Inspire 1 battery mod: never ending crusade ...

[Dobmatt]

Since day one it was obvious that Inspire 1 flight time is way too short for serious filmmaking. With TB47 battery and X5 camera payload Inspire could stay airborne for 10-11 minutes, perhaps 15-16 minutes with beefier TB48 battery. Things get even worst with arrival of excellent, but chubby X5R camera ... Sometime between 2015 and 2016 damoncooper pioneered - with heroic persistence and efforts, but successfully - the concept of employing hard wired auxiliary batteries to support weak TB cartridges. He reached solid 25 minutes of flight time with available LiHV packs of certain capacity and discharge rate. Within several months the thread he created on this forum (Battery Mod Info) ballooned to a record 100 pages long behemoth. Unfortunately the main topic and conclusive/valuable information get quickly buried deep under layers and layers of repetitive discussions carried by others. Damoncooper is a legend, gone fishing long ago ...

Meantime the scenario changed drastically, but the main goal remains the same: how to keep old Inspire 1 alive and kicking, having TB47/48 batteries available no more? There's a few ways to do it. By far none, however, is able to bypass the necessary involvement of original "smart" circuitry TB batteries are equipped with. Therefore for now we are at the mercy of these boards and battery tops, recycled from old exhausted ones. Moreover, almost all solutions are of DIY kind, requiring top notch skills. Here's the list of options and alternative solutions for beginning of 2021:

1. Damoncooper way. For those of us lucky enough to have relatively healthy TB47/48 batteries, reinforcing them with hardwired generic packs is still a valid way. The thread mentioned above contains vast and detailed info how to, mostly within first 25 pages.
2. HeliEngadin way. This is easy, assuming the availability of old battery. The company is re-cycling the circuitry and all hardware, replacing depleted cells with new ones. The price seems to be right, but you must ship retired battery to Switzerland.
3. TB47/48S battery cannibalizing. This is the most elegant, but rather desperate way. These batteries are used to power DJI M600 drone and are still available. The pack and housing is identical, but the battery top must be replaced. This involves re-soldering main leads, replacing balancing harness and temp probe, finally swapping data wiring configuration. Tasks not easy for weekend warriors, but doable.

HeliEngadin team is among first to employ the concept of replacing exhausted cells. The exact same replacement cells can be sourced from Chinese merchants, most likely on Aliexpress. The shipment cost to NA, however, is almost killing the whole idea. On the other hand, re-soldering and re-assembling is a mission next to impossible for unskilled person ... Meanwhile some other, equally brave (mad?) nerds are trying to solder different cells of bigger capacity. Cruzroy (

) is another batt modder and tireless crusader who unknowingly tried to replicate damon's approach with rather disappointing results, but recently tested custom China assembled packs of 9000 and even crazy huge 12000mAh capacity. This approach seems to be the most promising in search for long term solution. However, the access to original "smart" circuitry is still required. Moreover, certain telemetry data of old packs (i.e. battery capacity, cycles count) appears to be permanently embedded in memory and can't be reset without proprietary software intervention. It is also unclear if completely dead batteries are indeed locking the "smart" circuitry into non-reversible state of impotence. Sooner or later somebody will find the way to hack the code, but 3rd party circuit boards smart enough to deliver the goods are less likely to happen ...

 

[ReadyKilowatt]

Maybe hit up Jon Brotherton at JB Mod Parts and see if he'd be willing to take on the project. He re-celled my 3DR Solo batteries with good quality parts and fairly quick turn around.

 

[Dobmatt]

Maybe hit up Jon Brotherton at JB Mod Parts and see if he'd be willing to take on the project. He re-celled my 3DR Solo batteries with good quality parts and fairly quick turn around.

Thank you ... Checked, but this is a totally different universe ...

 

[Greg Huntoon]

Has anyone tried emailing DJI Support? I heard they were selling TB48's for the Inspire 1 but may be out at the moment. I also heard they may put in for a run of around 300 more of them for sale here in the US.

 

[matteog]

Has anyone tried emailing DJI Support?

I did contact them some weeks ago.
From their answer, I suppose they are not going to manufacture TB48 any longer...

 

[Dobmatt]

Are the cells actually the same from TB-48 to 48D to 48S? Firmware/form factor aside, are the cells actually the same and swappable to reclaim packs with a bad cell? Doable?

Exactly the same and doable, but PITA. On retired battery you must disconnect balancing harness, unsolder main wires from the pack, unlock the top part of plastic battery housing, push/pull the pack out, pry the cells apart and wiggle the temp prob and contact board out. The same must be done with a donor. The whole circuitry of a donor is useless and must be replaced with recycled. Pack housing disassembly is difficult without damaging snap-on joints ... Dangerous and difficult task, but doable ...

 

[Dobmatt]

February 26/2021 update ... Replacing exhausted cells with exact equivalent is extremely difficult, but doable for skilled hobbyist. What seems to be a mission impossible is to source them. Only a few AliExpress merchants claims availability, but:

1. The cost of shipping is outrageous, up to over 100USD for a set of 12 cells. That's more than the price of cells alone!!!
2. God only knows what you'll receive. My first attempt failed spectacularly, because the shipment contained unmarked cells of unknown specs. Definitely not as advertised! Total charge: 191.04 USD!!!
3. Dispute claim with AliExpress is a nightmare to go thru, because the seller's refund requires shipment back ... That is another 73USD to pay ...

No matter what I will do, I'm hitting this Chinese wall ...

 

[IronSky1]

This is design for a firm in Texas that wanted to mount a TL03 gimbal and FLIR Vue on the back of there Inspire 1(s) . I designed so it could be changed to accomadate batteries on sides as well as top. In the pics they will be using a Pixhawk for secondary camera (FLIR RC). If anyone has any idea let me know and possibly I can change.

 

[Dobmatt]

This is design for a firm in Texas that wanted to mount a TL03 gimbal and FLIR Vue on the back of there Inspire 1(s) . I designed so it could be changed to accomadate batteries on sides as well as top. In the pics they will be using a Pixhawk for secondary camera (FLIR RC). If anyone has any idea let me know and possibly I can change.

1. Inspire 1 is not powerful enough to handle such extra payload. The system will detect extensive power drain and most likely not allow for lift off.
2. COG shift will cause uneven power distribution for front and back motors.

I would consider additional 750 g (including auxiliary batteries) as a reasonably safe payload for Inspire 1, resulting in very short flight time.

 

[alacazaba]

This is design for a firm in Texas that wanted to mount a TL03 gimbal and FLIR Vue on the back of there Inspire 1(s) . I designed so it could be changed to accomadate batteries on sides as well as top. In the pics they will be using a Pixhawk for secondary camera (FLIR RC). If anyone has any idea let me know and possibly I can change.

View attachment 30578

i'd like to see any flight videos or reports on this - I have a flir camera that I would like to put on a secondary gimbal but aft weight and flight time have been a big concern. Could aftermarket xoar props/blades make a crucial difference?

 

[IronSky1]

I need to get feedback from customer on how it worked. The battery weight was a concern I had. I beleve customer had 4 batteries like the Tesla ones I used. The other weight is not a big problem I have run dual gimbals all the time on my Inspires with the only issue decreased flight time however, I did not use 4 batteries , extra GPS and all the rest of the components. I use EVO SS with GoPro 360 camera on bottom works fine since it is all self contained I have no rear camera control as this design does. (I will post what I find). I agree on payload my EVO SS with GP 360 adds 440g at rear balance is great no issues.

Update : 4/9/21 Maximum weight I have had is 1000g worked fine. By placing battery on top center and DJI camera front with FLIR on Rear CG is fine. My prefered way is simpler I use a EVO SS on rear to hold 2nd camera I can only control for BT range however, that works for setup and eliminate all the other components since it is self contained.
I have used GP Fusion Session and Hero in this configuration . The same will work with FLIR VUE however , you need to power from top battery mount.

 

[Skyline-Imaging]

Since day one it was obvious that Inspire 1 flight time is way too short for serious filmmaking. With TB47 battery and X5 camera payload Inspire could stay airborne for 10-11 minutes, perhaps 15-16 minutes with beefier TB48 battery. Things get even worst with arrival of excellent, but chubby X5R camera ... Sometime between 2015 and 2016 damoncooper pioneered - with heroic persistence and efforts, but successfully - the concept of employing hard wired auxiliary batteries to support weak TB cartridges. He reached solid 25 minutes of flight time with available LiHV packs of certain capacity and discharge rate. Within several months the thread he created on this forum (Battery Mod Info) ballooned to a record 100 pages long behemoth. Unfortunately the main topic and conclusive/valuable information get quickly buried deep under layers and layers of repetitive discussions carried by others. Damoncooper is a legend, gone fishing long ago ...

Meantime the scenario changed drastically, but the main goal remains the same: how to keep old Inspire 1 alive and kicking, having TB47/48 batteries available no more? There's a few ways to do it. By far none, however, is able to bypass the necessary involvement of original "smart" circuitry TB batteries are equipped with. Therefore for now we are at the mercy of these boards and battery tops, recycled from old exhausted ones. Moreover, almost all solutions are of DIY kind, requiring top notch skills. Here's the list of options and alternative solutions for beginning of 2021:

1. Damoncooper way. For those of us lucky enough to have relatively healthy TB47/48 batteries, reinforcing them with hardwired generic packs is still a valid way. The thread mentioned above contains vast and detailed info how to, mostly within first 25 pages.
2. HeliEngadin way. This is easy, assuming the availability of old battery. The company is re-cycling the circuitry and all hardware, replacing depleted cells with new ones. The price seems to be right, but you must ship retired battery to Switzerland.
3. TB47/48S battery cannibalizing. This is the most elegant, but rather desperate way. These batteries are used to power DJI M600 drone and are still available. The pack and housing is identical, but the battery top must be replaced. This involves re-soldering main leads, replacing balancing harness and temp probe, finally swapping data wiring configuration. Tasks not easy for weekend warriors, but doable.

HeliEngadin team is among first to employ the concept of replacing exhausted cells. The exact same replacement cells can be sourced from Chinese merchants, most likely on Aliexpress. The shipment cost to NA, however, is almost killing the whole idea. On the other hand, re-soldering and re-assembling is a mission next to impossible for unskilled person ... Meanwhile some other, equally brave (mad?) nerds are trying to solder different cells of bigger capacity. Cruzroy (

) is another batt modder and tireless crusader who unknowingly tried to replicate damon's approach with rather disappointing results, but recently tested custom China assembled packs of 9000 and even crazy huge 12000mAh capacity. This approach seems to be the most promising in search for long term solution. However, the access to original "smart" circuitry is still required. Moreover, certain telemetry data of old packs (i.e. battery capacity, cycles count) appears to be permanently embedded in memory and can't be reset without proprietary software intervention. It is also unclear if completely dead batteries are indeed locking the "smart" circuitry into non-reversible state of impotence. Sooner or later somebody will find the way to hack the code, but 3rd party circuit boards smart enough to deliver the goods are less likely to happen ...

Dobmatt -

You mentioned that the mod's were not for the weekend warrior? I am not skilled in any way but am eager to learn. The second thing would be good equipment (soldering dun) Something that gets hot quick and has a fine tip? I will have to go back and read the original posts on the mod for using the Matrice battery and the intelligent top of the Inspire. Thanks for the post.

 

[Dobmatt]

Dobmatt -

You mentioned that the mod's were not for the weekend warrior? I am not skilled in any way but am eager to learn. The second thing would be good equipment (soldering dun) Something that gets hot quick and has a fine tip? I will have to go back and read the original posts on the mod for using the Matrice battery and the intelligent top of the Inspire. Thanks for the post.

Good luck learning and trying to understand why I used "weekend warrior" expression. Make sure you have good home insurance and wear safety glasses when going thru the battery mod ...

 

[mrpackethead]

Hi All. I'm a relatively new owner of a old Inspire1. I'm using it for drone fishing, which it does very well. And we can buy them in quite good order 2nd hand, for quite moderate price. Reusing them and getting a new life out of them.

it happily drags out about 400m of line, with a moderately small trace ( all up about 400g including bait ). I fly it without a camera, which i guess helps reduce the load. My flights are short. Literally out and back, only fly up to 50' or so, drop the line and head straight back.. normally in and back inside of 2 minutes. Puts our hooks where we want them, to find the big fish.
As a background i'm an electronics engineer, and have access to a well equipped workshop, and done quite a bit of reverse engineering on lots of things.

My problem which is the same as everyones is getting new battery packs! I have one battery right now that appears to be in pretty good order, without many cycles on it. ( TB48 ). It gets me ~15 minuts flying right now..

I'm fine with making / buying an eternal battery pack(s)... I'm even thinking that attmpting to reverse engineer the function of the electronics, to see how it communicates with the rest of the machine.. Hopefully the 'chat' between the boards is not encrypted.. SOmetimes its all in the 'open' and you can work out whats going on. I'd have to make a effort/reward call, sometimes these reverse engineering processes are really complex to say the least, and you have to invest many hudnreds of hours to do it. ( at which point you say, i'ld be better off buying a new machine ).

I've read a lot of threads, and theres quite a bit of conflicting info, and its a bit hard to know whos info is right and wrong... So some questions..

The mod shown here

and

Seems to be quite feisble.

Rather than having to to swap complete head/battery units, can i just swap the batterys over? Does anyone know?

 

[Dobmatt]

Rather than having to to swap complete head/battery units, can i just swap the batterys over? Does anyone know?

I'm not sure I understand your question. Please elaborate.

 

[Brian Fist]

Rather than having to to swap complete head/battery units, can i just swap the batterys over? Does anyone know?

Actually, no, you cannot just "build" a head with a removeable pack and just swap over the battery pack.

The "head" has a BMS (Battery Management System) or "smart board" built into it that controls all charging/discharging and monitors the battery cells at all times.

The issue is it is meant to be PERMANENTLY connected to the cell pack as designed. There are a number of failure modes associated with the BMS and it's monitoring of the cell pack and under certain conditions it will "lock out" the pack if it sees a condition that it considers a "complete failure". Once that happens the BMS is no longer useable.

People have ended up "tripping" this condition in playing around with recelling a pack or trying to balance the cells in a pack manually.

Beyond that condition the BMS also determines the health of a pack on a ongoing basis. It has to do this so that it can force the aircraft to land before a catastrophic failure that would allow it to fall from the sky unexpectedly. That is why DJI drones have such a good record is that the batteries all are monitored in such a way that the drone is forced to land or has reduced flight time just to make certain that a "fall from sky" event doesn't happen.

If you were to do a swappable battery to a fixed BMS, it will never know the "real" state of charge and you WILL have a fall from sky event due to the fact that under certain conditions the BMS will actually shut down the drone, even in flight. Personally I have done battery drain exercises and had it hovering at 6 inches and under a number of conditions it will shut the drone off while hovering in lieu of catastrophic failures (such as serious battery chemical reactions that would result in fire/explosion).

There is also a limit on how much you can reprogram the BMS. There is not only a battery management chipset but an actual CPU that is programmed to handle all communications with the aircraft, and there is the real struggle, getting the CPU reprogrammed in a more "open" mode to make some assumptions about the battery pack itself. As it stands, it is 100% designed and programmed to be in constant monitoring mode on the fixed cell pack. There is no capability to "reset" itself every time you plug a new pack in. When you do that you need to do reprogramming to reset a bunch of parameters to get the new pack to be "seen" as a new pack. Trust me, I have gone the furthest in regards to reprogramming these and I spent a good amount of time and money in figuring it out.

If there was a "quick fix" for the battery issue, I would have posted it already. It is a complex system due to the implementation that DJI used for the BMS as the chipset is only used for a subset of functions. Most other batteries use a chipset in "plain vanilla" mode where everything is handled by the chipset itself. On these the CPU they put in for communications actually does a lot more than just relay the data, as it also handles error states and other complex conditions. Later products that DJI built use the management chipset for everything (as seen on the P4 or Mavic line), not so with the I1.

 

[Dobmatt]

... It is a complex system due to the implementation that DJI used for the BMS as the chipset is only used for a subset of functions. Most other batteries use a chipset in "plain vanilla" mode where everything is handled by the chipset itself. On these the CPU they put in for communications actually does a lot more than just relay the data, as it also handles error states and other complex conditions. Later products that DJI built use the management chipset for everything (as seen on the P4 or Mavic line), not so with the I1.

I totally agree with Brian. The more I'm thinking about all these home cooked remedies for powering the inspire 1, the more I'm convinced that this is a "mission impossible" scenario. In other words, all the hassle involved in development of a viable long term solution to replace disappearing TB47/48 batteries doesn't justify the efforts. Even relatively simple TB47S or TB48S battery pack transplant (still available for M600 and Ronin gear) may render behaviours difficult to explain, i.e. available capacity. In theory, new and healthy TB48S battery should hold 5700mAh/129.96Wh (the same as TB48). Yet somehow this is not true at all when the pack is disconnected from DJI board, and charged and balanced externally. During such test, fully charged and discharged to absolute zero (3.5V per cell) pack had only 5083mAh capacity, which means that with 15-20% remaining power I have only a bit over 4000mAh to play with ... Perhaps I've got just poorly manufactured pack, who knows. This re-packed battery delivers good juice for even the most brutal acceleration, but the flight time is more on TB47 side. Buddha only know why ...

 

[mrpackethead]

Thanks @Brian Fist for your reply. Sounds like you've done quite a lot of leg work.. I've been thinking about this for about 48 hours, so have a bit to catch up on....

You've confirmed a couple of things,... namely that the BMS is really expecting to be on the battery all the time. And that is actually a good thing... And secondly that the 'lockouts' are built in by design, and you can trip it, if you swap batterys over. That confirms a number of things that i've been reading.

I'm resonably familiar with the ti bq chipsets and have used them for a number of projects in the past ( i work for an electronics design company ).. and i'm pretty sure we have a debugger.. ( i'll go and have a look,we have LOTs of differnet programmers/dongles for the ever increasing numer of thigns we build )...

The Cpu certainly adds complexity to the problem. Do you know what the CPU is? Have you been able to pull its firmware or is it locked out? Has anyone established a schemeatic of the BMS Board that you know of.

It strikes me that really the only way this problem is going to be *really* solved is that someone/somepeople are going to have to reverse engineer the entire BMS, and build new ones.. The only current solutions today rely entirely on recycling the boards, which eventually is going to be a big issue..

If the firmware itself can't be obtained.. then its a case of look at all th communications between the BMS and the rest of the machine.. But that ( i've done a few similar ( not on drones ) projects for industrial controllers ) can be a *very* long an error prone task.


I was able to get hold of Vincent Ng, who was selling those 12000mA jumbo batterys for a while. Unforunatly thats no longer an option and he is no longer selling them, and has no intentions to sell them. What that supply line had though, was definatly some inside infomation.. They cwere able to reprogram the device, as it was showing the 12000mAh... They were using reccyled bms boards as well.. My guess is that Vincent was working with some folks in china, who had done the reverse engineering. I did ask about that but got no reply.

For me, the next thing to do is, to try to find some old batterys.. Might be worth trying some of the service providers around the place to see if they have any lurking around...

Thanks for your comments. Helped me with some focus.

 

[mrpackethead]

Later products that DJI built use the management chipset for everything (as seen on the P4 or Mavic line), not so with the I1.

This is an evolution in chipset design thats not just happening with drones.. Theres a lot of choices when it comes to being able to find a Chipset with both a programable CPU and a BMS.. Theres options to do it with FPGAS even! ( goodness knows why )..

 

[Brian Fist]

Actually it was a lack of confidence by DJI in the TI chipset. Nothing more.

I have something of an "inside line" on things from an engineering perspective and I can tell you all this, that DJI will aggressively defend it's intellectual property and prevent others from producing Inspire 1 replacement batteries. There are details I will not go into detail here, but lets just say it is a legal issue for them as well.

They have no choice, but there will NEVER be a third party DJI battery for the Inspire 1. Even if you reverse engineer the command set for the comms between the aircraft and battery, to produce a commercial product using that communication will end up in a lawsuit. DJI has always been adamant about protecting their IP and that protocol is still used in many other drones they produce.

Now, back to the chipset, I can 100% confirm I can reprogram the BMS chipset to use a "NEW" battery pack, and I can confirm that unless you do it properly you run into what dobmatt has and that is reduced capacity and longevity. You need to "recalibrate" the BMS to the new pack. Due to the way DJI has implemented the TI chipset it is not a matter of just putting the chipset in calibration mode. I have spent many many many hours working on this, including using larger battery packs and even though it may seem somewhat selfish to keep some of this information to myself, it is because I have spent a lot of time/money/energy working out these details and coming up with solutions. I originally went into this looking to do it for commercial reasons (see a need, fill a need and make a profit), and in doing so have a lot more invested in this than most. Now that doesn't mean I won't EVER share what I know, but I need to make sure that the information I have isn't subverted and used to "pump peoples egos" which seems to be the modus-operandi for those that wants hits on youtube to make money for themselves, as well as making sure people don't half-hack a "TRUE" solution in place and lead a whole lot of others down the wrong path. There is also the very REAL probability that people would use this information to reset cycle counts and dates/timers and sell people "like-new" batteries that are total garbage. Sorry, just look at the scheming and scamming goin on with eBay in regards to these batteries. I can tell you, if I was unscrupulous I could EASILY make a battery that will last only 5 minutes look and report like a new 20 minute TB48. After 3-5 cycles it would only report 1400mAh, but that is after the fact.

The few things I can verify is:

1) I can totally reset a battery (TB47/TB48) to "as shipped" calibrated status. This is used to repack a battery with new cells. You must recalibrate and re-age the BMS. This is where almost everyone else messes up and why the Swiss guys that rebuild the DJI batteries state that they don't change the cycle count is because there is a LOT that goes into redoing things. It is NOT a matter of just "zeroing it all out". There are counters, timers and everything else that once they are started you WILL mess it all up by just setting them to zero. There is a "fused" set of counters that once started cannot be reset back to "factory" mode. Doing so messes up ALL of the calibration stuff and you will see a VERY quick reduction of capacity, along the lines of what dobmatt was seeing.

2) I can also redo the capacity, cycling and charging parameters, including the cycle count. This allows me to change the capacity, the charge/discharge rates, even the bias used to balance the cells. I have built a 9000mAh battery as well as a 11400mAh battery and had them both work just fine, for reference. Packaging is a nightmare. I will say the "best" solution I have seen so far is the previously mentioned 12000mAh battery that was offered for a while. The big concern there is that the cell used are not LipoHV cells and are not rated for the continuous use the original DJI cells were.

3) All of the errors that display as far as cell status are NOT power fail modes set via the TI chipset. They are translated via the CPU. Now, that does not mean that DJI didn't just map a status bit in the TI tables to represent the failure modes, I am still doing some mapping to compare a set of failed batteries vs a non-failed battery to verify, it is just that I have not had a lot of time to finish that work.

4) DJI does use very high-quality cells. Most Lipo suppliers have a hard time producing these cells. I can also verify that almost ALL Lipo producers in China will state that DJI owns the exact specs for their cells and they CANNOT produce exact cells as a result. Now, I also know that the Swiss company shopped the Lipo manufacturers and convinced "someone" to produce them "like" cells for their rebuilds, so it CAN be done. I wouldn't want to hazard a guess at the quantities they had to commit to so they could secure that production. I also HIGHLY question the quality and viability of that rebuilt product for long-term use, since I have first hand experience with 3 different Lipo producers and they ALL have huge issues producing consistent quality. And that includes one producer that couldn't produce proper cells for that Swiss company either (since they couldn't produce for me as well). So unless they found some magical producer that can get near 98-100% viable product out, I would have to imagine there is only about a 80-85% useable product coming in (which is generous form what I have experienced), which is a logistical nightmare to deal with the bad product. Now this is with totally "built" packs that are pre-soldered, but anything less (such as individual cells and PCBs) is a rebuilders nightmare unless you are charging 2x what DJI was charging for them, which they are not. Point being that getting matched, rated, scaled and calibrated 12-cell "packs" is a MASSIVE endeavor. DJI produces just that and they STILL had failed product at times. I have on hand 7 "built" packs and only 4 are viable and out of those 4 only 3 are matched and only 2 came calibrated (which means they were flukes, not intentional builds), so I know what I am talking about first-hand.

Lastly, I can verify I have, on hand, 4 *NEW* TB48 batteries. I won't explain what/where and how I got them, but I might just share this source at some point here. All of these batteries have production dates of the cell packs of 10/2020 thru 11/2020 and serialized dates of the complete battery of 12/2020 for all. I will also state that I did not pay over $400 for any of them either. I won't state how much I paid, nor the sourcing (for now). Again, this is because I am more concerned of the source changing and limiting the availability and I know too many people "in the profession" that rely on these for "paying work" that are redoing their stocks as I type this that I would prefer to "get what they need" before I go public with this information.

As it stands, my personal stock includes 10 TB48 batteries, 4 brand new, another 4 with less than 20 cycles and the remaining 2 with less than 30 cycles. All are either 100% capacity or at or above 91% capacity (most are 94-97%), so I "personally" am set. I can verify that I flew for over 24 minutes with one of the new TB48 batteries and it NEVER did a serious voltage drop on hard acceleration the way the oldest batteries (TB47 with more than 74% capacity) of mine do.

Sorry to be so cryptic and evasive, but I would hope I explained exactly why I am doing such for now.