M2P Battery charger/cycler and battery management

[rmatile]

Is there a M2P battery charger/cycler out there?
When I fly, I try to be ready for a complete flying session, with the plan of depleting the 4 packs I have. Invariably I don't/can't fly the 4 packs totally out....
I'd love to have a charger and cycler that could take a battery, and discharge (or charge) it to a storage level.
Its a bit of a pain to bring everything home...and sometimes firing up everything, and get 4 packs to the storage charge (65% or so).
I have found a charger that will CHARGE to a storage level, but not DISCHARGE to a storage level...and that particular charger I don't think is made well, due to some inconsistencies when using it.
I'd love to hear if there is a charger/cycler out there of good quality that someone can recommend.
I would rather bring the batteries to a storage charge immediately, than wait for the auto-discharge to kick in...I just think its better long term for the battery.
Hoping you all have a great day.
thanks in advance
Ralph Matile

 

[msinger]

The IRCtek Battery Discharger can discharge a Mavic 2 battery down to 60%. Discharging batteries is of course not a fast process, so you'll likely need to order a few of these if speed is important.

 

[parkgt]

Always interesting that percentages are listed. Does no one know the optimum storage voltage for these HV Lipos?

 

[WithTheBirds]

Always interesting that percentages are listed. Does no one know the optimum storage voltage for these HV Lipos?

3.85v/cell is a good number. It is irrelevant to most here as we tend to rely on the indicated SOC level and we aren’t needing to work with voltages as we would with bare lipo packs.

 

[rmatile]

Its funny that you mention that....I've flown rc planes with nicads (yep..I'm that old), and even used nimh for the trans (and some flying) in the old days.....
When I changed over from brushed to brushless motors, I changed my fleet of planes all to the lipos.
I've always used around the 3.8v per cell as my storage number for lipos....I usually set my LVC on the ESC to the 3.7-3.8v/cell range.

Its just seems that the mainstream comments are directed at the POC nowadays, at least for the drones....I still prefer to use the voltage though,...and I really am glad the total and individual cell voltage is displayed.

 

[johnmeyer]

Always interesting that percentages are listed. Does no one know the optimum storage voltage for these HV Lipos?

Yes, somewhere between 3.82 and 3.85 volts seems to be the optimum voltage. Scroll down this "Battery University" page which describes storage practices for various battery chemistries and you'll see what voltages are recommended.

BU-702: How to Store Batteries – Battery University

Learn about storage temperatures and state-of-charge conditions

batteryuniversity.com

Note, however, that LiON batteries have a fairly narrow range of voltages that fall into the "storage" category, so make sure you are using a well-calibrated digital voltmeter or multimeter to make your mesaurements.

 

[rmatile]

Looks like I should re-visit the recommended storage voltage for these packs......thanks for the link johnmeyer

 

[rmatile]

OK...I was curious, so I discharged the packs for both my Phantom 3 Pro, and my M2P.
I did this by flying in my garage to discharge them...just a couple of feet off the ground, let them cool off and I documented the readings....now I'm going to let them sit for 10 days...or so, and look at them again....
Individual cells are between 3.0V and 3.4V....
I have one battery I'll watch the balance...(Phantom 3 Pro battery 3)
I don't quite understand how the % capacity number that DJI displays is calculated?...what its based on, or what it is supposed to mean?
Just wondering....

 

[WithTheBirds]

OK...I was curious, so I discharged the packs for both my Phantom 3 Pro, and my M2P.
I did this by flying in my garage to discharge them...just a couple of feet off the ground, let them cool off and I documented the readings....now I'm going to let them sit for 10 days...or so, and look at them again....
Individual cells are between 3.0V and 3.4V....
I have one battery I'll watch the balance...(Phantom 3 Pro battery 3)
I don't quite understand how the % capacity number that DJI displays is calculated?...what its based on, or what it is supposed to mean?
Just wondering....View attachment 75762

This might prove to be an interesting exercise however it is a waste of time- at least to the extent you might think the observed voltages prove more useful than the depicted %full (remaining state of charge (RSOC)). The resting voltages of LiPO cells prove close to useless in providing a reliable indication of pack capacity when powering a load. This is particularly true when the connected loads require higher current than a fraction of the C rating of the cells.

% capacity reported to the flight controller by the battery (parameter RSOC) = remaining capacity (RM)/full charge capacity (FCC). You might get to performing a very crude manual calculation of the remaining % wth a very accurate volt meter however it will be close to useless in practice.

The fuel gauging algorithm in our DJI batteries employs cell specific modelling- rate of discharge and temperature along with measured internal resistance and other factors all inform the algorithm to provide accurate estimates of usable capacity, time to empty (as depicted in the GO app) and remaining % (to within 1% accuracy based on the SOC manufacturers claimed specifications).

 

[rmatile]

Thanks "With the birds"
I use the cell voltage for monitoring and determining the best storage.....and also when flying, for avoiding the lower "safe" voltage limits.
Other than that...That's about it.
As far as RSOC, as I've never seen the algorithm, and I probably wouldn't understand it anyway! I use it more for "guidance" but not like a nuts on fuel gauge.

Also, per the attached M2P manual excerpt, I'm not sure of the reference to --discharge to the "maximum battery level" ---(which I'm not clear on THAT particular definition), and is it aligned with % capacity?

Also
They seem to refer to discharging to 60% maximum battery level.....in the auto discharge mode.
So where does that leave the individual cell voltage for storage?
Maybe the answer is elsewhere in the manual...but I didn't see it.

 

[raylo32]

I have struggled with this question a bit for the Mavic2 and my e-bike battery packs. My conclusion is that any battery type that comes with onboard smart BMS doesn't technically require using a discharger to get to storage mode as they will do this themselves over time. Hence no one seems to offer a one device charge/discharge/store solution like we normally see in the "dumb" RC LiPo world.

But I still feel better not leaving an unflown battery pack fully charged until its BMS bleeds off the charge, they say in about 10 days. This discharger is just the ticket. It works very fast and is very flexible as to discharge termination voltage settings. A little pricey but it works great and fast. I usually run it at between 5 and 10 amps with the Mavic2 batteries which is well below their ratings and discharge rates in flight.

GForce GD250 35 Amp LiPo Battery Discharger (35A/250W) [GFC0317]

The GForce GD250 35 Amp LiPo Discharger is a high current discharger capable of discharging all hobby batteries! Maximum discharge capacity of 35 A /... GFC0317

www.amainhobbies.com

 

[rmatile]

Thanks Raylo32,
I guess that's my bottom line...after a flying session, it seems like I always have a pack or two below storage voltage, or above storage that needs attention.

And I know I won't be flying for a week or so....so to protect battery life, I was looking for a device that would charge to a storage charge, or discharge to a storage charge....without waiting the 10 days.
If they had the option of changing the days, from 1-10, that would "mostly" satisfy my concerns.
I think my P3P has the option from starting a discharge from 3-10 days......the M2P does not.
After an automatic M2P discharge, I have no idea (yet) what the voltage ends up at in storage mode.
If the timing works out for me...I'm going to check it tho.

 

[raylo32]

There is a charger that will charge to ~storage. The RC Geeks unit has a switch that selects 100% charge or 65% charge. The 65% is good for automatically bringing up flown batteries to a consistent voltage. But it doesn't have the discharge function. It still puzzles me why no one sells a single device that will do it all like a regular RC LiPo charger.

Thanks Raylo32,
I guess that's my bottom line...after a flying session, it seems like I always have a pack or two below storage voltage, or above storage that needs attention.

And I know I won't be flying for a week or so....so to protect battery life, I was looking for a device that would charge to a storage charge, or discharge to a storage charge....without waiting the 10 days.
If they had the option of changing the days, from 1-10, that would "mostly" satisfy my concerns.
I think my P3P has the option from starting a discharge from 3-10 days......the M2P does not.
After an automatic M2P discharge, I have no idea (yet) what the voltage ends up at in storage mode.
If the timing works out for me...I'm going to check it tho.

 

[WithTheBirds]

Thanks "With the birds"
I use the cell voltage for monitoring and determining the best storage.....and also when flying, for avoiding the lower "safe" voltage limits.
Other than that...That's about it.
As far as RSOC, as I've never seen the algorithm, and I probably wouldn't understand it anyway! I use it more for "guidance" but not like a nuts on fuel gauge.

Also, per the attached M2P manual excerpt, I'm not sure of the reference to --discharge to the "maximum battery level" ---(which I'm not clear on THAT particular definition), and is it aligned with % capacity?

Also
They seem to refer to discharging to 60% maximum battery level.....in the auto discharge mode.
So where does that leave the individual cell voltage for storage?
Maybe the answer is elsewhere in the manual...but I didn't see it.

To my knowledge there is nowhere in the battery documentation that talks about minimum or storage voltage levels.

Yes- auto discharge does seem to atop at around 60%. We might presume 60% ti be a compromise considering safety and pack life while providing a margin to allow for self discharge and the SOC power consumption to try and avoid the cells reaching critical low voltage.

Perhaps you might like to familiarise yourself with the tech employed in our batteries. Texas Instruments has provided some great explanations- simply search impedance track and fuel gauging. My guess is you won't be worrying about tracking voltages then. The current BMS and SOC combo's can do a better job more reliably than we ever might.

 

[rmatile]

There is a charger that will charge to ~storage. The RC Geeks unit has a switch that selects 100% charge or 65% charge. The 65% is good for automatically bringing up flown batteries to a consistent voltage. But it doesn't have the discharge function. It still puzzles me why no one sells a single device that will do it all like a regular RC LiPo charger.

I have that charger....and I don't think its operating properly....takes hours to charge on one of the ports.....and there was a couple of other things as I recall..that I couldn't pin down, because at the time I had just expected it to work right.
I haven't needed to use it much, so I've avoided it....
I'll use it again....and document what I find...at least for myself.

 

[rmatile]

To my knowledge there is nowhere in the battery documentation that talks about minimum or storage voltage levels.

Yes- auto discharge does seem to atop at around 60%. We might presume 60% ti be a compromise considering safety and pack life while providing a margin to allow for self discharge and the SOC power consumption to try and avoid the cells reaching critical low voltage.

Perhaps you might like to familiarise yourself with the tech employed in our batteries. Texas Instruments has provided some great explanations- simply search impedance track and fuel gauging. My guess is you won't be worrying about tracking voltages then. The current BMS and SOC combo's can do a better job more reliably than we ever might.

Thanks...I'm probably splitting hairs....and I know it....when I see that they've allowed us to adjust the P3P to self discharge at our choice (from 3-10 days) but don't have the option in the M2P.....just makes me wonder....and sure...maybe holding at full charge for 10 days doesn't materially effect the batter's life, but again, if i know I'm not going to be using it...why not discharge earlier.....yeah..probably splitting hairs....so I will check out the Texas Instruments info.
thanks

 

[WithTheBirds]

Thanks...I'm probably splitting hairs....and I know it....when I see that they've allowed us to adjust the P3P to self discharge at our choice (from 3-10 days) but don't have the option in the M2P.....just makes me wonder....and sure...maybe holding at full charge for 10 days doesn't materially effect the batter's life, but again, if i know I'm not going to be using it...why not discharge earlier.....yeah..probably splitting hairs....so I will check out the Texas Instruments info.
thanks

Splitting hairs? For what its worth I don't leave a pack that I didn't get to fly sitting in wait of the 10 day auto discharge initiating either. I use the USB charge adaptor to knock the top off it dumping the power into whatever device I have that needs a charge.

And yes- I come from dumb LiPO's and kept more than one spreadsheet in an effort to track performance and try and manage storage. I always had one eye on the voltages also while tracking flight times. Hit LVC in flight and it was all over.

My point is simply that the Texas Instruments battery smarts seem to be very reliable and they do make things a LOT easier. You can trust the %full and time to empty indications.

I have a suspicion also that current LiPO chemistry is more tolerant than when first introduced. How many bare LiPO's might we have got several hundred cycles out of in RC aircraft?

 

[ff22]

There is a charger that will charge to ~storage. The RC Geeks unit has a switch that selects 100% charge or 65% charge. The 65% is good for automatically bringing up flown batteries to a consistent voltage. But it doesn't have the discharge function. It still puzzles me why no one sells a single device that will do it all like a regular RC LiPo charger.

I've recently acquired that version of their charger (after initially getting their charger that only FULLY charged).

But now I just thought of another question: Say I charge to that 65%. What does the INTELLIGENT battery do then? Does it do something over the next ten days. Or does it now lay almost dormant? Or what?

 

[Twon]

Aren’t these batteries “intelligent” so that I don’t have to be?

Do people actually have issues with these batteries if they aren’t cared for in a specific way?

 

[globetrotterdrone]

Aren’t these batteries “intelligent” so that I don’t have to be?

Do people actually have issues with these batteries if they aren’t cared for in a specific way?

I've tried to summarise it before: Battery Auto Discharge Timer

Some people like to handle their intelligent batteries like they had good experience with it for a very long time with other LiPo cells. Nothing wrong with that ...
For me, eventhough I would like to set the auto discharge to something around 3 - 5 days, but can't, will not worry too much with the batteries by following DJI's guidelines.
It is still open to debate whether you achieve a significant higher quality over lifetime or lifetime expectancy in general.

I did however order the 4 times parallel charger and going to adapt my cycle strategy: once depleted after flight I will hook on the batteries to charge to 65 % and then, when I certainly know I will fly again, will bump them up to the rest of 100 %. That however ups the cycles too. So, we'll see, what is going to be better anyway.