICO!! Look for ...
fuk off pops, always gotta throw a jab out there, don't you.
Genettico, any lipo will take as much as you give it, (not sure if you fly regular rc planes and helis).
I stated over a moth ago that these packs can take 10a, (which is more than double DJI's solution).
That should cut the charge time in half as promised last month.
I'm glad you took the ball and ran with it, your tests prove my theories.
Great job sharing info with the others, (I know it's time consuming).
As stated earlier, I will be using a 1000w supply to charge 4 packs and 2 radios at once.
(that will leave the supply 200w head room so it isn't stressed like the dji 100w)
All this makes sense. You need to get a good charger like Hyperion Duo 720i or I charger to get the job done. You can limit the Amperage from the setup menu prior to charging. PSU is doesn't matter but min 550W is recommended.
Also, I am not sure how much Max C charge the battery can handle. It would be a good idea to keep it 1C charge ( 5.8Amp) or 2C max (11.6Amp) by powered up the battery first otherwise as it is mentioned it will go into overload protection....
Could you leave a link to the charger that you will be using please. Not very good with all the numbers being through around, just want to get the bird up and flying as quick as possible.
Awesome feedback and very valuable information.. Thank you for s ...
Genettico, Thanks you taking the time to try and explain to the electrically handed capped here on the form. I am one of those people, if you know of a better charging system and have a link I would appreciate it! Hate waiting the hour and a half per battery.
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