Allan Bennett Posted August 2, 2021 Share Posted August 2, 2021 Switched on my trannie today to do some testing in the workshop, and got a 'Transmitter battery low' voice message. It's only been sitting for a couple of weeks since last charged and used, and it's only 14 months old ? Put it on the USB charger to get enough in it to finish my testing, and the green light turned blue within about 10 minutes, but the battery indicator showed only two bars. I've just checked it with my DVM and one cell is at 4.07 and the other at 1.32v. Any suggestions, please, for a good quality replacement Li-Ion pack? I know I can go to T9, but that's where this one came from so I'd like to try another brand. My balance charger can charge through balance leads only, so I might try it on there to see it the low cell charges. But what voltage should a Li-Ion be charged to? Is it safe to use the LiPo setting of 4.2v per cell? Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 5, 2021 Author Share Posted August 5, 2021 I put the battery on my PL8 charger the day before yesterday, and over a period of 4 hours it got both cells to 4.03v at a charge rate of 0.5C. Yesterday I put it on again and it got both cells to 4.20v quite quickly. The battery's been lying unconnected overnight, and I've just checked it now and both cells are at 4.14v. So, what caused the problem? It seems to me that one possibility is that the transmitter's inbuilt charge controller is not working correctly (it charges from a 5v USB cable), and has failed to charge one of the cells over a period of time. I've just Googled, and see that power management is on the secondary board (RF etc.), which was replaced under warranty a couple of months back due to antenna problems. I wonder if that is anything to do with it. Another is that the battery pack was faulty from the outset, and one cell is simply dying. Quote Link to comment Share on other sites More sharing options...
Kim Taylor Posted August 5, 2021 Share Posted August 5, 2021 I guess the only way to be sure is to load test it (i.e. leave it switched on) for an extended period, then re-charge using the onboard system, monitoring voltage as you go. Could I suppose be some fluke occurrence, but not something I'd feel comfortable with unless checked out. No help whatsoever to you I'm afraid, but I've been there with having a radio which I lost confidence in (not a Taranis, that's what I changed to and no issues so far) so I know that feeling in the pit of your stomach!!? Kim Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 5, 2021 Author Share Posted August 5, 2021 I'm thinking along the same lines as you Kim -- i.e. use the battery in the trannie, remove it from the trannie and check the cell voltages with a DVM, put it back in the trannie and charge it the normal way, then take it out and check the voltages again. If it's way off balance at the first check, that should suggest a bad cell; if it's okay at the first check but out of balance at the second, that'll indicate a charger failure. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 6, 2021 Author Share Posted August 6, 2021 Left the trannie switched on for about 5 hours. Took the battery out, and the cells measured 3.80 and 3.57v with my DVM. Put the battery back in the trannie and plugged in USB to charge it. It finished charging in less than an hour, but when I took the battery out to check it, it showed 4.10 and 3.88v. Put the battery on my PL8 charger and it quickly got both cells up to 4.20v. The fact that one cell discharged further than the other during the 5-hour trannie run suggests to me that it's a battery problem, with a dying cell. I've got a new pack coming, so I'll repeat the tests with it, to check that it's not a charger problem. Quote Link to comment Share on other sites More sharing options...
conrad taggart Posted August 8, 2021 Share Posted August 8, 2021 (edited) With regards to your initial question i use the Gen ace - the first battery shown here https://www.horusrc.com/en/blog/frsky-taranis-x9d-plus-se-2019/ It can be purchased from https://www.hobbyrc.co.uk/gens-ace-2600mah-2s-lipo-battery-for-taranis-2019 Let us know how you get on with your new pack and what battery you have opted for. I have noted small discrepancies in the voltage of my 2 cells and as a result every now and again I balance charge the battery using my ISDT charger. If your charger can do it, it might be worthwhile measuring and monitoring the internal resistance of your cells Edited August 8, 2021 by conrad taggart Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 8, 2021 Author Share Posted August 8, 2021 Thanks Conrad, I've got one coming from Overlander tomorrow. The one you've linked looks good because it's higher capacity than the stock one, though I've never had any issued (until now!) with an afternoon's flying. I've just checked my present pack again, after 24 hours unused, and then about 15 minutes of action in the workshop, and the cells are showing 4.15 and 3.61v. It's on my charger now, bringing them back up to 4.20v each, but I won't be using this pack again other than maybe for testing. My charger can't do internal resistance without main power leads. My new pack will have separate power and balance leads, so I'll be able to check it. Quote Link to comment Share on other sites More sharing options...
conrad taggart Posted August 9, 2021 Share Posted August 9, 2021 Alan keep an eye on your Transmitter's in-built charger. I just used my radio to charge my batteries for about 4 hours. At the start of the process there was a difference of 0.08 v between the cells. After stopping the charge 4 hours or so in (it was still charging) I found that the cells were 4.241 and 4.083. So one of the cells was past the maximum and the other had a fair bit to go and the difference in the cells doubled ! The Radios overall calibration of the battery is right, but it look likes the radio doesn't really balance charge or if it does, doesn't do a very good job ! I can't see anywhere where I can calibrate the individual cells (just the overall voltage). When I put the battery on my normal charger it wouldn't recognise it at first. It kept saying it was of the "wrong chemistry" presumably because one of the cells was over 4.20. When I discharged the battery a bit , the charger worked as per normal. Anyway I am in the process of discharging the battery to storage and will charge it again using a proper charger tomorrow, measure the cells , discharge it again to storage and charge it via the radio's inbuilt charger and do a comparison of the results. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 9, 2021 Author Share Posted August 9, 2021 Interesting observation Conrad. One of my original thoughts was that maybe the in-built charger was consistently not fully charging one of the cells, so that over time it just got lower and lower until the other day it was so low that the overall pack voltage triggered the low battery warning. Since I always charge before I go fly I generally don't look at the battery monitor symbol on the trannie, just assume that it's full because the charge light had gone out. I'll be checking that out more closely when my new pack arrives today. 1 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted August 9, 2021 Share Posted August 9, 2021 6 minutes ago, Allan Bennett said: I'll be checking that out more closely That's a good idea and I will be following your example from now on. ? Quote Link to comment Share on other sites More sharing options...
conrad taggart Posted August 9, 2021 Share Posted August 9, 2021 Interesting result and one I wasn't really expecting. Took my battery down to storage (perfectly balanced via my standalone charger) and the Radio's charger managed to charge them in about an hour and a half. Way faster than yesterday. The 2 cellls were 4.19 and 4.188 - a difference of only .002 ! This would seem to suggest that the radio's charger is fine when the batteries are balanced but it really struggles when they are not - i.e to get the right charge, not over charge a cell and do the charge within a reasonable period of time. There is also the question of what is causing the original imbalance in the first place. Anyway going to watch this carefully now - its a shame that it appears you can only get the overall voltage of the transmitter's battery from the telemetry. If you could obtain the value for the cells you could write a few lines of codes to warn you when they are out of balance by x %/amount. You could then either charge the battery properly using a dedicated charger or buy a replacement battery if required .... Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 9, 2021 Author Share Posted August 9, 2021 I think this one is resolved now. My new 2S Li-Ion arrived today, perfectly balanced at 3.52v per cell, so I put it on charge in my X9D+2019. After almost exactly 2 hours the green charge light went out, and when I checked the cells with my DVM they were 4.18v each. So the trannie's inbuilt charger seems to be working correctly, which means the fault was a bad cell in the 15-month-old original battery. But I'll still check the cell balance from time to time. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 13, 2021 Author Share Posted August 13, 2021 NOT resolved ? Today I checked the new pack, which had been in the trannie, switched off, since Mondy. One cell read 3.02v and the other 4.07v. So it seems like there's some fault in my X9D+2019 that's discharging one cell while switched off. The annoying thing is, it looks like I've thrown away (discharged with a light bulb then twisted the bared leads together) a perfectly good original battery. The trannie's going back to T9 on Monday to get sorted. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted September 1, 2021 Author Share Posted September 1, 2021 Richard at T9 has been on holiday, but today he phoned to report that the battery was 'dead' when he received the trannie, thus confirming my problem. He's put in a new RF board (which contains the charging circuit) and says the voltage has held up after recharging. He's going to monitor it another 24 hours before returning it. He did say that, talking to other FrSky people, he's now heard of other instances of cell discharging. So if you have an X9D+2019 make sure you check your cell voltages from time to time. 1 Quote Link to comment Share on other sites More sharing options...
Mike Chantler Posted September 2, 2021 Share Posted September 2, 2021 Allan, many thanks for sharing your investigations. I have a year old TX16s with two 18650s in it. Never thought to check the state of these cells after the charge light goes out! Will do now as I had some black screen problems recently (and I have a feeling that you can get at the cell voltages via the tx16 telemetry interface) Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted September 2, 2021 Author Share Posted September 2, 2021 The Taranis has a low battery warning, but what it doesn't tell you is that the cells are way out of balance -- in my case it was 4.07v and 1.32v which adds up to less than the alarm trigger of 6v. I inferred from what Richard said that it's specific to the X9D+2019, but no harm in checking any other trannie's battery from time to time. Quote Link to comment Share on other sites More sharing options...
MattyB Posted September 2, 2021 Share Posted September 2, 2021 Sigh..... Yet another instance of Frsky shooting themselves in the foot with poor QA/testing. I have used their gear for getting on for 8 or so years with almost no issues, but in recent times they do seem to be going to increasing lengths to annoy and frustrate users. If there was a compelling alternative I would probably think of jumping ship at this point, but that is hard to do when you look at the pricing of Jeti, Spektrum and Futaba and the relatively primitive telemetry functionality of the latter two. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted September 2, 2021 Author Share Posted September 2, 2021 My first Taranis (X9D+) has been no problem, and I'm addicted now to the voice alerts as well as OTX's programming flexibility. If Jeti or Futaba came up with a system that could run OTX (or a look-alike), I might consider jumping ship. On the other hand, if the new board in my X9D+2019 solves its problem, then no need. All my firmware is v2 now, so hopefully I can just leave things as they are from now on. Quote Link to comment Share on other sites More sharing options...
Kim Taylor Posted September 3, 2021 Share Posted September 3, 2021 All of the above prompted me to check the battery in my X9D+SE2019 'just in case'. I can report that the cells were balanced to within 0.01V using the onboard charger, so no issues with mine, but I'll keep an eye on it anyway. Quote Link to comment Share on other sites More sharing options...
Outrunner Posted September 3, 2021 Share Posted September 3, 2021 Prompted me to check my TX too. Radiomaster TX16s 2s lipo charged via built in USB socket, cells balanced perfectly? Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted September 3, 2021 Author Share Posted September 3, 2021 (edited) Just to be clear, mine was charging okay via its built in USB socket, but it was discharging one cell whether switched on or off. It only took mine 4 days switched off for one cell to drop to 3.02v, so you'll notice the problem quite quickly. Edited September 3, 2021 by Allan Bennett Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted September 7, 2021 Author Share Posted September 7, 2021 I got my trannie back from T9 on Saturday and, even though one cell was down at 3.13v at that time, since I recharged it indications thus far are that the new board has solved the problem. Cells have stabilised at about 4.15v with the trannie switched off, and with it switched on for about 4 hours today, they both went down to 3.84v. So, not the massive imbalance that I was seeing before. 1 Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted September 19, 2021 Author Share Posted September 19, 2021 After 12 more days of observation, all is well. The only thing I've noticed is that the built-in USB charger doesn't seem to charge to 4.20v per cell, and the cells are always 0.01v different from each other after charging -- e.g. today 4.17v and 4.16v. But measurements taken after use, or after the trannie's been sitting a while, have always shown exact balance. So I won't be monitoring it any more, other than checking the on-screen reading from time to time. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted September 19, 2021 Share Posted September 19, 2021 Get a HK 1500 LiFe pack for it. If that discharges then there is something wrong with your Tx since they will hold the charge for an almost indefinite period. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted September 20, 2021 Author Share Posted September 20, 2021 It's an Overlander Li-Ion pack in it, bought new when I first thought the original battery was at fault. But all seems well from the discharge point of view, so I'm satisfied. Quote Link to comment Share on other sites More sharing options...
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