All my batteries fried

[RayOZ]

I wouldn't count on bad solder just yet. Manual says LED2 blink twice per second = over current detected.
If it's a bad solder, I dont think it'll be able to detect all 3 cells' voltages, and since they are connected in series, it wouldn't have read 12.4V


if you have the adapter, you can turn the battery into a power bank. make use of the energy.
or remove prop, and run the motors to drain the power quicker.

 

[AerialViewSolutions]

Alright guys I'm back to report... My 2 batteries that were giving me the double blink were discharged and I charged them back up completely with the factory charger. This was before I came to the forums.... After this charge they were still giving me the double blink. Today I came home and put each of them onto my mavic and looked at the battery status. I'll post the voltages below. They're still off and not balanced but I'm not getting any error messages from the mavic now. Maybe the recharge has brought the voltages closer together where it doesn't recognize the fault? I ran the motors for a short time to see if a message would come up and it didn't. Maybe the problem fixed itself. But I'm still nervous about flying high and far!

 

[AerialViewSolutions]

 

[joejaxvic123]

I almost bought that charger. Is the voltage difference not an issue? I believe it is.

 

[AerialViewSolutions]

I almost bought that charger. Is the voltage difference not an issue? I believe it is.

There is definitely an issue here. There has to be some kind of threshold where it says for instance 0.00-0.09 difference is okay but greater than 0.10 is bad. These are just numbers I'm pulling from my head. Thunderdrone says that Fstop makes good products and I've watched Thunderdrones comments here for a while and he knows what he's talking about.

 

[joejaxvic123]

Strange problem. Hopefully there is a solution.

 

[AerialViewSolutions]

Strange problem. Hopefully there is a solution.

I've been researching this problem and it is very common. Seems like all of the batteries that experience this are under 30 charge cycles.

 

[BaNZ]

I was just about to buy this charger. I think fstop are also on the forum so perhaps they want to comment on this issue.

 

[Plawa]

For the record I have been using this hub for a year, never had any issues.. How much "charging" does it actually do? I wouldn't be surprised if the actual charging logic was still with the OEM charger/battery controller and the hub only acts as a switch between each battery and the OEM charger...

 

[RayOZ]

@AerialViewSolutions Do the charge cycle of few more times with the OEM charger and see if the voltage diff reduces.
Did you leave the batteries on the charger long after they've fully charged?

 

[fstop.labs]

Sorry to see that you have this problem! Let us go over these batteries

There are a few main things regarding lithium batteries.
1. SoC - State of charge, that is the % that you usually see, 50% = battery is at half capacity, it does not mean you can get the rated energy out of it.
2. CAC - Computed amp capacity, how much charge there are in the actual battery, this is an estimate!
3. SoH - State of health, how healthy it is, if your rated capacity is 1000mah, and you can only get 900mah out of it, your battery health is not at 100%

SoC is usually an absolute mapping between voltage and percentile, 4.2 (4.35 in this case) = 100%, 3.2 = 0%. You usually want to keep batteries between 90-10%
CAC is an integrated value - meaning it is calculated by taking the integral of current and time. Sort of like a faucet meter, you are flowing at 1 gallons per minute and you let it flow for 10 minutes, you end up with 10 gallons.

In the real world there is drift - the flow meter not very accurate. After 10 cycles it may be off by 10 gallons. There is where the SoC comes in, that is absolute, but noisy (due to cell polarization, hysteresis etc etc). These two values need to be fused together to get an accurate estimation of how much energy is left in the battery and the health of the battery.

There's more to it, but will keep it simple! how does it roll into this case?

1. Lithium batteries are complex so DJI employes a BMS to manage it, specially two TI chips (Battery Fuel (Gas) Gauge | Overview | Battery Management | Power Management | TI.com) the TI chips are configured for this battery and there is a 3rd chip on board, the MCU, to manage the communication between the TI chips (SPI) to DJI's protocall.

2. During charge, the charger applies a voltage V across the terminals, and the internals manage the current, voltage, balancing etc etc. DJI chargers, computer laptop chargers, even Tesla's supercharger all operate as a DC bias across the terminals of the battery. It is up to the TI chips to control the charge.

3. During charge, usually DJI does 3.6-4.0 volts, the balance resistors or the balance circuit activates, this is meant to balance each of the cells of the battery - the cells of the battery should vary no more than 0.05V depending on chemistry. The balance resistors are 1/2w (or 1/4) toggled by the TI chip via mosfets. This means if the cells are really out of balance, then it will have a hard time balancing the battery.

4. Smart BMS's (Ex: Tesla's) calculate the CAC per cell and factor that in during balance/charge etc. DJI just throws an error if these cells are not balanced.

5. What you can try to do to fix this issue is open the battery up, and manually balance each of the cells. These cells get out of balance between for various reasons.

6. Charge the battery up until it cannot be charged, open the it up and charge the remaining cells that are low. Then do a full charge, discharge cycle. If it still doesn't work then that cell's may really be messed up. (It means the CAC of that cell is low).

This charger is not the blue parallel charger and if opened up, the internals multiplex a DJI charger - it takes the power/signals of the DJI charger and reroutes it to the batteries around so in theory you are still using the original DJI charger. The first Mavic Pro I got had this problem with the the battery, 2 cycles in

 

[RayOZ]

Opening a fully charged battery? Shouldn't there be a caveat? Unless you have some experience with electronics, maybe don't attempt this?

 

[fstop.labs]

Opening a fully charged battery? Shouldn't there be a caveat? Unless you have some experience with electronics, maybe don't attempt this?

True! Just dont puncture any cells!

 

[kidroc]

The charger is built in the batteries that is just a hub that allows a little more charging current so you can charge a little faster i have used that same one one almost a year.. did you happen to just pull the batts out of the mavic without pressing the off/on sequence by chance? I have had great luck upgrading the batts on the pc with Asst2 and have always been able to fix that flashing problem.

 

[BJR981S]

DJI Smart Batteries will report a battery error if the individual cell voltage differences are greater than a predetermined limit. I am not exactly sure what the limit is but its only small. DJI do this as they suspect that the low cell is damaged and the battery discarded.

They will refuse to balance under these condition. The only way I have seen these recovered is to completely discharge the battery down till it no longer switches on and charge with the Original DJI charger.

Never use a third party charger on DJI batteries.

 

[Roc Rat]

Few of the rip off copy cat companies have the same level of quality control that the manufacturer has. On a kinda related note, if you ever have a need for a small generator for camping, etc. stick with Honda, Yamaha or any of the major names. Places like Harbor Freight sell cheap units that have a very radical "sign" wave (not sure that sign is spelled right) output which can fry delicate electronics like laptops. That's one of the reasons they can sell so much cheaper...they cut corners.

 

[VortexSpin]

Thats the best way as long as it doesnt drop below 10%.

Wondering then here. On screen message from the DJIGO4 app telling me to discharge battery to 5 percent? What’s up with that then?

 

[BJR981S]

Few of the rip off copy cat companies have the same level of quality control that the manufacturer has. On a kinda related note, if you ever have a need for a small generator for camping, etc. stick with Honda, Yamaha or any of the major names. Places like Harbor Freight sell cheap units that have a very radical "sign" wave (not sure that sign is spelled right) output which can fry delicate electronics like laptops. That's one of the reasons they can sell so much cheaper...they cut corners.

Indeed you are correct. It is spelt Sine as in Sinusoidal. and comes from trigonometry as in Sine, CoSine and Tan.

I don't know what the DJI chargers do as far as battery resting in the charge process, but a good battery charger will rest the charge for about 300ms.

I think what people also miss is that a constant current charge plus a journey voltage test is required and must be always below the defined charge C rating of the battery. The Charge current must be lowered as the battery charges.

The charge voltage must be appropriate for the current supply and taper off at the end of the charge cycle otherwise the battery will not balance correctly. There is no time to allow the high cells to discharge through the balance cct if you continue to pump a set current start to finish.

If the battery is not allowed to balance the overall voltage of the battery will still show charge is required but the high cell will be overcharged and damaged.

Also without resting the battery there is no way to determine what the battery voltage actually is, as a voltmeter will read the charge voltage not the battery voltage. You have to remove the charge voltage to read the battery voltage which will be lower.

If the clone charger charges your batteries faster than the standard charger. Be assured that it is exceeding the C rating and damaging the batteries.

I have seen people destroy RC transmitters by using power adapters that are rated above the OEM value. Like a 240 / 110V AC to 12V 50ma adapter spec and people using a 12V 2A adapter. Thinking that the 12 V is all they need to worry about.

What they don't realise its the charge current is limited to 50ma in the former and the voltage will sag below 12V if an attempt to drag greater than 50ma is possible. a 12V2A adapter will supply up to 2 amps before the voltage will sag.

Anyone that uses an alternate to the vendors power charger is taking a risk that could destroy your batteries.

Cheers Brian

Also be warned about DJI smart batteries. They can not be left like normal Lipos at storage charge. They need to be charged then discharged down to storage charge every 3 months at least.

The voltage monitor smart cct is constantly drawing a very low current but it is continual.

And do not trust the indicator lights on a Mavic battery. They will self discharge down to 2 lights or 2 lights plus 1 flashing when tested with the button. But if you put them on the charger they will go down to a single flashing charge light. i.e. the lights lie.

 

[BJR981S]

View attachment 36215 Wondering then here. On screen message from the DJIGO4 app telling me to discharge battery to 5 percent? What’s up with that then?

The battery is damaged. How the damage was done is not detectable. Discharging down to 5% or below reduces the risk of it catching fire.

Do not confuse this with the requirement to regularly (20 flights or so), discharge down till the battery will not switch on and then recharge. This is to calibrate the % battery left value as the battery deteriorates with age.

If you do not do this then you risk an in-flight failure with a flat battery as the calibration and % left gets more and more inaccurate every flight.


Cheers

 

[Pointbob]

only 6 mos warranty on batteries by Dji.

Sucks since most peeps assume the battery is smae warranty as the drone...1 year....but NOOOOOOOOOOOOOOOOOOOOOO....